Graftless Solutions for the Edentulous Patient (BDJ Clinician’s Guides) [2nd ed. 2023] 3031328469, 9783031328466

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BDJ Clinician’s Guides

Saj Jivraj Editor

Graftless Solutions for the Edentulous Patient Second Edition

BDJ Clinician’s Guides

This series enables clinicians at all stages of their careers to remain well informed and up to date on key topics across all fields of clinical dentistry. Each volume is superbly illustrated and provides concise, highly practical guidance and solutions. The authors are recognised experts in the subjects that they address. The BDJ Clinician's Guides are trusted companions, designed to meet the needs of a wide readership. Like the British Dental Journal itself, they offer support for undergraduates and newly qualified, while serving as refreshers for more experienced clinicians. In addition they are valued as excellent learning aids for postgraduate students. The BDJ Clinician’s Guides are produced in collaboration with the British Dental Association, the UK’s trade union and professional association for dentists.

Saj Jivraj Editor

Graftless Solutions for the Edentulous Patient Second Edition

Editor Saj Jivraj Anacapa Dental Art Institute Oxnard, CA, USA

ISSN 2523-3327     ISSN 2523-3335 (electronic) BDJ Clinician’s Guides ISBN 978-3-031-32846-6    ISBN 978-3-031-32847-3 (eBook) https://doi.org/10.1007/978-3-031-32847-3 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2018, 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Foreword 1

Dr. Saj Jivraj has assembled in this textbook a quintessential team of talented world-renowned surgeons and restorative dentists who extensively share their vast knowledge in the latest innovations in Implant Dentistry. In order to address the ever-increasing magnitude of patients in need of extensive implant treatment, graft-less implant solutions must be combined with an in-depth knowledge of surgical and restorative procedures through a rigorous and well-coordinated interdisciplinary approach. This textbook displays in an effective and methodical manner the modern foundation for the diagnosis and graft-less treatment of edentulous patients with fixed implant supported prosthetics. It provides clear and understandable concepts through basic and advanced implant principles that are required in the initial comprehensive diagnosis and digital workflow all the way through the interdisciplinary teamwork necessary to manage tilted and zygomatic implants, and ultimately produce high-quality implant full arch restorations. We have greatly benefited over the past years at Augusta University from the great teachings of Dr. Jivraj and we trust that this important work will be enjoyed worldwide as a reference textbook in modern Implant Dentistry. Louisiana State University School of Dentistry New Orleans, LA, USA

Gerard J. Chiche

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Foreword 2

It is my pleasure to be invited to write another foreword to this book for Dr. Saj Jivraj with whom I have interacted with for over 25 years in the capacity of being his programme director, colleague and friend. I have seen his stature grow with time; he is dedicated to give the best care to his patients and has been a sought-after presenter to major conferences all over the world. Dental Implants are one of the most useful tools that we have to replace missing teeth. Early in the process of using osseointegrated implants stringent protocols were required. One of the criteria included placement of dental implants in host bone. Over the years many ways of grafting bone were presented, autogenous grafts from extraoral and intraoral sites, as well as allografts and xenografts. Many articles and reviews have been published regarding the efficacy of the different materials used in grafting and the techniques used. Many of the articles compare techniques and graft types but many do not have the priority of placing implants into non-­grafted sites. This significantly reduces the variable of grafting. Compared to the earlier times when implants were placed into healed sites success rates in the longer term seem to produce very good long-term and predictable results. With the new technology of being able to alter screw channel directions to facilitate screw retention when implants are placed “off axis”, technicians better at fabricating replica of missing soft tissues we are able to have implants placed into host bone and avoid using grafts. This newer edition of the book is a comprehensive overview of graft-less techniques for full mouth implant rehabilitation from diagnosis to delivery. A strong emphasis has been placed on diagnosis and treatment planning. Many chapters are dedicated to the digital workflow and how digital technologies can help the clinician become more efficient. With sufficient information more easily collected the clinician is able to execute treatment with precision and predictability. I congratulate Dr. Jivraj on his book and the assembled contributors for providing clinicians with a comprehensive understanding of the risk vs benefit considerations when choosing treatment options for their patients based on the multiple factors that are outlined in this text. Ralph and Jean Bleak Professor Restorative Dentistry Herman Ostrow School of Dentistry of University of Southern California, Los Angeles, CA, USA

Winston Chee

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Preface

Implant dentistry has seen remarkable progress over the last 25  years. Clinicians strive for long-term predictable results. Many of the original concepts in implant dentistry have been challenged. To obtain fixed permanent teeth, patients often had to go through extensive surgical procedures and be transitioned in an uncomfortable removable appliance. Full arch fixed implant rehabilitation can be performed in a single day in the right indication and successful results can be achieved with an experienced team. Today, the “Graft-less Concepts” eliminate the need for grafting and long waiting periods prior to the reconstruction of the edentulous or the patients with “terminal dentition”. The ability to remove the patient’s failing dentition, place implants and fabricate a fixed, immediate load prosthesis has changed the manner in which many of our colleagues treat their patients in 2023. With that said as clinicians we should not be dogmatic in a particular treatment philosophy. Treatment planning should be based on a sound diagnosis. Risk factors should be understood and only in the right indication should a patient’s teeth be removed in favour of implant placement. There is always going to be a debate over how many implants should be placed in an edentulous arch. The answer to that question is “It Depends”. It depends on the patient’s medical history, it depends on the quality of bone, it depends on the anticipated occlusal force on the restoration and it depends on the operators skill. Although the All on 4™ concept has shown to be highly successful, it is indicated for specific clinical circumstances and should not be considered as a panacea for treatment of all edentulous patients. Unfortunately many patients have been treated with this concept incorrectly. Often there is ample bone to place 6–8 implants and diagnose the patient as having a tooth only defect. In this instance additional implants are placed to be able to segment the prosthesis and minimal or no bone reduction is required. Today we should be practicing minimally invasive full arch implant dentistry and be questioning the need for haphazard bone reduction. The authors of this text have outlined the importance of diagnosis, treatment planning, surgical as well as the prosthetic protocols and techniques for the treatment of the edentulous as well as the “terminal dentition” patients. The purpose of the book is to provide an understanding of diagnosis and treatment planning. Each clinician should understand and be fully familiar with analogue techniques before a digital workflow is adopted. Digital ix

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t­echnologies add to our armamentarium of tools but are by no means a substitute for analogue principles. The book has been designed so the chapters build on each other. It will take the reader on a journey from diagnosis to delivery. Diagnosis is critical from both a restorative and surgical perspective. An accurate diagnosis results in the correct treatment plan. Today we have many digital technologies that can assist us in our diagnostics. Armed with sufficient information the practitioner is able to execute treatment with precision and efficiency. We have some world-renowned talented clinicians who are experts in their respective fields who have laboured tirelessly to put this text together. Words cannot express how appreciative and honoured I am to have been able to work with them. Our hope is the reader will gain a solid foundation in treating the edentulous or soon to be edentulous patient. Enjoy. Oxnard, CA, USA

Saj Jivraj

Acknowledgements

“Teamwork is the ability to work together towards a common vision. The ability to direct individual accomplishments towards organisational objectives. It is the fuel that allows common people to attain uncommon results”. Andrew Carnegie

As the years pass, the things that become important really come into perspective. It is to these important aspects of my life that I wish to dedicate this book. To My Family First and foremost, and without hesitation I would like to thank my beautiful wife Dilaz. She is my life, my inspiration and a wonderful mother to my two beautiful children Sara and Zain. You said “yes” to everything which should have been “no”; you allowed me the time to become professionally what I dreamed about as a young graduate. You persevered when times got tough and gave up everything moving with me to the USA. For the countless hours I did not spend with you and the kids, for the unconditional love, friendship, and unwavering support I thank you. To Sara and Zain, words cannot express the profound love I have for you. You have taught me to appreciate life in ways I thought were not possible, the little things you do and say make me a better person, husband and father. I will always be by your side to support you in anything you do. Work hard and dream big and believe in the impossible. You can do what you set your mind to and don’t let anybody else tell you otherwise. I would also like to dedicate this book to the memory of two exceptional women: Mrs. Amina and Rukiya Jivraj who were taken from this world far too early. Not a day goes by when I don’t think of you. I feel your presence in all the important decisions that I make. I miss you both dearly and wish we could have created more memories together. When people say, “Life is too short”, I now understand what that means. I do know we will meet again, and it is that day to which I look forward. To My Colleagues I’d like to thank Drs. Winston Chee, Terry Donovan and George Cho and who believed in me and who provided me with the opportunity to complete my Prosthodontic education at the Herman Ostrow USC School of Dentistry. I will be forever grateful. Dr. Robert Schneider who opened doors and believed that one day I would realise my potential. Credit should also be reserved for Dr. Jonathan Gordon. He is an amazing surgeon and I continue

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to learn so much working with him. Many of the cases you see in this book are a result of our collaboration together. Lastly Dr. Hooman Zarrinkelk with whom I started the graft-less journey and who has also contributed many patient cases that are documented in this text. Without my co-authors this text would not have come to fruition. I would like to thank Dr. Hooman Zarrinkelk, Dr. Carlos Aparicio, Dr. Bobby Birdi, Dr. Sundeep Rawal, Dr. Faraj Edher, Dr. Steven Bongard, Dr. Glen Liddelow, Dr. Graham Carmichael, Dr. Keith Klaus, Dr. Jay Neugarten, Dr. Udatta Kher, Dr. Ali Tunkiwala, Dr. Stephanie Yeung, Dr. Andrew Dawood, Dr. Michael Klein, Dr. Frank Tuminelli, Dr. Satish Kumar, Dr. David Powell, Dr. Susan Tanner, Dr. Kian Karimzadeh, Dr. Vishy Broumand, Dr. Jayson Kirchhofer, Dr. Komal Majumdar, Dr. Ana Ferro, Dr. Mariana Nunes, Dr. Diogo Santos, Dr. Armando Lopes, Dr. Filipe Melo, Dr. Miguel de Araujo Nobre and Dr. Martin Wanendaya for their contributions to the text. The laboratory section was graciously written by Mr. Kenji Mizuno and Mr. Aram Torosian, and Mr. Michael Tuckman; I truly appreciate the countless hours they spent documenting the lab phase and putting it into a format that is practical. I would like to thank Digital Dental Arts Laboratory in Ventura. Much of the laboratory work documented is a result of their collaboration. I would like to acknowledge all the students and faculty involved with the advanced Prosthodontic and Periodontics programme at Herman Ostrow USC School of dentistry from whom I have learnt so much and continue to do so. I would be remiss if I did not thank my team at Anacapa Dental Art Institute. Laura Castellanos RDA has assisted me for the last 10 years and has been instrumental in developing protocols we use on a day-to-day basis. She is someone who always works with a smile on her face and makes a complex day go very smoothly. Sonia Escamilla for her positive demeanour, amazing leadership and ability to bring the best out of people, Ale Prado for keeping everything light when the day gets tough, and willingness to do whatever it takes, Maricel Estoque for her excellent patient management skills and warm and caring attitude towards everyone she meets, Erika Simental for her kindness and professionalism, Amber Padilla RDH who started the journey with me as my assistant and progressed to becoming a wonderful hygienist and Darlene Herrera RDH who has assisted me in the maintenance of these patients and whose attention to detail is exceptional. My whole team is amazing. They make coming into work each day enjoyable and always go the extra mile for our patients. Their dedication and commitment are second to none and I want to let you know I appreciate everything you do. Special thanks also go to my team at the Digital Dental Arts Laboratory in Ventura. Kenji Mizuno for his exceptional work ethic and the ability to get the job done, Dmytro Tytarenko for his skill in digital workflows and pushing me to become a better clinician, Margaryta Pisnia for her organisation and attention to detail, Ahmet Tanay for his positive demeanour and professional-

Acknowledgements

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ism and Artyom Avanesov for his amazing artistry in ceramics. Without a great Laboratory partner we cannot do what we do for patients. I would also like to thank Melker Nielsson for his friendship and advice over the years. It was through his guidance and support that I pursued graftless solutions as an option for my patients. To My Patients Who make each and every day enjoyable for me. Thank you for allowing me to compile these clinical photographs. It’s caring for these patients that makes my profession so rewarding and makes me look forward to the next day. To God Who has made everything possible. His guidance has allowed me to pursue my dreams and realise them. Saj Jivraj

Contents

1 D  iagnosis and Treatment Planning: A Restorative Perspective����������������������������������������������������������������������������������������   1 Saj Jivraj 2 S  urgical Diagnostic Considerations in Graft-Avoiding Dental Implant Reconstruction of Atrophic Jaws������������������������  15 Hooman M. Zarrinkelk 3 G  uided Surgery for Full-Arch Implant-Supported Restorations��������������������������������������������������������������������������������������  25 Michael Klein, Jay Neugarten, and Allon Waltuch 4 D  igital Workflows in Full Arch Implant Prosthodontics�������������� 101 Faraj Edher, Sundeep Rawal, and Saj Jivraj 5 3 D Printing Protocols in Full-Arch Reconstruction: A Complete Workflow �������������������������������������������������������������������� 117 Keith Klaus and Saj Jivraj 6 T  he Zygoma Anatomy-Guided Approach (ZAGA) for Preventing Complications Using Zygomatic Implants ���������� 129 Carlos Aparicio 7 P  terygoid Implants as Alternative to Bone Augmentation in Implant Dentistry ���������������������������������������������� 147 Vishtasb Broumand and Jayson Kirchhofer 8 S  cientific Basis of Immediate Loading and the Biomechanics of Graftless Solutions�������������������������������� 167 Bobby Hardeep Birdi, Komal Majumdar, and Saj Jivraj 9 F  P1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations������������������������������ 205 Martin Wanendeya and Saj Jivraj 10 G  raftless Surgical Protocol: Diagnosis to Delivery ���������������������� 263 Ana Ferro, Mariana Nunes, Diogo Santos, Armando Lopes, Filipe Melo, and Miguel de Araújo Nobre 11 S  urgical–Anatomical and Prosthetic–Biomechanical ZAGA Criteria to Determine the Zygomatic Implant Trajectory ���������� 295 Carlos Aparicio, Arnau Aparicio, and John Brunski xv

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12 C  linical Techniques for Immediate Loading �������������������������������� 313 Stephanie Yeung and Saj Jivraj 13 M  aterial Considerations for Full-­Arch Implant-Supported Restorations�������������������������������������������������������������������������������������� 337 Saj Jivraj and Sundeep Rawal 14 C  linical Steps for Fabrication of a Full-Arch Implant-Supported Restoration ���������������������������������������������������� 359 Udatta Kher and Ali Tunkiwala 15 S  peech and Facial Aesthetic Considerations for the Contour of Fixed Prostheses ���������������������������������������������� 387 Glen Liddelow and Graham Carmichael 16 L  aboratory Fabrication of Full-­Arch Implant-Supported Restorations�������������������������������������������������������������������������������������� 401 Kenji Mizuno, Aram Torosian, Saj Jivraj, and Michael Tuckman 17 P  rosthetic Complications with Immediately Loaded, Full-­Arch, Fixed Implant-Supported Prostheses�������������������������� 447 Frank J. Tuminelli, Saj Jivraj, Steven Bongard, and David Powell 18 M  anagement of Failure and Implant-Related Complications in Graft-Less Implant Reconstructions (for Atrophic Jaws) ������ 473 Andrew Dawood and Susan Tanner 19 M  aintenance of Full-Arch Implant-­Supported Restorations: Peri-­Implant and Prosthetic Considerations�������������������������������� 495 Satish Kumar, Kian Kar, and Saj Jivraj 20 C  linical Patient Presentations �������������������������������������������������������� 517 Saj Jivraj

Contents

Contributors

Arnau  Aparicio ZAGA Center, Private Practice QDT Center, Houston, TX, USA Carlos  Aparicio International Teaching Scholar Indiana University School of Dentistry, Indianapolis, IN, USA Director of Zygomatic Unit at Hepler Bone Clinic, ZAGA Center, Barcelona, Spain Bobby  Hardeep  Birdi University of Minnesota School of Dentistry, Minneapolis, MN, USA Private Practice, Vancouver, BC, Canada Steven Bongard  Private Practice, Toronto, ON, Canada Vishtasb  Broumand Oral and Maxillofacial Surgery Private Practice, Desert Ridge Oral Surgery Institute, Phoenix, AZ, USA Department of Oral and Maxillofacial Surgery, University of Arizona College of Medicine at Banner University Medical Center Phoenix, Phoenix, AZ, USA John Brunski  Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University, Stanford, CA, USA Graham Carmichael  School of Dentistry, University of Western Australia, Crawley, WA, Australia Craniofacial Unit, Princess Margaret Hospital, Subiaco, WA, Australia Maxillofacial Department, Royal Perth Hospital, Perth, WA, Australia Andrew  Dawood Department of Head and Neck Surgery, University College London Hospital, London, UK The Dawood and Tanner Specialist Dental Practice, London, UK Miguel  de Araújo  Nobre Research, Development and Education Department, Maló Clinic, Lisbon, Portugal Faraj Edher  Digital Dentistry Institute, BC Dental Study Club, University of British Columbia, Vancouver, BC, Canada Ana Ferro  Oral Surgery Department, Maló Clinic, Lisbon, Portugal Saj Jivraj, BDS, MS.Ed,  Anacapa Dental Art Institute, Oxnard, CA, USA xvii

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Kian  Kar Herman Ostrow School of Dentistry of USC, University of Southern California, Los Angeles, CA, USA Udatta Kher  , Mumbai, India Jayson Kirchhofer  Oral and Maxillofacial Surgery Private Practice, Desert Ridge Oral Surgery Institute, Phoenix, AZ, USA Department of Oral and Maxillofacial Surgery, University of Arizona College of Medicine at Banner University Medical Center Phoenix, Phoenix, AZ, USA Keith Klaus  Private Practice, Flowood, MS, USA Michael  Klein Advanced Implant Dentistry and Oral Restoration, Cedarhurst, New York, NY, USA Satish  Kumar Arizona School of Dentistry and Oral Health, A.  T. Still University, Mesa, AZ, USA Glen  Liddelow School of Dentistry, University of Western Australia, Crawley, WA, Australia Craniofacial Unit, Princess Margaret Hospital, Subiaco, WA, Australia Armando Lopes  Oral Surgery Department, Maló Clinic, Lisbon, Portugal Komal Majumdar  Om Dental Clinic, Navi Mumbai, India Filipe Melo  Prosthodontics Department, Maló Clinic, Lisbon, Portugal Kenji Mizuno  Anacapa Dental Art Institute, Oxnard, CA, USA Jay  Neugarten  Department of Oral and Maxillofacial Surgery, Weill-­ Cornell Medical Center, New York-Presbyterian Hospital, New York, NY, USA Mariana Nunes  Oral Surgery Department, Maló Clinic, Lisbon, Portugal David Powell  Private Practice, Toronto, ON, Canada Sundeep  Rawal  Implant Support Services, Chicago, IL, USA The Digital Dentistry Institute, Orlando, FL, USA

Aspen

Dental,

Diogo Santos  Oral Surgery Department, Maló Clinic, Lisbon, Portugal Susan Tanner  The Dawood and Tanner Specialist Dental Practice, London, UK Aram Torosian  Ronald Goldstein Center for Esthetic and Implant Dentistry, Dental College of Georgia at Augusta University, Augusta, GA, USA Michael Tuckman  Osteon Medical, Mulgrave, VIC, Australia Frank  J.  Tuminelli American Board of Prosthodontics, Saint Paul, MN, USA VA NY Harbor Healthcare System, New York, NY, USA Hofstra Northwell School of Medicine, Hempstead, NY, USA

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Private Practice, Manhasset, NY, USA Ali Tunkiwala  Mumbai, India Allon  Waltuch Advanced Implant Dentistry and Oral Restoration, Cedarhurst, New York, NY, USA Martin Wanendeya  Ten Dental, London, UK Stephanie Yeung  Private Practice, Los Angeles, CA, USA Hooman  M.  Zarrinkelk Diplomate American Board of Oral and Maxillofacial Surgeons, Chicago, IL, USA Fellow American College of Oral and Maxillofacial Surgeons, Washington, DC, USA Private Practice, Ventura, CA, USA

1

Diagnosis and Treatment Planning: A Restorative Perspective Saj Jivraj

Abstract

Treatment of the edentulous patients with implant-supported restorations presents a significant challenge to the treating clinician. Patient expectations in regard to aesthetics, phonetics, form, and function are high. There are a myriad of factors that need to be evaluated to determine if the patient is a suitable candidate for a fixed vs. a removable implantsupported restoration. Evaluation of the edentulous patient is also complicated by the fact that patients may not only be missing clinical crown height but in addition may have experienced a combination of tooth, soft tissue, and bone loss, with associated changes in facial form. The purpose of this article is to evaluate the diagnostic factors that are critical in treatment planning a patient for fixed implant-supported restorations. The predictability of successful osseointegrated implant rehabilitation of the edentulous jaw as described by Branemark et  al. [1] introduced a new era of management for the edentulous predicament. Implant rehabilitation of the edentulous patient remains one of the most complex restorative challenges because of the number of variS. Jivraj (*) Anacapa Dental Art Institute, Oxnard, CA, USA

ables that affect both the aesthetic and functional aspect of the prosthesis. The routine treatment for edentulism has been complete dentures. Epidemiological data has reported that the adult population in need of one or two dentures would increase from 35.4 million adults in 2000 to 37.0 million adults in 2020 [2]; and the researchers warn that their estimates may be “significantly conservative”. Clinical studies have reported that patients with dentures have shown only a marginal improvement in the quality of life when compared with implant therapy [3]. The common reasons for dissatisfaction in patients using dentures include but are not limited to pain, poor retention and stability, and difficulty eating [4]. A review of the literature noted that prostheses supported by osseointegrated implants significantly improved the life of edentulous patients when compared with conventional dentures [5]. Many patients tolerate complete dentures despite the dissatisfaction. Reasons for this could be: • Anatomic. They have been told they are not implant candidates because of pneumatized sinuses and severe resorption of the posterior mandible. • Cost. • Lack of education. They have not been educated about dental implants and do not

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_1

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visit a dentist because they feel nothing can be done for them.

Most patients will look toward an implant rehabilitation hoping to acquire a fixed prosthesis. Treatment planning of edentulous patients Restoration of the edentulous patients with with fixed restorations on dental implants has dental implants is costly whichever method is undergone a paradigm shift since the introducused to restore the patient. Fixed reconstructions tion of graftless solutions. In particular, the require more laboratory assistance and implant All-on-4 method™. parts and, thus, are a lot more costly. Today, patients have options whereby in the Due to economic factors, many patients have right indication complete rehabilitation can be been provided with implant- and mucosa-­ accomplished by the use of four implants per supported overdentures. arch. The major advantages of this procedure However, cost needs to be considered not only are the reduced number of implants and the during fabrication of the prosthesis but also dur- ability to bypass extensive grafting procedures. ing maintenance. Overdentures seem to have This rehabilitation not only satisfies aesthetics more post-insertion maintenance than their fixed and function but also considerably reduces counterparts. If this is consistent, it could be costs for the patient. This ultimately results in questioned whether an economic indication for increased patient acceptance and an increased choosing an overdenture could be justified when number of patients treated. Very few patients there is sufficient bone to support implants for a today are able to afford extensive implant rehafixed prosthesis. The patient must be made aware bilitations on six to eight implants, and the that maintenance costs for removable prostheses All-on-4™ or graftless protocol is gaining popon implants will be higher than that of a fixed ularity as being the treatment of choice for the prosthesis. Today, clinicians are seeing an edentulous patient. increasing number of dentate patients where the Clinicians must be cognizant that the All-on-4 dentition is terminal. These patients would have concept™ is indicated for specific clinical situabeen edentulous a long time ago if it had not been tions namely: for the efforts of skilled restorative dentists. Clinical treatments have involved maintaining 1. There is minimal bone in, with pneumatized nonrestorable teeth for as long as possible to sinuses and posterior mandibular resorption. avoid a removable appliance. Patients understand In this circumstance the clinician can only that maintaining a terminal dentition has conseplace four implants due to anatomical limitaquences on the bone. However, the fear of edentions. To avoid grafting tilted implant, contulism forces them to ignore failing oral cepts are employed. conditions. 2. Adequate lip support. In spite of the increasing numbers of 3. Where the patient has lost a significant amount edentulous or soon-to-be edentulous patients, of bone and strategic implant placement is there still appears to be many reasons why required to obtain bicortical anchorage. patients avoid treatment with dental implants. These reasons could include: It is the authors’ opinion that more than four implants are required when: • The fear of wearing a removable appliance in the transitional phase. 1. There is an abundance of bone and • The notion that the proposed treatment is biomechanically cantilevers can be avoided. time-consuming and unpredictable. 2. The patient presents with a dentition that • The number of visits involved and the fear of exhibits signs and symptoms of excessive pain. force. • Cost.

1  Diagnosis and Treatment Planning: A Restorative Perspective

3. Patient has uncontrolled metabolic disease which compromises healing. 4. Poor quality bone. The advantages and considerations of placing more implants and preserving bone include the following: 1. There is the ability to segment the prosthesis and complication management becomes easier for the clinician. 2. If in the future an implant were to fail, there are enough implants where the patient may not have to undergo surgery again. 3. The thought process that making an impression on four implants is easier than making an impression on five or six does not hold merit. Today, with advancements in digital technologies, analogue impression making may soon become obsolete at multiunit abutment level. 4. When placing implants, the clinician must begin with the end in mind visualizing the definitive restoration. Zirconia requires specific connector dimensions and requires appropriate distance between implants. Zirconia also requires specific thickness for biomechanical integrity. The implants together with the multi-unit abutments must be positioned three dimensionally to allow for this. 5. Maintenance of bone in between the implants can be obtained by banking roots. 6. If a catastrophic failure were to occur and all the implants were lost, then the clinician still has the opportunity to retreat the patient. Treatment planning should be based on a thorough diagnosis to culminate in an appropriate treatment plan for the patients presenting clinical situation. Unfortunately, the All-on-4™ concept has been used as a panacea for full arch implant reconstruction, and often patients are treated dogmatically with this treatment protocol. Often bone is removed needlessly to satisfy a certain treatment philosophy.

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Minimally invasive full arch implant dentistry adheres to concept of preserving and maintaining bone. Bone reduction is virtually eliminated, and the patient maintains their own gingiva. Although four implants are considered standard, the placement of additional implants is considered advantageous. As a practicing clinician, implant failure is always a concern and should one of four implants fail, the definitive restoration needs to be remade at the restorative dentist’s cost. If more than four implants have been placed, then there are reserve implants to work with. As in all phases of dentistry, diagnosis is critical in obtaining a predictable outcome. An incomplete or erroneous diagnosis can yield unsatisfactory results for both the patient and treating clinician. The decision-making parameters when rehabilitating patients require the clinician to make a decision as to whether a fixed or a removable prosthesis would be more suitable. Zitzmann and Marinello [6] and Jivraj et al. [7] described in detail parameters that need to be evaluated. A fixed restoration should not be promised to a patient until all diagnostic criteria are evaluated. These criteria must include quality and quantity of bone available to support implants, lip line, lip support, and aesthetic demands. Implants should not be placed until a definitive treatment plan has been established as implant positions may vary depending on type of prostheses to be delivered. From a diagnostic perspective, several parameters need to be evaluated before deciding upon the type of prosthesis that is most appropriate for the patient. The following considerations pertain to restorative treatment planning (Fig. 1.1). Surgical considerations will be presented in a separate chapter. Diagnostic considerations include but are not limited to: 1. Positioning of the maxillary and mandibular incisal edge 2. Restorative space 3. Lip support

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Fig. 1.1  Factors that need consideration before deciding upon a fixed vs. removable implant rehabilitation

4. Smile line and lip length 5. Contours and emergence 6. Tissue contact 7. Occlusion

1.1 Positioning the Maxillary and the Mandibular Incisal Edge The maxillary incisal edge position is determined utilizing the principles of aesthetics and phonetics. Traditional guidelines tell us that when the patient makes the “F” sound, the incisal edge should touch the vermillion border of the lower lip. Once the incisal edge position has been established, the length for the central incisors is determined. On average, the length of the central incisors is 10.5 mm; this can be more in elderly patients who exhibit gingival recession [8]. The axial inclination of the central incisor should be placed so as to provide adequate support for the upper lip. Once the crown length, angulation, and coronal form have been determined, the distance between the cervical crown margin and residual bone must be established to determine if adequate space exists

for the anticipated restoration. Often the maxillary incisal edge is over-erupted and treatment planning involves repositioning the incisal edge more apically (Fig. 1.2). Putting the maxillary central in the right position may require alveolectomy to provide sufficient running room from the head of the implant fixture to the emergence profile as it exits the free gingival margin [9]. To determine if a fixed or removable restoration would be appropriate, a wax try-in is done without a flange. For a fixed restoration, the clinical crown should ideally end up at the soft tissue level of the alveolar ridge. In this situation, minimal resorption would have occurred, interarch space will be favourable, and an optimal tooth-lip relationship is present. When a large vertical distance exists between the cervical aspect of the tooth and the alveolar ridge but the tooth-lip relationship is favourable, pink ceramic or acrylic may be utilized to disguise the tooth length and a fixed restoration is still possible. When there is both a vertical and horizontal discrepancy between the ideal position of the tooth and the alveolar ridge, and the tooth-lip relationship is not optimal, this may be an indication for use of a removable

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Fig. 1.2  Re-positioning the incisal edge more apically will have an impact on the implant placement. Alveolectomy will need to be performed prior to implant placement in this patient’s case

prosthesis. The flange will provide adequate lip support, and the teeth can be positioned appropriately to satisfy the parameters of aesthetics. It is the authors’ opinion. The mandibular incisal edge is positioned for function. The clinician must provide shallow guidance, sufficient to provide posterior disclusion in both protrusive and lateral excursions. Anterior guidance must be smooth and distributed amongst as many anterior teeth as possible. A thorough evaluation must be made of the existing mandibular incisal edge position. When patients are missing posterior teeth and have been diagnosed as having lack of posterior support, the mandibular incisal edge is often in the incorrect position. The clinician must decide whether to reshape, reposition, restore, or remove if the maxillary arch is being considered for implant-­ supported restorations. Conventional prosthodontic guidelines will place the mandibular incisal edge just at the level of the lower lip with 0.5–1.0 mm of the incisal edge visible. Guidelines in relation to the lower mandibular occlusal plane can also be sought from anatomical landmarks such as the retromolar pad. If the clinician is planning a fixed implant-­ supported restorations for the mandible, adequate restorative space must be provided. The over-­ eruption of teeth brings with it an excess of bone, which must be reduced prior to the implants being placed.

1.2 Restorative Space Insufficient restorative space is the most common error when planning full arch restorations. Inadequate space results in either premature failure of the restoration or changing the treatment plan from one restoration to another to accommodate the space requirements. To accommodate adequate designs, different types of restorations require different dimensional tolerances [7]. Accurately mounted casts are critical in assessing prosthetic space limitations. Spatial constraints must be considered as a matter of practicality. The limiting factor in edentulous patients is the available inter-arch space [10]. Adequate restorative space is critical, and guidelines exist depending upon the type of prosthesis being treatment planned. There must be adequate space for bulk of restorative material that also permits a prosthesis design to establish aesthetics and hygiene. If space is limited, re-­ establishing a patient’s vertical dimension or altering the opposing occlusion should be considered [11]. Guidelines for space requirements for ceramic-based restorations are 10–13  mm for a screw retained ceramic-based restorations and 14–16 mm for acrylic resin/titanium-based restorations. Clinicians should select the material that requires the least bone removal and satisfies the requirements of aesthetics, contour, and biome-

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6 Fig. 1.3 Inadequate restorative space can result in restoration fracture

Fig. 1.4  Resin-based restorations require 15–18 mm of restorative space

chanics. Acrylic titanium restorations are very rarely done in the maxillary arch due to the amount of restorative space and bone removal required. They should be reserved for the mandibular arch when opposing a maxillary denture (Figs. 1.3 and 1.4) [6, 7].

1.3 Lip Support One of the best diagnostic tools is the patient’s existing maxillary denture. The clinician can evaluate the patient’s denture to determine what likes and dislikes there are regarding aesthetics, speech, and function. Each point should be noted for improvements in the new restoration. There is

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Fig. 1.5  Looking at the profile view of the patient with the denture in and out can give the clinician an indication if the flange of the denture is required for lip support

Fig. 1.6  This patient has an obvious lack of lip support with a concave facial profile

always a tendency for patients to prefer fixed over removable prostheses. It is the restorative dentists’ responsibility to determine if this is feasible. Facial support is an important decision in this regard. Assessment of the patient’s facial support with and without the denture in place, with the patient facing forward and in profile, needs to be made so the clinician can determine which type of prostheses would be more suitable (Figs. 1.5 and 1.6). Facial support, if inadequate, is obtained mainly by the buccal flange of a removable restoration. Lip support is derived from the alveolar ridge shape and cervical crown contours of the anterior teeth. Resorption of the edentulous maxilla proceeds cranially and medially, and this often results in a retruded position of the anterior maxilla.

When evaluating a diagnostic setup with the anterior teeth in proper relation to the lip, the position of the anterior teeth is often anterior to the alveolar ridge (Figs. 1.7 and 1.8). Depending on the severity of the resorption, there can be a discrepancy between the ideal location of the teeth and the ridge. This, in turn, leads to a discrepancy of the anticipated position of the implants in relation to the teeth. This discrepancy must be taken into consideration to achieve a prosthesis that satisfies the parameters of adequate speech, lip support, hygiene, sufficient tongue space, and patient acceptance. If the anticipated position of the teeth and implant results in a large horizontal discrepancy, a number of options must be considered before finalizing implant placement.

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Fig. 1.7  When requesting a diagnostic denture setup from a dental technician, a flangeless try-in should be requested

Fig. 1.8  Patient with flangeless try-in. This patient is a candidate for a fixed implant-supported restoration

Fig. 1.9  If a patient with inadequate lip support requests fixed restorations, the clinician must assess to see if this is possible. On occasion bone must be removed and the

implant placed higher up so the emergence of the restoration can start higher up

1  Diagnosis and Treatment Planning: A Restorative Perspective

If the horizontal discrepancy is quite large, options include: (a) Bone reduction and a deeper implant placement to allow the contours of the restoration to satisfy the parameters of lip support and hygiene. Without bone reduction, undesirable contours in the restoration are developed, which make it very difficult for the patient to maintain hygiene (Fig. 1.9). (b) LeFort 1 osteotomy—Most patients are reluctant to undergo this type of surgery (c) Use of a removable flange and fabrication of an implant-supported overdenture

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1.4 Smile Line and Lip Length The movement of the upper lip during speech and smiling should be evaluated. Tjan et al. [8] described the average smile as having the position of the upper lip such that 75–100% of the maxillary incisors and interproximal gingival are displayed. In a high smile line, additional gingival was exposed, and in a low smile line, less than 75% of the maxillary anterior teeth are displayed. Lip length should also be evaluated because it influences the position of the maxillary anterior teeth. In a patient with a short upper lip, the maxillary anterior teeth will be exposed in repose (Fig. 1.10), whereas in patients with a long upper lip, the anterior teeth will usually be covered. Dentate patients with a terminal dentition may present with excessive gingival display. Causes of excessive gingival display include but are not limited to:

Fig. 1.10  A short lip poses a challenge. The transition zone may be visible

Fig. 1.11  For an edentulous patient, the denture is removed and the patient asked to smile without the denture in place; the ridge should not be visible

S. Jivraj

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Fig. 1.12  If the ridge is visible, alveolectomy may be necessary to hide the transition zone, depending upon the type of restoration to be fabricated

1. Vertical maxillary excess 2. Short upper lip 3. Hyperactive upper lip 4. Dentoalveolar extrusion 5. Delayed passive eruption 6. Multiple aetiologies [12] The clinician must have an adequate diagnosis prior to embarking upon a treatment plan. Edentulous patients should be asked to smile with and without the denture in place (Figs. 1.11 and 1.12). If the soft tissue of the edentulous ridge cannot be seen, the transition between an implant-supported prosthesis and the residual ridge crest will not be visible, resulting in flexibility for colour matching and the contour change of the prosthesis at the junction of the soft tissue. If the alveolar ridge crest is displayed during smiling, the aesthetics can be very challenging because the junction between the restoration and the gingival complex will be visible and bear aesthetic consequences. If the patient has minimal resorption, conventional metal ceramic restorations or zirconia-based restorations supported by implants can be planned, and the existing soft tissue can be developed to enhance aesthetics. However, if an implant-

supported denture (hybrid/profile prosthesis) is being planned, the alveolar ridge display will detract from the aesthetics. In situations like this, alveolectomy as part of a proactive protocol must be considered prior to implant placement. If alveolectomy is not performed, the restorative outcome will display the transition zone, which, ultimately, is very difficult to retreat. Alveolectomy must only be performed when there is an indication for it, and the minimum amount of bone must be removed to satisfy the clinical objectives.

1.5 Contours and Emergence The contours of the restorations have to be planned from the outset. The emergence profile of the restorations should be straight as it exits from the gingival margin. Often this requires alveolectomy to create sufficient space. The restorative dentist requires this space to develop adequate mechanics, aesthetics, and cleansability. This space creation must be communicated to the surgeon through the use of a bone reduction guide, and it becomes the surgeon’s ­responsibility to provide this space [13]. One misconception about graftless protocols is that they always require a significant amount of bone reduc-

1  Diagnosis and Treatment Planning: A Restorative Perspective

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Fig. 1.13  Haphazard bone reduction need not be done; there has to be a specific reason for alveolectomy

Fig. 1.14  A bone reduction guide must be stable and have a reference point from which the surgeon can measure

tion. Bone reduction has to have a rationale, and the minimum bone reduction must be done to satisfy the requirements of implant placement and fabrication of a biomechanically sound restoration [14]. Rationale for bone reduction include but are not limited to: 1. Adequate buccolingual width of bone to place implants 2. Adequate space for hygiene 3. Adequate space for biomechanics of the restoration 4. Adequate space so that the patient can clean the undersurface 5. Hide transition zone 6. Improve emergence of the restoration (Figs. 1.13 and 1.14)

1.6 Appropriate Tissue Contact As in any aspect of restorative dentistry, the provisional is key to the success of the definitive restoration. From a patient’s perspective, the communication of aesthetics and phonetics is important. From a clinician’s perspective, biomechanics, occlusion, and cleansability are key areas of concern. The original hybrid prostheses were designed to provide a “highwater” design. This was done predominantly to facilitate oral hygiene. Today, patients often complain of food entrapment with these types of designs. The provisional/immediate load prosthesis must satisfy the following criteria: (a) Reduce food entrapment—Following 3 months of healing, the acrylic provisional

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Fig. 1.15  The undersurface of the immediate load provisional restorations must be convex and highly polished

Fig. 1.16  The provisional restoration must be used to shape the tissue over time. When the clinician makes an impression, the tissue surface should be concave so the restoration surface can be convex

should be relined so that it compresses the tissue surface and creates a concave tissue surface allowing a convex restoration surface. (b) Provide cleansable contours by developing the tissue as outlined above (Figs. 1.15 and 1.16). (c) Eliminate speech impairment. The t and d sounds relate to the palatal aspects of the maxillary prosthesis, and this area can be adjusted to accommodate for that. The “S” sound is developed utilizing the closest speaking space and this should also be corrected in the provisional prior to proceed to the definitive restoration. (d) The tissue contact should be intimate, but accessible to oral hygiene procedures. (e) The tissue surface should be highly polished.

1.7 Occlusion Occlusion in this article pertains to the occlusion on the immediate load provisional restoration. Occlusion for the definitive prosthesis will be addressed in a subsequent article. In regard to occlusion, there are no literature references citing the superiority of one occlusal scheme over another, one tooth form over another, and patients’ preference of one occlusal scheme to another. Unfortunately, there are no randomized controlled clinical trials guiding the clinician to develop the occlusal scheme on the immediate load provisional prosthesis. Most occlusal schemes are based on biomechanics and distribution of the occlusal forces over areas which are most likely able to tolerate them. Clinical guidelines for developing occlusion include but are not limited to [10, 15–17]: (a) Good AP spread of implants

1  Diagnosis and Treatment Planning: A Restorative Perspective

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Fig. 1.17  Force distribution requirements of the immediate load transitional restoration

(b) Minimum vertical overlap (c) Bilateral simultaneous contact (d) No interferences in lateral excursion (e) Cross-arch stabilization with a passive screw retained acrylic prosthesis which has sufficient rigidity to withstand occlusal forces without breaking (f) No cantilevers (g) Occlusal contacts from canine to canine only with shimstock drag on the posterior teeth. The rationale for this approach is centred around bone quality and occlusal forces. The posterior implants are in the weakest bone quality. The occlusal forces are highest the further we go back in the mouth. The rationale is to protect the implants in the weakest quality bone being subjected to the highest occlusal forces. If this requires developing a ramp on the palatal aspect of the anterior teeth, this should be completed with cold cured acrylic resin. If the patient has a severe class two incisor relationship, the above will not be possible in which case occlusal contacts are evenly distributed around the arch (Fig. 1.17). Achieving successful outcomes with graft less solutions is significantly more challenging than with conventional restorations. Diagnosis and appropriate treatment planning are critical in obtaining a successful outcome. Implant concepts have undergone a significant evolution, not only in terms of designs, materials, and surfaces but also in clinical and technical management.

Clearer understanding of both the surgical and restorative protocols enables the clinician to better plan the outcomes of implant therapy.

References 1. Branemark PI, Hansson BO, Adell R, Breine U, Lindstrom J, Hallen O, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl. 1977;16:1–132. 2. US Bureau of the Census. Statistical abstract of the United States: 1996. 116th ed. Washington, DC: US Bureau of the Census; 1996. p. 15, tables II, No. 16, p 17, table II, No. 17. 3. Allen PF, McMillan AS.  A review of the functional and psychosocial outcomes of edentulousness treated with complete replacement dentures. J Can Dent Assoc. 2003;69(10):662. 4. Heath MR. The effect of maximum biting force and bone loss upon masticatory function and dietary selection of the elderly. Int Dent J. 1982;32:345–56. 5. Turkyilmaz I, Company AM, McGlumphy EA.  Should edentulous patients be constrained to removable complete dentures? The use of dental implants to improve the quality of life for edentulous patients. Gerodontology. 2010;27(1):3–10. 6. Zitzmann NU, Marinello CP.  Treatment plan for restoring the edentulous maxilla with implant supported restorations: removable overdenture versus fixed partial denture design. J Prosthet Dent. 1999;82(2):188–96. 7. Jivraj S, Chee W, Corrado P. Treatment planning of the edentulous maxilla. Br Dent J. 2006;201(5):261–79. 8. Tjan AH, Miller GD, The JG. Some aesthetic factors in a smile. J Prosthet Dent. 1984;51:24–8. 9. Schwarz MS, Rothman SL, Rhodes ML, Chafetz N.  Computed tomography: part II.  Pre-operative

14 assessment of the maxilla for endosseous implant surgery. Int J Maxillofac Implants. 1987;2:143–8. 10. Schnitman PA, Wohrle PS, Rubenstein JE, DaSilva JD, Wang NH.  Ten-year results for bra°nemark implants immediately loaded with fixed prostheses at implant placement. Int J Oral Maxillofac Implants. 1997;12:495–503. 11. Wicks RA.  A systematic approach to definitive planning for osseointegrated implant prostheses. J Prosthodont. 1994;3(4):237–42. 12. Robins JW.  Differential diagnosis and treatment of excess gingival display. Pract Periodont Aesthet Dent. 1999;11(2):265–72. 13. Bedrossian E.  Implant treatment planning for the edentulous patient. Maryland Heights: Mosby Elsevier; 2008.

S. Jivraj 14. Balshi TJ, Wolfinger GJ, Balshi SF.  Int J Oral Maxillofac Implants. 1999;14(3):398–406. 15. Brunski JB, Int J. Oral Implantol. 1988;5(1):31–4. 16. Malo P, Rangert B, Nobre M. “All on 4”, immediate function concept with Branemark implants for completely edentulous mandible. A retrospective clinical study. Clin Implant Dent Relat Res. 2003;5(Suppl 1):2–9. 17. Capelli M, Zuffeti F, Testori T, Del Fabbro M.  Immediate rehabilitation of completely edentulous jaws with fixed prosthesis supported by upright and tilted implants. A multicenter clinical study. Int J Oral Maxillofac Implants. 2007;22:639–44.

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Surgical Diagnostic Considerations in Graft-Avoiding Dental Implant Reconstruction of Atrophic Jaws Hooman M. Zarrinkelk

According to the US National Health Surveys conducted over the past five decades, the rate of Treatment of edentulism has always been a edentulism has been declining from 18.9% in challenge to the dental profession. 1957–1958 to 4.9% of the adult population in Reconstruction of atrophic jaws caused by 2009–2012 (NHANES: U.S.  Depart of Health edentulism has necessitated sometimes comand Human Services). The continuing decline plex grafting procedures. Grafting procedures will be offset partially by population growth and carry significant morbidity and cost associated population aging such that the predicted number with them. Today, there is great interest from of edentulous patients will only decline from the public and dental professionals in the less-­ today’s more than 20 million to 12.2 million indiinvasive graftless approaches to the atrophic viduals in 2050 [1]. On the global scale, the numjaw rehabilitation. Graftless approaches to ber of edentulous individuals is predicted to be treatment involves a specific manner of placemuch higher, and therefore, treatment of edentument of sufficient number of dental implants lism will be a daily challenge to clinicians for in strategic positions of patients’ existing bone many years to come. Edentulous patients suffer structures. The surgeon must understand the from functional deficiencies caused by their lack three absolute surgical requirements for sucof natural dentition or poor-fitting removable cessful treatment. Diagnostic factors to be appliances [2]. Today’s aging population is more considered by the surgeon to fulfil these absoactive and social than the past generations and lute requirements for rehabilitation are diswill demand a much higher quality of life. cussed in this chapter. Historically, treatment of edentulism, and in particular atrophic edentulism, has been towards reconstruction of the tissue lost through natural atrophy. The lack of adequate bone volume for conventional implant-supported appliances and H. M. Zarrinkelk (*) complex surgical treatments to correct the defiDiplomate American Board of Oral and Maxillofacial ciencies are the major obstacles facing both Surgeons, Chicago, IL, USA patients and clinicians involved in their care. Fellow American College of Oral and Maxillofacial Over the past 30 years, advances in bone and soft Surgeons, Washington, DC, USA tissue grafting procedures and materials have Private Practice, Ventura, CA, USA made the concept of tissue regeneration in the e-mail: [email protected] Abstract

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_2

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maxillofacial region more routine and predictable but remain technique sensitive [3–6]. Autogenous bone grafts, xenografts, allografts, or alloplasts have been utilized to augment deficient areas of the maxilla and mandible for preparation of implant sites. In the case of atrophic edentulous jaws, the gold standard remains autogenous bone. However, selection of the appropriate surgical technique and graft material remains difficult to ascertain from the heterogenic and often poorly designed available ­literature [7–9]. The financial burden on patient and community as well as pain and morbidity associated with grafting procedures are large obstacles to treatment. There will be increased pressure on the medical community to reign in the cost associated with treatments rendered. Clinicians are required to justify the rationale for more costly and invasive procedures if less costly and invasive procedures are as effective. There is growing evidence that edentulous patients can be treated with fixed full-arch dental restorations while avoiding major grafting procedures with as few as four dental implants [10–12] (Fig. 2.1). It is with the above understanding that we begin to appreciate the great interest in the dental community to learn about the less-invasive surgical concepts and protocols that rehabilitate the edentulous patient without bone grafts. The goal of this article is to provide a brief overview and introduction to the absolute surgical diagnostic and treatment planning requirements for surgeons and restorative dentists.

H. M. Zarrinkelk

Diagnosis and treatment planning of the edentulous patient is a complex and challenging task. Treatment planning of this often older and medically compromised patient population should always begin with a complete medical evaluation. In brief, any uncontrolled disease process that would compromise complete bone and soft tissue healing should exclude a patient from implant therapy. Diabetes, osteoporosis, and cardiovascular diseases may be of concern but if controlled are not absolute contraindications for implant therapy [13]. Currently, the most worrisome contraindication for implant therapy is intravenous bisphosphonate or other antiresorptive therapies [14]. The surgical evaluation of the patient’s oral condition should be systematic and methodical. The diagnostic criteria are ultimately used by the surgeon to determine the correct course of action to satisfy the three absolute surgical requirements: 1. Space: Adequate inter-arch space required for the prosthesis. 2. Spread: Adequate A-P spread to support the prosthesis (Fig. 2.2). 3. Stability: High primary stability of placed dental implants. The surgical diagnostic criteria discussed in this article will apply to a patient who is being treatment planned for a full-arch, fixed metal-­ ceramic, FP1 [15], implant-supported fixed den-

Fig. 2.1  Successful, aesthetic, and functional rehabilitation of patient utilizing a graftless approach to maxilla and mandible. Four implants per jaw were used in an immediate load protocol

2  Surgical Diagnostic Considerations in Graft-Avoiding Dental Implant Reconstruction of Atrophic Jaws

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Fig. 2.2  The A-P spread is determined by the distance between the lines intersecting the platform of the distal implants and the most anterior implants. The A-P spread

should be as large as possible to compensate for the magnified occlusal forces of the cantilever

ture [16], profile prosthesis [17], or fixed-removable (overdenture) [18] prosthetic restoration. The surgeon must evaluate the following anatomic factors for all restorative options listed above:

defect, whereas subsequent loss of supporting bone and soft tissue creates what is termed a “composite defect” [19]. In patients where a tooth-only defect with minimum resorption of the supporting structures has occurred, a metal-ceramic/zirconiaceramic FP1 implant-­supported prosthesis is the most appropriate. A FP1 prosthesis can be fabricated on four implant anchorage with precise implant position and minimal bone contouring when indicated. However, in most cases, edentulous patients present with varying degrees or horizontal as well as vertical composite defects. To assess the magnitude of the resorptive defect, a digital or analogue dental setup with appropriate tooth position, inter-arch relationship, and occlusion must be completed. The denture setup is subsequently duplicated in a transparent clear acrylic and worn by the patient. With the clear denture in place, two dimensions are measured:

1. Magnitude of three-dimensional anatomical defect. 2. The position of the prosthetic transition line relative to the animated lip position. 3. The relative position of the planned incisors to the existing alveolar ridge. 4. The volume and quality of alveolar bone available in the maxilla and mandible. 5. Position of the inferior maxillary sinuses, nasal cavity, alveolar nerve, and mental foramen. The prosthetic diagnostic criteria and concerns will be discussed in another chapter. Loss of teeth and subsequent resorption of supporting structures create an anatomical defect within the maxillofacial structures that will have profound influence on the type of the restoration best suited to the patient. Subsequently, the type of restoration selected to satisfy the patient’s condition and desires will determine the implant positions. Therefore, loss of tissue should be assessed first to determine the correct position of the osseous anchorage. Loss of teeth creates a “tooth-only”

1. The relative space between the cervical line of the denture teeth to the residual ridge. This measurement represents the available restorative space (Fig. 2.3). 2. The facial surface of the teeth to apex of the residual crest, representing the lip support requirements. With the data available from these two measurements, the restorative and surgical clinicians

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can determine the appropriate restoration for the patient. The decision to fabricate a metal-ceramic appliance without pink ceramic gingiva vs. a hybrid appliance is made by the restorative dentist based on the relative position of the proposed teeth to the existing alveolar ridge and lips. The surgical specialist must have a clear u­ nderstanding of the space required to satisfy the aesthetic and structural requirements of the planned restoration [20, 21]. In the case of a fixed implant denture, approximately 15  mm of space is required per arch measured from the incisal edge to implant platform. The management of restorative space is an absolute prosthetic requirement but a surgical

Fig. 2.3  Assessment of available restorative space by utilization of clear acrylic dental setup. Note the distance from planned incisal edge to the existing alveolar ridge. Horizontal and vertical relationship between the incisal edge and the alveolar ridge can be measured

Fig. 2.4  Examples of both tooth and tissue-borne bone reduction guides. This guide is used by the surgeon to determine the desired position of the alveolar platform for implant placement. The final incisal edge position is simu-

H. M. Zarrinkelk

responsibility. If insufficient inter-arch space is detected, then space should be created. Most often, the creation of space is accomplished by bone reduction or alveolectomy. The surgeon and restorative dentist should collaborate on determination of the magnitude of bone reduction required in each of the jaws to satisfy prosthetic requirements. The dimensions of alveolectomy are communicated to the surgeon by the “bone reduction guide”. This surgical stent is a tissue or tooth-supported acrylic stent fabricated on an altered plaster model with markings for reduction (Fig. 2.4). A large horizontal deficiency will create a prosthetic ledge which will be both unaesthetic and unhygienic for the patient. The surgeon may alter the vertical position of the dental implants relative to the incisal edge to allow for an appropriate labial curvature of the appliance. The available vertical dimensions of the bone must be taken into consideration. If insufficient vertical bone dimension exists to allow appropriate vertical position of the implants, then a removable implant-supported overdenture with a flange may be selected [22]. The next step in clinical evaluation of patient is assessment of the “transition line”. This line represents the junction of the dental prosthesis and residual alveolar gingiva. The failure to assess the visibility of the transition line may result in an unaesthetic outcome for the patient

lated in the stent and surgeon removes appropriate height of alveolar bone to assure sufficient restorative space and proper prosthetic labial contours

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Fig. 2.5  Transition line is defined as the junction of hybrid dental prosthesis and natural gingiva. Assessment of visible alveolus (line) during lip animation and smiling is critical preoperatively to ascertain the magnitude of

bone reduction in order to hide the transition line above the smile line and avoid an unaesthetic result for the patient (arrow)

Fig. 2.6  The measurement of subnasale to stomion represent the lip length. The change in this measurement between repose and animation represents the magnitude

of lip mobility and must be considered during treatment planning. An active lip may necessitate substantial bone reduction to hide the transition line

(Fig. 2.5). The transition line may become visible during normal animation of the lips particularly during smiling. The edentulous patients’ typical hesitation to smile during examination may be a source of underestimation of the exposure. Therefore, the evaluation of the lip animation should begin during the initial conversations with patients. This should be documented using photographs and video. Next, lip length is measured from subnasale to stomion with the patient providing their biggest smile. This is requested with the denture in place (Fig. 2.6). Subsequently, the denture is removed and patient asked to smile and verified with measurement of lip length. Any visible alveolar ridge during the maximal smiling is noted and measured. Ideally in an edentulous patient, the final transition line should be 3–5 mm above the highest animated smile line. For an edentulous patient with a visible ridge on smil-

ing, the decision to conserve or resect alveolar bone is based on the patients’ aesthetic demands. If artificial ceramic or acrylic gingiva is unacceptable to the patient, then the dental implants will have to be placed in precise teeth positions and a metal-ceramic/zirconia-ceramic prosthesis of appropriate teeth proportions constructed. If a patient has a composite defect and the ridge is visible, then metal-ceramic prosthesis without gingival porcelain may not be feasible. In this class of patient’s teeth will appear long and unaesthetic without gingival coloured soft tissue component. In a situation where alveolar ridge is visible and artificial gingiva are not of aesthetic concern to the patient, then alveolar resection is indicated. Extra attention should be paid to patients with short or hyperactive lips. The dimension of alveolar reduction will be the sum of visible ridge measurement plus an additional

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H. M. Zarrinkelk

Fig. 2.7  Prefabricated provisional shell and surgical stent

3–5 mm of reduction. The entire visible alveolar ridge from the pre-maxilla to the tuberosity must be considered when planning for alveolectomy. Once the vertical dimensions of alveolectomy in all zones of the maxilla or mandible are determined, the patient radiographs will be evaluated to assess the anticipated remaining alveolar bone below the sinus and nasal cavity and above the inferior alveolar nerve. Factors such as patients’ age, excessive gingival show, or aesthetic demands may be contraindications to alveolectomy. In such cases the technical and cost-saving advantages of the graft avoiding procedures may still be realized. For these cases the implants are placed in precise three-dimensional positions to allow for appropriate emergence profile of the appliance. A tissue or tooth indexed surgical guide is fabricated (Fig. 2.7). The final position of the teeth is determined via the guide. Implants are placed to satisfy the three absolute surgical requirements discussed earlier. Implants are placed with minimal tissue reflection and trauma. Implant angulation and depth are adjusted to provide enough space for multi-unit abutments or angled screw channel system (Fig. 2.8). The emergence of the multiunit abutment access screw should be through the cingulum of the incisors (Fig. 2.9). A provisional replacing just the tooth portion (Fig. 2.10) and a definitive restoration (Fig. 2.11) can be fabricated for the patient while avoiding alveolectomy. In summary, the decision to resect or preserve the alveolar bone is determined by a number of

Fig. 2.8  Precise implant position with consideration of the final tooth position

Fig. 2.9  Appropriate emergence of the multi-unit abutment screw through the palatal aspect of the tooth

functional and aesthetic factors. The goal of the space creation through bone removal is to facilitate fabrication of a prosthesis with adequate flexure resistance and appropriate contours where the transition line is not visible in conversation or smile. The third and final step in systematic diagnosis of an edentulous patient is radiographic deter-

2  Surgical Diagnostic Considerations in Graft-Avoiding Dental Implant Reconstruction of Atrophic Jaws

Fig. 2.10  A tooth only provisional in the maxilla sculpting tissues (Provisional Courtesy of Saj Jivraj B.D.S.)

Fig. 2.11  A definitive zirconia restoration adapted to the tissue in the maxilla (Definitive restoration courtesy of Saj Jivraj B.D.S.)

mination of available bone for dental implant placement. Three-dimensional radiography and virtual planning software has made the diagnosis and treatment planning predictable. Bedrossian has described the delineation of maxilla into three zone for a simplified treatment planning [19]. A treatment plan can be developed by the clinician after determination of presence of sufficient bone in the three zones of the maxilla. The alveolar bone of the anterior maxilla from canine to contralateral canine is designated as zone 1, the premolar region as zone 2, and the molar region as zone 3 (Fig. 2.12). If zones 1, 2, and 3 have available bone volume, then preferred number of axial implants may be placed (Fig. 2.13a). If zones 1 and 2 are available, then tilted posterior implant in combination with axial or tilted anterior implants can

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Fig. 2.12  The three zones of maxillary alveolar bone used in a simplified treatment planning protocol as described by Bedrosian. Zone 1  =  incisor region (red), zone 2  =  bicuspid region (gold), zone 3  =  molar region (green)

be considered (Fig. 2.13b). And finally if zone 1 is the only available bone, then zygomatic or pterygoid plate implant concepts may be considered for posterior support and axial or tilted implants for anterior support (Fig.  2.13c). If complete atrophy of the maxilla is evident with unavailability of bone in all three zones of the maxilla, then two zygomatic implants bilaterally may be used to provide support for the prosthesis (Fig.  2.13d). The reason for tilting of implant up to 45 degrees is to avoid placement of implants in anatomic structures such as the maxillary sinus, nasal cavity, or mental foramen. Tilting of the distal implants increases the A-P spread by positioning the platform of the implant further posteriorly while avoiding the mentioned structures (Fig. 2.14). By bypassing these structures, bone grafting procedures are avoided or minimized. If any combination of the implant position schemes satisfy the three absolute requirements of spread, stability, and space, then immediate loading of the appliance is considered. Selection of the appropriate implants for each case must begin with a complete understanding of the available implants systems and corresponding straight or angled prosthetic abutments. Lekholm and Zarb [23] have classified the degree of resorption of the alveolar process and basal bone. A classification was also proposed for associated bone quality. Selection of implant length and diameter is dependent on alveolar anatomy and bone density. A thorough preoperative as well as intraoperative evaluation of the alveolar

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a

b

c

d

Fig. 2.13  Treatment planning of the edentulous maxilla can be done by evaluation of bone availability in the three zones of the maxilla: (a) zones 1+ 2 + 3 = Axial implant placement; (b) zones 1 + 2 = Axial anterior + tilted poste-

Fig. 2.14  Tilting of the implants up to 45° (blue) allows distalization of the platform of the implant while avoiding structures such as the maxillary sinus. The primary benefit of this manoeuvre is the reduction of the cantilever effect (gold)

ridge will guide the diameter of implant used. The goal of surgeon should be to maintain adequate bone thickness of at least 2 mm along the entire length of the implant [24]. Assuming that the minimal implant diameter used will be narrow platform or 3.3–3.5  mm (Nobel Biocare, Zurich, Switzerland), a minimum of 5–6 mm of alveolar crest ridge width is required in planning of the implant positions. Wider alveolar ridges allow for placement of wider implants with more flexibility of components and increased bone/ metal contact surface area for osseointegration and therefore should be favoured. Bone reduction

rior implant placement; (c) zone 1 only = Axial anterior + zygoma implant placement; (d) No Zone = quad zygoma implant concept

creates decortication of the alveolar ridge and exposure of the spongy marrow space for implant placement. Alveolar atrophy or bone reduction will have the beneficial effect of bringing the crest of the alveolus closer to confluence of dense bone plates of the piriform rim. The position of the distal tilted implant should be so that the eventual prosthetic cantilever is minimized. Implant length selection is to assure primary stability by engagement of areas of dense bone such as the piriform rim, nasal floor, or inferior border of the mandible while placing the implant platform as far posteriorly as possible [25] (Fig. 2.15). Therefore, in the maxilla the posterior implant if angled should be at the minimum long enough to reach from the bicuspid region to the piriform rim. In the mandible the distal implant is positioned with the platform above the mental foramen and tilted to avoid the anterior loop of the Inferior alveolar nerve while engaging the dense inferior border cortex. Decision on number of implants to be placed is beyond the scope of this article and is not an absolute criteria for success. The appropriate number of implants for each individual patient is dependent on factors such as health status, type of bone, type and size of implant used, type of prosthesis planned, biomechanical configura-

2  Surgical Diagnostic Considerations in Graft-Avoiding Dental Implant Reconstruction of Atrophic Jaws

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Fig. 2.15  Primary stability of the implants placed is critical to osseointegration and success. The immediate stability is dependent on design of implant used and the quality

of bone engaged. The goal should be to engage areas of jaws with dense bone such as inferior border of the mandible, nasal floor, or piriform rim, for example

tions of the placed implants, and other variables [26]. However, as early as 1977, Brånemark suggested that positioning four implants in the edentulous maxilla and mandible in an adequate A-P spread configuration can successfully reconstruct the patient oral handicap and prevent further bone loss [27]. Today, there is growing evidence that immediate loaded, axial, or tilted dental implants utilizing the patients existing bone structures while following strict biological and biomechanics principals discussed can provide patients a viable long-term solution to edentulism [28–31].

4. Triplett RG, Nevins M, Marx RE, Spagnoli DB, Oates TW, Moy PK.  Pivotal, randomized, parallel evaluation of recombinant human bone morphogenetic protein-­ 2/absorbable collagen sponge and autogenous bone graft for maxillary sinus floor augmentation. J Oral Maxillofac Surg. 2009;67:1947–60. 5. Keller EE, Tolman DE, Eckert SE. Maxillary antral-­ nasal inlay autogenous bone graft reconstruction of compromised maxilla: a 12 year retrospective study. Int J Oral Maxillofac Implants. 1999;14:707–21. 6. Block MS, Baughman DG. Reconstruction of severe anterior maxillary defect using distraction osteogenesis. Bone grafts and implants. J Oral Maxillofac Surg. 2005;63:291–7. 7. Aghaloo TL, Moy PK.  Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants. 2007;22(suppl):49–70. 8. Blackburn TK, Cawood JI, Stoelinga PJW, Lowe D. What is the quality of evidence base for pre-implant surgery of the atrophic jaw? Int J Oral Maxillofac Surg. 2008;37:1073–9. 9. Esposito M, Grusovin MG, Coulthard P, Worthington HV. The efficacy of various bone augmentation procedures for dental implants: a Cochrane systematic review of randomized controlled clinical trials. Int J Oral Maxillofac Implants. 2006;21:696–710. 10. Brånemark PI, Svensson B, van Steenberge D.  Ten year survival rates of fixed prostheses on four or six implants ad modum Branemak in full edentulism. Clin Oral Implants Res. 1995;6:227–31. 11. Agliardi E, Panigatti S, Clericó M, Villa C, Maló P.  Immediate rehabilitation of the edentulous jaw with full fixed prostheses supported by four implants:

References 1. Slide GD, Akinkugbe AA, Sanders AE.  Projections of US edentulism prevalence following 5 decades of decline. J Dent Res. 2014;93(10):959–65. 2. Kerschbaum T.  Long-term prognosis of conventional prosthodontic restorations. In: Naert I, Van Steenberghe D, Worthington P, editors. Osseontegration in oral rehabilitation. London: Quintessence. p. 33–49. 3. Stellingsma C, Raghoebar GM, Meijer HJ, Batenburg RH.  Reconstruction of the extremely rebreed ­mandible with interposed bone grafts and placement of endosseous implants. A preliminary report on outcome of treatment and patients satisfaction. Br J Oral Maxillofac Surg. 1998;36:290–5.

24 interim results of a single cohort prospective study. Clin Oral Implants Res. 2010;21:459–65. 12. Maló P, de Araújo NM, Lopes A, Moss S, Molina G. A longitudinal study of the survival of all-on-4 implants in the mandible with up to 10 years of follow-up. J Am Dent Assoc. 2011;142:310–20. 13. Laney WR, Tolman DE. The Mayo Clinic experience with tissue-integrated prostheses. In: Albrektsson T, Zarb GA, editors. The Brånemark Osseointegrated implant. Chicago: Quintessence; 1989. p. 165–95. 14. American Association of Oral and Maxillofacial Surgeons. Position paper: medication-related osteonecrosis of the jaw—2014 update. Chicago: American Association of Oral and Maxillofacial Surgeons; 2014. 15. Misch CE. Fixed prosthesis replaces only the crown. In: Contemporary implant dentistry. 2nd ed. St Louis, MO: Mosby; 1999. p. 68–70. 16. Sadowsky SJ.  The implant-supported prosthesis for the edentulous arch: design considerations. J Prosthet Dent. 1997;78(1):28–33. 17. Schnitman P. The profile prosthesis: an aesthetic fixed implant-supported restoration for the resorbed maxilla. Pract Periodont Aesthet Dent. 1999;11:143–51. 18. Fortin Y, Sullivan RM, Rangert B.  The Marius implant bridge: surgical and prosthetic rehabilitation of the completely edentulous upper jaw with ­moderate to severe resorption: a 5-year retrospective clinical study. Clin Implant Dent Relat Res. 2002;4:69–77. 19. Bedrossian E.  Implant treatment planning for the edentulous patient, a Graftless approach. St. Louis: Mosby; 2011. 20. Aboul-Ela LM.  The evaluation of the interocclusal distance in complete dentures. Egypt Dent J. 1967;13:56. 21. Owen WD, Douglas JR.  Near or full occlusal vertical dimension increase of severely reduced inter-­ arch distance in complete dentures. J Prosthet Dent. 1971;26:134. 22. Fortin Y, Sullivan RM, Rangert BR.  The Marius implant bridge: surgical and prosthetic rehabilita-

H. M. Zarrinkelk tion for the completely edentulous upper jaw with moderate to severe resorption: a 5-year retrospective clinical study. Clin Implant Dent Relat Res. 2002;4(2):69–77. 23. Lekholm U, Zarb GA.  Osseointegration in clinical dentistry. Chicago: Quintessensce; 1985. p. 199–209. 24. Ding X, Lia SH, Zhu XH, et  al. Effect of diameter and length on stress distribution of the alveolar crest around immediate loading implants. Clin Implant Dent Relat Res. 2008;11:279. 25. Jensen OT, Adams MW. The maxillary M-4: a technical and biomechanical note for the all-on-4 management of severe maxillary atrophy. J Oral Maxillofac Surg. 2009;67:1739. 26. Brunski JB.  Biomechanical aspects of the optimal number of implants to carry a crossarch full restoration. Eur J Oral Implantol. 2014;7(Suppl2):S111–32. 27. Brånemark PI, Hansson BO, Adell R, et  al. Osseointegrated implants in treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl. 1977;16:1–32. 28. Bedrossian E.  Immediate function with zygomatic implant: a graftless solution for the patient with mild to advanced atrophy of the maxilla. Int J Oral Maxillofac Implants. 2006;21(6):937–42. 29. Malo P, Nobre M, Lopes A.  The rehabilitation of completely edentulous maxillae with different degrees of resorption with four or more immediately loaded implants: a 5-year retrospective study and a new classification. Eur J Oral Implantol. 2011;4:227–43. 30. Krakmenov L, Kahn M, Rangert B, et  al. Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Int J Oral Maxillofac Implants. 2000;15:405–14. 31. Duyck J, et al. Magnitude and distribution of occlusal forces on oral implants supporting fixed prosthesis: an in  vivo study. Clin Oral Implants Res. 2000;11:465–75.

3

Guided Surgery for Full-Arch Implant-Supported Restorations Michael Klein, Jay Neugarten, and Allon Waltuch

Abstract

This chapter will discuss and instruct the user in the type of data required for surgical and prosthetic planning, how to collect that data, and how to create a prosthetic plan and then a surgical plan. The different types of devices and techniques for guided surgery will be described and differentiated. Step by step instruction for implementation of each type of guided surgery will be covered. The discussion will start with a review of understanding what is seen in surgical planning software and will be followed by what diagnostic data is required for prosthetic and surgical planning and how to collect it. The different types of guided surgery and the specifics of their techniques (data, planning, preparation, implementation) for full-arch restorations including all forms of surgical guides, dynamic navigation, and robotic surgery will be described. Freehand surgery or conventional shell surgi-

M. Klein (*) · A. Waltuch Advanced Implant Dentistry and Oral Restoration, Cedarhurst, New York, NY, USA e-mail: [email protected] J. Neugarten Department of Oral and Maxillofacial Surgery, Weill-Cornell Medical Center, New York-­Presbyterian Hospital, New York, NY, USA e-mail: [email protected]

cal guides are thought of as quicker and easier paths to surgery; however, with today’s technology, even using the most comprehensive planning and preparation for guided surgery, the clinician can often go from the initial patient consultation directly to performing guided surgery at the next visit.

3.1 Why Perform Guided Surgery as Opposed to Freehand Surgery or Using a Conventional Shell Surgical Guide? The ultimate goal of any implant surgical technique is to create precision, accuracy, and efficiency for the ideal functional and aesthetic result for any given patient. Freehand surgery relies completely on the clinical expertise and experience of the implant surgeon. It requires a complete understanding of the surgical anatomical considerations as well as a thorough understanding of the three-dimensional prosthetic, aesthetic, and functional implications of the specific implant position chosen [1]. This all must be decided real time at the time of surgery. The use of a conventional shell surgical guide brings a lot of information to the surgery in regard to the surgical as well as prosthetic implant positioning [2]. However, guided surgery allows a very thorough surgical and prosthetic planning with com-

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_3

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plete integration of the two plans [3, 4]. All the planning is then translated into tools that guide the clinician to systematically perform the ideal surgical procedure to produce the planned foundation for the planned prosthetic restoration. The rationale for guided surgery for full-arch restorations is the same for single and limited span bridges. The steps required for guided surgery include data collection, presurgical prosthetic restoration design, surgical planning, and the implementation of the plan through presurgical manufactured devices or real-time technology used during surgery. There are multiple techniques for guided surgery including surgical guides, real-time dynamic guided surgery, and robotic surgery.

3.2 Planning Software An understanding of planning software is critical to be able to properly evaluate both surgical and prosthetic plans. There are software dedicated to surgical planning that have basic prosthetic planning features. These features are designed for placement of a virtual prosthetic restoration contours to enable surgical planning

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while visualizing three dimensionally the prosthetic restoration and the impact of the surgical implant position on the restoration (e.g., what type of abutments would be necessary, can the restoration be screw retained or does it have to be cementable, will a custom abutment be required, what are the dimensions of aesthetic tooth placement, and can a crown and bridge style (FP-1) restoration be made with natural soft tissue or will a pink prosthetic apron be required). These prosthetic planning options are not designed to be used to create stl manufacturing files to produce a provisional restoration. There are separate prosthetic planning software (e.g., 3Shape design, exocad, Dental Wings, etc.) where pure prosthetic design is done. These prosthetic restoration design stl files can be imported into the surgical planning software to aid in surgical planning, as well as to be used as manufacturing files to produce provisional restorations. Proper planning today includes comprehensive prosthetic planning merged with surgical planning. This type of planning software can then design surgical guides and produce stl manufacturing files for the surgical guides or guide dynamic or robotic implant surgery (Fig. 3.1).

Fig. 3.1  Comprehensive treatment planning is done very efficiently by integrating CT scan data and iOS scan data in diagnostic planning software

3  Guided Surgery for Full-Arch Implant-Supported Restorations

3.2.1 Surgical Planning Software Surgical planning software requires two types of datasets to be able to properly plan prosthetically driven implant surgical procedures. The two sets of data are the dicom data from a CT scan (Fig.  3.2a, b) (most commonly cone beam CT scan data) of the patient and the intraoral surface (iOS) scans of the patient (iOS scans of the maxilla, mandible, and bite) (Fig. 3.3). Conventional analogue impressions may be taken of the patient and then converted into digital data with a laboratory scanner (Fig. 3.4a, b) or your CBCT scanner [5, 6]. The iOS scans (or lab scanned models) are used to perform a virtual diagnostic prosthetic wax up for the patient. The CT scan dicom data is used to be able to analyse in 3D the bone structures as well as the soft tissue structures in and around the bony structures. Surgical planning software integrates both these datasets so that in a

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one 3D image there can be surgical and prosthetic analysis (as well as the influence of each on the other) (Fig. 3.5a, b). Surgical planning software will accept the dicom data from cone beam or conventional CT scanners.

Fig. 3.3  Intraoral surface scan technology enables virtual models for every full-arch implant patient

b

Fig. 3.2 (a, b) The convenience of having a cone beam CT scanner directly in the dental office enables rapid comprehensive diagnostic patient evaluation

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a

b

Fig. 3.4 (a, b) Those clinicians who do not yet have the capability to take intraoral surface scans may take conventional impressions and have the stone models scanned in a laboratory scanner

a

Fig. 3.5 (a, b) The merging of the CT scan data with the surface scan data in surgical and prosthetic planning software allows for true comprehensive treatment planning

3  Guided Surgery for Full-Arch Implant-Supported Restorations

b

Fig. 3.5 (continued)

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This dicom data will then be reformatted by the surgical planning software into user-friendly pictures. The picture orientations include a panoramic view (Fig.  3.6a), axial view (Fig.  3.6b), cross-sectional view (Fig.  3.6c), and 3D reconstruction (Fig. 3.6d) [7, 8]. There will be multiple pictures from each of these views, the number depending on slice thickness and parameters set by each proprietary software. The reformatted CT dicom data by itself has a lot of information to allow the clinician to completely evaluate the surgical site; however, when combined with surface scans of the existing teeth and soft tissue in the patient’s mouth, a much more thorough analysis can be done. The volume and position of bone as it relates to the prosthetic restoration gives critical information when designing and evaluating the plan for guided surgery: what is the aesthetic dimension of a tooth, where will the free gingival margin be, is there enough room for all the required b

Fig. 3.6 (a–d) Surgical planning software will reformat the CT dicom data into panoramic views, axial views, cross-­ sectional views, and a complete 3D reconstruction

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c

d

Fig. 3.6 (continued)

complex comprehensive planning efficient and effective [9].

3.2.2 Prosthetic Planning Software

Fig. 3.7  The outline of the diagnostic wax-up can be seen in blue with critical measurements taken for diagnostic assessment in the cross-sectional view

prosthetic components, will bone have to be reduced or bone grafting be done to accomplish the desired result for the patient (Fig. 3.7-crosssection with measurements and pros profile). All these factors require incorporation of the prosthetic planning with the surgical planning. Today’s technology creates a workflow to make

Prosthetic planning and design software is a free-­ standing software that has many design features. Stl files of the patients’ mandible and maxilla are obtained through intraoral surface scanning in the dental clinic, or by laboratory scanning of models of the patients’ mandible and maxilla. Vertical dimension and correct centric records are also taken by the intraoral or lab scanners. Full-face photographs can also be introduced and incorporated into the planning with the intraoral (iOS) or lab scanning. Design features include the ability to extract teeth, place virtual teeth of all shapes and sizes, as well modify any of the tooth dimensions as appropriate to any specific patient. Features to add pink aprons as well as many other patient specific items are in many of these prosthetic design software. A specific prosthesis design (for an anticipated restoration) can be made. This prosthesis design (including teeth to be extracted, etc.) can then be imported into the surgical planning software to aid in creating the ideal surgical plan for each specific patient.

3  Guided Surgery for Full-Arch Implant-Supported Restorations

Decision-making for the full-arch patient can then be made as to appropriate implant type, size, position, abutment type, number of implants, prosthetic pink apron or crown and bridge restoration, and material type for provisional and final a

c

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restoration (zirconia, titanium bar, peek, PMMA, nanoceramics, porcelain to metal, etc). This prosthetic plan can also be used as a manufacturing file to 3D print or CNC mill prosthetic restoration (Figs. 3.8a–g, 3.9a–i, and 3.10a–p) [10, 11].

b

d

e

f

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Fig. 3.8 (a, b) Preliminary data for prosthodontic evaluation includes full-face photography and intraoral photos. (c, d, e) Intraoral surface scans are taken and a virtual diagnostic wax-up is completed. The virtual diagnostic wax-up is integrated into the full-face photo. This is a critical factor which shows here that the tooth transition zone will not be exposed in the smile line. Therefore, this patient may have a

crown and bridge style restoration with no pink apron even though the teeth may be a little long. (f, g) Once the diagnostic wax-up is confirmed, it may be integrated into the surgical planning software. Surgical implant planning must follow the tooth position from the diagnostic wax-up, as it has been determined that a crown and bridge style prosthesis will be made with teeth emerging from natural soft tissue

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a

c

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Fig. 3.9 (a, b) Pretreatment smiling photos and intraoral photos are taken. (c, d, e) Intraoral surface scans of the maxilla and mandible are articulated. Virtual extractions are done, and a complete wax-up of the maxilla is completed with a pink prosthetic apron in anticipation of excessively long teeth being seen in the patient’s smile. (f, g) The virtual wax-up is integrated into the smile of the

g

patient verifying the need for a prosthetic pink apron. (h, i) The determination from the diagnostic wax-up of the need for a pink prosthetic apron determines rules for implant positioning. This includes freedom from mesial to distal tooth position, as you will not see teeth emerging from natural soft tissue

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h

i

Fig. 3.9 (continued)

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a

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Fig. 3.10 (a–d) The diagnostic data for the edentulous arch will include photos of the full face and smile, intraoral photos, and dual-scan CT scan data. (e, f, g) The two datasets from the dual scan CT scans are used in the surgical planning software to merge the denture tooth (or diagnostic wax-up) position with the bone. The internal surface of the denture creates the simulated soft tissue for the planning software; therefore, it is critical that there is an intimate fit of the denture to the soft tissue when scanning. (h, i) The scanned denture (from the dual scan technique) is modified to an ideal virtual wax-up for the

l

patient’s aesthetic requirements. (j, k, l) The virtual waxup is merged with the patient’s photos to confirm the incisal edge. (m, n, o) The virtual wax-up may be converted into a diagnostic try-in to confirm tooth position, and aesthetics, tooth measurements, midline, as well as exposure of the transition zone in the smile line. (p) The determination of aesthetic tooth length from the virtual wax-up and diagnostic try-in instructs the surgical planning. This restoration will be a crown and bridge style restoration with aesthetic tooth lengths. Ideal implant tooth positioning is critical

3  Guided Surgery for Full-Arch Implant-Supported Restorations

m

n

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o

p

Fig. 3.10 (continued)

3.2.2.1 Incorporating Prosthetic Planning into Surgical Planning Software Historically, prosthetic planning was incorporated into surgical planning by the use of a radiographic guide while taking the CT scan. This required creating a physical diagnostic template by mounting diagnostic casts of the patient and creating a diagnostic setup of anticipated tooth position. This would then be converted into a CT scan appliance (usually removeable) which the patient would place into their mouths prior to taking the CT scan. Radiopaque markers would be placed into these appliances by incorporating either barium sulphate into the acrylic being used to create the teeth in the appliance or gutta-­percha or some other radiopaque materials which would be placed into the teeth in the appliance to dem-

onstrate the contours of the proposed prosthesis design. Removable dentures or fixed provisional restorations could also be duplicated and used this way. This can be effective, but it is time-­ consuming and requires extra visits and there is limited data gained from this (only pure surgical planning can be done) (Fig.  3.11a–e—ct appliance picture and ct to go with it) [12]. Today, the most efficient process to incorporate prosthetic planning into a surgical plan is to incorporate intraoral scans (iOS) of the patient into the surgical planning software. These intraoral scans are taken at the initial consultation visit of the patient with any conventional intraoral scanner. For the full-arch implant patient, a full face and profile picture should also be taken to aid in planning. The full face can be incorporated into the prosthetic planning software. Using

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this integrated data, the prosthesis design is then made. The profile picture is used to anticipate changes to the lip position if there will be changes to the overjet or any bodily or angular movement of the anterior teeth (maxilla or mandible) anteriorly, posteriorly, or arch circumference changes. The stl file of the prosthesis design is then a

c

b

d

Fig. 3.11 (a–e) Dentures duplicated with barium sulphate mixed with acrylic were an effective way of demonstrating tooth position in CT scan data prior to the

a

Fig. 3.12 (a, b) Analysis of the patient’s smile line reveals a high smile line exposing the tooth to soft tissue interface (the transition zone), as well as an unaesthetic smile. The profile picture clearly demonstrates the buccal flaring of the maxillary anterior teeth. (c, d) When the diagnostic wax-up (yellow) is overlayed on the pretreatment intraoral surface scans (turquoise), the retraction of the maxillary anterior teeth can be seen. (e, f, g) The diagnostic wax-up is then imported into the surgical planning software to aid in proper implant positioning. The pre-

imported into the surgical planning software for the surgical planning. Alternatively, diagnostic casts of the patient can be scanned using a laboratory scanner, and then the same protocol of including full-face photography, prosthesis design in prosthetic design software followed by surgical planning can be done (Fig. 3.12a–i). e

development of the dual-scan technique. These CT scan appliances could then be converted into surgical guides

b

treatment photographs revealed a high smile line. The diagnostic wax-up was designed with ideal tooth dimensions. The integration of the datasets was then used to evaluate the residual bone position available for implant placement and what the distance to the free gingival margin would be. This then determined that an aesthetic tooth to soft tissue relationship could be developed even with the patient’s high smile line. (h, i) The immediate provisional restoration placed at implant surgery demonstrates effective presurgical evaluation and planning

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d

e

h

Fig. 3.12 (continued)

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a

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c

Fig. 3.13 (a, b, c) Photos of the patient with lips at repose, smiling, and wide smiling aid the diagnostic wax-up

3.2.2.2 Data Required for Full-Arch Implant Restoration Surgical Planning These are the sets of data required: surface scans of the mandible and maxilla if there are any teeth present; dual CT scans for patients with an edentulous arch that requires planning; one of the CT appliance, and one of the arch that requires planning with the CT appliance in place (today that is usually a cone beam CT scan); a full-face photograph of the patient with a wide smile, regular smile, and their lips at repose (ideally also a profile picture (Fig. 3.13a–c), consider a video of the patient speaking and smiling if that will aid with any virtual wax-up); and any conventional radiographs or clinical measurements (periodontal charting, mobility charting, etc.) that will aid and support in an appropriate diagnosis. 3.2.2.3 Dual-Scan Technique If the arch that is being treated with the full-arch implant treatment is edentulous, then a dual-scan technique should be employed. If the patient is wearing a denture and the tooth position in the denture will be copied (arch circumference, incisal edge position, occlusal plane position, overall tooth position), then scan markers (usually five radiopaque balls) can be affixed to the denture to create a scan appliance. The denture should be stable when seated in the patient’s mouth; if not, then reline the denture first (Fig. 3.14). If there is

Fig. 3.14  The dual-scan technique requires scanning the patient with an acrylic prosthesis. This prosthesis must seat completely and be stable on the soft tissue. The patient’s denture may be used if their denture is representative of where teeth are to be positioned in the final restoration. A reline of the patient’s denture is recommended if it is not a recently made prosthesis

no denture or there will be changes to the tooth position, then a diagnostic denture should first be made.

3.2.2.4 Placing the Radiopaque Markers There are radiopaque markers that are fixed in position with preplaced adhesive, or you may cut

3  Guided Surgery for Full-Arch Implant-Supported Restorations

holes in the denture and place barium or gutta percha as markers (Figs. 3.15a, b and 3.16a, b). Ideally place five markers in an anterior posterior and mesial to distal distant positions around the arch to create a tripod position. These markers are for use to combine the two CT scans in the dual-scan technique. They are not intended for the planning itself. The markers may be placed in or on the buccal or lingual denture flanges (including the palate). A CT scan is taken off the scan appliance at low Ma (usually 2–3  Ma) a

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(Fig. 3.17), and then a separate scan is taken with this appliance seated in the patients’ mouth at conventional settings (Fig. 3.18a, b). Many cone beam CT scanners have preset settings for the dual-scan technique. These two scans are integrated in the surgical planning software (Fig. 3.19). The low Ma setting of the scan appliance allows the denture acrylic to be seen. The tooth position and soft tissue position are thus seen to aid in proper diagnosis and planning (Fig. 3.20) [13]. b

Fig. 3.15 (a, b) Five radiopaque balls are placed around the arch on the removeable prosthesis used in the dual-scan technique

a

b

Fig. 3.16 (a, b) Radiopaque material such as gutta-percha may be placed into holes cut into the prothesis to be scanned via dual-scan technique

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Fig. 3.17  The removeable prosthesis with radiopaque markers is scanned independently in the CT scanner and a second time in the patient’s mouth

a

Fig. 3.19  The independent prosthesis scan is integrated with the patient scan in the surgical planning software

b

Fig. 3.18 (a, b) The radiopaque balls can be seen in the independent removeable prosthesis CT scan as well as in the patient scan

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All surgical guides have several common elements. They use most of the common planning software for their planning. The planning software will require the capability for designing the surgical guide after the actual implant planning is complete. The software that plans and then designs the surgical guide will output an stl file that is used for manufacturing the surgical guide. Commonly these guides are 3D printed from this stl file (Fig.  3.21); however, CNC machining the guide can also be done from these stl files (CNC machining surgical guides usually is more time-­consuming and costly than 3D printing) (Fig.  3.22). Metal sleeves are placed into these surgical guides that are compatible with the surgical tools that are part of the different types of systems used with guides during surgery. These metal sleeves are specific to these surgical systems and different implant systems. The sleeve type is indicated in the guide design software so that the hole to receive the sleeve is manufactured to the sleeve specification (Fig. 3.23a–c). Fig. 3.20  The profile of the tooth position in the removeable prosthesis can be clearly seen. The soft tissue profile is created by the intimate fit of the removeable prosthesis to the soft tissue

3.2.3 Surgical Guides 3.2.3.1 Types of Surgical Guides Surgical guides are custom devices that seat on the soft tissue, teeth, bone, or a combination of teeth and soft tissue. They may be secured in position by fixing to teeth, bony landmarks, or soft tissue by pinning them to the bone with pins or screws. Guides may even on occasion be used with just finger pressure on the guide while it sits on the soft tissue. The data collected for surgical and prosthetic planning is the same regardless of the type of guide used. The surgical planning may have slight differences depending on the type of guide used.

Fig. 3.21  3D printers efficiently and cost-effectively manufacture surgical guides

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3.2.3.2 Fully Guided Surgical Guides Fully guided surgical guides will guide the entire sequence of drilling including insertion of the implant. They will produce a completed osteotomy with the planned overall location, angle, and depth for any given implant. The sleeves used in the surgical guide will have a large internal lumen to accommodate and guide the specific tools (guides with handle-spoons, DGS tool, or large barrelled drills) specific to the surgical system and implant system being used. This large lumen will also accommodate and guide an implant insertion key to deliver the implant to its planned position. Although fully guided systems are designed for the entire sequence of drilling and implant placement, it may be used for the drilling sequence only partially or with or without implant placement. It is a tool to be used according to the preferences of the clinician.

Fig. 3.22  Surgical guides can be produced with CNC machining; however, this is usually a more timeconsuming process

a

b

Fig. 3.23 (a, b, c) The surgical design software has libraries of sleeve designs. The guided surgical system to be used dictates the library selection in the software. After

The Indications and Benefits of the Fully Guided Surgical Guide The fully guided surgical guide provides guidance for the complete osteotomy drilling sequence and implant insertion and seating. They guide the entire preparation of the implant osteotomy to set the location, angle, and depth of the osteotomy. Implant insertion can then be completed seating the implant to its final position, including controlling the prosthetic connection orientation (Fig. 3.24a, b).

c

manufacturing the surgical guide, the metal sleeves are installed in the surgical guide

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Fig. 3.24 (a, b) The Keystone Paltop implant is guided through the surgical guide to its final position with a dedicated implant insertion key. The combined design of the

implant insertion key and sleeve design determine the implant placement depth as well as the implant prosthetic connection orientation

The major benefits of the fully guided surgical guide are the ability to rapidly locate osteotomy 3D positions and continue rigid guidance through the entire drilling sequence. After confirming appropriate pilot osteotomy position, the complete drilling sequence is completed being guided by the surgical guide ensuring implant positioning the duplicates the surgical planning. Using a fully guided surgical guide ensures complete rep-

lication of the surgical plan from the planning software. In the case of immediate provisionalization, a provisional restoration can be premade with holes corresponding to planned implant locations. This predesigned and pre-surgically fabricated provisional restoration can then be rapidly completed by luting temporary cylinders to the provisional restoration while seated on the final implant position (Fig. 3.25a–z5).

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a

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Fig. 3.25 (a, b, c) A comprehensive evaluation of the patient included full-face photos and 3D-printed and mounted diagnostic cast. The mounted casts demonstrated the class three bony relationship of the maxilla to the mandibular tooth position. (d, e, f) Intraoral surface scans were taken to aid in the evaluation of the existing tooth positions created by his removeable maxillary and mandibular prosthesis. Scans were taken with and without the mandibular prosthesis. (g) The panoramic view of the CT scan shows adequate vertical height for implant placement. (h) Careful surgical planning was done using the dual-scan technique. (i, j) The implant positions from the surgical planning software were integrated into the prosthetic planning software creating a virtual model of planned implant position. This new prosthetic model is now used to create a provisional prosthesis design with prosthetic component libraries. (k, l, m) The provisional prosthesis design is completed based on anticipated

implant positions from the surgical planning software. (n, o, p) The provisional prosthesis stl file is used to 3D print the provisional prosthesis. The prosthesis design includes holes larger than the anticipated temporary cylinders to be used to allow for leeway in the final implant position. (q, r, s) The surgical guide is 3D printed and secured to the patient’s maxilla with lateral pins. (t, u, v) Following implant insertion, multi-unit abutments were placed. Temporary cylinders are secured to the multi-unit abutments. The provisional prosthesis was seated over the temporary cylinders, and the cylinders were cured into place with a flowable resin material. (w, x) The provisional prosthesis was trimmed, polished, and inserted into the patient’s mouth. (y, z1, z2, z3, z4, z5) The final prosthesis design modifications were based off the provisional prosthesis design. These Nexus iOS restorations were designed as titanium milled bars overlaid with monolithic zirconia supported by Keystone Paltop implants

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Fig. 3.25 (continued)

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Fig. 3.25 (continued)

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What Data Do You Need to Prepare the Guides The data required to prepare a fully guided surgical guide is the same data used for pilot surgical guides: the dicom data from a CT scan and iOS (intraoral surface) scans of the mandible and maxilla with a centric mounting and any other data required to properly plan implant positions (e.g., photos, conventional radiographs, clinical charting). If the arch is edentulous, then the dicom data from a dual-scan technique will be required (the dual-scan technique has been previously described). A comprehensive surgical plan is developed from this data (including a virtual wax-up). All this data is utilized in surgical planning software that has a surgical guide design module (e.g., 3Shape Implant studio, Exoplan, Anatomage, Columbia scientific SimPlant, Blue Sky Bio, etc.). These planning software have libraries of guide sleeves. The planning laboratory will select the library for the fully guided sleeve appropriate to the procedure, surgical guided system, and implant system being planned. The guide design software will automatically incorporate the geometry required to house this guide sleeve in the guide design. After manufacture of the guide (3D printing or machining), the laboratory will insert the appropriate guide sleeve.

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for rapid preliminary osteotomy position, assessment of the position, and ability to allow for flexibility to alter the osteotomy position during surgery. Different surgical design software have different functionality. There are software that will automatically lock in the 3D sleeve position depending on the fully guide system selected, while others will allow the designer to decide the vertical height sleeve position. Some fully guided systems have dedicated drill lengths that ­correlate to implant length; other systems may have varying length drills. Systems with dedicated drill length to implant length are easier to use, while systems with variable length require more thinking during the procedure but allow for more flexibility and a greater range of applications. This all must be taken into consideration during planning (Fig. 3.26a, b). There is also flexibility where within one guide you can have some osteotomies using pilot sleeves while other osteotomies may have sleeves to control full guidance. This may be done for the reasons described for selecting pilot or full guidance. In the full-arch surgical scenario, there is the frequent use of lateral pins to secure the surgical guide (pilot or fully guided); these lateral pins usually use a pilot guide-type sleeve dedicated to lateral pins. When patients have remaining teeth that will be extracted, consideration should be given to 3.2.3.3 Surgical Planning utilizing two or three teeth to secure the surgical Considerations (Surgical, guide during osteotomy preparation and only Prosthetic) extracting those teeth after osteotomy preparaThe surgical planning for a fully guided surgical tion. If these teeth will interfere with implant guide will be the same as for any other computer-­ positions, consider using two surgical guides guided technique (fully guided, dynamic guid- staggering tooth extraction or using the teeth to ance, robotic). When there is questionable secure a pilot surgical guide that will create latplanning due to poor data being used for planning eral pin osteotomies. Once the lateral pin osteoto(patient movement during CT scan, inadequate mies are complete, the lateral pin surgical guide surface structure capture in iOS or lab scanning, is removed. The remaining teeth are then questionable or immature bone grafts, unclear extracted, and a second surgical guide is inserted CT data), new data should be acquired. If this is and secured in position with lateral pins that will not possible, then consideration for use of the engage the previously made lateral pin osteotopilot guide should be taken due to its allowance mies (Figs. 3.27a–y and 3.28a–z).

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b Implant information

Sleeve Height Minimum Drill Length*

Sleeve

Implant position (UNN) Manufacturer Type Order number Length, mm Diameter (Ø), mm Color Sleeve information

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Name Type Order number Offset, mm Color

Implant

Drill information Minimum drill length

Fig. 3.26 (a, b) The calculation for sleeve placement in the surgical guide is determined by measuring from the coronal end of the implant position to a measurement dictated by the surgical guide system being used. The length of the implant planned and the additional dimension for the apex of the

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3 Paltop Advanced 3.75x13.0 20-70003 13 3.75 Green Paltop 4mm Engage Universal 30-70409 12 Silver 25

drill are added to complete the calculation for sleeve position. The Keystone Paltop guided system uses a variable measurement with consideration for soft tissue thickness and three lengths of drills to choose from. A drilling report lists the proper drill length to use for the final guide design

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Fig. 3.27 (a, b, c) Lateral pin placement considerations include not interfering with definitive implant positions and creating a wide anterior to posterior spread to develop surgical guide fixation and stability. Planning the lateral pin sites must consider surgical accessibility to the lateral pin sleeves. (d, e, f) The stl file shows the surgical guide design and the removeable overlay which fits over the surgical guide. When assembled together the overlay aids in

positioning the surgical guide during lateral pin placement. (g, h, i, j, k, l) The printed surgical guide is seated on the edentulous maxilla and secured with lateral pins. Pilot osteotomies are drilled through the guide and unreflected soft tissue. The surgical guide may then be removed, and an incision was made to expose the alveolar crest. Pilot osteotomy positions can then be evaluated

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Fig. 3.27 (continued)

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Fig. 3.28 (a, b) This patient will demonstrate the use of two sequential surgical guides. A failing maxillary dentition can be seen. (c, d) A diagnostic wax-up is performed and integrated into the surgical planning software. (e, f, g) The surgical plan was designed for two phases. The anterior teeth were virtually extracted allowing seating of a surgical guide supported by remaining posterior teeth for placement of the anterior implants. (h, i, j) A second phase plan was then made to include extracting the posterior teeth and design of a second surgical guide to place the remaining posterior implants. (k, l, m) The surgical guide was prepared, maxillary anterior teeth extracted, and the first phase surgical guide seated, supported, and retained by the posterior teeth. (n, o) The anterior osteotomies were prepared through the surgical guide. Keystone Paltop Dynamic implants were placed through the surgical guide. (p, q) Immediate provisionalization procedures were begun following the Nexus iOS protocol. Multi-unit abutments were

g

inserted and torqued to 30  ncm. Nexus scan gauges were placed, and first-stage iOS scanning per the Nexus protocol was completed. (r, s) The remaining maxillary teeth were extracted, and the second phase surgical guide was inserted. The full coverage of the palate secured the surgical guide; however, the addition of lateral pins would have given additional stability to the guide. The Keystone Palto fully guided surgical system is used even in limited inter-arch space. (t, u) Multi-unit abutments were placed on the second phase posterior implants. Nexus scan gauges were placed on all the multi-units and were scanned per the Nexus protocol for immediate provisionalization. Multi-unit healing abutments were then secured to the multi-unit abutments and suturing was completed. (v, w, x, y, z) The provisional restoration was 3D printed and finished with a pink apron. The immediate provisionalization was completed by inserting the provisional restoration, securing it with multi-unit screws and evaluating and adjusting the occlusion

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Fig. 3.28 (continued)

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Fig. 3.28 (continued)

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Fig. 3.28 (continued)

3.2.3.4 Surgical Systems Used with Fully Guided Surgical Guides There are three types of surgical systems used with fully guided surgical guides. All three ­systems integrate with surgical guides that have a master sleeve as part of the surgical guide. This master sleeve guides the surgical system to prepare the correct osteotomy 3D position and insertion of the dental implant. There are systems that use drill guides with handles, sometimes called spoons. These spoons fit into the master sleeve in a retrievable manner. The spoons/drill guides are sized so the external diameter of the spoon fits precisely into the master sleeve in the surgical guide. The spoons have varying internal diameters that both guide the actual drills and allow them to spin free. The clinician follows the drilling protocol appropriate to the implant system choosing the appropriate spoon according to drill diameter and changing spoons to accommodate the changing diameters of the drills. The limitations of this type of system include having to be very careful with irrigation as much of it is blocked due to the drill fitting precisely in the spoon. The drills are long and must be placed

directly perpendicular to and over the master cylinder and sleeve to be able to enter the spoon for drilling. This requires the patient to open very wide, and there will be limitations to interarch space as you prepare osteotomies in the posterior maxilla and mandible. The drills spinning in the spoons may also cut small flakes of the cylinder (usually made of titanium), and these flakes may end up in the surgical site (which will require careful inspection and cleaning) (Fig. 3.29a–f). The second fully guided system has drills where the shaft/barrel of the drill has varying sizes to mate with the master cylinder in the surgical guide. There are varying diameters of the cutting segment of the drills, but all drills have a shank segment that will guide the drill while cutting bone. This shank segment guides the drill to place. The limitation of this type of system includes blocking irrigation to the drill as well as limitations due to interarch space as previously discussed with spoon-type systems. Depending on the system if the cutting segment of the drill engages the master cylinder during drilling, then flakes of the master cylinder may also fall into the surgical site (Fig. 3.30a, b).

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Fig. 3.29 (a, b) Guided surgical kits that use drill guides on handles (spoons) have dedicated drills that mate with the drill guides. (c, d) The use of a drill guide on a handle (spoon) to guide the drill requires multiple hands. The

f

guide should be supported in position while the drill guide handle needs to be held and the drill is operated by a third hand. (e, f) The implant is inserted into the final position through the surgical guide by a dedicated implant driver

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Fig. 3.30 (a, b) This drill system uses a large bore shank that fits into the diameter of the drill guide sleeve. The metal sleeve in the surgical guide directly guides the drill

The third type of fully guided system is a newer innovation that uses contra-angle guidance. There is a dedicated contra-angle handpiece that engages a device called a DGS (digital guidance sleeve) (Fig. 3.31). This DGS fits precisely into the master cylinder in the surgical guide in a manner that allows vertical and rotational movement of the DGS. All drills used in the drilling protocol are designed to fit into the DGS.  The DGS will guide the entire preparation of the osteotomy. The DGS has a window for irrigation to enter and cool the drill during osteotomy preparation (Fig.  3.32a, b). The cutting edges of the drill do not engage the

master cylinder, so there are no flakes of material from the master cylinder. Guidance is provided by the DGS in the master cylinder (Fig.  3.33a, b). The DGS does not have any cutting edges. The drills may enter the master cylinder at an angle because they do not engage the master cylinder (so there is freedom of movement around the drill). There is only uprighting of the drills when the DGS enters the master cylinder, and this is only the last several millimetres (Fig.  3.34a–c). Therefore, most osteotomies even posteriorly can be prepared to completion when using contra-angle guidance.

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Fig. 3.32 (a, b) Irrigation cools the length of the drill during the drilling process by entering a window in the side of the DGS

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Fig. 3.33 (a, b) The drill is guided by engagement of the DGS with the sleeve in the surgical guide. No cutting flutes touch the surgical guide sleeve

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Fig. 3.34 (a, b, c) The drill does not engage the drill guide cylinder and is smaller in diameter than the drill guide sleeve. Therefore, the drill can be brought into the sleeve at an angle and only uprighted when the drill

c

reaches the bone. Most implant osteotomies can be performed with guidance even with limited interarch distance

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How Do You Use the Guide During Surgery The surgical guide is prepared for surgery usually with a cold sterilization technique. The guide should be tried into the patient’s mouth prior to beginning the surgery to ensure proper seating. If there are teeth that will be extracted that interfere with seating, then this try-in will be done only after tooth extraction. The surgical guide that is tooth borne should be designed with windows anteriorly and posteriorly that demonstrate complete seating of the surgical guide. When the guide is seated, the edges of the window (or opening in the guide) will be in intimate contact with the tooth or structure beneath it; if there is any space, then the guide is not seated and must be removed and evaluated to determine why it is not seated (Fig.  3.35a, b). The most frequent causes of not seating are deep embrasure spaces, diastemas between teeth, and significant undercuts. All these may be resolved by removing from the surgical guide the material that is causing the interference. This can usually be done liberally because there will still be adequate guide planes to secure the surgical guide. Try not to remove material adjacent to the guide windows. It is always possible that there was an inadequate impression or intraoral scan. Care must be taken to always record good data. In the case of the edentulous arch, the surgical guide seats on the soft tissue (fully guided surgical guides may also be made as bone-borne guides). The guide should be very stable when inserted and held in place with two fingers. The patient should be able to bring their teeth into occlusion or in contact with the opposing arch so that the opposing arch can a

secure the guide position without displacing it. A rigid bite registration may be used to accomplish this (Fig. 3.36a–h). Once the edentulous full-arch surgical guide is held stably in place, the osteotomies for lateral pins may be performed to secure the surgical guide in place. The drilling of the osteotomies for the lateral pins should be done prior to any soft tissue reflection. One drill (usually a 2 mm twist drill) is used to create the osteotomy. The lateral pin that is part of the pilot system should be placed, and then the next lateral pin osteotomy is performed. Usually, the first pin may be the most distal pin followed by the contralateral distal pin, followed by an anterior lateral pin. Following securing the guide in a tripod fashion, any additional pins including vertical ridge and palatal pins are placed (Fig. 3.37a–l). Following confirmation of seating and securing the guide, the implant surgical procedure may be continued. In the case where there are remaining teeth that are not supporting the guide, these may be extracted (if not already done). Incisions, flap reflection, surgical debridement, and ridge preparation are now completed. In consideration for ridge preparation, adjusting the alveolar ridge so that it will be perpendicular to the osteotomy preparation will aid in ensuring proper positioning of the initial drill. If there will be drilling into the bone that is at an angle (other than perpendicular), the drill may slip from its intended position even with guidance from a surgical guide (Fig. 3.37a–z14). In the edentulous arch, it is recommended to make pilot osteotomies prior to any soft tissue reflection. The surgical guide will be most stable

b

Fig. 3.35 (a, b) Windows are designed in the surgical guide so there can be confirmation of complete seating of the surgical guide

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Fig. 3.36 (a, b, c) The surgical guide is seated on the soft tissue. There should be confirmation that the surgical guide seat is stable. Two fingers can be used to check stability and positive seating. (d, e, f, g) A rigid bite registration material is placed in between the surgical guide and the opposing dentition, while the guide is held firmly in position. After completion of setting of the bite registration material, the

patient is instructed to continue biting their teeth together. The dedicated lateral pin drill creates an osteotomy, and then a lateral pin is placed. The second lateral pin osteotomy is prepared, and its lateral pin is placed. The final lateral pin osteotomy is prepared and its lateral pin placed. (h) Following securing the surgical guide with the lateral pins, the implant pilot osteotomies may be begun

prior to reflecting the soft tissue. After preparing pilot osteotomies, the lateral pins may be disengaged, the surgical guide removed, and incision and soft tissue reflection performed. If the soft tissue can be left unreflected posteriorly (mandibular retromolar pads, maxillary tuberosity, palate), the combination of posterior soft tissue support with lateral pins will allow for a very stable surgical guide. After reflecting the soft tissue (this can usually be done as a modest reflection), the osteotomy positions can be evaluated visually as well as with guide pins placed. The fully guided surgical guide is removed, and the clinician may assess the osteotomy 3D position by placing a guide pin in the osteotomy. Location, depth, assessment of surrounding bone, angle and orientation to adjacent implant pilot osteotomies, proximity to adjacent implant osteotomies, proximity to adjacent clinically visible structures,

orientation to adjacent structures, and anticipated restorability are shown (Fig. 3.38a–c). All can be evaluated at this point prior to committing to this osteotomy as the final osteotomy position. Intraoperative radiographs (periapical, panoramic, or CT scan) may be taken with guide pins in place to assess the osteotomy position in the bone where it is not clinically visible. Proximity to adjacent implants, mental foramen, inferior alveolar canal, maxillary sinus, floor of the nose, pterygoid complex, etc. may be assessed and adjustment made if necessary to the osteotomy position. These adjustments may be to location, angle, as well as osteotomy depth. If the adjustment is made to correct the osteotomy position because the pilot drill slipped while cutting on a sloped ridge, then the fully guided surgical guide may be reinserted and secured to position with the lateral pins. The pilot drill must be reused in

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a

d

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c

e

Fig. 3.37 (a, b, c, d, e) This full-arch case was planned as a full-arch sequential extraction case with the provisional restoration supported by provisional abutment teeth. The diagnostic data was collected including full-­ face photo and iOS scans. A diagnostic wax-up was completed and integrated into the full-face photo to evaluate the tooth length and exposure with a wide smile. Although the wax-up shows long teeth, the smile line with the incisal edge of the incisors in the appropriate position does not show excessive tooth length. (f, g, h, i) The diagnostic wax-up was integrated with the CT scan data and surgical planning was completed. No pink apron was required due to the patient’s low lip line. A crown and bridge style restoration was planned so tooth positions were adhered to in the surgical planning. (j, k, l, m, n) The patient presented for a presurgical appointment and provisional abutment teeth were prepared and iOS impressions taken. The wax­up was transferred to the virtual model with the prepared teeth, and a PMMA provisional was manufactured to fit precisely to the abutment teeth. The model with the prepared teeth and diagnostic wax-up was then integrated with the CT scan and implant planning. The surgical guide was designed to seat on the prepared abutment teeth following tooth extraction. (o, p, q, r) The teeth planned for removal were extracted leaving the planned provisional abutment teeth. The surgical guide was seated on

the prepared abutment teeth and osteotomy preparations were performed. (s, t, u) Following osteotomy preparation, implant body try-ins were placed to confirm the implant 3D position. After confirmation of implant position, the surgical guide was reinserted and the implants were placed. (v, w) Angled implants were placed posteriorly so angulated multi-unit abutments were tried in to verify correct orientation of the implant prosthetic connection. The design of the Keystone premium multi-unit allows for subcrestal implant placement without requiring bone profiling for seating of the angled multi-unit abutment. (x, y, z1, z2) The prepared provisional restoration was then inserted onto the retained provisional abutment teeth. The occlusion was checked and the provisional restoration cemented. (z3) Postoperative radiographs confirm proper implant positioning according to the presurgical plan. (z4) Following 4 months of healing and confirmation of integration, the provisional abutment teeth were extracted. Multi-unit abutments were placed and iOS impressions taken. (z5, z6, z7) The provisional restoration was designed and manufactured. The screw access hole positions confirm good implant placement. (z8, z9, z10) The provisional restoration was inserted and radiographs were taken. (z11, z12, z13, z14) Two weeks post-tooth extraction, the soft tissues show good healing and adaptation to the provisional contours

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Fig. 3.37 (continued)

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Fig. 3.37 (continued)

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z9

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z13

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Fig. 3.37 (continued)

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Fig. 3.38 (a, b, c) When there may be questionable seating of the surgical guide, the initial osteotomies will benefit from verification. This edentulous mandible has a plan with angled implants placed in close proximity to the

c

mental foramen. The pilot osteotomy was performed followed by placement of a guide pin and exposure of the mental foramen

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the corrected osteotomy opening. Verification should then be done by removing the guide and visually confirming the corrected osteotomy. The fully guided sequence may then be continued. However, if the pilot osteotomy correction was due to improper planning, poor data, or changes in the bone, then following correction that osteotomy must be completed freehand. Once the osteotomy position is confirmed, the clinician will reinsert the surgical guide and rapidly continue the osteotomy preparation to completion with the subsequent drills for the fully guided kit and implant system being used. Care should be taken not to deviate from the position due to poor quality of bone in areas where there may be dense bone on one side of the osteotomy and poor quality of bone on an opposing side. This can lead to changing the final osteotomy position. This consideration most frequently should be considered when placing implants into immediate extraction sites where there is usually dense bone to the lingual or palatal and air or poor-quality bone to the buccal of the implant position (Fig.  3.39a, b). To prevent displacement of the osteotomy, think about the dense bone while drilling and hold the drilling path true to the surgical plan. The other cause for deviation is drilling into a sloped ridge (e.g., anterior mandible). Always review the surgical plan prior to surgery and have it available for viewing during surgery. If there has been deviation, then remove the guide and evaluate. If the malposition is in angle or location that is slightly off (up to 1 mm) from the planned osteotomy, then take the pilot drill and expand the incorrect osteotomy to the correct anticipated location

a

or change the angle within the opening of the osteotomy if the entry point is correct. Levelling the bone so it is perpendicular to the drill entry also aids in drilling true to the planned osteotomy position. This is all done freehand and must be done with great care. These adjustments may be to location, angle, as well as osteotomy depth. If the adjustment is made to correct the osteotomy position because the pilot drill slipped while cutting on a sloped ridge, then the fully guided surgical guide may be reinserted and secured to position with the lateral pins. The pilot drill must be reused in the corrected osteotomy opening after reinserting and securing the surgical guide. Verification should then be done by removing the guide and visually confirming the corrected osteotomy. The fully guided sequence may then be continued (Figs. 3.40a–z23 and 3.41a–z3). Once osteotomy creation is complete, then remove the surgical guide and place implant try in bodies (appropriate to the implant system being used) to confirm correct osteotomy location, angle, and depth. This will also aid when evaluating the final seating position of the implant (Fig. 3.39a, b). Most fully guided systems will then have implant drivers or keys to deliver the implant through the surgical guide to the correct position. The implant insertion key usage is system dependent. Some systems will deliver the implant to a bottomed-out implant key position. These systems control placement position through sleeve position in the surgical guide. Other systems will have markings and numbers that correlate to a drilling report produced by the surgical planning

b

Fig. 3.39 (a, b) The implant body try-in confirms the successful palatal positioning of the implant and confirms implant parallelism as well as complete osteotomy depth preparation

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Fig. 3.40 (a, b, c) Diagnostic records including dual CT scan, iOS scans, and full-face photos were taken. (d, e, f) The dual-scan data and the iOS scan data were imported into the prosthetic planning software to complete a diagnostic wax-up. The diagnostic wax-up was then integrated with the patient’s full-face photos. (g, h, i) The diagnostic wax-up was 3D printed and confirmed with a try-in. (j, k, l) The surgical plan was created. The tooth length to soft tissue is measured, and it is determined that a crown and bridge style restoration may be made with teeth emerging from natural soft tissue. This style of restoration dictates the surgical positioning of the implants to tooth-specific sites with proper emergence profile dimensions. (m, n, o) The surgical guide was seated and secured to the maxillary soft tissue with lateral pins. (p, q) The Keystone Paltop fully guided kit was used beginning with the combined pilot drill with a soft tissue trephine. This patient had a very wide zone of keratinized tissue which allowed flapless surgery. (r, s, t) The combined pilot drill with a soft tissue trephine was guided by the surgical guide. Frequently, there will be incomplete cutting when using a soft tissue trephine through a surgical guide. To complete the soft tissue removal, an independent soft tissue trephine was used to sever any remaining soft tissue attachment. (u, v, w) The Paltop fully guided protocol was then followed beginning with the 2  mm twist drill with a 20  mm length. The DGS engages the drill guide sleeve by the drill always entering the previous prepared osteotomy. The drilling with every drill is complete when the DGS bottoms out on the surgical guide. (x, y, z1) The next length (25 mm) 2 mm twist drill is used with the DGS engaging the guide sleeve until it bottoms out on the surgical guider. There is also a 30 mm length twist drill in the kit. The drilling length 20, 25, or 30 mm is dictated by the drilling report produced in the guide design software. (z2, z3) The drill diameter is now increased to the 3.25 mm drill 20 mm length followed by the 25 mm length (according to the drilling protocol indicated on the drilling report). (z4, z5, z6) The drill diameter is increased according to the drilling protocol indicated on the drilling report. This fully guided kit has diameters of final shaping drills for implant diameters 3 mm, 3.25 mm, 3.75 mm, 4.2 mm, and 5 mm. The colour bands indicating drill diameter and length can be seen through the DGS window. All the shaping drills come in the 20, 25, and 30 mm lengths. (z7, z8, z9) Once the final

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osteotomy preparation is complete (the final drill protocol may include undersizing or countersinking depending on bone quality), the contra-angle adaptor is inserted into the contra-angle along with the implant insertion key indicated on the drilling report. The implant is then inserted to the depth indicated on the drilling report and can be seen on the shank of the implant key. The connection orientation can also be controlled by aligning the flat of the implant key with the midbuccal groove on the surgical guide sleeve. (z10) The lateral pins are disengaged and the surgical guide is removed. Implant depth can be evaluated and adjusted with a torque driver as well as obtaining a true insertion torque umber. The insertion torque felt when used with the implant key in the surgical guide is not accurate due to the contact of the implant key with the surgical guide sleeve. (z11, z12) Immediate provisionalization was planned so the four anterior multiunit abutments were placed and torqued to 30ncm. The sleek and debulked contours of the Keystone multi-unit abutment allow for subcrestal implant placement without bone interfering with abutment seating. (z13, z14) Four scan bodies are placed on the four anterior multi-unit abutments, and a scanning appliance is inserted engaging the lateral pin osteotomies. iOS sans are taken which record the anterior implant position in relation to the scanning appliance which enables transfer of the tooth position as well as CR and VD. (z15, z16, z17, z18) The scanning appliance is removed. The anterior scan bodies are removed, and the posterior KDG premium angled multi-units are placed. The design contours of these angled multi-units frequently do not require bone profiling to be seated. The Nexus scan gauges were placed on all implants, and the Nexus scanning protocol for accurate implant position transfer was performed. (z19, z20) The presurgical diagnostic wax-up was integrated with the final implant and multi-unit positions, and the provisional design file was 3D printed. The screw access hole positions in the 3D printed provisional demonstrate the careful planning and surgical implementation with a guided surgery protocol. (z21, z22) The provisional restoration is inserted, the multi-unit abutment screws tightened, and the occlusion evaluated and adjusted. (z23, z24) At 1 month postop, good soft tissue healing is seen with aesthetic tooth dimensions. Surgery Dr Michael Abrams

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Fig. 3.41 (a, b, c) A plan for immediate implant placement with immediate provisionalization was made for this patient with a failing maxillary dentition. (d, e) iOS scans of the patient’s maxilla, mandible, and bite were taken. A diagnostic wax-up of the maxilla was completed. (f, g) The diagnostic wax-up was integrated with full-face photos to confirm aesthetics and evaluation of the soft tissue in the transition zone. (h, i, j, k) The iOS scans were integrated with the patient’s cone beam CT scan and then overlayed with the diagnostic wax-up. Implant planning was then completed. (l, m) Careful analysis of anterior tooth length, distance from the free gingival to implant connection, as well as divergence of implant positions was completed prior to finalizing the surgical and prosthetic plan. (n, o, p) The surgical guide was designed to be tooth borne for maximum stability. (q, r, s) Only the teeth inter-

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fering with implant position were extracted prior to implant placement. Multi-unit abutments were placed on the implants. Nexus scan gauges were placed and secured to the multi-unit abutments, and the Nexus scanning protocol was followed. The remaining teeth in the maxillary arch were critical to integration of the multi-unit abutment positions with the presurgical wax-up. Following scanning, the remaining teeth were extracted. (t, u, v, w) The diagnostic wax-up file was integrated with the multi-unit abutment positions and the provisional design was completed. (x, y) The provisional design was 3D printed from the stl file. Postprocessing and finishing included adding pink gingival tissues to the posterior units. (z1, z2, z3) The provisional restoration was inserted, and the occlusion adjusted. Final radiographs confirm complete seating of the provisional restoration

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Fig. 3.42 (a, b, c, d, e) The drilling report indicates the appropriate drill length (25 mm), implant size (3.75 × 13), as well as the depth measurement on the implant driver to deliver the implant to its planned depth (Offset-12)

software. These drilling reports indicate the drilling depth as well as the correct vertical implant delivery position by indicating a number that will correlate to a number on the implant delivery insertion key (Fig.  3.42a–e). The implant insertion keys will also have features that indicate implant connection orientation. Control of the connection orientation is critical when using angled multi-unit abutments. The indication for use of an angled multi-unit abutment is to align the restorative platform of the multiunit abutment into proper alignment and restorative path of draw with the other multi-unit abutments. Straight multi-units are nonengaging, so connection orientation is not critical; however, to take advantage of angled multi-unit abutments (which are engaging), connection orientation is critical (Fig. 3.37v, w). The insertion torque felt when inserting the implant through the guide will not be accurate due to the rubbing of the implant insertion key against the sleeve in the surgical guide. It is recommended to evaluate insertion torque without the surgical guide in position. This can be done by turning the last 1–3 insertion turns without the surgical guide and with a torque driver (Fig. 3.43). Options That Aid Immediate Provisionalization Some surgical planning software (e.g., 3Shape, Exocad, etc.) will allow the conversion of the surgical planning stl into their prosthetic planning software. This will create a model with

Fig. 3.43  Final implant seating should be done with a torque driver without the surgical guide. When the implant driver comes in contact with the surgical guide sleeve, true insertion torque cannot be felt

the planned implants in place as if the implants were in the patient’s mouth and iOS impressions had been taken. Abutments may be selected and the provisional prosthesis designed. However, due to the reality that the actual implant positions will not be exactly in the positions planned, the provisional must be designed with space around the abutment that will allow for slight variations between the planned implant position and the actual implant position after placement. This will allow passive seating of the provisional restoration with a quick reline process to secure the abutment cylinders to the provisional prosthesis for a screw retained provisional or a quick crown and bridge style reline for a cementable provisional prosthesis (Fig. 3.25a–w).

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Limitations of the Guide Fully guided surgical guides when used for the complete surgical protocol require a commitment to the planned implant position. There are occasions where the data used for planning was incomplete (poor impression analogue or IOS), difficult to read CT scans due to a lot of metal artifact, or not up to date data (there was additional healing or pathology resulting in a clinical reality that is different from the data used for planning). On occasion, the patient cannot open wide enough for the selected surgical tools. In these scenarios the surgical guide may not be able to be used or may only act as a pilot guide, or perhaps osteotomies can be completed but implant insertion is done freehand. Consideration should always be given to use the guide for the guidance and information to best serve the individual clinician and patient. That may mean some osteotomies have pilot guidance and some full guidance, maybe the osteotomies are prepared and implant delivery is freehand. Moreover, difficult implant placement for angled implants, sited adjacent to mental foramen maxillary sinus, etc. are managed with the surgical guide (Fig. 3.44) [14].

Fig. 3.44  Long drill lengths in patients with limited interarch space can usually be managed with the DGS guided surgery systems. However, the implant delivery with the implant insertion driver and implant will be longer and may require freehand implant insertion

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3.2.3.5 Pilot Guides Pilot guides will just guide the initial drill used for positioning the implant. They will produce an osteotomy with the planned overall location, angle, and depth for any given implant. Generally, the drill diameter used is 1.5–2 mm in diameter. The sleeves used in the surgical guide will then only have an internal lumen to accommodate and guide the specific diameter for the pilot drill being used. The pilot drill can be universal to any implant system as it only guides the initial osteotomy whose diameter at this point is generic to all systems. The Indications and Benefits of the Pilot Guide Pilot surgical guides provide rapid guidance for the initial pilot drill (usually 1.5 or 2 mm in diameter) while allowing flexibility for the clinician to make changes at the time of surgery. Following pilot osteotomy preparation, the pilot guide is removed and the clinician may assess the osteotomy 3D position by placing a guide pin in the osteotomy. Location, depth, assessment of surrounding bone, angle and orientation to adjacent implant pilot osteotomies, proximity to adjacent implant osteotomies, proximity to adjacent clinically visible structures, orientation to adjacent subcrestal structures, and anticipated ­restorability can all be evaluated at this point prior to committing to this osteotomy as the final osteotomy position. Intraoperative radiographs (periapical, panoramic, or CT scan) may be taken with guide pins in place to assess the osteotomy position in the bone where it is not clinically visible. Proximity to roots of adjacent teeth, implants, mental foramen, inferior alveolar canal, maxillary sinus, floor of the nose, pterygoid complex, etc. may be assessed and adjustments made to the osteotomy position. These adjustments may be to location, angle, as well as osteotomy depth. Once the osteotomy position is confirmed or adjusted, the clinician can rapidly continue the osteotomy preparation to completion with the subsequent conventional drills indicated for the implant system being used following the path created by the pilot osteotomy. Care should be

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taken not to deviate from the position due to poor quality of bone or areas where there may be dense bone on one side of the osteotomy and poor quality of bone on an opposing side (such as an extraction site). This can lead to changing the final osteotomy position (Fig. 3.45) [15]. The major benefits of the pilot surgical guide are the ability to rapidly locate osteotomy 3D positions while giving the clinician flexibility to make changes during the surgical procedure. When designing the surgical guide for a fully guided surgical guide, the guide sleeves may also be too close in proximity to an adjacent guide sleeve or tooth, and this may require use of a

Fig. 3.45  Great care must be taken when preparing osteotomies in extraction sockets. The palatal or lingual bone will push the drill buccally into the open space of the extraction socket causing the implant to be angled buccally

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smaller-diameter guide sleeve such as a pilot guide sleeve (Fig. 3.46a, b). Data You Need to Prepare Pilot Guides The data required to prepare a pilot guide is the same data for fully guided surgical guides: the dicom data from a CT scan and iOS (intraoral surface) scans of the mandible and maxilla with a centric mounting and any other data required to properly plan implant positions (e.g., photos, conventional radiographs, clinical charting). If the arch is edentulous, then the dicom data from a dual scan technique will be required (the dual-­ scan technique has been previously described). A comprehensive surgical plan is developed from this data (including a virtual wax-up). All this data is utilized in surgical planning software that has a surgical guide design module (e.g., 3Shape Implant studio, Exocad, Exoplan, Anatomage, Columbia scientific SimPlant, Blue Sky Plan, etc.). These planning software have libraries of guide sleeves. The planning laboratory will select the library for the pilot guide sleeve appropriate to the procedure being planned (Fig. 3.47). The guide design software will automatically incorporate the geometry required to house this guide sleeve in the guide design. After manufacture of the guide (3D printing or machining), the laboratory will insert the appropriate guide sleeve.

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Fig. 3.47  Most surgical planning software with surgical guide design features will have pilot sleeve libraries

Surgical Planning Considerations (Surgical, Prosthetic) for the Pilot Guide The surgical planning for a pilot guide will be the same as for any other computer-guided technique (fully guided, dynamic guidance, robotic). There is also flexibility where within one guide you can have some osteotomies using pilot sleeves, while other osteotomies may have sleeves to control full guidance. This may be done for the reasons described for selecting pilot or full guidance. Pilot guides are secured in position with teeth or lateral pins just as with fully guided surgical guides (see fully guided surgical guides). Pilot guides are used with the same techniques as the preliminary pilot drill of fully guided sequences. All the same considerations and techniques described for fully guided surgical guides should be followed. Surgical Tools Used with Pilot Guides The surgical armamentarium used with the pilot guide includes pilot drills that are indicated to be used with the pilot guide sleeves placed into the pilot surgical guide. This is system dependent. The drills and guide sleeves should be utilized as a system so that rigid initial drilling guidance is controlled while allowing adequate tolerances for the spinning of the drill. Some systems will have one dedicated drill, while others may have two or three different lengths (Fig. 3.48).

Fig. 3.48  Pilot drill kits are designed to be used with specific pilot guide sleeves

How to Use the Guide During Surgery Follow the surgical protocols described for fully guided surgery through the pilot osteotomy step. When the pilot guide is used, the guide pins can be evaluated relative to the opposing arch and anatomic landmarks including the mental foramen (if exposed). After evaluation of the correct pilot osteotomy placement, the drilling protocol

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may be completed freehand. It is recommended to periodically check to confirm no deviation from the plan during freehand drilling. In a dense anterior mandible, this is unlikely to happen. In the posterior mandible and maxilla, potential

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deviation is a more common occurrence. The anterior maxilla, posterior mandible (molar sites), and all extraction sites are more prone to potential deviation during freehand drilling (Fig. 3.49a–l).

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Fig. 3.49 (a, b) Data required for surgical and prosthetic planning for a pilot guide is the same as with fully guided surgery and requires the same data. For the edentulous arch, the dual-scan protocol is used, and decision-making about pilot guide or fully guided is only made after analysis of the data. (c, d, e) The surgical guide will use the same lateral pin systems as fully guided guides. Pilot drill systems that use different length pilot drills may be colour coded. The pilot sleeves may be colour coded to indicate which length drill is used in which sleeve position. (f, g) The pilot surgical guide is secured with lateral pins prior to tissue reflection to ensure it is secured in the most stable position. (h) After the pilot osteotomies are created, the

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pilot surgical guide is removed and guide pins are placed to verify the osteotomy positions. The relationship and orientation of the pins are analysed relative to each other as well as the opposing arch. After confirmation of osteotomy positions, the osteotomies are completed freehand. (i, j) Immediate provisionalization options are the same as with a fully guided surgical procedure. In this patient, multi-unit abutments were placed followed by securing titanium temporary cylinders to the multi-unit abutments. (k, l) The provisional restoration was prepared from the diagnostic wax-up with large holes in planned implant positions. The provisional was then fitted and relined over the temporary cylinders

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Limitations of the Guide Surgical guides must be positioned correctly. Any deviation in positioning of the guide will result in improper implant positioning. This deviation can be in  location, angle, as well as depth. Care must be taken to ensure proper seating with verification of that position. When using a pilot guide, attention must be paid to not

deviating from the pilot position (unless it is indicated to do so). The patient’s ability to open wide must also be a consideration when using guided surgery guides. The drill length must take into account the height of the surgical guide. They will usually be 20–30 mm in length in addition to the height of the head of the contra-angle.

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3.2.3.6 Bone-Borne Guides The Indications and Benefits of Bone-­ Borne Guides Bone-borne guides seat directly on the bone which will require reflection of the soft tissue. Bone-borne guides will have a very stable base to secure the guide as long as no significant osteoplasty is done to the seating area of the guide [16]. Bone-borne guides are secured in place by broad coverage of bone and do not require teeth to secure them in position. A large surgical flap is usually required to provide access to seat the guide. Bone-borne guides are also used as bone reduction guides to guide indicated osteoplasty. Bone-borne guides may be designed as pilot surgical guides or fully guided surgical guides following the considerations listed previously. The Data You Need to Prepare Bone-Borne Guides The data required to prepare a bone-borne guide is the same data required for pilot guides and for fully guided surgical guides: the dicom data from a CT scan and IOS (intraoral surface) scans of the mandible and maxilla with a centric mounting and any other data required to properly plan implant positions (e.g., photos, conventional radiographs, clinical charting). If the arch is edentulous, then the dicom data from a dual-scan technique will be required (the dual-scan technique has been previously described). A comprehensive surgical plan is developed from this data (including a virtual wax-up). All this data is utilized in surgical planning software that has a surgical guide design module (e.g., 3Shape Implant studio, Columbia scientific SimPlant, Blue Sky Bio, etc). These planning software have libraries of guide sleeves. The planning laboratory will select the library for the guide sleeve appropriate to the procedure being planned. The guide design software will automatically incorporate the geometry required to house this guide sleeve in the guide design. After manufacture of the guide (3D printing or machining), the laboratory will insert the appropriate guide sleeve (surgical planning considerations: surgical, prosthetic).

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Surgical planning considerations will follow the same protocols and considerations as described for the pilot and fully guided surgical guides. When planning the bone-borne guide, usually all remaining teeth in the arch will be extracted prior to seating the guide. Care must be taken to not remove excessive bone during the virtual planning as this will prevent complete seating of the bone-borne guide. The surgical planning for a bone-borne guide will be the same as for any other computer-guided technique (fully guided, dynamic guidance, robotic). When there is questionable planning due to poor data being used for planning (patient movement during CT scan, inadequate surface structure capture in iOS or lab scanning, questionable or immature bone grafts, unclear CT data), then new data must be acquired. In the full-arch surgical scenario, if broad bone coverage will be used to provide a stable and secure surgical guide, then lateral pins may not be required. Surgical Tools Used with Bone-Borne Guides The surgical tools will be the same for bone-­ borne guides as pilot or fully guided surgical guides. These surgical systems are all previously described in each of the pilot and fully guided sections. How to Use the Guide during Surgery When using a bone-borne guide, the remaining teeth in the arch are extracted and all pathology removed. If any osteoplasty was planned that will not affect the proper seating or retention of the surgical guide, then perform the osteoplasty prior to seating the guide. An incision large enough to allow access to fully seat the guide is done with adequate flap reflection. This will require the incision and flap reflection to usually be extended two teeth beyond the most distal extent of the bone-borne guide. The flap reflection must also extend well beyond the borders of the flanges of the surgical guide to allow complete seating of the bone-borne guide. The surgical systems are used in the same manner as described in the sections for pilot guides and fully guided surgical

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guides. Verification of seating of the guide is also done through windows in the guide that demonstrate intimate contact of bone with the guide. This is the reason that care must be taken with a

any osteoplasty done prior to seating the guide. Following verification of guide seating, follow the protocols and procedures for pilot or fully guided surgical systems (Fig. 3.50a–p).

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Fig. 3.50 (a, b, c) Following surgical planning the bone-­ borne guide is designed on the virtual bone model and converted into a manufacturing stl file. (d, e) The bone-­ borne guide may be used to create a bone reduction guide as well as a surgical guide. (f, g) The bone-borne guide has the advantage of creating a very stable base in the edentulous arch. In order to create this stable base, a broad area needs to be covered with the guide which will require a more extensive flap reflection. (h, i) The bone reduction guide will be designed to cover the same area as the subsequent surgical guide for drilling. Intimate fit of the guide should be seen to ensure proper seating and guide orientation. (j, k) This guide was designed to reduce the bone in the areas planned for implant placement while preserving the adjacent bone to support the

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provisional removeable denture. (l) The complete seating of the surgical guide for implant osteotomies and placement is verified with windows to see intimate contact of bone to surgical guide. (m, n) The bone-borne guide may be designed as a pilot or fully guided surgical guide. Care must be taken to create windows to verify complete guide seating in areas that the bone will not be modified prior to implant osteotomy preparation. (o) The surgical kit for the bone borne guide is selected based on the sleeve system used in the guide. The sleeve systems used and surgical kits used are the same for bone-borne guides as tooth- or soft tissue-borne guides. (p) Implant placement with bone borne guides is accomplished following the same protocols as with tooth-borne or soft tissue-borne guides

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Options That Aid Immediate Provisionalization See provisionalization of implants planned and placed with fully guided surgical guides. Limitations of the Bone-Borne Guide The bone-borne guide will require a longer incision and more extensive flap reflection than for pilot and fully guided surgical guides. There is no option of a flapless surgery or a minimally invasive surgical flap design. Verification of seating can be difficult, and adjustment to the guide when seating is more difficult to accomplish successfully. If there is scatter at the level of the bone in the CT dicom data or immature bone that does not show up clearly in the images, then the guide will be made improperly and will not seat (Figs.  3.51a, b, 3.52 and 3.53). The tooth-borne or soft tissue-borne guides can be made to seat properly regardless of any scatter caused by metal artifact in the CT images because the iOS images are used for the guide design and there will not be metal scatter in that data.

3.2.3.7 Stackable Surgical Guides The Indications and Benefits of Stackable Guide Systems Stackable surgical guides are surgical guide systems that provide a stable secure foundation that does not rely on teeth in the arch. The surgical guide integrates with a foundation platform, and the platform acts as a guide for bone reduction. After guided implant placement through the surgical guide, the surgical guide is removed from the foundation component, and an additional platform that supports the correct positioning of the provisional restoration integrates with the foundation. The provisional restoration is secured to the provisional cylinders while positioned on the foundation at the correct vertical position, A-P position, angle, and occlusion. Some of the resources for stackable systems are Roe-Chrome, N-Sequence, Co-Diagnostics, etc. [17].

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Fig. 3.51 (a, b) When double images are seen in the axial or cross-sectional images, it means the patient moved during the CT scan and the scan data will not be accurate for surgical planning

Fig. 3.52  The distortion caused by scatter reflecting off metal restorations can make the ct images difficult to read and use

The Data You Need to Prepare the Guides The data required to prepare a stackable guide is the same data required for pilot guides and for fully guided surgical guides: the dicom data from a CT scan and iOS (intraoral surface) scans of the mandible and maxilla with a centric mounting and any other data required to properly plan implant positions (e.g., photos, conventional

Fig. 3.53  This CT cross-sectional image shows an image with very poor bone quality that can sometimes make it difficult to properly preposition the implant at the surgical planning phase of guided surgery

radiographs, clinical charting). If the arch is edentulous, then the dicom data from a dual-scan technique will be required (the dual-scan tech-

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nique has been previously described). A comprehensive surgical plan is developed from this data (including a virtual wax-up). All this data is utilized in surgical planning software that has a surgical guide design module. The planning and design software for stackable guides vary and may be proprietary to the stackable system. These planning software have libraries of guide sleeves. The planning laboratory will select the library for the pilot guide sleeve appropriate to the procedure being planned. The guide design software will automatically incorporate the geometry required to house this guide sleeve in the guide design. After manufacture of the guide (3D printing or machining), the laboratory will insert the appropriate guide sleeve.

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guide for positioning of the lateral pins. The foundation component may seat on the bone and be secured to the bone. After positioning of the foundation component, this foundation component may guide the amount of bone reduction required for each individual arch. After bone reduction the surgical guide component stacks onto and integrates with the foundation component. The implant osteotomies and implant delivery are accomplished according to the protocol of the fully guided surgical system used and implant system specifics. The surgical guide component is removed leaving the foundation component in place. Multi-unit abutments are placed. Provisional cylinders are secured to the multi-­ unit abutments. The provisional restoration is positioned either on a prosthetic platform that Surgical Planning Considerations stacks onto the foundation component or to the (Surgical, Prosthetic) foundation component itself. The provisional The surgical planning for a stackable surgical cylinders are then cured to the provisional either guide will be the same as for any other computer-­ at one time or sequentially. The provisional is guided technique (fully guided, dynamic guid- then removed and finished in the laboratory addance, robotic). When there is questionable ing any deficient material and then trimming and planning due to poor data being used for planning polishing. The foundation component is removed (patient movement during CT scan, inadequate from the patient’s mouth and any required bone surface structure capture in IOS or lab scanning, grafting performed. Multi-unit healing abutments questionable or immature bone grafts, unclear are secured to the multi-unit abutments at a lower CT data), then consider acquiring new data. insertion torque, then the abutments were inserted Some stackable guides fix the foundation plat- at, and suturing is completed. The bone grafting form to place with lateral pins, while others use a and suturing may be done while the provisional is bone borne approach for their foundations. being completed in the laboratory. The provisional is now seated and occlusion evaluated and Surgical Tools Used with Stackable Guides adjusted (Fig. 3.54a–v). Stackable guides may be used with the same surgical systems as fully guided surgical guides. Options That Aid Immediate These guided surgical systems and their usage Provisionalization have been previously described. Stackable guides are generally used for bone reduction guidance, implant osteotomy positionHow to Use the Stackable Surgical Guide ing, implant placement, as well as positioning the During Surgery predesigned provisional in the correct position; The stackable guide technical protocols vary the provisional is designed according to the speaccording to the specific type of stackable guide cific protocols of each stackable system. (e.g., Chrome, N-Sequence, Co-Diagnostics, etc). However, the basic surgical workflow is Limitations of the Guide positioning of the foundation component. This The stackable guides rely on accurate initial posimay be done with a lateral pin positioning guide tioning of the foundation component. If there is that uses a pilot guide type of drilling process. an inaccuracy in the positioning of the foundation The foundation component may engage this component, that error will translate through to

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Fig. 3.54 (a) This patient was planned for fixed full-arch restorations in the maxilla and mandible with immediate provisionalization. A stackable guide solution was chosen to manage the surgical and immediate provisionalization stages. (b, c) A guide to seat the foundation bar is fit to the mandibular teeth. (d, e) The foundation bar is secured to the mandible with lateral pins prior to extraction of the remaining mandibular teeth. (f) The remaining mandibular teeth are now extracted. The foundation bar is positioned in the planning software to the level that bone reduction is required. (g, h) The bone is reduced to the level of the foundation bar. (i) The surgical guide is now fit securely into the foundation bar. (j, k) The Keystone Paltop fully guided kit is used with the stackable guide to create all implant osteotomies. (l, m) The implants are placed through the stackable guide to their final position. (n) The surgical guide component is removed from the foundation bar after completion of implant placement. (o, p) The provisional restoration platform is seated securely into the foundation bar. If it does not seat passively, then

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there is bone interfering with the platform. It is critical that it seats passively. The multi-unit abutments are seated without the prosthetic platform in place. The platform is reseated after seating the multi-unit abutments. The prosthetic platform holds the provisional restoration in the planned vertical dimension and centric relation position. (q, r) Temporary cylinders are secured to the multi-unit abutments. The premade provisional restoration is seated on the restorative platform so that it fits intimately to the platform. The screw access chambers are blocked out with wooden sticks, and resin is injected around the temporary cylinders to secure the temporary cylinders to the provisional restoration. (s) The prosthetic platform holds the provisional restoration in the planned vertical dimension and centric relation. (t, u, v) The provisional restoration is finished in the laboratory filling in any gaps in the resin securing the provisional cylinders. The finished polished provisional restoration is seated on the multi-unit abutments and secured with multi-unit screws

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The Indications and Benefits of Robotic Implant Systems Haptic robotic-guided systems are indicated 3.2.3.8 Robotic Surgery for single to full-arch implant placement and A robotic dental implant system is a computer-­ for implant bone levelling. The outcome benecontrolled device used to assist in the placement fits are precise, accurate, predictable, and of dental implants. It typically includes a robotic reproducible implant placement [19]. arm that is guided by software to precisely posi- Intraoperatively, the benefits are as follows: the tion the implant in the jawbone. The system inte- device is directly connected to the patient, grates imaging technology, such as CT scans and physical guidance (haptic feedback), depth intra-oral scanning to create a 3D model of the control, and intraoperative changes along with jawbone to plan the implant placement. The goal visual, audible, and tactile feedback. The abilof a robotic dental implant system is to increase ity to perform flapless or minimal invasive surthe accuracy, consistency, and predictability of gical access is also a clear and favourable implant placement, which can lead to better out- indication for haptic robotic-guided implant comes for patients [18]. The currently available placement. The attachment of the device to the FDA-approved robotic system on the market is patient is either based on the existing teeth, or called Yomi (made by Neocis Inc) (Fig.  3.55). if teeth are of poor quality, limited structure, or The Yomi device is approved for single to full-­ not present, a bone-borne device is placed. In arch implant placement and bone levelling. This the Yomi system, these are called Yomi link type of robotic system gives the surgeon real-­ teeth (YLT) or Yomi link bone (YLB) time feedback. This is also known as haptic guid- (Figs. 3.56 and 3.57). The planning software is ance. Robotic haptic guidance implant placement proprietary to the Yomi system and not comallows the surgeon to follow the alignment and patible with any other systems available. A trajectory to the planned implant placement. It CBCT is necessary for implant planning with a will restrict all movements to the surgeon except field of view documenting the planned surgical for occlusal to apical movements (up and down). site. The software system allows for complete The apical movement is limited and restricted to visualization of teeth, roots, nerves, sinuses, the inferior aspect of the implant planned and inferior alveolar nerve mapping. A CBCT position. can be obtained and used preoperatively for the implant positioning as well as the positioning and orientation of the provisional restoration.

Fig. 3.55  The Yomi robot with the key components labelled is necessary to perform full-arch implant placement

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Fig. 3.56 (a, b, c) Yomi link bone which is used to connect the patient to the patient tracking arm to place mandibular implants. Bone screws can be visualized to

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securely connect the patient to the Yomi link bone. These are placed below or in between planned implant sites

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Fig. 3.57 (a, b) 2 Yomi link bones connected to the patient: one in the maxilla for placing maxillary implants and one to the mandible for the mandibular implants.

Bone screws can be visualized connecting the patient to the Yomi link bone for the maxilla and mandible

preplanning, but a day of surgery CBCT scan must be obtained to align the robot with the physical guidance to the patient. Implant and prosthetic planning are complete to the robotic planning software. The prosthetic planning is either through a prosthetic library or using a dual-scan approach.

Data Necessary for Robotic Implant Placement The data necessary is the same as for guided surgery; however, there needs to be physical connection of the robot to the patient. With robotic-guided surgery, a day of surgery CBCT must be obtained. This would allow for a patient to be seen for a con-

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sult and surgery all in the same day if desired. However, most implant patients are seen initially for a consult and then scheduled for surgery at some point in the future. The approach moving forward will be based on two appointments. On the patient’s first appointment, photos and a CBCT would be obtained from the implant site. The site would be evaluated and considered for implant placement regardless of modality to place the implant. Volume of bone and quality of soft tissue are all factors to consider. The site must be evaluated from a prosthetic approach. One would collaborate with the restorative dentist and approach the overall treatment plan similar to freehand, guided, and dynamic guidance surgery. After establishing candidacy of the patient for proper prosthetically placed implant(s), the patient can be scheduled for surgery.

Surgical Tools Used with Robotic-Assisted Surgery Robotic surgery can be accomplished with any dental implant system. The handpiece and drill base are specific to the robotic system and cannot be interchanged. In addition, the YLT and YLB are necessary. Whichever device is used must be firmly attached to the patient. Even the slightest amount of movement will result in suboptimal accuracy. If the YLB or YLT is loose, it must be reconnected to the patient and the process repeated. There is a specific handpiece as well for bone levelling. Both the implant and straight handpiece for the robot are tested and specific only for that robot. They are not interchangeable to other systems. While in surgery the clinician will be able to perform the osteotomy and implant placement with their eyes on the surgical field.

Surgical Planning Considerations (Surgical, Prosthetic) Surgical planning for robotic implant placement is the same as fully guided or dynamic guidance. The ability to accomplish the plan starts with appropriate data. Poor-quality CBCT or prosthetic plan will result in a less than optimal outcome with robotic implant surgery. The planning considerations have been previously described.

How to Use the Haptic Robotic Implant System On the day of surgery, either a YLB or YLT is placed. In planning a single or multiple implants, the YLB would be placed (Figs.  3.56, 3.57 and 3.58a, b). The YLB or YLT is placed on the arch where the implants are to be placed. If implants are planned for both the maxilla and mandible on the same day, the “link” would be placed on both

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Fig. 3.58 (a, b) Fiducial array in place on a YLB and ready for scanning. The dual-arch YLB is in place after extractions and is now prepared for implant placement

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arches. The YLT is attached to the dentition using a polyarylamide (Ixef). The YLT is attached to the patient using at least three bone screws. The screws are 2.0 mm × 16,18, or 20 mm long with consideration of where the dental implants will be placed. These screws can be placed monocortically or bicortically. Bicortical will ensure a higher level of osseous stability to the YLB (Figs. 3.56, 3.57 and 3.58a, b). The bone screws should be apical as possible but balancing engaging a quality of bone to establish stability for the link. Once the YLB or YLT are placed and stable, the fiducial array screwed on and attached to the YLT/YLB for the arch having surgery and a CBCT is taken. The fiducial array is unscrewed off the YLT/YLB.  The CBCT is imported as dicom format into the Yomi planning software. The data goes through postprocessing and adjudication. If a preplan was done, the plan is imported and aligned to the day of surgery scan. In addition, a dual-scan technique can be utilized (Fig. 3.59). This is similar to what was discussed previously in the guided surgery section. Implants are placed in a traditional fashion and drilling protocol that the surgeon is comfortable using. Once the surgeon is ready, a known landmark must pass a landmark test. A site on the CBCT plan is cross-referenced clinically to assure accuracy and consistency. Every bur placed into the handpiece and used in surgery must be measured for length, as the width is known (Fig.  3.60).

Fig. 3.59  Dual-scan protocol showing the implant emergence through the transitional prosthesis. This is accomplished in the Yomi planning software

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Both these dimensions are entered into the Yomi software. The landmark must pass or the entire plan/setup is not accurate. After the landmark is passed, the implant surgery can proceed. The implants can be placed flaplessly, flapped, as well as immediately into extraction sockets. When teeth need to be removed, it is the author’s preference to have them extracted the day of implant surgery but prior to the preoperative planning CBCT.  This is to obtain a clear picture of the bone level and osseous architecture. A recent software innovation is the ability to create or approach an osteotomy using lateral access. This allows for access in those patients with small mouth openings or difficult access. As stated above every drill in the implant osteotomy prepa-

Fig. 3.60  Measuring the length of drill bite. This information is integrated into the Yomi software prior to implant drilling. This is repeated for each drilling that is attached to the handpiece

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ration sequence must be measured and properly recorded for the osteotomy site preparation to be correct (Fig.  3.60). As the surgeon is ready to move the robotic arm, the system is placed in free mode which allows the surgeon to approach the implant site. Upon close proximity to the site, a verbal command of “guided” is stated to the driver. The driver is the assistant or technician who will carry out the verbal commands of the surgeon and data enter the commands using mouse clicks and/or keystrokes into the computer that is controlling the Yomi robot. In the guided position, the surgeon moves the handpiece into its ultimate locked position by angulating or rotating the handpiece under direct visualization as seen on the Yomi computer screen (Fig. 3.61). As the locked position is confirmed, auditory signalling of beeps directs the surgeon that the final position has been reached (Fig.  3.61). At that time the handpiece is “locked on”, meaning in the exact three coordinates that the implant was planned for that implant site (Fig. 3.62). Once the proper osteotomy is created, the implant is then placed. If at the time of implant drilling a change is desired by the surgeon, the plan can be altered intraoperatively within the software, and the plan adjustment will be immediate to facilitate the change. As the surgeon prepares the osteotomy, visual, auditory, and tactile information is delivered to the surgeon. Once the handpiece is “locked on” to the planned implant position, the

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Fig. 3.61 (a, b) Demonstrating the guided position of the handpiece and then approaching the “locked-on” position. Figure 3.60b shows the implant drill aligned with the tra-

Fig. 3.62  Shows the patient tracking arm connected to the mandible. Implant handpiece with drill in place

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jectory of the planned osteotomy. The drill is active in the osteotomy

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osteotomy is completed based on their drilling protocol to proper width and depth. Upon completion of the implant osteotomy, the implant is delivered on a standard implant mount. Prior to placement the distance from the top of the implant is entered into the Yomi. Insertion torque and RPMs for implant placement are based on the discretion of the surgeon. This sequence is repeated for each implant or one drill can be used on all sites or variations of such. Once the implant(s) are in place, final site verification should be performed to assess if any shifting occurred to the YLT or YLB.  The Yomi link device would be removed. At this point next steps would be based on surgeons/restorative dentist desires; either immediate loading protocols or cover screws or healing abutments would be pursued. A postsurgical CBCT would follow for confirmation of the synergy between plan and actual treatment (Fig. 3.63a, b). A recent addition to the robotic implant system is the ability to perform robotic-assisted bone levelling using the Yomi under haptic guidance. In the planning software, a bone levelling plane is established. The handpiece utilized for this approach is a straight handpiece 1:1 aspect ratio. The boundaries are confined by the surgeon’s area to bone level. The boundaries are manipulated in the software and executed by the surgeon in similar fashion to the implant placement. Landmark site verification must pass as in the implant placement algorithm to ensure proper spatial relationships between the Yomi and the patient. The Yomi software aligns the patient in space as the clinician identifies the same land-

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mark in the clinical setting. A known landmark must adjudicate clinically. If the clinical reference and the software reference point do not coordinate, the bone levelling sequence should be aborted based on the dataset. If it is the clinician’s desire to use bone levelling robotically and there is a mismatch, the data gathering and adjudication must be repeated and passed before proceeding to the robotic haptic-assisted levelling. The bur length is measured prior to landmark check. Currently, only one bur is FDA cleared for use in this approach. Upon completion of the bone levelling, the handpiece is changed to the implant handpiece, and the implant workflow described above would be executed.

3.2.3.9 Real-Time Dynamic Guidance Real-time dynamic navigation for implant placement utilizes an implant system that uses augmented freehand to optimize implant placement to improve outcomes, improve implant stability, and reduce surgical time. The surgical technique uses a device which generates a 3D visual implant plan and visual feedback as the implants are placed into the jaw bone (Fig. 3.64) [20]. One of the benefits is the ability to guide the placement of dental implants in real time during surgery. The technology includes a surgical navigation system that uses 3D imaging and real-time tracking to guide the implant placement, allowing for more accurate and precise placement of the implants. The goal is to deliver better outcomes for patients, such as improved implant stability, reduced surgical time, and less trauma to surrounding tissue.

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Fig. 3.63 (a, b) Prosthesis with projection of the implants through the scanned position of the teeth. Postoperative CBCT showing the position of the dual-arch implant reconstruction

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The Indications and Benefits of Real-Time Dynamic Guidance Systems The technology allows the clinician to accurately and precisely place and implant(s) in the 3D arena [21]. Real-time navigation can be particularly useful in cases where the patient has a complex jaw anatomy, limited jawbone, or other anatomic challenges that may make traditional implant placement more difficult The use of real-­ time navigation can be beneficial for guided ­surgery, where the surgeon uses a preoperative plan to place the implant in a specific location and orientation. Real-time navigation can be used to place immediate-load dental implants, which are loaded with a prosthetic tooth or bridge immediately after placement. Data Necessary for Real-Time Dynamic Guidance Implant Placement The data necessary for dynamic guidance is similar to guided and robotic implant placement as has been previously described. Surgical Planning Considerations (Surgical, Prosthetic) Surgical planning for robotic implant placement is the same as fully guided or robotic implant placement. The ability to accomplish the plan starts with appropriate data. Poor-quality CBCT Fig. 3.64  Surgical implant is facilitated through real-­ or prosthetic plan will result in a less than optimal outcome with robotic implant surgery. The time dynamic navigation such as the example below planning considerations have been previously described. X-Nav and Clarinov are two brands of real-­ time dynamic navigation systems for dental implant placement. They are computer-aided surgery systems that use 3D imaging and real-time tracking to guide the placement of dental implants. They both work with a variety of implant systems and are designed to work both traditional implant placement and guided surgery protocols. The system is intended to improve the accuracy and precision of implant placement, which can lead to better outcomes for patients, such as improved implant stability, reduced surgical time, and less trauma to surrounding tissue.

Surgical Tools Used with Real-Time Dynamic Guidance Implant Placement Real-time dynamic guidance systems use infrared cameras or optoelectronic computer navigation to track in the fiducial markers. The technology employed by the existing optoelectronic CA navigation devices onto the market is based on either visible light or infrared stereoscopic cameras (Fig.  3.65). There are over 18 devices currently available that use varied technology to accomplish real-time dynamic guidance. Optoelectronic navigation devices require a continuous direct line-of-sight of the fiducial markers to ensure consistent accuracy.

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Fig. 3.65  Example of such visible light or infrared light is seen below with clear line of sight to the sensors

How to Use the Real-Time Dynamic Guidance Implant Placement The day of surgery a tooth or bone-borne device specific to the system being used will be attached to the patient. The patient then has a CBCT taken with the tooth or bone-borne device/fiducial array in place. For some systems the teeth-borne device can be created prior to the day of the implant surgery. The digital tomogram is exported from the CBCT in a DICOM file format and imported into the CA navigation device for planning of the surgical implant placement. The software planning module of the CA navigation device enables the clinician to determine the desired implant size, location, and angulation. Both radiopaque teeth

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or dual scanning with intraoral scanning are options to use to develop prosthodontically driven treatment planning. The calibration to register the spatial relationship between the surgical field and the drill tip position and angulation of the drill is done based on protocols dependent on which CAR navigation device is being used. Visualizations of the drill relative to the CBCT image of the patient’s anatomy from various perspectives that are native to the CA navigation system were conducted. Recalibration is done from precision to twist and between different twist drills in the drilling sequence. Dynamic tracking and navigation of the surgical tool are ­accomplished by utilizing a stereoscopic camera and fiducial markers that maintain a rigid relationship to the surgical field and to the surgical tool used for osteotomy (Fig.  3.65). The operator’s navigation of the surgical tool relative to the preplanned implant site location can then be guided by both visual and auditory means. There are differences in the calibration methods specific to each CA navigation system. The procedure is performed using either flapless or a full-thickness mucoperiosteal flap at the intended surgical site(s). The osteotomies are prepared according to the implant manufacturers’ protocol. The drilling handpiece is not proprietary to the CA navigational system implant surgery. As the osteotomy is prepared, the surgeon visualizes the cross-hairs on the digital screen display to ensure they are within the confines of the plane (Fig. 3.66a, b). The handpiece and surgeon have complete freedom in all directions as the osteotomy is prepared. There are no boundaries or constraints within the CA navigational system. The feedback is both visual and auditory. These systems do not have physical or haptic feedback. There is the feasibility to make intraoperative adjustments to the plan. Bone levelling in many of the CA navigational devices is another option as well.

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Fig. 3.66 (a, b) Picture represents a surgeon’s view of key three-dimensional views for implant placement and the handpiece and array. As the handpiece is moved, real-­

3.3 Conclusion Surgical guides for surgical guidance during implant surgery can take many forms. They should not be used as a replacement for surgical skill and understanding. They should be used to help predictably implement a well-thought out surgical and prosthetic plan. They will produce efficiency and generally allow for a more minimally invasive procedure. They can aid in simplifying the immediate provisionalization procedure. The clinician should be prepared and have the ability to make real-time changes during the surgical procedure even when using a surgical guide. Computer-generated surgical guides are dependent on good CT scan data and iOS (or lab scan) data. Inaccurate data will produce a surgical guide that will not guide the clinician to the planned implant position. Computer guidance is not a replacement for surgical skill, understanding biology, or expertise and experience to make real-time decisions during surgery and implement them real time.

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References 1. Yogui FC, Verri FR, de Luna Gomes JM, Lemos CAA, Cruz RS, Pellizzer EP.  Comparison between computer-guided and freehand dental implant placement surgery: a systematic review and meta-­ analysis. Int J Oral Maxillofac Surg. 2021;50(2):242– 50. ISSN 0901-5027. https://doi.org/10.1016/j. ijom.2020.08.004. 2. Gargallo-Albiol J, Barootchi S, Marqués-Guasch J, Wang HL.  Fully guided versus half-guided and freehand implant placement: systematic review and meta-analysis. Int J Oral Maxillofac Implants. 2020;35:1159–69. https://doi.org/10.11607/ jomi.7942. 3. Becker CM, Kaiser DA.  Surgical guide for dental implant placement. J Prosthet Dent. 2000;83(2):248– 51. ISSN 0022-3913. https://doi.org/10.1016/ S0022-­3913(00)80018-­9. 4. Weber H-P, Margvelashvili-Malament M, De Souza AB. Clinical applications of digital dental technology in implant surgery. In: Clinical applications of digital dental technology; 2023. p.  217–39. https://doi. org/10.1002/9781119800613. 5. Ganz SD.  Techniques for the use of CT imaging for the fabrication of surgical guides. Atlas Oral Maxillofac Surg Clin North Am. 2006;14:75–97. 6. Lee CYS, Ganz SD, Wong N, Suzuki JB.  Use of cone beam computed tomography and a laser intra-

3  Guided Surgery for Full-Arch Implant-Supported Restorations oral scanner in virtual dental implant surgery: part 1. Implant Dent. 2012;21(4):265–71. https://doi. org/10.1097/ID.0b013e31825e5739. 7. Ganz SD.  Computer-aided design/computer-aided manufacturing applications using CT and cone beam CT scanning technology. Dent Clin N Am. 2008;52(4):777–808. ISSN 0011-8532. https://doi. org/10.1016/j.cden.2008.07.001. 8. Hakobyan G, Grigoryan H, Manukyan M, Martirosyan T, Sahakyan H. Computer-supported implant guided surgery using 3D planning software. Bull Stomatol Maxillofac Surg. 2022;26(7):67–73. https://doi. org/10.58240/1829006X-­2022. 9. El Chaar E. Digital workflow in surgery. In: Practical techniques in periodontics and implant dentistry; 2022. p. 132–7. https://doi.org/10.1002/9781119793588. 10. Kernen F, Kramer J, Wanner L, et al. A review of virtual planning software for guided implant surgery— data import and visualization, drill guide design and manufacturing. BMC Oral Health. 2020;20:251. https://doi.org/10.1186/s12903-­020-­01208-­1. 11. Vercruyssen M, Laleman I, Jacobs R, Quirynen M. Computer-supported implant planning and guided surgery: a narrative review. Clin Oral Implants Res. 2015;26:69–76. https://doi.org/10.1111/clr.12638. 12. Klein M, et al. A computerized tomography (CT) scan appliance for optimal presurgical and preprosthetic planning of the implant patient. Pract Periodont Aesthet Dent. 1993;5(6):33–9; quiz 39. 13. Moura GF, Siqueira R, Meirelles L, Maska B, Wang H-L, Mendonça G.  Denture scanning technique for computer-guided implant-supported restoration treatment of edentulous patients. J Prosthet Dent. 2021;125(5):726–31. ISSN 0022-3913. https://doi. org/10.1016/j.prosdent.2020.03.034. 14. Meloni SM, De Riu G, Pisano M, Tullio A. Full arch restoration with computer-assisted implant surgery and immediate loading in edentulous ridges with dental fresh extraction sockets. One year results of 10 consecutively treated patients: guided implant surgery and extraction sockets. J Maxillofac Oral

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4

Digital Workflows in Full Arch Implant Prosthodontics Faraj Edher, Sundeep Rawal, and Saj Jivraj

Abstract

Treatment of edentulous patients with implant-­ supported restorations presents significant challenges for clinicians in meeting high patient expectations for aesthetics, phonetics, form, and function. With the introduction of innovative digital technologies into clinical practice, the delivery of implant-borne prosthetics has been significantly advanced. This chapter describes the six phases of the digital workflow, namely, preliminary digital data acquisition, treatment planning in software, surgical execution with guidance, definitive data acquisition, functional verification, and delivery of the definitive restoration. We highlight the benefits of digital technologies, including precision, predictability, cost and time savings, and improved patient outcomes. The chapter also covers specific aspects of the digital workflow, such as obtaining IOS scan F. Edher Digital Dentistry Institute, BC Dental Study Club, University of British Columbia, Vancouver, BC, Canada S. Rawal (*) Implant Support Services, Aspen Dental, Chicago, IL, USA

data, CBCT imaging, facial scans, adjunctive photography, and the use of surgical guides, CAD/CAM, and digital impressions. Additionally, the chapter describes the use of different types of guided implant placement and the functional verification process and provides an in-depth overview of the digital workflows in full-arch implant prosthodontics and highlights the benefits of these technologies for both clinicians and patients. The delivery of tooth- and implant-borne prosthetics has been significantly advanced by the rapid introduction of innovative digital technologies into clinical practice. These technologies allow for greater ease, cost efficiencies, and improved workflows. When detailing what is commonly known as the digital workflow, the process can be defined by six distinct phases: 1. Preliminary digital data acquisition. 2. Treatment planning in software. 3. Surgical execution with guidance (and immediate load provisional prosthetics). 4. Definitive data acquisition. 5. Functional verification. 6. Delivery of definitive restoration.

The Digital Dentistry Institute, Orlando, FL, USA S. Jivraj Anacapa Dental Art Institute, Oxnard, CA, USA

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_4

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4.1 Preliminary Digital Data Acquisition Preliminary digital data acquisition is the entry point into an entire ecosystem of digital workflows that result in precision, predictability, and cost and time savings that in turn create more comprehensive affordable solutions for patients. This phase consists of: 1. Obtaining iOS scan data. 2. CBCT imaging. 3. Facial scans. 4. Adjunctive photography or videography if needed. Intraoral scanning is one of these technologies that has significantly increased the exactness of measurement for the digital planning of patient cases. It has streamlined both the gathering of diagnostics and the predictability of results. However, intraoral scanners and digital impression systems are much more than just data acquisition. The application of intraoral scanning and the digital workflow is also highly impactful in dental

Fig. 4.1 (a) Facial scan. (b) Facial scan combined with intraoral scan

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implant therapies, especially fixed full-­ arch modalities, enabling the clinician to execute prosthodontically driven treatment plans with a reduced number of procedures. The information collected by intraoral scanners can all be managed through software tools, permitting the technician to create virtual master models that contain all essential information [1]. Highly valuable ingredients to successful outcomes then begin with a distinct coordination between the surgical and the prosthodontic treatment. The initial evaluation of the patient including the digital acquisition of facial aesthetics, digital iOS scans with digital intraoral jaw relationship records, and any adjunctive photographic images are then merged in a software with radiographic analysis utilizing three-­ dimensional CBCT scanning. All data including facial scans and intraoral digital impressions are then transferred to CAD/ CAM software (Fig.  4.1a, b) which allows for digital smile design. This is the process of identifying the position of teeth and supporting structures based on aesthetics and function in relation to the existing facial and intraoral soft tissue and bone anatomy [2].

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4.2 Treatment Planning in Software Providing clinicians with comprehensive software tools to transform the smiles of their patients, digital applications are wholly changing the dental profession. The impact of technology on the delivery of care has enabled clinicians to be increasingly more analytical and meticulous in planning and rigidly focused on the predictability of outcomes. There is no question that the impact of digital technology in a dental practice has grown significantly. Marinello states that virtually all current clinical and technical prosthodontic procedures can be supported by new digital processes and that communication between dentist, surgeon, dental technician, and patient has become markedly faster and more efficient. Most clinicians who have embraced the complete digital regiment also realize increased profitability as a result of streamlined efficiency. The technology has touched planning, designing, and manufacturing of surgical guides, provisionals, as well as fixed and removable definitive restorations. In some cases, the digital technology drives every phase of the treatment plan from diagnosis to delivery.

Fig. 4.2  Data manipulated in digital planning software

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Patients also benefit substantially from the digital revolution. Along with less time spent in the dental chair, procedures are less invasive, and costs to the doctor are generally passed to the patients, resulting in availability of care to a wider range of patient populations. Patients feel they have some participation in the planning of their treatment, positively influencing the dentist-­ patient relationship, the acceptance of care, and satisfaction with the results. Designing a smile that a patient can preview in advance of treatment has become a critical tool in case acceptance, and full-arch therapy is no exception. Clinicians recognize that emotional factors impact treatment planning and, with the assistance of software, can now incorporate intraoral scanning with 2D images and videography to overlay a restorative plan on a patient’s photograph, providing a glimpse of what can be expected from treatment (Fig. 4.2) [3]. From the 2D proposed design, utilizing intraoral scanning to create stereolithic files and cone beam CT, the design can be translated to a three-dimensional design in various software, which can then be shared with the patient (Fig. 4.3). Patient confidence and satisfaction are both increased when the scanning and design software invite them more intimately into the planning process.

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Fig. 4.3  Digital mockup

4.3 Surgical Execution: Guided Implant Placement Once the proposed design is approved by the patient, the same data can be imported into dental implant planning software to determine the position of dental implants. This is beneficial because digitally planning the treatment for the placement of dental implants is most effective when the planning is prosthetically driven [4]. This allows three-dimensional precision in placement of the implants which in turn makes prosthetic fabrication much easier. The implant-placing clinician then incorporates the appropriate files from the planning software into the guided modality of choice. Three types of guided implant placement are currently used in dentistry: static guided surgery with a printed resin or laser sintered metal guide, dynamic camera-based navigation applications, and robot-assisted dental implant placement. The onset of virtual planning has significantly advanced freehand surgical procedures, but the concept of guided surgery, which led to camera navigation and eventually robotic guidance, has enhanced the processes utilized for precise placement of implants. It has also significantly reduced the risk of damage to vital anatomical structures

such as nerves and neighbouring teeth. Additionally, guided implant placement optimizes implant position in relation to the prosthetic requirements by engaging more bone, leading to primary stability for immediate loading [5]. Indeed, as the accuracy of surgical implant placement has been shown to greatly influence prosthetic results, the precision afforded by a range of digitally based guidance technologies has been credited with enabling restoratively optimized dental implant procedures [6–9]. Stereolithographic static guides are perhaps the prevalent form of surgical guidance for implants [10]. Their clinical use, however, can be limited by both manufacturing and positioning errors, as well as by fracture or fabrication time, thus potentially increasing time to treat a patient. Moreover, static guides do not permit real-time changes to the treatment plan in response to surgical conditions while still providing guidance to the clinician [11–15]. Unlike the fixed protocols dictated by static stereolithographic resin or laser-sintered metal surgical guides, digital capabilities have emerged that allow dynamic intraoperative adjustments [16–18]. The first available dynamic systems provided “navigation,” characterized by real-time visual feedback. With navigation, the operator

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manually matches the current position of a drill intraorally with the plan model derived from cone beam computed tomography (CBCT) scans of the patient, and this is viewed on a monitor [18]. Navigation systems provide information on drill deviation with respect to position or depth; however, unlike with static guides, there is no physical prevention against excursions from the prescribed treatment plan. Therefore, navigation may still be considered an augmented “freehand” approach that is dependent ultimately on the fine motor skill of the operator (Fig. 4.4) [17, 18]. As mentioned, guided dental implant placement has been evolving since the development of physical static guides as far back as 2004 (which are still viable in practice today although with less flexibility than the current navigational and robotic options) [19]. According to Block and Emery, who are pioneers in the use of dynamic navigation, control of the depth and angulation of implants became more predictably accurate, surgeons could more consistently avoid the inferior alveolar nerve, and flap mobilization could be minimized to promote a less invasive procedure for the patient [20]. The use of navigation assists the case collaboration between the surgical and restorative clinicians in integrating the virtual plan to the orchestration of the treatment, thereby enabling the achievement of a high level of patient-specific results. Dynamic navigation has been widely adopted because it is a flexible, time- and cost-effective workflow; however, as Block and Emery further indicate, the clinician must undergo a learning curve to gain proficiency and will need to factor in training and simulation [20]. A new class of surgical dental technology, robotic-assisted dental surgery (RADS), offers intriguing novel functionalities. One of these is the concept that, in addition to providing the auditory and visual inputs of navigation, RADS is

Fig. 4.4  Navigation-guided surgery

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capable of providing physical guidance through haptic feedback. Robotic haptics function by providing directional and proportional guidance forces and constraining instrumentation trajectory in accordance with the prescribed surgical plan. Robotic surgical guidance has been in a state of continual refinement since its introduction in 2017. Because it is still in its infancy, numerous multi-centre evidence-based studies will be required to produce the anticipated superior data outcomes. Robotic guidance brought the term “haptic” into the surgical vocabulary. Haptic refers to physical guidance in addition to visual and auditory guidance during implant surgery; the software program utilizes a CBCT scan of the patient and allows the 3D planning of ideal implant positioning based on bone availability, biomechanical load, and the design of the definitive prostheses. The robotic assistance then provides the surgeon with physical guidance of the drills to the desired position, angulation, and depth. When the orientation is accurate to the plan, there is no robotic (haptic) resistance; if the drills deviate, the robot will constrain the tool axis to the planned orientation. Haptic refers to the surgeon experiencing a vibrating resistance to the normal sensations of drilling or implanting [21]. While static, navigational, and robotic guides all provide valuable digital assistance in achieving aesthetic, functional outcomes, the future of robotic guidance promises to achieve the highest degree of accuracy. Static guides run the risk of fracture and can impede the clinician’s visibility as well as access for irrigation to the osteotomy site; moreover, it is impossible to adjust the actual plan during the surgical procedure and still perform a guided surgery. Intraoperative navigation allows for clinician adjustments and provides real-time visual information through a display, although there tends to be a more rigid adherence to the digital plan. Furthermore, the procedure that is performed is essentially freehand with no physical boundary. Haptic guidance currently promises to provide the best adherence to the plan as it originates in the minds of the clinicians. One case that highlights the application of preliminary digital data acquisition, treatment

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planning in software, and surgical execution through guidance is presented below. A male patient presented with classic ectodermal dysplasia, the congenital anomaly caused by a single abnormal gene or pair of abnormal genes [22]. The typical malformation of the alveolar ridge, bone deficiency, and absence of tooth buds were evident (Fig. 4.5). Maxillofacial rehabilitation of adults inflicted with ectodermal dysplasia is most successfully accomplished through therapeutic protocols utilizing osseointegrated dental implants and advanced ceramic prosthodontics to provide aes-

Fig. 4.5  Intraoral view, patient with ectodermal dysplasia

Fig. 4.6  Digital planning of patient in Fig. 4.5

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thetically pleasing smiles [23]. The treatment plan for this patient was for implementation of a definitive prosthesis in the maxillary arch built on four implants—two in the anterior aesthetic zone and two posterior tilted implants placed adjacent to the anterior wall of the sinus (Fig. 4.6). A fully integrated digital design was created focusing on the patient’s desired outcomes of creating a highly aesthetic, natural-looking smile with ideal form and function as close to a natural dentition as possible. The smile design created using 3Shape design software and surface scanning images were merged with STL and CBCT files to engineer a virtual surgical plan, and then a pre-manufactured screw-retained fixed provisional restoration was fabricated (milled PMMA manufactured on Zirkonzahn 5 axis mills) that would function as the basis for the desired result (Figs.  4.7 and 4.8). Robotic guidance was employed to ensure the surgeon could make real-­ time plan adjustments if the bone or soft tissue contraindicated the treatment plan. The provisional was already prepared with one of the anterior abutments embedded to facilitate alignment with the remaining implants (Fig.  4.9). The patient eventually was restored in both the maxilla and mandible with four implants in each arch

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to create a functional, aesthetic smile that was expected to be enduring (Fig. 4.10). The above case mentions immediate loading during the surgical execution phase with a full-­ arch fixed provisional prosthesis. In the mid-­ 1990s, implantology science was substantially streamlined through experimentation with immediate loading of dental implants. A significant development was the shifting of focus to a conversion prosthesis, fabricated to serve as a prototype of the definitive prosthesis. This innovative approach aided in the stabilization of implants in healing bone and enabled patients to have both

Fig. 4.7  Digital planning for surgical guide

Fig. 4.8  Digital planning for provisional

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immediate aesthetic gratification and a more natural return to function after surgery (Fig. 4.11). The refinement of the immediately loaded conversion prosthesis and the development of protocols to ensure longevity had far-reaching impact even beyond increased patient acceptance. The establishment of occlusion for the final restoration was always a primary concern, and patients wearing a conversion prosthesis for a minimum of 3 months afforded the clinician an opportunity to evaluate and record a highly precise occlusal relationship. Models of the existing conversion prosthesis could be articulated against the cast of the opposing dentition. The master cast with the conversion prosthesis in place was also articulated against the same opposing dentition model (Fig. 4.12). The stone cast of the conversion prosthesis then served as an ideal prototype for the final prosthesis [24]. The advantages of digital workflows have also impacted the immediate conversion protocols and possibilities. Utilizing guided implant placement, the clinician and lab team can accurately predict the final position of where the implants would be placed, allowing for more predictable methods for fabricating the provisional prosthesis. Using virtual planning software, a mucosa-­ borne static guide can be planned for the accurate placement of fixation pins. The same fixation pin

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Fig. 4.9  Provisional prepared with provisional abutment embedded

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position can be integrated into the design of additional bone reduction and implant placement static guides, in addition to a prefabricated provisional prosthesis with access holes premade to allow for intraoral pickup of the temporary cylinders after implant placement. The prefabricate provisional prosthesis can reduce the time needed during the chairside conversion as it is designed without flanges and a convex intaglio surface. This multi-component system depends on the accurate positioning of the fixation pins to ensure all other elements are correctly positioned based on the planning (Figs. 4.13, 4.14, and 4.15) [25].

Fig. 4.10  Implant-supported restorations for patient in Fig. 4.5

Fig. 4.13  Digitally generated surgical guide

Fig. 4.11  Provisional prosthesis in maxilla

Fig. 4.12  Cross-mounting of provisional prosthesis to transfer incisal edge position, occlusal plane, and occlusal relationships

Fig. 4.14  Digitally generated bone reduction guide

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Fig. 4.16  Intraoral view of bone reduction guide with adjusted bone

Fig. 4.15  Digitally generated provisional

A challenge when depending on fixation pins to seat different components is in correctly ­repositioning the fixation pins. Stackable guided systems overcome this challenge as the guide is designed to have a base component that is positioned and secured with fixation pins, onto which other components can be attached. For instance, a soft tissue-supported guide can initially be used to position the base and place the fixation pins. Afterwards, the soft tissue-supported guide can be detached from the base, and a bone reduction guide placed. This can be followed by removing the bone reduction guide and placing an osteotomy guide that connects to the base, and finally a prefabricated provisional prosthesis can be positioned in place onto the base guide with premade holes to allow for chairside conversion and pickup of the abutments to the prosthesis (Figs. 4.16, 4.17, and 4.18) [26, 27]. However, a major limitation of the stackable guide system is intrinsic in its multiple templates secured through the same anchor pin base sites and the related errors that may accumulate during their positioning. Static guided surgery accuracy is related to type of support, with tooth-supported template more accurate than tissue-supported. Bone-supported template are the least accurate and had the highest degree of surgical invasiveness because of the need to raise a large full-­thickness flap to seat the guide on the bone surface [28].

Fig. 4.17  Intraoral view of implant placement guide

Fig. 4.18  Intraoral view of digitally designed and milled provisional

Dynamic guidance can also be utilized to create workflows for effective immediate conversion. Pozzi et al. describe a method where dynamic guided protocols are utilized to place the dental implants based on virtual planning but also to create prosthetic guide pin preparations in the bone. These prosthetic guide pins are digi-

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tally designed as attachments of the prefabricated prosthesis to be aligned and fit three to four corresponding bone recipient sites that are planned as “mini-implants”, allowing for the accurate positioning of a pre-fabricated prosthesis designed with inserts that fit into the guide pin preparations [28]. The above described methods all utilize a prefabricated provisional prosthesis with holes pre-­designed based on the planned position of the dental implants. The pickup and conversion process is still required intraorally to allow for the fabrication of a fixed provisional prosthesis. However, as guided implant placement accuracy improves, there have been reports of pre-­ fabricated bars and provisionals being made using 3D-printed models with the planned implant positions, to allow for the immediate insertion of a full-arch implant-supported provisional prosthesis immediately after implant placement. The risks associated with this workflow are that if there are any discrepancies between the implant planning and the final position of the implants, the pre-fabricated prosthesis will not fit or will not achieve a passive fit [29].

4.4 Definitive Data Acquisition The traditional treatment plan commences with extremely comprehensive analyses of the patient’s face, converting multi-angular photographs into computer-generated results that consider midline, lip lines, and even the distance between the eyes and mouth [3]. In addition to drawing very specific guidelines into the restorative plan for the clinician, contemporary software affords the patient a preview of the ­ result, which often may be the chief motivational factor for acceptance of treatment (Fig. 4.19). As discussed, an exciting innovation occurs when these digital technologies are utilized in initial diagnosis, treatment planning, and surgical execution of full-arch fixed implant therapies as the digitally designed smile can then be utilized in the definitive phase of therapy. Software allow for the provisional prosthetics to be merged with new digital data and translated to harmonize the

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position of the teeth with the patient’s face [3]. Software of this nature aids in positioning maxillary central incisors, the occlusal plane, and tooth size and shape. Most importantly, because the final prosthesis can be an exact fabrication of the interim prosthesis, the patient is able to visualize the aesthetics and approve the comfort and function of the prosthesis during the preliminary therapy so that this can be easily translated to the definitive therapy with high patient satisfaction. The provisional prosthesis is therefore critical to utilizing digital workflows that allow for more efficient definitive data acquisition for the fabrication of the final prosthesis. One of the most common techniques in definitive data acquisition is the double digital scanning technique, which involves the superimposition of the digital impression of the provisional prosthesis to the digital impression of the scan bodies. The provisional prosthesis digital impression captures the prosthetic setup. The scan bodies digital impression registers the implant abutment positions and allows for capturing the soft tissue and ridge. Superimposing these two digital files requires maintaining stable common reference points between the two scans. In some cases, attached and stable mucosa such as on the hard palate can be utilized as the common reference. In situations where there is not enough stable soft tissue to reliably superimpose and merge the two digital scans, reference markers can be utilized. Several reference markers have been described by clinicians. The most commonly used are fiducial markers attached to the soft tissue on the palate or on keratinized soft tissue on the buccal aspect of the mandibular ridge (Figs.  4.20 and 4.21). When the accuracy of this technique was assessed, the superimposition showed that the 3D implant deviations between the digital and conventional stone casts were less than 90 μm. Based on these findings, the digital scans led to a potentially clinically acceptable virtual cast, which made a complete digital workflow feasible. This could decrease treatment time by making the maxillomandibular interocclusal records unnecessary and going from impression directly

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Fig. 4.19  Digital software used to convey anticipated changes to patient

Fig. 4.20  Reference markers with provisional in situ for scanning

Fig. 4.21  Reference markers in place with scan bodies

to prosthesis prototype try-in, followed by the fabrication of the final prosthesis [30].

A similar method can be utilized at the time of implant placement and immediate provisionalization if fixation anchor pins are utilized for the guided system. The double digital scanning technique and the anchor pins allow for superimposition of the STL files from the two digital scans regardless of the presence of keratinized mucosa in the mandible. The anchor pins serve as fiducial markers and facilitate the superimposition of the two STL files. This leads to one master STL file that is used for the CAD/CAM fabrication of the PMMA prototype prosthesis in a complete digital workflow [30]. An additional method utilizing scannable impression pins has been described that allows to have stable landmarks for the superimposition of the multiple STL files from digital scans but does not rely on landmarks placed on the soft tissue. The scannable impression pin is hand tightened on the multi-abutment which is a stable and reproducible landmark on the ridge. This allows for intraoral scanning at the time of the implant placement or at any other time, making this technique possible in all clinical scenarios. The main benefit of intraoral scanning after tissue healing is the better adaptation of the definitive prosthesis to the underlying tissue. Another advantage of the complete digital workflow, including the present workflow, is that it allows for complete

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new digital teeth setup, if required, using patient’s existing interim prosthesis as a reference [31]. The main advantage of all these efficient double digital scan protocols is that all the required information for the fabrication of the definitive prosthesis is acquired from the immediately loaded provisional prosthesis. The technique also allows for making maxillomandibular records simultaneously with the impression since all the diagnostic information is provided within the provisional prosthesis. Additional advantages of the current technique are all related to the digital workflow. Firstly, it may improve patient experience, removing the need for conventional impressions and long clinical procedures. Complete digital workflow reduces lab time by eliminating certain conventional lab procedures, such as fabricating stone models, mounting, and articulating. It also removed the need for teeth setups in wax and processing the prostheses. These time efficiencies in both clinical and laboratory procedures may be a financial benefit for all parties involved, including the patient [31]. Another technology that has gained in prevalence in recent years is the use of stereophotogrammetry in fixed-full arch applications. Stereophotogrammetry is a method of making precise measurements by using reference points within photographs without any contact with the measured object. It was first proposed as a way to determine misfit between dental implants and their frameworks and later found to be a suitable substitute for traditional impressions. Today, technical advances have led to commercially available stereophotogrammetry systems with high accuracy for both partially and completely edentulous patients. This high level of accuracy can now lead to eliminating the need for a verification jig after a final impression, making the process more efficient while also retaining all of the benefits mentioned for the double digital scanning technique. However, one of the limitations of stereophotogrammetry is that it still requires an intraoral scan to be taken for accurately capturing the soft tissue. In this way,

Fig. 4.22  Stereophotogrammetry markers in situ maxilla

Fig. 4.23 Stereophotogrammetry mandible

markers

in

situ

the combination of both stereophotogrammetry and intraoral scanning enhances the overall accuracy of capturing both hard and soft tissue, making it an optimal solution (Figs.  4.22 and 4.23).

4.5 Functional Verification Even though the digitally fabricated prototypes presented with accurate fit, a verification remains the standard process of the full-arch implant workflow reconstructions. This can be done in different ways such as intraoral splinting of abutments and then connecting analogues prior to the pouring of a jig cast or similarly back-pouring the conversion prosthesis after connecting analogues. A digital alternative to verification is using the

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STL data from a digital impression to fabricate a arch restorations in the coming years. New innodigitally designed milled or printed verification vations in resin technology along with jig through a complete digital workflow. As men- advancements in hardware technology will allow tioned previously, exciting innovations in stereo- clinicians to utilize 3D printing across all phases photogrammetry may eliminate the need for of the fixed full-arch digital workflow including verification of the spatial positioning of the diagnostics, provisionalization, and ultimately, implants or abutments for full arch fixed therapy. definitive restorations. However, today there is much more One case that highlights the application of the accomplished with this verification step than just digital workflow through to definitive digital verifying the spatial relationship of the implant acquisition, functional verification, and definitive positions. In addition to this information, the phase of therapy is presented below. verification also includes verifying tooth posiA patient presents for treatment with existing tion, vertical dimension of occlusion, jaw rela- maxillary posterior implants, previously osseointionship, form, and function, and this is tegrated but unrestored, and a periodontally failaccomplished by utilizing a prototype that is ing anterior dentition (Fig.  4.24). An intraoral either milled or printed prior to fabrication of the scan of both the implants (using scan bodies) and definitive prosthesis. The accuracy of fit of the the anterior teeth provided the laboratory with the generated prosthesis prototype and a definitive necessary digital files to design posterior teeth prosthesis is crucial for long-term success [32, that would harmonize with the anterior teeth 33]. Therefore, if a misfit of the PMMA proto- (Fig. 4.25). The same file was then sent for milltype prosthesis is found, the prototype can be ing or 3D printing to create the full-arch provisectioned and re-luted intraorally, and the sional restoration. It is essential that the laboratory adjusted prototype can be rescanned in the lab and copy milled into the final prosthesis. As always, the accuracy of fit of the prototype prosthesis is directly correlated to the accuracy of the full-arch digital impression, and the complete digital workflow without the need for a physical cast removed the errors introduced with 3D printing master casts and inserting implant analogues which may incorporate additional errors [34]. Many patients today choose implant-­ supported dental solutions as, along with almost instant gratification, they also provide psycho- Fig. 4.24  Patient with periodontally failing dentition and posterior implants unrestored logical security, increased self-confidence, more secure chewing ability, and improved phonetics and aesthetics [35]. Both the milling and print5 ing of prostheses have evolved, and current tech12 4 13 nology includes software that can simultaneously create the substructure, veneer, and soft-tissue replication in a single process. These manufactured prostheses, if based on accurate clinical recording and careful laboratory digitizing, can deliver a true-to-nature smile that requires no clinical adjustments [36]. Of note are innovations in additive manufacturing or 3D printing that will continue to make great strides as an Fig. 4.25  Intraoral scan and digital files for laboratory optimal manufacturing solution for fixed full- restorative design

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Fig. 4.26  Milled provisional ready to load additional implants

Fig. 4.27  Occlusal view of milled provisional

Fig. 4.28  Anterior teeth extracted and anterior implants placed

accurately digitizes the records in order to exactly replicate what was presented clinically (Figs. 4.26 and 4.27) [35]. At the patient’s second visit, anterior teeth were extracted, and additional anterior implants placed (Fig.  4.28). Abutments were connected, and then temporary cylinders were installed. The provisional was screwed into the posterior

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Fig. 4.29  Implant supported provisional placed

implants, and the anterior implants were connected to the digitally produced provisional prosthesis (conversion prosthesis protocol—the immediate loading of a non-removable interim prosthesis) (Fig. 4.29) [37]. The immediate loading of a fixed transitional prosthesis allows for adequate tissue protection and significantly elevates the patient’s level of function and self-­ esteem immediately post-operatively [37]. After the appropriate healing time, intraoral scanning of the provisional teeth, all sides, and surfaces and in occlusion with the opposing dentition took place. The provisional prosthesis was then unscrewed, and a material-based impression was made of the implant positions. Along with this one physical analogue step, a digital impression of the implants, both anterior and posterior, using scan bodies was taken, and during the same appointment, the master cast was fabricated and mounted using the existing provisional, and then scanning of the provisional on the master cast in occlusion was accomplished using the intraoral scanner. This entire body of data acquisition which was made in one clinical visit provides the body of information required for the laboratory to produce the definitive prosthesis. This is a case in which the entire treatment plan from the collection of diagnostics to the delivery of the definitive prosthesis was driven by reliance on digital technology and resulted in an effective functional and aesthetic solution that was pleasing to the patient in a minimal number of visits. Digital implant dentistry workflows have transformed the way in which care is delivered from dentist to patient. Through the six phases of the digital workflow, namely, preliminary digital

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data acquisition, treatment planning in software, surgical execution with guidance (and immediate load provisional prosthetics), definitive data acquisition, functional verification, and delivery of definitive restorations, therapies have been enhanced to meet the needs of patients in the most optimal ways possible. Acknowledgements Figures 4.20 and 4.21 provided by Dr. Armand Bedrossian D.D.S.

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115 11. Sigcho López DA, García I, Da Silva SG, Cruz LD.  Potential deviation factors affecting stereolithographic surgical guides: a systematic review. Implant Dent. 2019;28(1):68–73. 12. de Almeida EO, Pellizzer EP, Goiatto MC, et  al. Computer-guided surgery in implantology: review of basic concepts. J Craniofac Surg. 2010;21(6):1917–21. 13. D’Haese J, Ackhurst J, Wismeijer D, et  al. Current state of the art of computer-guided implant surgery. Periodontol 2000. 2017;73(1):121–33. 14. Happe A, Fehmer V, Herklotz I, et al. Possibilities and limitations of computer-assisted implant planning and guided surgery in the anterior region. Int J Comput Dent. 2018;21(2):147–62. 15. Kola MZ, Shah AH, Khalil HS, et  al. Surgical templates for dental implant positioning; current knowledge and clinical perspectives. Niger J Surg. 2015;21(1):1–5. 16. Block MS, Emery RW, Lank K, Ryan J.  Implant placement accuracy using dynamic navigation. Int J Oral Maxillofac Implants. 2017;32(1):92–9. 17. Stefanelli LV, DeGroot BS, Lipton DI, Mandelaris GA. Accuracy of a dynamic dental implant navigation system in a private practice. Int J Oral Maxillofac Implants. 2019;34(1):205–13. 18. Mandelaris GA, Stefanelli LV, DeGroot BS. Dynamic navigation for surgical implant placement: overview of technology, key concepts, and a case report. Compend Contin Educ Dent. 2018;39(9):614–21. 19. Marra R, Acocella A, Rispoli A, et  al. Full-mouth rehabilitation with immediate loading of implants with computer-guided flap-less surgery: a 3-year multicenter clinical evaluation with oral health impact profile. Implant Dent. 2013;22(5):444–52. 20. Block MS, Emery RW. Static or dynamic navigation for implant placement—choosing the method of guidance. J Oral Maxillofac Surg. 2016;74(2):269–77. 21. Srivastava R, Jyoti B, Kushwaha S, Priyadarshi PK.  Computer aided navigation for predictable dental implantology: a review. Natl J Integr Res Med. 2019;10(3):63–7. 22. Freire-Maia N.  Ectodermal dysplasia. Hum Hered. 1971;21:309–12. 23. Petropoulos VC, Balshi TJ, Wolfinger GJ, Balshi SF.  Ectodermal dysplasia: an 11-year follow-up of siblings with 2 implant treatment approaches. Implant Dent. 2014;23(4):387–93. 24. Balshi TJ, Wolfinger GJ, Alfano SG, et al. Fabricating an accurate implant master cast: a technique report. J Prosthodont. 2015;24(8):654–60. 25. Makarov N, et  al. Computer-assisted implant placement and full-arch immediate loading with digitally prefabricated provisional prostheses without cast: a prospective pilot cohort study. Int J Implant Dentistry. 2021;7:80. https://doi.org/10.1186/ s40729-­021-­00369-­0. 26. Baruffaldi A.  A suggested protocol to increase the accuracy of prosthetic phases in case of full-arch model-free fully guided computer-aided implant placement and immediate loading. Oral Maxillofac

116 Surg. 2020;24:343–51. https://doi.org/10.1007/ s10006-­020-­00849-­4. 27. Yang JW, et  al. Digital workflow for full-arch immediate implant placement using a stackable surgical guide fabricated using SLM technology. J Prosthodont. 2021;30:645–50. 28. Pozzi A, Hansson L, Carosi P, Arcuri L.  Dynamic navigation guided surgery and prosthetics for immediate loading of complete-arch restoration. J Esthet Restor Dent. 2021;33:224–36. https://doi. org/10.1111/jerd.12710. 29. Lanis A, Alvarez del Canto O, Barriga P, Polido WD, Morton D. Computer-guided implant surgery and full-­ arch immediate loading with prefabricated—metal frame-work—provisional prosthesis created from a 3D printed model. J Esthet Restor Dent. 2019;31:199– 208. https://doi.org/10.1111/jerd.12458. 30. Papaspyridakos P, et  al. Double full-arch implant rehabilitation with monolithic zirconia. J Prosthodont. 2020;29:460–5. 31. Marinis A, et al. Digital workflow for double complete arch zirconia prostheses utilizing a novel scan body. J Prosthodont. 2022;31:4–8.

F. Edher et al. 32. Chochlidakis K, Romeo D, Ercoli C, Papaspyridakos P. Complete digital workflow for prosthesis prototype fabrication with the double digital scanning (DDS) technique: a prospective study on 16 edentulous maxillae. J Prosthodont. 2022;31:761–5. https://doi. org/10.1111/jopr.13569. 33. Sinada N, Papaspyridakos P.  CAD/CAM verification for implant rehabilitation. J Prosthodont. 2021;30:651–5. 34. Papaspyridakos P, et  al. Complete digital workflow for full-arch implant rehabilitation. J Prosthodont. 2021;30:548–52. 35. Balshi TJ, Balshi SF.  A new digital solution for implant supported restorations. Inside Dental Technol. 2017;8(3):40–6. 36. Marchak CB.  CAD/CAM-guided implant surgery and fabrication of an immediately loaded prosthesis for a partially edentulous patient. J Prosthet Dent. 2007;97(6):389–94. 37. Stephen P, Thomas B, Daniel S.  Modifications of existing prosthesis with osseointegrated implants. J Prosthet Dent. 1986;56(1):61–5.

5

3D Printing Protocols in Full-Arch Reconstruction: A Complete Workflow Keith Klaus and Saj Jivraj

Abstract

The application of computer-aided design and computer-aided manufacturing (CADCAM) to full-arch implant rehabilitation has spawned new digital workflows for prosthetic design and manufacture. Technologies such as cone beam computed tomography (CBCT), photogrammetry, intraoral scanning, facial scanning, and 3D printing may eliminate many of the steps used in traditional analog workflows. As the treatment planning for full-arch implant rehabilitation is highly complex, new workflows must allow clinicians to treat the patient more efficiently and effectively; otherwise, the workflows will not be utilized. Regardless of the workflow chosen, the overall goal is to manufacture a part that may be used during treatment. 3D printing allows the clinician to manufacture study models, surgical guides, prosthetic try-ins, provisionals, etc. This chapter outlines the use of 3D printing in full-arch implant treatment to reduce cost, reduce time, and allow for a more streamlined manufacturing process.

K. Klaus (*) Private Practice, Flowood, MS, USA S. Jivraj Anacapa Dental Art Institute, Oxnard, CA, USA

5.1 3D Printing in Dentistry The combination of highly accurate manufacturing and a wide range of materials makes 3D printing suitable to dentistry [1]. Charles Hull first filed the patent for a 3D printer in 1986 [2], originally for rapid prototyping. Since then, the technology has progressed tremendously. Making its way into medical and dental applications, 3D printing has become accepted by surgeons and restorative dentists across the globe. Many practitioners are reaping the benefits of a more cost-­effective and time-saving process over traditional methods [3]. Being an additive manufacturing process, 3D printing involves layering resin materials one by one until the part is completed. With subtractive techniques, such as milling, material is removed from a block by a bur rotating at high speeds. The milling process is then limited to the diameter, shape, and length of the bur being used. 3D printing reduces the amount of wasted material, generates less noise, and cuts down on labor costs as compared to subtractive manufacturing. 3D printing is also much faster than milling [4]. For dental applications, the main differentiating factor is the material properties of the printable resin compared to a solid preformed puck. The advent of 3D printing continues to yield more efficient and cost-effective manufacturing of dental prosthetics. Where subtractive manufac-

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_5

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turing techniques such as milling have dominated the realm of full arch provisional prosthetics, additive techniques with 3D printers and their newly upgraded resins are gaining in popularity at a rapid rate. The most common additive technology in 3D printing for dentistry is stereolithography with vat polymerization, whereby resin is contained in a vat, and a light source under the vat polymerizes the resin in incremental layers. The light source may be a laser source (SLA) or digital light processing (DLP). If a print is to be used as a definitive prosthesis, the 3D-printed materials must exhibit the following characteristics as published by Schweiger et al.: 1. The material must have the ability to withstand high mechanical stress and the chemical processes inside the oral cavity. 2. The material must not release harmful chemicals while also having smooth surface contours to prohibit bacterial deposits. 3. The production must be practical, cost-­ effective, and precise at the micrometer level [5].

5.2 3D Printing Resins Recent improvements in resins and printing technologies have introduced materials suitable to implant-supported prosthetics. These new age resins are highly accurate in marginal fit. They also offer esthetics that rival their milled resin counterparts. A study conducted by Park et al. [4] showed that a printed prosthesis had a smaller internal gap than a milled prosthesis, given that ideal parameters were utilized for the print. This finding is likely due to the fact that a milled product is limited to the bur size and shape being used. The newage 3D printers along with their esthetic and functional resins has allowed the ability to 3D print surgical study models, surgical guides, try-in prosthetics, and provisional prosthetics for full-arch rehabilitations. Perhaps, the only

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downside to 3D printing resins compared to milling resins is the lack of current clinical trials [6].

5.3 Surgical Study Models Surgeons benefit greatly from having presurgical study models printed, sterilized, and available for reference during surgery. The data gets segmented from CBCT imaging and saved as an . STL file. This file then is easily printed on a 3D printer and may be used for planning the full-arch surgery, as landmarks are easily recognized. These resins are available in a variety of colors.

5.4 Radiopaque Resin for Try-In prosthesis Complete edentulous cases require using the dual scan technique [7] in order to properly align data to make a surgical guide. As there are no teeth present to serve as common references between a digital mesh file of the jaw and the CBCT scan of the jaw, an appliance is required that may relate the two files together. Partial edentulous cases and cases with a lot of metal restorations may also benefit from a dual-scan technique. The dual-scan technique involves creating a removable appliance, often a denture, with radiopaque fiducial markers. The intaglio of the appliance must be relined with a radiopaque material such as Blu-Mousse® PVS bite registration material. The fiducial markers are often radiopaque glass beads and may be attached to the denture through stickers or resin adhesive. The patient receives a CBCT scan with the altered prosthesis in the mouth, and a separate CBCT scan on just the prosthesis is taken. The files are now able to be accurately aligned and may be used for surgical guide design. New radiopaque resins allow for a printed try-in denture to become the fiducial as the radiopaque alignment object, much like a barium sulphate dupli-

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Fig. 5.1  Radiopaque try-in visible on a CBCT

cate denture [8]. The CBCT is taken with the radiopaque try-in fully seated on the respective arch, as shown in Fig. 5.1. There is no need to take a second CBCT as the resin is easily detectable, and the design is already in the CADCAM software to make the alignment predictable. The reline is also not necessary so long as there is intimate contact with the gingiva by the intaglio of the try-in prosthetic. This benefit reduced cost and removes a step in the workflow. Another benefit is the ability to digitally design and 3D print the try-in denture, lowering costs associated with lab processing fees.

5.5 Surgical Guide Resin 3D printing surgical guides allow for more complex guide manufacturing while also reducing cost to manufacture compared to milling surgical guides. Once again, burr size limits the ability to mill certain shapes. With 3D printing, higher-­resolution parts are easily achieved. In regard to surgical guides, the appliances may

have a more intimate fit while also allowing for more definition for parts and pieces such as guide sleeves and transverse pin sleeves. Most surgical guide resins are autoclavable and therefore integrate well into aseptic surgical techniques.

5.6 Hybrid Ceramic Resin Printing resin manufacturers have begun to develop hybrid resins incorporating ceramic filler to improve material properties. These new hybrid ceramic resins are significantly stronger than the earlier resins that were marketed purely for provisional restorations. Many of these ceramic resins have obtained approval for final restorations. The improvement in material properties, namely, fracture toughness, has allowed for the production of same-day immediate load full-arch prosthetics. Figures  5.2 and 5.3 show an immediate load mandibular full-arch prosthesis printed on a SprintRay 55S Pro (Pro 55S, Sprintray, Los Angeles, USA) in OnX Tough resin (OnX Tough,

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Fig. 5.2  Printed mandibular immediate provisional

Fig. 5.3  Complete denture opposing printed mandibular immediate prosthesis

SprintRay, Los Angeles, USA) hybrid ceramic resin. Print time often is under 30  min, and it takes even less time to cure, stain, and glaze. Studies are needed to compare the material properties of these hybrid ceramic printed prosthetics to their milled PMMA counterparts.

5.7 Pretreatment Planning for a Successful Digital Alignment The clinician must follow proper surgical planning beginning with prosthetic design. Patients undergoing full-arch treatment present as com-

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pletely dentate, partially dentate, or completely edentulous. Regardless of the protocol used for provisionalization, a proper and complete surgical and prosthetic workup is mandatory. The prosthesis is almost always designed in CADCAM software prior to surgery. There are numerous digital workflows available; however, most workflows require the alignment of the preand post-surgical plans in order to digitally transfer the prosthetic design so that it may be manufactured. This alignment will use a common reference point from the pre- and post-surgical scans. Reference points are qualified into two groups: hard and soft reference points. Hard reference points most commonly are existing teeth, implants, temporary anchorage devices (TADs), or composite resin. Soft tissue reference points are almost always keratinized gingiva due to their lack of movement. Using soft tissue reference points can be extremely difficult to use on day of surgery due to bleeding and inflammation. Intraoral scanners have difficulty scanning a bloody field. The rugae of the palate make a nice point for reference; however, the mandible lacks this anatomy. For these reasons, the most predictable common reference points will be hard reference points. Figures 5.4 and 5.5 show alignment using hard and soft tissue reference points, respectively. It is important to note that the blue mapping corresponds to 0 deviation between scans. The alignment was done in Exocad CADCAM software (Exocad GmbH, Darmstadt, Germany). Following alignment, the technician completes the digital design, making changes to tooth position if needed. It is important to ensure a convex intaglio surface. Once the design is complete, the prosthesis design file is sent to the 3D printer for printing. It is imperative that the surgical and prosthetic team understand which landmarks will be used as reference before surgery; otherwise, alignment may be extremely difficult and the outcome will suffer.

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Fig. 5.4  Digital alignment using soft tissue references in EXOCAD

Fig. 5.5  Digital Alignment of photogrammetry data using hard reference points pre- and post-op

5.8 Edentulous and Dentate Workflows Workflows for dentate and edentulous cases are handled differently. If a patient is dentate, there is opportunity to leave several teeth in order to align using hard reference points. When possible, it is recommended to keep teeth that may help in preserving the vertical dimension of occlusion (VDO). For these reasons, dentate workflows may be easier from an alignment and design perspective. An edentulous case will obviously require something other than teeth for alignment. In these edentulous cases, utilizing a reference denture may prove very beneficial. The reference denture may either be a patient’s existing denture or a printed denture out of try-in resin. Much like an analogue conversion, the multiunit abutments (MUAs) are fitted with healing caps. The reference

denture is then relieved so that it seats completely over the healing caps. A wash impression is completed, and an intraoral scanner is used to scan the relined reference denture in 360°. The opposing arch is then scanned. The relined denture is then reinserted in the mouth, and the bite registration is recorded via intraoral scanner. The relined denture captures both the soft tissues and hard reference points in the MUA healing caps. The single 360 reference denture scan may be split in the CADCAM software for use in prosthetic design, yielding both tooth position and a gingiva scan. A very important benefit of using the reference denture workflow allows for the operated jaw record to be scanned outside the mouth, making the scan much easier. The restorative dentist is also able to evaluate the proposed tooth position, VDO, midline, etc. of the reference denture prior to designing the day of surgery immediate prosthesis.

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5.9 Photogrammetry Being introduced by Jemt and Lie in 1994, photogrammetry’s use in full-arch implant rehabilitations has given practitioners a new tool for digital acquisition of implant positions. Through the decades, the technology has improved vastly. Jemt and Lie only described the use of the technology for extraoral use. At the time, their application was to use photogrammetry to analyze implant framework distortion [9]. Today, we are able to obtain implant position records intraorally in a matter of minutes, greatly reducing chair-­ time. Photogrammetry allows for a precise implant location, essentially eliminating the need for a physical impression. It has been well documented that intraoral scanning alone introduces inaccuracies when scanning across the full arch. While many methods are utilized to reduce this error, the most accurate workflows still very much depend on the operator and are widely deemed as unsuitable. Photogrammetry has proven to accurately record implant positions while also improving patient and dentist satisfaction. Work time is also reported to be reduced [10, 11]. The technology uses fiducials that are seated on the implant multiunit abutment (MUA) much like scan bodies. The photogrammetry device then scans these fiducials and records the data in an extensible markup language (XML) file. This data acquisition does not include any surface topography. The implant position data stored in the .XML file is used to export a geometry consistent with an existing implant component such as MUAs, healing caps, cylinders, etc. These geometries are then aligned to an intraoral scan, thus combining the datasets. The CADCAM software may then complete the prosthetic digital design using the intraoral scan data for the jaw scans and using the photogrammetry data for the implant positions. Utilizing photogrammetry in this manner allows for the design and manufacture of an implant supported fixed dental prosthesis (FDP) with a passive fit. To verify accuracy,

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Sinada and Papaspyridakos described a process to digitally design and mill a verification jig utilizing the photogrammetry datasets [12]. Photogrammetry will continue to grow in acceptance as companies are quickly bringing the devices to the full-arch market.

5.10 Printed Conversion Prosthesis There are numerous advantages to immediate loading a fixed provisional prosthesis, the conversion prosthesis [13]. A traditional conversion prosthesis begins as a denture, either an existing denture if adequate or an immediate denture if the patient is dentate. This denture is then converted to the fixed provisional by being bonded to implant temporary cylinders using acrylic resin. The process requires premade holes in the denture whereby the cylinders may fit with a gap in which to flow acrylic resin. This method of fabrication is not without its complications. Some common complications of manual conversions include poor bonding to the denture base and contamination of the acrylic resin used for bonding [14]. In a printed conversion workflow, the prosthesis is designed and manufactured after implants have been placed. The designed prosthesis is then either sent to a printer or a milling machine. Many practitioners follow a model whereby a milled polymethylmethacrylate (PMMA) provisional is delivered the day of or day after implant insertion. As milling takes longer and costs more to manufacture compared to printing, the ability to print the immediate prosthesis would cut down on time and cost. Since there are no predrilled holes, strength is improved in a conversion prosthesis that is monolithic and not attached to cylinders with acrylic resin. With either method of manufacturing, the restorative dentist has the opportunity to make alterations to the prosthetic design following surgery. An alternative to milling the provisional is 3D printing.

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As discussed previously, 3D printing has vast cost and time savings when compared to milling PMMA. Until recently, the available printed resins were prone to fracture and therefore not dependable to withstand the occlusal forces during the healing phase of full-arch implant therapy. Current resins are approaching the strength of milled PMMA.

5.11 Prototype Provisional Prosthesis Following the healing period, the converted prosthesis often requires revision prior to proceeding to the final restoration. It is imperative to revisit tooth position, shape, shade, and gingival contact. The following records are acquired for predictable prosthetic design: 1. 360-degree prosthesis scan if there were chairside alterations to the intaglio 2. Gingiva scans 3. Opposing jaw scans 4. Bite registration scans 5. Photogrammetry 6. Photography 7. CBCT These records may be obtained in one visit, thus combining many of the traditional analogue full arch workflow appointments. The lab takes this data and creates a new prototype provisional prosthesis. At this phase in treatment, a printed prototype prosthesis has significant benefits. Reducing the manufacturing time and overall cost affords the restorative dentist to offer multiple prototypes. Once the prototype prosthesis is approved by the patient, the lab only needs to copymill the design in the material of choice. The ability to copymill the design exactly provides a distinct advantage, as patients may be quick to notice even slight changes between the provisional and final prostheses.

Fig. 5.6  Before photos showing rampant decay

5.12 Case Presentation The following patient presented to our clinic requesting solutions to her dental complaints concerning rampant caries. She was experiencing pain when eating and becoming socially reclusive due to her chronic dental conditions. The patient had a medical history including Sjogren’s syndrome, pre-diabetes, rheumatoid arthritis, and obesity. The vast majority of recently placed direct composite restorations were experiencing recurrent decay, visualized in Fig. 5.6. Multiple options were presented including full-mouth rehabilitation with full coverage restorations, combination full coverage restorations with implant restorations, and full-mouth fixed implant FDPs. The patient ultimately decided to proceed with full-arch fixed implant prosthetics for her full-mouth rehabilitation. Preliminary diagnostics were recorded including CBCT, photographs, and intraoral scanning. 2D and 3D mockups were completed using EXOCAD software. The plan for the maxilla was to follow a sequenced treatment beginning with preparation of select natural teeth to retain a tooth-supported full-arch provisional. This approach reduced risks to the implants by not immediately loading. Once the teeth were prepared, an intraoral scan was completed and used to create a surgical guide that indexed to

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the natural tooth preparations as well as a printed provisional to be retained by the natural teeth. On the day of surgery, the unprepped teeth were atraumatically extracted. A tooth-supported surgical guide was utilized to complete the osteotomies. Immediate implants were placed. The gap between implant and buccal plate was grafted according to the dual-zone protocol as described by Tarnow et al. [15] with healing abutments supporting the keratinized gingiva. Implants were added in sites 2 and 15 and cover screws placed. The provisional was cemented to the natural teeth, and the patient was dismissed. The second surgical appointment involved immediately loading the mandible with a printed prosthesis (Figs.  5.7, 5.8, 5.9, 5.10, and 5.11). Using EXOPLAN, the lower jaw scan was modified by digitally extracting teeth for future implant placement. The remaining teeth were used to support a surgical guide. The planned teeth were extracted atraumatically and osteotomies completed. All implants were placed with appropriate insertion torque for immediate loading. Photogrammetry records were completed with the iCAM 4D (iCam4D, iMetric4D Imaging, Courgenay, Switzerland). The records were aligned to intraoral scans, and the provisional prosthesis was designed in EXOCAD.  Rather than extract the guide supporting teeth, a root submergence technique (RST) as described by Salama et al. was followed [16]. The provisional was printed in OnX on a SprintRay Pro 55S. The prosthesis was finished and delivered [17]. The patient was then dismissed. The patient was allowed to heal for 4 months, at which time a third surgical procedure was completed. At this surgery the teeth supporting the maxillary provisional would undergo RST.  The posterior implants were uncovered. MUAs were seated and torqued. Photogrammetry scans were again utilized to record implant position. After aligning to the intraoral scan, EXOCAD was used to design the implant-­ supported provisional. The provisional design was printed out of nanoceramic OnX resin by

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Fig. 5.7 MUA caps placed and ready for intraoral scanning

Fig. 5.8  Photogrammetry scan bodies in place

Fig. 5.9  Mandibular printed immediate fixed provisional inserted

5  3D Printing Protocols in Full-Arch Reconstruction: A Complete Workflow

Fig. 5.10  Panoramic view from CBCT radiograph following second surgery

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Fig. 5.13 Photogrammetry scan bodies in place for revised MUA selection

Fig. 5.14  Rendering from Exocad showing new design with less buccal contour Fig. 5.11  Maxillary tooth-supported provisional opposing lower implant-supported provisional

Fig. 5.15  Intraoral photo showing improved marginal height discrepancy

Fig. 5.12  Intraoral photo showing gingival margin height discrepancy

SprintRay. At this point in treatment, all implants had integrated successfully. The patient was satisfied with the provisionals; however, the gingival zeniths had discrepancy (Fig.  5.12). Site #7 specifically had a

margin that was too apical. The multi-unit abutment was changed from a straight to a 17°. A new photogrammetry scan was taken to quickly obtain the new implant location (Fig. 5.13). This record was brought into EXOCAD, and a new prototype restoration was designed with reduced buccal contour (Fig. 5.14). The 2-week followup revealed a more coronal position of the gingival tissue (Fig.  5.15). CBCT was taken to

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Fig. 5.16  CBCT analyzing distance from printed provisional to the coronal extent of the RST tooth root

Fig. 5.17  Implant-supported printed provisionals

evaluate the apical tissues of the teeth treated with RST. The CBCT was also used to evaluate the distance from the ovate pontics to the coronal portion of these teeth that underwent RST (Fig.  5.16). The patient was sent home to continue to evaluate the provisionals (Fig.  5.17).

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Fig. 5.18  Tissue healing following removal of preliminary fixed provisional

Fig. 5.19  Tissue healing following revised provisional

Following a few months, the provisionals were removed to assess soft tissue contours (Figs. 5.13 and 5.14). Once the patient was satisfied with the prototype restorations, the final definitive zirconia prosthetics were fabricated and inserted (Figs. 5.18 and 5.19).

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References

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stereophotogrammetric technique for rehabilitation with immediate loading of complete-arch, implant-­ supported prostheses: a randomized controlled pilot 1. Tian Y, et  al. A review of 3D printing in dentistry: clinical trial. J Prosthet Dent. 2017;118(5):596–603. technologies, affecting factors, and applications. https://doi.org/10.1016/j.prosdent.2016.12.01. Scanning. 2021;2021:9950131. 11. Gómez-Polo M, et al. Stereophotogrammetric impres2. Hull CW.  Apparatus for production of three-­ sion making for polyoxymethylene, milled immedidimensional objects by stereolithography. U.S. patent ate partial fixed dental prostheses. J Prosthet Dent. 4,575,330, 8 Aug 1984. 2018;119(4):506–10. 3. Vasamsetty P, et  al. 3D printing in dentistry— 12. Sinada N, Papaspyridakos P.  Digitally designed and exploring the new horizons. Mater Today Proc. milled verification jigs generated from photogramme2020;26:838–41. try data acquisition: a clinical report. J Prosthodont. 4. Park GS, Kim SK, Heo SJ, Koak JY, Seo DG. Effects 2021;30(8):651–5. https://doi.org/10.1111/ of printing parameters on the fit of implant-­ jopr.13409. Epub 2021 Aug 9. PMID: 34296484. supported 3D printing resin prosthetics. Materials 13. Balshi TJ, Wolfinger GJ.  Conversion prosthesis: (Basel). 2019;12(16):2533. https://doi.org/10.3390/ a transitional fixed implant-supported prosthesis ma12162533. PMID: 31395801; PMCID: for an edentulous arch--a technical note. Int J Oral PMC6720497. Maxillofac Implants. 1996;11(1):106–11. PMID: 5. Schweiger J, Edelhoff D, Güth JF. 3D printing in 8820130. digital prosthetic dentistry: an overview of recent 14. Swamidass R, Goodacre CJ.  Conversion of digital developments in additive manufacturing. J Clin dentures for immediate loading of complete arch Med. 2021;10(9):2010. https://doi.org/10.3390/ implant prostheses. J Prosthodont. 2021;30(S2):143– jcm10092010. PMID: 34067212; PMCID: 9. https://doi.org/10.1111/jopr.13323. PMID: PMC8125828. 33988279. 6. Della Bona A, et  al. 3D printing restorative materi15. Tarnow DP, Chu SJ, Salama MA, Stappert CF, als using a stereolithographic technique: a systematic Salama H, Garber DA, Sarnachiaro GO, Sarnachiaro review. Dent Mater. 2021;37(2):336–50. E, Gotta SL, Saito H. Flapless postextraction socket 7. Verstreken K, Van Cleynenbreugel J, Martens K, implant placement in the esthetic zone: part 1. The Marchal G, van Steenberghe D, Suetens P. An image-­ effect of bone grafting and/or provisional restoration guided planning system for endosseous oral implants. on facial-palatal ridge dimensional change—a retroIEEE Trans Med Imaging. 1998;17(5):842–52. spective cohort study. Int J Periodontics Restorative https://doi.org/10.1109/42.736056. Dent. 2014;34(3):323–31. https://doi.org/10.11607/ 8. Basten CHJ, Kois JC. The use of barium sulfate for prd.1821. PMID: 24804283. implant templates. J Prosthet Dent. 1996;76(4):451–4. 16. Salama M, et al. Advantages of the root submergence 9. Jemt T, Lie A. Accuracy of implant-supported prosthetechnique for pontic site development in esthetic ses in the edentulous jaw: analysis of precision of fit implant therapy. Int J Periodontics Restorative Dent. between cast gold-alloy frameworks and master casts 2007;27(6):521–7. by means of a three-dimensional photogrammetric 17. Peñarrocha-Oltra D, Agustín-Panadero R, Pradíes G, technique. Clin Oral Implants Res. 1995;6(3):172–80. Gomar-Vercher S, Peñarrocha-Diago M.  Maxillary https://doi.org/10.1034/j.1600-­0501.1995.060306.x. full-arch immediately loaded implant-supported fixed PMID: 7578793. prosthesis designed and produced by photogrammetry 10. Peñarrocha-Diago M, Balaguer-Martí JC, Peñarrocha-­ and digital printing: a clinical report. J Prosthodont. Oltra D, Balaguer-Martínez JF, Peñarrocha-Diago 2017;26(1):75–81. https://doi.org/10.1111/ M, Agustín-Panadero R.  A combined digital and jopr.12364. Epub 2015 Dec 14. PMID: 26662261.

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The Zygoma Anatomy-Guided Approach (ZAGA) for Preventing Complications Using Zygomatic Implants Carlos Aparicio

Abstract

The previously described systems for zygomatic implant placement, such as the original surgical procedure, the slot technique or the extra-sinus technique, promote a specific surgical technique that should be universally applied to all patients. However, different morphologies of the edentulous maxilla can be identified, both between and within individuals. Using the same type of osteotomy in all situations will often result in bulky prosthetic constructions, poor hygiene, possible sinus complications and/ or soft tissue dehiscence. We present the ZAGA protocol for decision-­ making before performing zygomatic osteotomy. The ZAGA concept aims to promote patient-specific therapy by adapting the type of osteotomy to the patient’s anatomy. Surgical treatment of the implant bed is guided by the patient’s anatomy according to specific prosthetic, biomechanical and anatomical criteria. In most cases, the so-called late complications are refrained from.

C. Aparicio (*) International Teaching Scholar Indiana University School of Dentistry, Indianapolis, IN, USA Director of Zygomatic Unit at Hepler Bone Clinic, ZAGA Center, Barcelona, Spain e-mail: [email protected]

The results of using the combination of the ZAGA concept together with the new ZAGA implant designs consistently show: –– Less traumatic osteotomy. –– Better implant stability. –– Better bone-to-implant contact together with better bone sealing around the implant neck. Additionally, the rate of late sinus complications dramatically decreases, and more anatomic rehabilitation is achieved.

6.1 Introduction The clinical scenario of the severely atrophic maxilla is represented by a very thin bone separating the nose/maxillary sinus from the overlying soft tissue. An eventual osteotomy through this minimal bone layer would barely achieve sufficient bone-to-implant contact to initially stabilize the implant (Fig. 6.1). Under these conditions, it would be difficult to achieve and maintain secondary stability—osseointegration—capable of sealing the zygomatic implant (ZI) at the level of its neck. It would then increase the risk of development of late rhino/sinus-oral communication. In a recent retrospective study of up to 22 years of duration, Vrielinck et al. [1] analysed the survival and complications associated with a total of 940 implants placed in 302 adult patients with atrophic maxilla. The survival rate of the ZI was

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_6

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a

b

Fig. 6.1 (a, b) Radiographic CBCT images processed with DTX Studio Implant planning software. The 3D and 2D images illustrate the plan for the path of the implant (a) in the position of the right second premolar and (b) in

the position of the left second premolar. The condition of extreme maxillary atrophy makes it impossible to place regular implants and dramatically reduces the chances of success of an eventual sinus graft

89.9%, and the mean time between implant placement and failure was 4.8 years. The immediate loading protocol presented a superior survival rate compared to the delayed loading protocol. Among infectious biological complications, sinusitis was the most reported (n  =  138) and occurred over a mean follow-up period of 4.5 years. Bone may resorb with function and time in patients with minimal crestal bone around the entry point of the zygomatic implant. Thus, Becktor et al. in 2005 [2] speculated that the lack of bone support would end in transverse mobility of the

long coronal part of the ZI that would facilitate orosinus communication (Fig.  6.2), which is consistent with finite element analysis studies by Freedman in 2013 [3] and 2015 [4] showing increased tensile forces on the zygoma in situations where alveolar implant support is not achieved. There is no empirical evidence as to what is the minimum amount of residual bone capable of supporting in the long term the different masticatory loads applied from the zygomatic implant to the bone-implant junction of the sinus floor. In fact, the circumstances affecting bone-to-implant contact, quality, and maintenance at the entrance

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Fig. 6.3  Intraoral clinical image showing mucosal recession around a rough surface implant. Note the signs of tissue infection associated with the recession Fig. 6.2  CBCT radiographic image showing a total occupation of the left maxillary sinus. The image also shows an implant entering the sinuses through the palatal area. The white circle highlights the lack of bone implant sealing at the level of the palatal entrance. Note also the perpendicular angle of attack of the implant in the zygomatic zone

level can differ drastically from patient to patient. Possible variables would be: –– The difference between the final diameter of the drill and the diameter of the implant –– The accuracy of implant insertion –– The quality of the anchorage/stability of the zygomatic implant allowing or not micromovements –– The quality of the soft tissue attachment –– The biotype of the soft tissue around the implant/abutment head –– The type of oral hygiene maintenance –– The history of periodontitis –– Excessive probing of the implant sulcus –– Habits such as smoking, etc. To achieve a long-lasting successful outcome in zygomatic implant surgery, attention must be paid to the prevention of late complications, particularly oral-antral or nasal communications or soft tissue recession/infection (Fig. 6.3).

6.2 Technique Evolution 6.2.1 Original Technique In the early 1990s, several reports were published on the possibility of anchoring attachments to the zygomatic bone for both nasofacial [5] and dental prostheses [6]. Subsequently, Brånemark et  al. published in 2004 [7] the first long-term follow­up study on the placement of zygomatic implants, sometimes simultaneously with on-lay bone grafts. It was after this study that zygomatic implants were considered within the scientific implant dentistry. During this study, 28 patients received 52 zygomatic implants and 106 conventional fixations. Additional bone grafting was considered necessary in 17 patients. All patients were followed closely for 5–10 years. The surgical procedure for zygomatic implant placement consisted of a “window” antrostomy in the upper lateral quadrant of the anterior maxillary wall (Fig. 6.4). The sinus mucosa was then reflected, and “no special effort was made to keep it intact”. It was thus established that the implant had to have an intra-sinusal path. According to Brånemark, “the direction of fixation of the zygoma was selected to provide optimal stability

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Fig. 6.4  Typical “emotional window” osteotomy of the original surgical technique. The implant placement required a second osteotomy since the final position of the implant, indicated by the probe, does not correspond to the position of the first osteotomy

against prosthetic requirements”. In different words, to maintain the path inside the sinuses, the implant path had a more or less palatal entry depending on whether the curvature of the maxillary wall was more or less pronounced. This longterm study by Brånemark reported three ZI failures and a 94.2% survival rate. The 5-year prosthetic rehabilitation success rate was 96%. At least 96 conventional implants ranging from 10 to 20 mm in length were placed. The success rate of the initially placed conventional implants was approximately 71%. In 2 patients out of 28, 1 of the 2 ZIs placed was disconnected from the prosthesis due to suppuration at the palatal entrance of the zygoma attachment combined with a sinus infection. Four patients had recurrent sinusitis during the follow-up time (Fig.  6.1). The treatment of these six cases was the same: an antrostomy of the inferior meatus was performed, and the results were satisfactory. Four other patients had radiographically diagnosed sinusitis with occupied but clinically asymptomatic maxillary sinuses. No treatment was considered necessary in these cases. Depending on the criteria we apply, the percentage of cases presenting sinusitis, as defined by Lanza Kennedy in 1997 [8], would be 21%, while if we also apply the radiological criteria of Lund Mackay 1993 [9], the percentage of rhinosinusitis in the original PI Brånemark study would amount to 35.7%. Due to the palatal position of the zygomatic fixations, it was necessary to thin the palatal flap

Fig. 6.5  Slot osteotomy performed before implant placement. As in the “window” osteotomy, there is a mismatch between the final position of the implant and the previous osteotomy that decreases the implant-bone contact

and remove the fatty tissue to refrain from soft tissue inflammation around the definitive abutments. Despite the palatal emergence of the prosthesis, no patient discomfort or speech difficulties were recorded.

6.2.2 The Slot Technique In 2000, Stella and Warner [10] described the sinus slot technique in a technical note with the objectives of offering a solution to the prosthodontic shortcomings of the original Branemark technique and reducing postoperative pain. To this end, the authors proposed elevating a reduced flap only to the inferior aspect of the infraorbital nerve and to the mid-inferior aspect of the zygomatic process of the maxilla. Unlike the original technique, they did not uncover the angle formed by the frontal and temporal processes of the zygomatic bone, since, in theory, the groove provided them with the direction of the implant (Fig. 6.5). Second, a reduced groove-shaped antrostomy was proposed instead of a window osteotomy. The groove was performed in the planned direction before implant placement. They reasoned that in an already highly resorbed maxilla, a sinus window, as in the original technique, may further compromise the remaining precarious alveolar bone support.

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Stella and Warner [10] also proposed a crestal entry for the zygomatic implant to achieve more anatomical prostheses. Local anaesthesia and intravenous sedation were also introduced. Although the slot technique improves minimizing antrostomy and prosthesis design, the method was also not without drawbacks. For instance, the authors did not provide any specific criteria for adopting variations within this process that would refrain from oro-antral communication when penetrating the sinuses through a too thin alveolar ridge, nor did they define possible variations in implant trajectory in different anatomic situations. Moreover, since the “slot” antrostomy is performed before implant placement, it does not always correspond to the implant shape. For the same reason, the slot may not even be necessary in the presence of concavities in the maxillary wall. In other words, the ability to seal the maxillary wall with the implant is limited.

zygomatic implant placement at the EuroPerio meeting in Madrid, Spain. This new technique, indicated in cases of maxillary wall concavity, used an external approach to the maxilla to place zygomatic implants (Fig. 6.6). The 1-year study for this new technique was first published in English literature by Ouazzani from Aparicio’s group in 2006 [11]. Migliorança et  al. in 2006 [12] published a similar approach to Aparicio’s group in Portuguese, which they called the externalized technique. In a 3-year prospective study in 2008, Aparicio et al. [13] reported the results of extra-sinus placement of zygomatic implants in 20 consecutive patients recruited from October 2004 to October 2005. The minimum follow-up period was at least 3 years. Thirty-six zygomatic implants were used, with smooth, turned titanium surfaces according to the initial zygomatic fixture design (Nobel Biocare AB, Göteborg, Sweden). According to the authors, the indication for using the extra-sinus approach was the presence of buccal concavities in the lateral wall of the maxillary sinus, which would cause an eventual intra-sinus trajectory of the zygomatic implants to lead to the placement of the implant head at a distance greater than 10 mm from the centre of the alveolar ridge. In these cases of a very concave maxil-

6.2.3 Exteriorized Technique The next step in the evolution of the technique occurred in 2005, when Aparicio’s group presented a 1-year follow-up of a new technique for a

Fig. 6.6 (a) In the clinical image, we can see how the bone remnant at the alveolar level has been used to prepare the entrance of the Straumann ZAGA Round type implant through it and not through the palatal bone. Due to the pronounced concavity of the maxillary wall, the path of the implant proceeds outside the wall until it enters the zygomatic bone. The white circle highlights the preservation of the alveolar bone to support the soft tissue

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connective fibres and thus refrain from recession. (b) The clinical image shows a Straumann ZAGA Round implant in the most anterior zone where the alveolar bone has been preserved. The posterior area belongs to a ZAGA 4 type without remaining alveolar bone, so a Straumann ZAGA Flat design has been chosen. The white circle highlights the preservation of the alveolar bone, and the arrows indicate the close bone-to-implant contact achieved

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lary wall, the implant trajectory was prepared by drilling the alveolar crest sufficiently from its palatal side, pointing towards the zygomatic arch, and without making a previous window opening in the maxillary sinus. Prioritization was given to the anatomical prosthesis on the palatal entry, enabling the implant entry to occur at the maxillary ridge. And depending on the concavity of the wall, the implant would have an “aerial path” (Fig. 6.6). On the condition of passing through a ridge sufficient in volume and architecture, the integrity of the sinus membrane was preserved, and the creation of a “window” or “slot” prior to surgery was eliminated. Maló et al. in 2008 [14] introduced a modified approach called the extra-maxillary technique that would suit all anatomies. However, it involved systematic contouring of the alveolar ridge to achieve exclusive anchorage into the zygoma bone. So when patients presented with an over-contoured anterior-maxillary sinus wall, the sinus membrane was inevitably perforated because it was in the direct pathway of the drill direction. Of the 18 patients who underwent a 1-year follow-up, 4 suffered sinus infections representing 22% of sinusitis. Further study on the extra sinus technique was published by Migliorança’s group in 2011 [15]. The authors reported a 98.7% survival rate for zygomatic implants, only two of them showed soft tissue recession, and no patients experienced sinusitis. Incomprehensibly, the success criteria used were the same as for regular implants including marginal bone height and probing depth.

6.3 The ZAGA Concept ZAGA is a philosophy and concept for the rehabilitation of the atrophic maxilla described by Aparicio in 2011 [16] and 2012 [17]. ZAGA is the acronym for “zygoma anatomy-guided approach”, which is a descriptive name that identifies a new technique and distinguishes it from previously published techniques intended to be universally applied to all patients. The ZAGA concept differs in that it seeks a specific treatment for each patient. This is so in multiple

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aspects such as the type of incision according to the biotype and amount of soft tissue: –– The surgical protocol of positioning and design of the osteotomy –– The type of drilling with lateral or perpendicular cut depending on the type of osteotomy projected –– The procedures and individualized recommendations to better preserve the bone and soft tissue in the ZICZ –– Various instruments such as drills to facilitate the surgery –– The choice of implant design that is chosen for each site There is a tendency to confuse the ZAGA anatomical classification with the “ZAGA concept” which is a philosophy that promotes first recognizing the type of anatomy of the patient in need of oral rehabilitation and then providing this patient with a specific therapy. In other words, instead of forcing the patient’s anatomy to adapt to a particular process and/or implant, the use of the ZAGA concept matches its strategies and tools according to the patient’s anatomy. Indeed, the use of the same type of technique in all anatomical situations described in the original and other protocols often results in bulky prosthetic constructions, impaired hygiene, eventual sinus complications, and/or soft tissue dehiscence. The zygoma anatomy-guided approach (ZAGA), on the other hand, aims to promote patient-specific therapy. Surgical treatment of the implant site is guided by the anatomy of that patient and that site, not by a universal “magic recipe”. Consequently, the implant trajectory can be intra-sinus, extra-sinus, or intermediate, using the maxillary wall as an additional source of anchorage (Fig. 6.7). In fact, its aim is to maximize the primary stability of a prosthesis-guided zygomatic implant, which implies a conservative osteotomy. At the same time, the ZAGA concept aims to prevent potential late complications of the procedure, such as oral-antral fistula and soft tissue recession/infection, by following the steps detailed in Table  6.1. Overall, the

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Fig. 6.7  Some clinicians mistakenly identify the ZAGA concept with the placement of externalized implants. The ZAGA concept proposes the adaptation of the path of the implant, and the osteotomy, to the patient’s anatomy. The series of clinical images that we present here shows the

different paths that the zygomatic implant can have according to the ZAGA philosophy. Note how the choice of implant design varies also in relation to the type of path. Essentially, ZAGA is a patient-specific therapy

Table 6.1 Key steps and protocols in the ZAGA concept

in 2011 [16]. He identified five basic skeletal forms of the alveolar crest complex, maxillary wall-­zygomatic buttress complex, and implant path. The classification represents the anatomical differences on the trajectory of an implant placed from the posterior premolar/molar area during its alveolar and anterior maxillary wall zygomatic path. Indeed, the ZAGA classification was intended to describe anatomic differences on the double posterior zygomatic implant trajectory (Fig. 6.8). However, it did not refer to an eventual anterior zygomatic implant passageway. Currently, the indications for zygomatic implants have been broadened since they are used not only in cases of lack of bone in the posterior maxilla but also in clinical cases of extreme anterior and posterior maxillary atrophy [18, 19]. Then, four implants anchored in the zygomatic bone ZI are placed (Fig. 6.9). In these new situations, the indication for reaching the zygomatic bone using an intra-nasal implant path, in the same manner as an intra-sinus path that was prescribed on the original technique, cannot be extrapolated. The reduction of subnasal bone volume frequently forces the surgeon to choose an extra-nasal/extra-sinus implant trajectory, preventing future complications like nasal or sinus fistula by avoiding nasal or sinus penetration. The frequent scenario in a fourzygomatic implant indication is then a very resorbed maxilla where before establishing the

– The identification of the patient’s anatomy – The determination of an implant trajectory guided by the prosthesis according to specific criteria that determine the location of the zygomatic implant critical zone (ZICZ), the antrostomy z(AZ), and the zygomatic anchor zone (ZAZ) – The selection of the appropriate minimally invasive osteotomy design for the residual anatomy preventing channel or tunnel complications – The selection of appropriate implant design for the type of osteotomy chosen – The appropriate procedures in each case to maintain the bone and soft tissue refraining from complications – The use of a systematic method to define success or failure in each rehabilitation

ZAGA concept provides clinicians with the decision criteria necessary to obtain a satisfactory and predictable outcome over time. It establishes protocols for determining the key landmarks that will define the zygomatic implant trajectory or ZAGA zones, which will be explained in the next chapter. In this way, an individualized, patient- and site-­specific implant trajectory is determined.

6.3.1 The ZAGA Classification To better understand the influence of anatomy on a prosthetically driven implant trajectory, Aparicio described the “ZAGA classification”

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Fig. 6.8  In the figure we can appreciate the different schemes that represent the ZAGA classification for zygomatic implants whose head has a posterior position at pre-

molar/molar level. The percentages show the frequency of this situation

–– –– Fig. 6.9  Clinical occlusal image showing the final position of four zygomatic implants, two anterior and two posterior. This technique is known as quad zygoma and is now sufficiently documented to be used routinely in cases of extreme maxillary atrophy. Customarily, the path and anatomical particularities found in the anterior region differ from those found in the posterior region. In this case, two Straumann ZAGA Round implants were placed in the anterior area classified as ZAGA 3 and two Straumann ZAGA Flat implants were placed in the posterior areas corresponding to a ZAGA type 4 anatomy

osteotomy, the surgeon must analyse the remaining anatomy (Fig. 6.10) to visualize balance and prevent possible late complications, such as fistula or soft tissue dehiscence/infection, related to nasal/sinus perforation or an eventual extramaxillary zygomatic implant position respectively [20].

6.3.1.1 Group ZAGA Type 0 –– The maxillary wall is flat or convex. –– Providing a minimum of 4 mm high × 6 mm wide in an adequate architecture, a circular

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osteotomy is performed through the remaining alveolar crest. The implant neck is located on the alveolar crest to minimize the risk of late soft tissue complications. A threaded circular implant section is used to seal the tunnel-shaped osteotomy. The antrostomy is placed immediately across the alveolar crest. Sinus lining integrity at the crestal level is not preserved. The implant body reaches the zygomatic bone using an intra-sinus path. The implant comes in contact with bone at the alveolar crest and zygomatic bone and sometimes at the lateral sinus wall (Fig. 6.11).

6.3.1.2 Group ZAGA Type 1 –– The maxillary wall is slightly concave. –– Providing a minimum of 3–4 mm high × at least 5 mm wide in an adequate architecture, a circular osteotomy is performed through the remaining alveolar crest. The implant neck is mostly located on the alveolar crest to minimize the risk of late soft tissue complications. –– A threaded circular implant section is used to seal the tunnel-shaped osteotomy. –– To properly reach the zygomatic bone, the drill performed the osteotomy slightly through the maxillary wall.

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Fig. 6.10  ZAGA anatomical classification and frequency percentages for zygomatic implants originating in the anterior zone. The main difference will be in the implant/

nose relationship of the anterior implant rather than the implant/sinuses of the posterior

Fig. 6.11  Intraoperative clinical image showing the drill in charge of widening the osteotomy entrance to accommodate the implant neck. Note that an “emotional” osteotomy, neither in window nor in slot, has not been performed previously. The line drawn with a pencil on the external face of the wall (white arrows), as well as the position of the retractor and the knowledge of the anatomy, will guide the surgeon in the initial osteotomy. The entire path of the implant will be intra-sinus

Fig. 6.12  Intraoperative clinical image showing preparation for zygomatic implant placement in a ZAGA type 1 maxilla. There is enough alveolar bone for an alveolar tunnel osteotomy. The maxilla is slightly convex so part of the implant body is exteriorized

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6.3.1.3 Group ZAGA Type 2 –– The maxillary wall is concave. –– The alveolar architecture is not enough to The antrostomy is placed immediately across allocate the implant neck. The final osteotomy the alveolar crest. has a channel section with floor and lateral Sinus lining integrity at the crestal level is not walls but no roof. The implant head is partially preserved. located on the alveolar crest. Although the implant can be seen through the –– An implant section in the shape of a flat arc of wall, most of the implant body has an intra-­ the circumference is preferably used to seal sinus path. the channel type of osteotomy. The implant comes into contact with bone at –– In an anterior placement, the drill avoids nasal the alveolar crest, lateral sinus wall, and zygofloor perforation to reach the zygomatic bone. matic bone (Fig. 6.12). The osteotomy is performed through the ante-

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Fig. 6.13  Intraoperative clinical image showing preparation for zygomatic implant placement in a ZAGA type 2 maxilla. The remaining alveolar bone is more sparse than in types 0 and 1. Although a tunnel preparation can be attempted (white circle), it is more advisable to refrain from perforating the membrane in this area by using a channel osteotomy from the beginning

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rior maxillary wall, displacing the initial alveolar drilling towards the buccal area. The antrostomy is placed as far as possible from the crest level. Sinus lining integrity at the crestal level is preserved. The implant can be seen through the maxillary wall, and most of the body has an extra-sinus path. The implant comes into contact with bone at the alveolar crest, lateral sinus wall, and zygomatic bone (Fig. 6.13).

6.3.1.4 Group ZAGA Type 3 –– The maxillary wall is very concave. –– The alveolar architecture is enough to allocate the implant neck in diameter. Then a circular osteotomy is performed through the remaining alveolar crest. –– The implant neck is located on the alveolar crest. –– The drill will perform a circular osteotomy following a trajectory that goes from the palatal to the buccal alveolar bone. The drill “flies” over the most concave part of the ante-

Fig. 6.14  The patient had a knife-edge anterior ridge. It was decided to remove the two affected canines. We did not remove the residual alveolar bone. Note (white arrow) the implant crossing the alveolus of the canine. The middle part of the implant body is floating without osseous contact

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rior sinus wall to penetrate the zygomatic bone.1 A threaded circular implant section is used to seal the tunnel-shaped osteotomy. The antrostomy is placed as far as possible from the crest level. Sinus lining integrity at the crestal level is preserved. Most of the implant body has an anterior extra-sinus path. The middle part of the implant body is not touching the most concave part of the wall. The implant comes in contact with bone in the coronal alveolar and apical zygomatic bone (Fig. 6.14).

6.3.1.5 Group ZAGA Type 4 –– The maxilla and the alveolar bone show extreme vertical and horizontal atrophy. In a quad case, the reduction of sub-nasal bone volume forces the surgeon to an extra-nasal/ extra-sinus implant pathway. –– The alveolar architecture is not enough to allocate the implant neck. The final osteotomy For classification procedures, borderline situations where a pronounced maxillary wall concave curvature is concomitant with a zygomatic implant neck diameter too close to the remaining alveolar thickness that is not capable of completely covering the implant neck, but most of it is buried into the alveolar bone, were also classified as ZAGA A-3. 1 

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Fig. 6.15  Intraoperative occlusal image showing a typical ZAGA type 4 situation in the posterior areas. Two Straumann ZAGA Flat implants have been selected to close the channel osteotomies

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has a channel section with floor and lateral walls but no roof. The implant head is located partially buccally of the alveolar crest. The antrostomy is placed as far as possible from the crest. The osteotomy aims to “sink” the implant as much as possible while respecting sinus lining integrity at the crestal level. The drill has arrived at the apical zygomatic entrance following a path outside the sinus wall. Most of the implant body has an extra-sinus/ extra-maxillary path. Just the apical zygomatic part of the implant is totally surrounded by bone. The implant comes in contact with bone in the zygomatic bone and part of the lateral sinus wall (Fig. 6.15).

6.3.2 The ZAGA Minimally Invasive Osteotomy In the ZAGA concept, two osteotomies are not used as in the previous techniques. In the original or slot technique, the first osteotomy had a visualization purpose, for example, the window osteotomy or the slot osteotomy. This “emotional” osteotomy was performed before a second osteotomy necessary for implant placement and is generally not necessary because, due to the sinuous anatomy of the maxillary-zygoma complex, the window or the slot does not allow visualiza-

Fig. 6.16  The white arrows show the detail of the “emotional” osteotomy in “window” performed by the surgeon before the osteotomy necessary to place the implants. The circles indicate that the apical zones of the implants are designed to achieve maximum stability by incorporating a rough surface, threads, and tapered profile, which have been left in the air outside the bone. In other words, the window osteotomy has rendered the implant less effective

tion of the apical drilling point (Fig. 6.16). On the contrary, the ZAGA concept performs only one osteotomy: the one necessary to place the implant and it does it by under-preparing the bone at all levels. In this way, the osteotomy, according to the ZAGA concept, achieves greater stability and better sealing of the implant by increasing the contact of the implant with the bone. That is why it is known as minimally invasive ZAGA osteotomy. To preserve the integrity of the sinus and refrain from soft tissue complications, implant osteotomy can be performed as a tunnel or channel depending on the architecture of the residual alveolar bone forming the sinus floor and the contours of the maxillary lateral wall. Bone-to-­ implant contact or support should be achieved throughout its path, especially at the alveolar level, for better load distribution in both tunnel and channel osteotomy techniques. As a general rule, the volume and architecture of the alveolar/basal process and the curvature of the anterior maxillary wall will define the coronal position of the implant. In other words, if an intui-

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tively adequate thickness of circumferential alveolar bone support can be found at the neck of the zygomatic implant (i.e., greater than 4  mm in height and 6–7 mm in width) when exploring the residual ridge, the first choice should be a tunnel-­ type osteotomy through that bone. The ZAGA concept proposes to call this circular-shaped osteotomy, performed through sufficient bone, a “tunnel osteotomy”. The reason is that at the coronal bony entry, it has a floor, side walls, a more or less complete roof, and an exit on the opposite side. ZAGA concept recommends opting for the “tunnel osteotomy” whenever possible, regardless of the curvature of the maxillary wall. The rationale is as follows: a ZI, with an adequate threaded neck profile, surrounded by sufficient bone at the coronal entry and stabilized by an adequate apical zygomatic and coronal prosthetic anchorage, will achieve osseointegration at the neck level. This will be able to seal the sinus entrance in the long term. A tunnel can be achieved depending on the existing architecture of the remaining alveolar bone at the chosen entry point. This type of osteotomy is typical of ZAGA type 0, 1, and 3 situations of the maxillary wall accompanied by adequate thickness and geometry of the alveolar bone support circumferential to the implant neck (Fig. 6.17). The tunnel osteotomy, by definition, has a circular profile entrance that must be sealed by a round section implant. When the alveolar bone thickness/architecture is inadequate to achieve at least 3–4 mm of circular bone-to-implant contact, implant placement following the ZAGA concept is shifted buccally to refrain from late oro-antral communication or sinus infection. In these cases, the position of the antrostomy is moved as far as possible from the level of the ridge to maintain the integrity of the sinus membrane at this point. The osteotomy is performed by preparing, in the remaining alveolar bone and in the maxillary wall, a space in the form of a channel capable of accommodating most of the circumference of the implant (Fig.  6.18). This type of osteotomy, unable to provide complete coverage of the implant’s midbody and neck, is referred to by the ZAGA concept as a “channel osteotomy”. This groove is prepared in the coronal alveolar bone and some-

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Fig. 6.17  The white arrows show the tunnel-shaped osteotomies performed in the remaining alveolar bone. Note that the direction of attack comes from palatine obliquely since the amount of bone we would find in a direction perpendicular to the ridge would be insufficient to stabilize an implant. It has been possible to preserve the integrity of the membrane by moving the antrostomy away from the coronal critical zone

Fig. 6.18  Both osteotomies have the shape of a channel. In both, the amount of residual alveolar bone is extremely small. Therefore, it was decided to move the entry buccally. The transparency of the membrane (arrow) indicates that we have to stop the depth of the preparation in order not to tear the membrane

times also in the lateral maxillary wall and zygomatic buttress. The depth limit for excavation of the channel is the integrity of the membrane at this level. Like a waterway or channel, the sulcus has a floor and lateral walls with more or less height but no ceiling. The indications for the two types of ZAGA osteotomy are described in Table 6.2 (Fig. 6.19).

6  The Zygoma Anatomy-Guided Approach (ZAGA) for Preventing Complications Using Zygomatic… Table 6.2  The ZAGA osteotomy types. Description and indications ZAGA tunnel osteotomy: 1. Intra-sinus path: adequate residual alveolar bone volume below the maxillary sinus (e.g., in ZAGA 0 and 1)  (a) Osteotomy has an entry point to the maxillary sinus through sufficient alveolar bone which is used to embrace the implant neck  (b) Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature  (c) Antrostomy is placed at the sinus side of the tunnel osteotomy  (d) Additional facial (window) antrostomy or sinus lift is not recommended (e.g., in ZAGA 0)  (e) Straumann ZAGA® Round implant section is recommended 2. Extra-sinus path: residual alveolar bone below the maxillary sinus has a triangular architecture, inadequate to host a regular implant, and is concomitant with pronounced maxillary wall concave curvature (e.g., in ZAGA 3 and some 2 types)  (a) Osteotomy has its entry and exit points within the residual alveolar bone  (b) Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature  (c) Antrostomy location is determined by the number of implants to be placed and the curvature of the zygomatic buttress  (d) Straumann ZAGA® Round implant section is recommended ZAGA Channel Osteotomy Advanced alveolar bone atrophy. Alveolar bone has inadequate volume and architecture to host the neck of the ZI (e.g., in ZAGA 4 and some 2 types) – Osteotomy is buccally offset through the residual of the alveolar bone and maxillary wall – Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature – Antrostomy location is placed as far as possible from the ZICZ, in relation to the number of implants to be placed and the zygoma buttress curvature – Straumann ZAGA® Flat implant section is recommended

The results of the so-called ZAGA concept were described in 2014 by Aparicio et al. [21] in a controlled study. In the aforementioned comparative study, long-term results (survival rate, implant stability, sinus conditions, prosthesis

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design, soft tissue sealing, etc.) were reported. For comparison, a cohort group of 22 consecutive patients treated with the original classical zygomatic technique and followed for at least 10 years was used as a control [22]. Their results were compared with those obtained in another cohort group of 80 consecutive patients treated with the ZAGA protocols and with a mean follow-up of 4.62 years. All patients included in the test group had at least 3 years of prosthetic follow-up, including a presurgical comparison and a final CT scan. Of note, both groups of patients received the same implant design: the original Brånemark zygomatic fixation with a threaded machined surface (Nobel Biocare AB, Gothenburg, Sweden). The results showed that both classic and ZAGA procedures achieved similar positive clinical results with respect to implant survival and implant stability. However, patients treated with the ZAGA concept had immediate rehabilitations minimizing very significantly the risk of pathology associated with the maxillary sinuses compared to the original technique. In addition, less bulky, more comfortable, and easier-to-clean prostheses were achieved. Recently, Clarós et al. [23] published a study on the prevalence of maxillary sinus alterations after zygomatic surgery. The study also compared the differences in sinus alterations between the intra-sinus and ZAGA approaches. The retrospective study included 200 patients restored with zygomatic implants with a follow­up of at least 5 years after surgery. The surgeries were performed between 2004 and 2014 at different centres. Patients were divided into two radiological groups according to the type of surgical procedure: the first group, Group 1, original zygomatic intra-sinus surgical technique (OI-­ ST), included 40 patients with 80 implants placed with the classic intra-sinus approach, including those placed through sufficient bone of the floor of the maxillary sinus, and the slot technique. The second group, Group 2, included 160 patients treated with 320 zygomatic implants placed according to the ZAGA concept. To facilitate an unbiased radiological classification, patients with ZAGA type 0 were excluded from the ZAGA Group.

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Fig. 6.19  Diagram representative of the importance of implant design. Both for a tunnel osteotomy and a channel osteotomy, the threads will be necessary to transmit the

masticatory forces to the bone in order to achieve and maintain the osseointegration and, therefore, the bone at the ZICZ level

All patients included in the study underwent at least one CT scan preoperatively and another at least 5 years postoperatively. The results showed a statistically significant increase in radiographic evidence of sinusitis in patients after zygomatic implant surgery. This indicated that zygomatic surgery may cause sinus alterations. A significant increase in the prevalence of sinus symptoms was also found in the OI-ST with respect to the ZAGA concept.

6.3.3 The ZAGA Flat and ZAGA Round Zygomatic Implants: The Story of a Breakthrough

alveolar bone, there are few, if any, implant designs that suit the needs of zygomatic implant patients with severely atrophic jaws. This section describes the origins of the “adapted to the anatomy” new portfolio of zygomatic implants designed by Carlos Aparicio. The Straumann company is currently the universal distributor of the ZAGA® Round and ZAGA® Flat zygomatic implant designs. These implants feature several unique distinct attributes, which makes them a major step forward for the growing field of zygomatic implant rehabilitation. The invention, design, industrial technology transfer, and commercialization are all textbook examples from beginning to end.

Because a typical zygomatic implant trajectory involves the atrophic alveolar bone, maxillary wall, and zygomatic bone, it presents greater peculiarities than an implant trajectory in a conventional implant indication. However, although numerous implant designs can be used in residual

6.3.3.1 The Clinical Points to Solve Created with the clinical needs of the end user in mind, this portfolio represents, for commercial reasons, a reduction of the original larger portfolio. The goal was to make it possible for the surgeon to manage different unsolved problems.

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–– The management of an eventual limitation of the surface area suitable for anchorage in the zygomatic bone, especially when performing quadruple surgeries –– The problem of overly wide implant transporters that often interfere with the bony ridge, so valuable for soft tissue maintenance –– The interference of wide implant transporters with anterior hard bone or another implant when placing implants in the opposite quadrant of a compromised maxilla –– Difficulty in obtaining primary stability in certain zygomatic bones with low quantity or quality –– Difficulty in anchoring and stabilizing soft tissues at the ridge level –– The need for a threaded design to maintain crestal alveolar bone –– High soft tissue stress when placing implants extra-maxillary in ZAGA types 2 and 4 –– Bacterial adhesion to the rough surfaces of the implant Backed by its scientific approach and building on its legacy of innovation, the Straumann Company assumed the choice of the final protected design and universal distribution of ZAGA Round and ZAGA Flat zygomatic implants. The correct use and indication for the rehabilitation of zygomatic implants together with various patterns to prevent long-term complications represent the main goal of this achievement. Thus, the final design of the Straumann-ZAGA zygomatic implant includes: –– Use of commercially pure Grade 4 titanium with no aluminium vanadium alloys –– A narrower apex diameter of 3.4 mm, which is achieved because the implants are fabricated from special cold-worked grade 4 titanium, which in bench experiments has been shown to increase fatigue strength

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–– A tapered apex portion to improve primary stability and accommodate minimally invasive ZAGA osteotomies –– Turned implant body and head to refrain as much as possible from bacterial adhesion –– Rough surface apex to accelerate secondary stability away from possible contamination –– A 55° angular correction in the implant platform that optimizes prosthetic versatility –– A model, ZAGA Flat, with a flat midsection to reduce soft tissue stress when placed extra-­ maxillary and prevent dehiscence –– One model, ZAGA Round, with a round midsection to accommodate a tunnel-type osteotomy if intra-sinus placement is used –– Macro- and micro-threads in the neck to stabilize the bone at that level and prevent oro-­ antral communication –– A transporter with the same outer diameter as the implant to facilitate implant placement and preserve the osseous ridge Modifications in the design of any implant should be technically, clinically, and scientifically validated. Fortunately, after a long and successful period of preclinical and mechanical testing, human donor placement, and non-­ interventional clinical trials, the Zygoma Round and Flat implants were launched by Straumann in October 2020. The added use of the Straumann ZAGA Round and ZAGA Flat implants used in conjunction with the ZAGA concept contributes greatly to avoiding immediate or late complications while maintaining excellent rehabilitation stability. Understanding the reasons, strategies, and engineering of the zygomatic implant design changes implemented in the new Straumann ZAGA Round and ZAGA Flat designs will help the clinician to optimize their use (Fig. 6.20). The relationships between the changes, their indication, and their effect are explained in Table  6.3 taken from Aparicio et al. [24].

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Fig. 6.20  Representative diagram of the different diameters in the two ZAGA zygomatic implant designs distributed by Straumann Table 6.3  Influence of implant design on ZAGA minimally invasive osteotomy goals (from Aparicio et al. [24]) Goal Place the implant head at the optimal dental position using a prosthetically driven implant trajectory Achieve optimal anterior-posterior distribution of the implants Achieve maximal implant primary stability

Implant feature Implant axis 55° correction

Preserve as much bone as possible at the maxillary wall and alveolar bone Maximize bone-toimplant contact (BIC) along the length of the whole implant. This includes the alveolar, maxillary wall, and zygomatic bone Achieve complete sealing of the osteotomy by the implant body Protect sinus integrity at the implant head/neck level to prevent late sinus-oral communication

Threads and/or micro-threads are incorporated at the implant head/neck level The tapered apical design experiences an increased diameter at the level of the implant neck. The drilling protocol shows a difference between the implant diameter and the last drill diameter (0.5 mm at the apical level, increasing to 1.4 mm at the implant neck/head) Two types of implant section, round and flat

Reduced apical diameter

Apical tapered self-cutting design

Implant-to-­abutment connection is not located at the ZICZ Threads and/or micro-threads at the head neck level Machined surface at implant head and body

Prevent soft tissue dehiscence

A design presenting a flat surface is available

Results Easier ideal prosthetic positioning Implant-to-­abutment junction is not located at the zygomatic implant critical zone (ZICZ). This eliminates the possibility of bone resorption due to eventual bacterial leakage The reduction of the apical diameter increases the possibility of divergent positioning of the implant shafts, thus improving the final AP distribution If a conservative osteotomy is performed, the difference between the diameter of the last drill and the progressive section of the implant achieves greater primary stability Threads, together with implant stability, facilitate osseointegration and bone stability Increased BIC along the entire length of the implant

The clinician may decide which design would better adapt to the performed osteotomy No bacterial leakage and subsequent bone resorption are expected at the ZICZ Threads, together with stability and alveolar bone contact, will enhance the possibility of osseointegration If a soft tissue recession occurs, machinesurfaced implants will maintain surrounding soft tissue health better than a rough-­surfaced implant By facing the flat surface against the soft tissue, any eventual compression of its vessels is diminished, thus decreasing the possibility for dehiscence

6  The Zygoma Anatomy-Guided Approach (ZAGA) for Preventing Complications Using Zygomatic…

6.4 Conclusions

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7. Brånemark P-I, Gröndahl K, Ohrnell L-O, Nilsson P, Petruson B, Svensson B, et  al. Zygoma fixture in the management of advanced atrophy of the maxThe main differences between the documented illa: technique and long-term results. Scand J Plast Reconstr Surg Hand Surg. 2004;38:70–85. techniques for the rehabilitation of the atrophic 8. Lanza DC, Kennedy DW. Adult rhinosinusitis defined. maxilla using zygomatic implant-anchored prosOtolaryngol Head Neck Surg. 1997;117:S1–7. theses have been reviewed. Unlike previous tech9. Lund VJ, Mackay IS.  Staging in rhinosinusitis. niques that use two osteotomies to place the Rhinology. 1993;31(4):183–4. zygomatic implant, placement following the 10. Stella JP, Warner MR.  Sinus slot technique for simplification and improved orientation of zygomaticus ZAGA concept requires only one osteotomy that dental implants: a technical note. Int J Oral Maxillofac is performed by infra-preparation of the residual Implants. 2000;15(6):889–93. bone. This is why it is known as minimally inva- 11. Ouazzani W, Arevalo J, Sennerby L, Lundgren S, Aparicio C.  Zygomatic implants. A new surgical sive ZAGA osteotomy. Comparative studies approach. J Clin Periodontol. 2006;33(Suppl, second between the original technique and the ZAGA part):128. concept show clear advantages in the ZAGA phi- 12. Migliorança R, Ilg JP, Serrano AS, Souza RP, losophy since immediate, less aggressive, and Zamperlini MS. Sinus exteriorization of the zygoma fixtures: a new surgical protocol. Implant News. bulky rehabilitations are achieved. The percent2006;3:30–5. age of long-term sinus problems decreases dra13. Aparicio C, Ouazzani W, Aparicio A, Fortes V, Muela matically with using the ZAGA concept. The R, Pascual A, et al. Extra sinus zygomatic implants: results obtained in clinical studies performed folthree-year experience from a new surgical approach for patients with pronounced buccal concavities in lowing the minimally invasive ZAGA concept the edentulous maxilla. Clin Implant Dent Relat Res. together with the new implant designs are clearly 2010;12:55–61. E-Pub 2008. superior in terms of reduction of complications to 14. Maló P, de Nobre M, A, Lopes I. A new approach to those found with zygomatic implants and tradirehabilitate the severely atrophic maxilla using extra maxillary anchored implants in immediate function: a tional techniques. pilot study. J Prosthet Dent. 2008;100(5):354–66. 15. Migliorança RM, Coppedê A, Dias Rezende RCL, de Mayo T. Restoration of the edentulous maxilla using References extra sinus zygomatic implants combined with anterior conventional implants: a retrospective study. Int J Oral Maxillofac Implants. 2011;26(3):665–72. 1. Vrielinck L, Moreno Rabie C, Coucke W, Jacobs R, Politis C. Retrospective cohort assessment of survival 16. Aparicio C. A proposed classification for zygomatic implant patients based on the zygoma anatomy guided and complications of zygomatic implants in atrophic approach (ZAGA): a cross-sectional survey. Eur J maxillae. Clin Oral Implants Res. 2023;34(2):148– Oral Implantol. 2011;4:269–75. 56. https://doi.org/10.1111/clr.14027. 2. Becktor JP, Isaksson S, Abrahamsson P, Sennerby 17. Aparicio C.  Zygomatic implants: the anatomy-­ guided approach. 1st ed. New Malden: Quintessence L. Evaluation of 31 zygomatic implants and 74 reguPublishing Company; 2012. lar dental implants used in 16 patients for prosthetic reconstruction of the atrophic maxilla with cross-­ 18. Duarte LR, Filho HN, Francischone CE, Peredo LG, Brånemark P-I.  The establishment of a protocol for arch fixed bridges. Clin Implant Dent Relat Res. the total rehabilitation of atrophic maxillae employ2005;7:159–65. ing four zygomatic fixtures in an immediate loading 3. Freedman M, Ring M, Stassen LFA.  Effect of alvesystem--a 30-month clinical and radiographic followolar bone support on zygomatic implants: a finite ­up. Clin Implant Dent Relat Res. 2007;9:186–96. element analysis study. Int J Oral Maxillofac Surg. 19. Davo R, Pons O, Rojas J, Carpio E. Immediate func2013;42:671–6. tion of four zygomatic implants:1-year report of a pro4. Freedman M, Ring M, Stassen LFA. Effect of alveolar spective study. Eur J Oral Implantol. 2010;3:323–34. bone support on zygomatic implants in an extra-sinus position--a finite element analysis study. Int J Oral 20. Aparicio C, Polido WP, Chow J, David L, Davo R, De Moraes EJ, Fibishenko A, Ando M, Mclellan G, Maxillofac Surg. 2015;44:785–90. Nicolopoulos C, Pikos MA, Zarrinkelk H, Balshi 5. Jensen OT, Brownd C, Blacker J. Nasofacial prostheTJ, Peñarrocha M. Identification of the pathway and ses supported by osseointegrated implants. Int J Oral appropriate use of four zygomatic implants in the Maxillofac Implants. 1992;7(2):203–11. atrophic maxilla: a cross-sectional study. Int J Oral 6. Aparicio C, Brånemark PI, Keller EE, Olive Maxillofac Implants. 2021;36:807–17. https://doi. J. Reconstruction of the premaxilla with autogenous org/10.11607/jomi.8603. iliac bone-in combination with osseointegrated implants. Int J Oral Maxillofac Implants 1993: 8: 21. Aparicio C, Manresa C, Francisco K, Aparicio A, Nunes J, Claros P, et  al. Zygomatic implants placed 61–67.

146 using the zygomatic anatomy-guided approach versus the classical technique: a proposed system to report rhinosinusitis diagnosis. Clin Implant Dent Relat Res. 2014;16:627–42. 22. Aparicio C, Manresa C, Francisco K, Ouazzani W, Claros P, Potau JM, et al. The long-term use of zygomatic implants: a 10-year clinical and radiographic report. Clin Implant Dent Relat Res. 2014;16:447–59. 23. Clarós P, Końska N, Clarós-Pujol D, Sentís J, Clarós A, Peñarrocha-Diago M, Aparicio C.  Prevalence of

C. Aparicio maxillary sinus alterations after zygomatic surgery. A comparative study between intra-sinus and ZAGA approaches. J Dent Oral Maxillofac Surg. 2021;3(1). https://doi.org/10.31579/2643-­6612/0018. 24. Aparicio C, Polido W, Chow J, Davó R, Al Nawas B. Round and flat zygomatic implants: effectiveness after a 1-year follow-up non-interventional study. Int J Implant Dent. 2022;8:13. https://doi.org/10.1186/ s40729-­022-­00412-­8.

7

Pterygoid Implants as Alternative to Bone Augmentation in Implant Dentistry Vishtasb Broumand and Jayson Kirchhofer

Abstract

The ultimate dental implant challenge is reconstruction of the severely resorbed maxilla especially in patients with long-term edentulism or multiple previous failed attempts at dental implant placement and full-arch implant rehabilitation. Before implant dentistry, complete dentures, which are limited by poor retention and lack of support that the alveolar ridge offers in atrophic maxillae, were the only option for these patients. Pterygoid implants are now a valid and valuable resource for the rehabilitation of the posterior atrophic maxilla. This chapter will cover pterygoid implant surgical and presurgical planning, surgical procedures, and protocols, including multiple techniques commonly utilized to place and restore these implants comprehensively.

V. Broumand (*) · J. Kirchhofer Oral and Maxillofacial Surgery Private Practice, Desert Ridge Oral Surgery Institute, Phoenix, AZ, USA Department of Oral and Maxillofacial Surgery, University of Arizona College of Medicine at Banner University Medical Center Phoenix, Phoenix, AZ, USA

7.1 Introduction Placement of dental implants in patients with vertical and horizontal deficiencies of the maxilla, or with tumour or trauma-related defects, is often limited by the extensive pneumatization of the sinus cavities and, furthermore, by the poor quality and inadequate quantity of remaining bone (Fig.  7.1). Many surgical procedures have been developed to rebuild the atrophic maxilla for subsequent dental implant placement, such as allogeneic bone grafting with mesh, autogenous iliac crest block grafting, Le Fort I osteotomies with interpositional grafts, and sinus augmentation procedures. None of these procedures yield immediate results with long periods of healing, multiple required surgical procedures, and increased financial burdens/hurtles. Furthermore, complications and failures of these reconstructive efforts are common (Fig. 7.2) [1]. In more contemporary literature, in order to avoid extensive bone grafting procedures, pterygoid and angled implants with or without zygomatic implants have been recommended for the dental rehabilitation and reconstruction of this group of patients, even though the palatal and posterior resorptive pattern of the edentulous maxillae may also limit the horizontal bony volume necessary to successfully place angled endosseous implants (Fig. 7.3) [2–4]. Severe atrophy of the maxilla can be due to various factors such as tumour resection, general-

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_7

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Fig. 7.1  Example of a severely atrophic maxilla (a). Sagittal and panoramic view demonstrating the maintenance of dense bone at the pterygomaxillary junction despite a severely resorbed maxillary alveolus (b, c)

Fig. 7.2  Coronal CBCT slice demonstrating a large oroantral fistula of the left maxilla caused by multiple failed sinus augmentation bone grafting procedures

ized aggressive periodontitis and other infections, and genetic disorders or syndromes. Fabrication of a prosthesis with adequate retention and stabil-

ity for patients with an atrophic edentulous maxilla presents a significant challenge for even the most skilled surgeon. Treatment concepts with pterygoid implants have evolved as an alternative for bone augmentation procedures. Placement of an implant through the maxillary tuberosity and into the pterygoid plate at the pterygomaxillary junction is called a ­tubero-­pterygoid or, more commonly, a pterygoid implant. Though close in anatomical proximity, they are not the same as tuberosity implants which obtain their stability solely from the poor-­ quality bone of the tuberosity. Pterygoid implants were first proposed by Linkow in 1975 [1, 5] as an alternative to rehabilitate the atrophic maxilla avoiding the need for further surgeries, such as

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Fig. 7.3  Pterygoid implants in conjunction with (a) traditional AOX; (b) trans-nasal and trans-palatal implants; (c) hybrid zygomatic implants and traditional nasomaxillary implants; (d) quadruple zygomatic implants

sinus lifts or alternative ridge augmentation with bone grafting [6, 7]. The first pterygoid implant was placed by Tulasne in 1985 [5]. In 1992, Tulasne and Tessier first described the technique and initially described a success rate of 80%. Tulasne later reported a success rate of 92% in 1999. Nonetheless, during the past years, several studies have reported a much higher success rate, ranging from 90.7% to 99% success as reported by Balshi and Araujo [8–14]. Dental implant placement in the posterior maxilla poses a challenge due to the quality and quantity of bone, the anatomy of the maxillary sinus, and difficulty of access. To overcome these challenges, several surgical procedures such as sinus lifts, ridge augmentation, tilted implants, short implants, and zygomatic implants have been used by many clinicians, though not all patients are candidates for such techniques. All of these procedures have their own limitations, and the pterygomaxillary junction provides an excellent source of D1 cortical bone for placement of implants in the rehabilitation of the posterior maxilla [15]. Pterygoid implants serve to reduce the anterior-posterior (AP) cantilever for full-­ arch hybrid prostheses and are commonly used as rescue implants in cases of failed hybrid 4-implant supported cases.

Placement of pterygoid implants involves an osteotomy starting in the tuberosity region with a mesiocranial oblique trajectory proceeding posteriorly toward the pyramidal process of the palatine bone. It is subsequently advanced superiorly between both the medial and lateral pterygoid plates of the pterygoid process destined for the pterygoid, or scaphoid, fossa of the sphenoid bone. Placement of pterygoid implants can present some challenges compared to conventional dental implants as it is a blind procedure hinged solely on the surgeon’s knowledge of the anatomy. Surgical access is limited, and serious injuries can occur if, unintentionally, other vital structures are encountered/injured. The descending palatine artery or maxillary artery may be severed if the implant is placed too far apical. An implant can also invade the pterygomaxillary fossa and the pterygoid plexus of veins leading to significant haemorrhage [16]. The pterygoid plexus is a valve-free venous plexus located in the infratemporal fossa, is continuous with the cavernous sinus, and eventually becomes the maxillary vein as it drains inferiorly. There is only a risk of bleeding to the plexus if, during surgery, the implant extends too far laterally as the pterygoid plexus is found lateral to the pterygoid implant target area (Fig. 7.4).

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Cavernous venous sinus

Inferior ophthalamic vein

Emissary vein connecting pterygoid venous plexus to cavernous sinus Superficial temporal vein Maxillary vein

Deep facial vein

Facial vein

Pterygoid venous plexus

Retromandibular vein External jugular vein Internal jugular vein

Fig. 7.4  The pterygoid plexus is found lateral to the lateral pterygoid plate. Significant haemorrhage may be encountered if the pterygoid implant osteotomy is created with an excessively lateral angulation

3rd part of Maxillary A 2nd part of Maxillary A Upper head of lateral Pterygoid Muscle

Neck of mandible (cut) 1st part of Maxillary A

Lower head of lateral Pterygoid Muscle

Maxillary Artery External carotid artery

Fig. 7.5  The internal maxillary artery may be encountered if the osteotomy is extended too far superiorly leading to potentially life-threatening haemorrhage

It is imperative to have a thorough knowledge of the regional anatomy because nearby vital structures can be injured during the blind placement of these technique sensitive implants. The pterygomaxillary fissure connects the infratem-

poral fossa to pterygopalatine fossa and is a conduit for the internal maxillary artery which traverses the pterygomaxillary fissure 18.7  mm above the pterygomaxillary suture (according to Uchida) (Fig. 7.5) [17, 18].

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Fig. 7.6 (a, b) The greater palatine canal and descending palatine artery have a variable anatomic location and should always be evaluated with preoperative imaging. (a) Schematic of the palatal anatomy with the greater palatine foramen exiting at the third molar (most common variation). (b) Axial CT image demonstrating the location of the greater (red) and lesser (green) palatine arteries and their close proximity to the pterygomaxillary complex

When placing a pterygoid implant, it is essential to pay attention to its proximity to the greater palatine canal and neurovascular bundle as it also houses the descending palatine artery, one of the terminal branches of the maxillary artery [19]. Unfortunately, the location of the greater palatine foramen is quite variable: 16.3% at the second maxillary molar site, 6.8% between the second and third molar, 63.9% at the third molar, and 2.2% distal to the third molar site (Fig. 7.6) [20].

7.2 Indications Treatment concepts with zygomatic implants have evolved as an alternative for challenging bone augmentation procedures. The combination of conventional implants and zygomatic implants, namely, a “hybrid zygoma,” has been used successfully for restoration of the moderately atrophic maxilla [21– 27]. Placement of anterior conventional implants without large grafting procedures may prove to be

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extremely difficult in the severely atrophic premaxilla. In such situations, quadruple zygomatic implants can be used for the dental rehabilitation of the edentulous maxilla in combination with the use of pterygoid implants [28–31]. Pterygoid implant placement procedures, which do not require any adjunctive procedures such as grafting, have become a logical choice for dental rehabilitation of the moderately atrophic maxilla, especially in patients with conventional implants in the premaxilla or failed sinus grafting procedures in the posterior maxilla [32]. When placed with zygomatic implants, a pterygoid implant, in combination with conventional implants in the premaxilla, can counteract the long lever arm created by zygomatic implants and prevent prosthetic screw loosening as well as increase the odds of long-term success of the zygomatic implants. When successfully placed, pterygoid implants diminish the posterior prosthetic cantilever significantly. One of the most important reasons and advantages for the use of pterygoid implants is the elimination of the need to perform sinus lift surgeries or bone grafts. This can also significantly decrease the patient morbidity and shorten the treatment time, as these implants can be used for immediate loading with a fixed prosthesis (Fig. 7.7). They are also quite useful in conjunction with zygomatic implants to reduce the posterior cantilever associated with zygomatic implants. Unlike maxillary tuberosity implants, pterygoid implants anchor in dense cortical bone of the pterygomaxillary junction, allowing a better primary stabilization which is known to be a critical factor for long-term success [33–35]. Pterygoid Implants are only manufactured by a few dental implant companies. They are relatively long and specifically designed with the characteristics of the pterygomaxillary region in mind. Pterygoid implants range in length from 18 to 26  mm and generally have a sharp, self-­tapping apex to ensure a secure anchorage when inserted in the pterygoid fossa [32]. Some manufacturers fabricate the implant with a coronal portion that has a wide thread profile in order to provide compression in the region of the tuberosity where the bone is often porous and of poor quality and low density.

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Fig. 7.7 (a–c) Patient with immediately loaded pterygoid and zygomatic implants on day of surgery. Note the complete reduction of posterior cantilever by utilization of

pterygoid implants. (a) Digital design of day-of-surgery temporary prosthesis; (b) temporary resin prosthesis occlusal; and (c) smiling photos shortly after delivery

7.3 Contraindications

7.4 Pertinent Clinical Anatomy of the Pterygomaxillary Contraindications to placement of pterygoid Region implants are limited mouth opening which leads to decreased access, lack of a maxillary tuberosity, recent LeFort or pterygomaxillary fracture, and presence of impacted maxillary third molars.

Support for the pterygoid implants is derived from the maxillary tuberosity, the pyramidal process of the palatine bone, and the pterygoid process of the sphenoid bone. The tuberosity of the maxilla has been shown to be soft, type III or type IV bone.

7  Pterygoid Implants as Alternative to Bone Augmentation in Implant Dentistry

The anatomy of the pyramidal process of the palatine bone often dictates the trajectory of the implant as it can alter the shape and size of the pterygomaxillary suture. The variations in this Fig. 7.8 (a) Palatine bone—the anatomy of the pyramidal process of the palatine bone often dictates the trajectory of the implant; (b) the pterygoid fossa is the apical aiming point for pterygoid implants

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suture can often dictate changes in implant trajectory vertically and horizontally depending on the form and size of the pyramidal process of the palatine bone as seen in Figs. 7.8 and 7.9.

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Fig. 7.9  Sphenoid bone, (a) inferior view; (b) anterior view. The desired trajectory for the pterygoid implant is between the medial and lateral pterygoid plates within the pterygoid fossa

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7.5 Preoperative Planning A thorough clinical examination in the planning process for pterygoid implants, although mandatory, is incomplete without a proper radiologic evaluation as three-dimensional assessment must be considered. In order to properly evaluate a patient for all angled implants, and especially zygomatic or pterygoid implants, a panoramic radiograph gives distorted and incomplete information. One must be able to thoroughly evaluate

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the size and shape of the maxillary sinuses, health of the sinuses, the height of the maxillary tuberosity and the pterygomaxillary process, width of the pterygomaxillary process, mediolateral thickness and anterior posterior length, and the position of the nasal floor [36]. The examination of choice is three-dimensional computed tomography (CT) scans which also allow for construction of surgical guides as well as stereolithographic models to facilitate the orientation of pterygoid and zygomatic implants during the surgery (Fig. 7.10) [37].

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Fig. 7.10 (a–c) Three-dimensional evaluation of the pterygomaxillary complex via CT imaging is of utmost importance when planning pterygoid implants. (a)

Sagittal, (b) axial, and (c) coronal cuts are used to understand the complex anatomy which may be variable from patient to patient

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7.6 The Surgical Approaches for Pterygoid Implants

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ity bone. The pyramidal process of the palatine bone is the second bone to be encountered. The drill or osteotome should hit this like a “brick After local anaesthetic administration, a full-­ wall.” Once the sharp spade drill hits dense bone, thickness flap extending to the posterior border of then the operator should switch to the Noris the tuberosity is developed. A small amount of 2  mm sharp osteotome. Using this sharp osteobone reduction is performed with a large head tome and a mallet, gently tap until you feel a bone rongeur followed by a straight handpiece dense bone wall and then continue tapping until flame shape tungsten bur in order to (a) achieve you hear an increase in sound frequency. In order an optimal platform for implant placement, (b) to avoid fracturing the pterygomaxillary comcreate a flat bone surface, and (c) create pros- plex, it is recommended to drill with a 2 mm twist thetic space for the future screw-retained hybrid drill to 18  mm or until perforating through the prosthesis. Pterygoid implant positioning should pterygomaxillary complex and into the pterygoid be carefully studied using helical or cone-beam fossa. The length of the implant may differ computer tomography (CBCT) imaging of the depending on the entry point of the implant, i.e., patient. Careful planning is important as these second vs. third molar site (Fig.  7.12). Next, a implants require a bucco-palatal and a mesio-­ Noris 3  mm osteotome is used to gently tap to distal angulation [38, 39]. There are two depth. If the bone is super dense, use the 2.8 mm ­commonly employed techniques used to place twist drill to widen osteotomy prior to placing the pterygoid implants, both of which will be dis- pterygoid implant by hand. cussed here. Regardless of surgical technique used, the implant is preferably placed by hand with a minimal torque value of 30  N  cm for 7.6.2 Description of the Technique: Pterygoid Implants with Drill immediate loading. With this technique, the goal Guided Technique (Fig. 7.13) is insertion of implants in the pterygomaxillary junction using the residual alveolar-basal bone as anchorage of a standard implant antero-­inferiorly. Clinically, the anatomy of the tuberosity, the The two techniques used are placement of ptery- length from the planned starting point to the end goid implants with either the osteotome guided of the tuberosity, and the relative position of the sinus are used as landmarks for the starting drill. technique or the drill guided technique. Operator’s experience and haptic awareness are extremely important in this step as the placement of pterygoid implants allows no direct 7.6.1 Description of the Technique: vision to the end point. Implant placement folPterygoid Implants lows standard procedures, but some techniques with Osteotome Guided are used to increase primary stability, in particuTechnique (Fig. 7.11) lar underpreparation, osseodensification, and Clinically, the anatomy of the tuberosity, the bi-corticalization. For the pterygoid implants, the implant bed length from the planned starting point to the end preparation follows the following sequence. The of the tuberosity, and the relative position of the sinus are all used as landmarks for the initial first needle-type drill and the second 2.0  mm entry point of the sharp pilot drill or osteotome. diameter pilot drill from a Helix long implant kit One must advance the sharp pilot “spade”-shaped (Neodent) are used clockwise, full length, until drill through the soft tuberosity until dense bone perforation of the pterygomaxillary process is is encountered. An osteotome is used first by achieved. This allows the bi-corticalization of the some surgeons. When using the sharp osteotome, implants. The three following drills used (2.0, it may migrate in the soft bone, and the operator 2.35, and 3.75 mm) are Neodent Helix Long or can often push entirely through this soft tuberos- Noris Medical Pterygoid with counter-clockwise

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Fig. 7.11  Osteotome guided technique—(a) axial view of the maxilla demonstrating the appropriate bucco-­ palatal angulation of the osteotomy; (b) sagittal view demonstrating the appropriate mesio-distal angulation of the osteotomy. (c) The osteotome technique is first initiated using the 2  mm pterygoid osteotome which is advanced through the tuberosity and continued until hitting the “brick wall” of the palatine bone. (d) The white-­ banded 2.3 mm twist drill is then used to perforate through

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Fig. 7.12 (a) Proper angulation for an implant entering at the second molar site. (b) Proper angulation for an implant entering at the third molar site. (c) Note the sig-

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the dense palatine bone to the desired osteotomy depth. (e) The 3 mm osteotome is then used to gently expand the osteotomy. (f) The red-banded 2.8 mm twist drill is then used to open dense apical portion of the osteotomy. (g) The pterygoid implant is gently hand tightened into the osteotomy taking extreme care to follow the same angulation used for the previous steps. Any alteration in angulation may lead to fracture of the pterygomaxillary junction and loss of the ability to place a subsequent implant

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nificantly greater length required when entering from the second molar site compared to the third molar site

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Fig. 7.13  Drill guided technique—(a) axial view of the maxilla demonstrating the appropriate bucco-palatal angulation of the osteotomy; (b) sagittal view demonstrating the appropriate mesio-distal angulation of the osteotomy from the third molar entry point. (c) The drill guided technique is first initiated using the 2 mm twist drill which is advanced through the tuberosity and continued through the “brick wall” of the palatine bone. (d) The 2.35  mm twist drill is then used to further widen the dense palatine bone to the depth of the osteotomy. (e) The 3.75 mm twist

drill is then used to gently expand the inferior aspect of the osteotomy. Note that this drill is not carried to the full depth and is stopped approximately 3–5 mm short of the planned implant length. (f) The pterygoid implant is gently hand tightened into the osteotomy taking extreme care to follow the same angulation used for the previous steps. Any alteration in angulation may lead to fracture of the pterygomaxillary junction and loss of the ability to place a subsequent implant

rotation of the final drill in order to increase bone density of the tuberosity via osseodensification. Together, these two techniques result in the high primary stability of pterygoid implants. The implant enters in the region of the former maxillary second or third molar and follows an oblique mesio-cranial direction proceeding posteriorly towards the pyramidal process of the palatine bone. It subsequently proceeds superiorly/cranially between both wings of the pterygoid process and finds its encroachment in the pterygoid, or scaphoid, fossa of the sphenoid

bone [38, 39]. All pterygoid implants should anchor with 50 + N cm torque, and the most common length is 18  mm when utilizing the third molar entry point. After implant placement, a multi-unit-type abutment is placed on each implant, generally an angled 17° or 30° abutment (Fig.  7.14). The flap is then sutured in place as described by de Sousa [40]. A previous removable provisional denture can be converted to a fixed, screw-retained full acrylic FP-3 prosthesis following the denture conversion technique described by Misch [41].

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Fig. 7.14  30° neodent multi-unit abutment in place on pterygoid implant site 16

7.7 Prosthetic Considerations In most cases, we consider an immediate-load protocol, although a delayed load protocol is also possible [42–44]. The immediate one-stage protocol requires the immediate cross-arch splinting of the zygomatic and/or pterygoid implants at the time of surgery. The patient’s existing or new denture is converted to a hybrid bridge. The denture is altered to accommodate the multi-unit abutments with temporary cylinders in order to splint the zygomatic or pterygoid implants. The patient’s existing denture is then converted into a fixed provisional bridge using the same direct or indirect conversion technique described for the conversion protocol used when immediate loading is considered. During the first month of the healing stage, the patient is seen every week to adjust the occlusion as it must remain equally balanced across the entire arch. After healing of the bone and soft tissues, approximately 6 months later, abutment level final impressions of the zygomatic and/or pterygoid implants are obtained for the fabrication of a definitive fixed hybrid with a titanium bar [45–47]. Once the final restorations are delivered, it is recommended to use a waterpik water flosser twice daily, especially at bedtime. It is also recommended to brush twice daily with a soft manual toothbrush using a non-abrasive, non-whitening toothpaste. Recall appointments are advised at 3 months, 6 months, and 1 year after delivery of the final appliance. At the yearly

V. Broumand and J. Kirchhofer

appointment, the appliance is removed to clean the underside of the hybrid restoration and the multi-unit abutments, especially for patients that have difficulty maintaining hygiene. Periapical and panoramic radiographs are taken each year at the recall appointment for 3 years following insertion, and then once every 3 years, or as deemed necessary thereafter. From a prosthetic standpoint, pterygoid implants minimize the time to rehabilitation by avoiding secondary grafting, bypass the need of a distal cantilever, and make it possible to place second molars in the final full-arch prosthesis. Even though they are placed in the pterygomaxillary region at an angle, once osseointegrated, these pterygomaxillary implants resist all axial and nonaxial forces better than any other implants placed in the maxilla. As illustrated in our cases, patients tolerate the distal position of the implant, showing no difficulty in speech or swallowing. Patients also demonstrate no difficulty in maintenance of oral hygiene. The success rate of these implants and restorations is highest when they meet criteria for an immediate prosthetic load with adequate vertical restorative space to avoid prosthetic or screw fracture [48].

7.8 Clinical Cases 7.8.1 Case #1: Trans-nasal and Trans-palatal Implants in Conjunction with Pterygoid Implants (Fig. 7.15) The case shown here illustrates maxillary rehabilitation using a combination of trans-palatal, trans-nasal, and pterygoid Neodent implants for an implant supported maxillary hybrid bridge in a 67-year-old male with terminal maxillary dentition. Due to the significant amount of preoperative bone loss as well as the alveolar ridge reduction required prosthetically by his high smile line, insufficient bone remained for traditional AOX implant placement. Note the significant increase in anterior-posterior spread gained by the addition of the pterygoid implants.

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a

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d

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Fig. 7.15 (a, b) A 67-year-old male presenting with terminal maxillary dentition and failing previous restorations and mobile anterior teeth. Due to the significant amount of preoperative bone loss as well as the alveolar ridge reduction required prosthetically by his high smile line, insufficient bone remained for traditional AOX implant placement. Trans-nasal and trans-palatal implants were used in conjunction with pterygoid implants to restore an atrophic maxilla after the removal of remaining terminal

maxillary teeth. Note the significant increase in anterior-­ posterior spread gained by the addition of the pterygoid implants. (a) Preoperative panoramic imaging, (b) postoperative panoramic imaging on the day of surgery with multi-unit abutments and scanning caps in place. (c, d) Another example of trans-nasal and trans-palatal implants used in conjunction with pterygoid implants

7.8.2 Case #2: Hybrid Zygoma in Conjunction with Pterygoid Implants (Fig. 7.16)

7.8.3 Case #3: Quadruple Zygomatic Implants in Conjunction with Pterygoid Implants (Fig. 7.17)

The case shown here illustrates maxillary arch rehabilitation using a combination of two zygomatic and three traditional implants in the anterior maxilla in combination with pterygoid implants. This 40-year-old male presented with terminal maxillary dentition, Angle’s class-III malocclusion, and a constricted maxillary arch. The patient was told by other providers that he was not a candidate for full-arch implants due to the atrophic nature of his alveolar bone in conjunction with his constricted and hypoplastic maxilla. A hybrid zygomatic and traditional implant approach, along with pterygoid implants, was utilized to restore the maxillary arch. The patient is currently in the process of restoring his mandibular dentition.

The case shown here illustrates full mouth rehabilitation using a combination of four zygomatic and two pterygoid implants in the maxilla and implant retained lower hybrid Zirconia bridges with four dental implants utilizing an immediate load protocol in a 61-yearold male who presented with terminal maxillary and mandibular dentition. Due to the long history of partial edentulism, significant bone loss had led to a severely atrophic maxilla with inadequate bone volume for traditional, transnasal, or trans-palatal implant placement. He was treated with quadruple zygomatic implants in conjunction with pterygoid implants to fully restore his dentition.

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a

b

c

d

Fig. 7.16 (a–d) A 40-year-old male presenting with terminal maxillary dentition, Angle’s class-III malocclusion, and a constricted maxillary arch. The patient was told by other providers that he was not a candidate for full-arch implants due to the atrophic nature of his alveolar bone in conjunction with his constricted and hypoplastic maxilla. A hybrid zygomatic and traditional implant approach,

along with pterygoid implants, was utilized to restore the maxillary arch. The patient is currently in the process of restoring his mandibular dentition. (a) Preoperative panoramic imaging; (b) preoperative intraoral photograph; (c) postoperative panoramic imaging; (d) smile photograph of temporary maxillary prosthesis

a

b

c

d

Fig. 7.17 (a–d) A 61-year-old male presenting with terminal maxillary and mandibular dentition. Due to the long history of partial edentulism, significant bone loss had led to a severely atrophic maxilla with inadequate bone volume for traditional, trans-nasal, or trans-palatal implant placement. He was treated with quadruple zygomatic

implants in conjunction with pterygoid implants to fully restore his dentition. (a) Preoperative panoramic imaging, (b) preoperative intraoral photograph; (c) panoramic imaging following delivery of final prostheses; (d) intraoral photograph following delivery of milled zirconia final prostheses

7  Pterygoid Implants as Alternative to Bone Augmentation in Implant Dentistry

7.9 Complications It is important for the treating surgeon to have a clear knowledge of the intricate anatomy of the maxilla and the pterygomaxillary complex prior

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undertaking surgery for the placement of pterygoid implants (Fig. 7.18). The overall frequency of complications with pterygoid implants is variable and includes implant failure, haemorrhage, trismus, tuberos-

a

Pterygomaxillary fissure (Laterally) Greater wing of sphenoid (Superiorly) Perpendicular plate of palatine bone (Medially) Pterygoid process (Posteriorly) Pyramidal process of palatine bone (Inferiorly) Posterior surface of maxilla (Anteriorly)

b

Maxillary artery Pterygoid vein plexus

Fig. 7.18  The (a) bony and (b) vascular anatomy of the pterygomaxillary region

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ity or pterygoid complex fracture, and displacement into the infratemporal fossa.

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7.11 Conclusion

Pterygoid implants provide an aid to a graftless solution in an atrophic maxilla. The pterygomaxil7.10 Discussion lary complex, though seemingly distant, provides anchorage for fixed solutions without any need for Dental implant placement in the posterior max- bone grafting or sinus lift procedures. Pterygoid illa poses a challenge due to the poor quality and implants provide strong cortical anchorage even in inadequate quantity of bone, the anatomy of the the atrophic maxilla. Studies have shown them to maxillary sinus, and difficulty of access. To be an alternative treatment option for patients with overcome these challenges, several surgical pro- highly atrophic maxillae without the need for cedures such as sinus lifts, ridge augmentation, extensive augmentation procedures. The availabiltilted implants, short implants, and zygomatic ity of dense cortical bone for engagement of the implants have been used by many clinicians, implant encourages its use. Pterygoid implants although not all patients are candidates for such have high success rates, similar bone loss levels to techniques. All of these procedures have their those of conventional implants, minimal compliown limitations, and the pterygomaxillary junc- cations, and good acceptance by patients [6, 7, 51]. tion provides us an excellent source of D1 cortiAdditionally, when anterior implants fail or are cal bone for placement of implants for not feasible, addition of pterygoid implants seems rehabilitation of the posterior maxilla [15, 49]. to be a valid primary or rescue solution for the fullPterygoid implants serve to reduce the antero-­ arch rehabilitation with immediate loading of the posterior cantilever significantly and are com- atrophic maxilla, avoiding more invasive and timemonly used as rescue implants in cases of failed consuming procedures like the sinus lifts and large hybrids. bone grafts. In some cases, quadruple zygomatic Treatment concepts with pterygoid implants implants can be avoided if adequate pterygoid have evolved as an alternative for challenging anchorage is obtained as they provide additional bone augmentation procedures. In some cases, a support with increased composite torque value combination of conventional implants and zygo- and, more importantly, improved A-P spread for matic or pterygoid implants has been used suc- prosthetics, eliminating large cantilevers [33, 34, cessfully for restoration of the moderately atrophic 52, 53]. Pterygoid implant use can significantly maxilla [21–27]. Placement of anterior conven- eliminate the posterior cantilever and, thus, can tional implants without large grafting procedures decrease screw and restoration fractures which may prove extremely difficult in the severely atro- ultimately can lead to failure of full-arch implant phic premaxilla. In such situations, quadruple supported prosthesis [54] zygomatic implants with or without pterygoid Surgical demonstration of Osteotomy and implants can be used for the dental rehabilitation drill guided pterygoid implant methods of the edentulous maxilla [28–31, 50]. (Figs. 7.19 and 7.20).

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Fig. 7.19 (a–i) Step-by-step surgical demonstration of pterygoid implant placement utilizing the osteotome guided method. (a) Demonstration of appropriate angulation using 2.0 mm pterygoid osteotome; (b) initiation of osteotomy using 2.0  mm pterygoid osteotome with the third molar entry site; (c) 2.0 mm pterygoid osteotome hitting the “brick wall” stop of palatine bone; (d) 2.0  mm white-stripe twist drill perforating through the dense pala-

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tine bone; (e) 3.0 mm pterygoid osteotome being advanced to planned osteotomy depth; (f) 2.8 mm twist drill preparing the apical aspect of the osteotomy; (g) hand placement of 4.2 × 20 mm Noris implant; (h) implant in place with ideal depth for adequate restorative space; (i) postoperative panoramic imaging demonstrating improved antero-­ posterior spread by use of pterygoid implants with quadruple zygomatic implants

c

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Fig. 7.20 (a–h) Step-by-step surgical demonstration of pterygoid implant placement utilizing the drill guided method. (a) 2.0 mm Neodent twist drill; (b) initial osteotomy being created with 2.0 mm twist drill; (c) 2.35 mm twist drill widening osteotomy to depth; (d) 3.75  mm twist drill widening the coronal aspect of the osteotomy

d

h

(stopping short of full depth); (e) placement of 4.0 × 20 mm Neodent Helix GM Long implant; (f) demonstration of adequate torque for immediate loading; (g) 30° Neodent multi-unit abutment torqued in place; (h) postoperative panoramic image demonstrating ideal antero-posterior spread by use of pterygoid implants

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8

Scientific Basis of Immediate Loading and the Biomechanics of Graftless Solutions Bobby Hardeep Birdi, Komal Majumdar, and Saj Jivraj

Abstract

The implementation of graftless solutions requires the clinician to have a clear grasp of many detailed clinical concepts. Diagnosis is critical for long-term success of the procedure. There has been a paradigm shift in treatment of the edentulous patient with dental implants. Today, the graftless approach combines three published variables: 1. Four to six implants to support a full-arch fixed restoration. 2. Use of tilted implants for graftless anchorage. 3. Immediate loading to provide immediate function. For an optimal outcome, it is imperative that concepts of immediate loading, biomechanics of the restoration design, and management of the occlusal scheme be understood. The patients’ medical history must also be B. H. Birdi University of Minnesota School of Dentistry, Minneapolis, MN, USA Private Practice, Vancouver, BC, Canada K. Majumdar Om Dental Clinic, Navi Mumbai, India S. Jivraj (*) Anacapa Dental Art Institute, Oxnard, CA, USA

thoroughly evaluated for relative contraindications to immediate load. The clinical application of the graftless concept has been well accepted, and survival rates in excess of 98% have been reported in the literature (Busenlechner et  al., Int J Oral Maxillofac Implants 31:1150–1155, 2016). The purpose of this chapter is to shed light on the science and biomechanical aspects of immediate loading of the edentulous patient utilizing a graftless approach.

8.1 Defining Immediate Loading The term immediate loading does not have an established universal definition. Two variables exist when one attempts to define immediate loading: 1. The acceptable interval between implant placement and prosthetic loading. 2. The type of forces exerted on the implant and prosthesis [1]. The following classification proposed by Esposito et al. [2] has been the most accepted. Immediate loading is considered the establishment of occlusal function of implants during the first week after implant placement, early loading within 1  week and 2  months and conventional loading from 2  months onwards; the separate

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_8

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consideration of delayed loading was suppressed for being unnecessary.

B. H. Birdi et al.

The interim prosthesis should satisfy the following requirements (Figs. 8.1, 8.2, 8.3, and 8.4) [12–17]:

8.2 General Factors in Immediate Loading The main factor to consider in immediate loading is biomechanical force distribution and how this relates to natural healing. Thus, implant osseointegration must be attained despite the forces experienced during the healing phase; otherwise, fibrous encapsulation of the dental implants will result [3]. Implant primary stability, that is, the ability of the implant to withstand an applied torque of 35–40 N cm without rotation, is the prerequisite to immediate loading [2, 4]. Given that implant initial stability has been attained, the main clinical factor that influences successful immediate loading treatment is the design of the immediately delivered interim full-­ arch restoration. The clear majority of these types of full-arch restorations are screw-retained in design and cross-arch splinted [5]. Screw-­ retained prostheses have been suggested to have fewer complications when compared to their cement-retained counterparts [6, 7]. Thus, it is suggested that all interim restorations be screw-­ retained and cross-arch stabilized as this is the most evidence-based design. There are a number of prosthetic considerations that must be understood prior to embarking upon the immediate load process. Meticulous attention to detail is required for the process to be successful. An important prerequisite for predictable healing is absence of micro-motion. Brunski et al. [8] reported that micro-motion of 100 μm may constitute a threshold value for machined implant surfaces to osseointegrate adequately. Favourable loading conditions can be achieved by splinting the implants together immediately after placement. Micro-motion at the bone implant interface is limited, thus facilitating the healing process [9–11].

Fig. 8.1  Screw-retained, cross-arch stabilized interim prosthesis to be immediately loaded

Fig. 8.2  Interim prosthesis with adequate AP spread and minimal cantilever

Fig. 8.3  Interim prosthesis intra-orally with minimal vertical and horizontal overlap

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Fig. 8.4  Requirements of immediate loading

1. Provide cross-arch stabilization with a screw-­ retained rigid prosthesis with no cantilevers. 2. No premature occlusal contacts. 3. No interferences in lateral excursion. 4. Minimal vertical and horizontal overlap. 5. An occlusal scheme which protects the implants most at risk.

that on a cellular level, osteoclasts have been shown to be present on the surface of the cut native bone surrounding the implant 4 days after implant placement [19]. Thus, it may be advantageous to place the immediate interim restoration as soon as possible after the implants have been surgically placed.

8.3 Specific Elements of Immediate Loading

8.4 Occlusion

Immediate loading is considered the establishment of occlusal function of implants during the first week after implant placement [2]. The timing of when the prosthesis is delivered after the surgical placement of the implants is important, as it relates to the bone healing around the dental implants, and the continued stability of the implants in the osseous structure. Glauser et al. [18] have established that the primary initial stability that is attained at the time of surgical implant placement decreases significantly after 1 week. Furthermore, it has been shown that bone remodelling begins to significantly occur at the 1 week time point [19–22]. This helps to establish the first week after surgical placement of the dental implants as the safest time to deliver the immediate prosthesis. However, it must be stated

Agreement on the occlusal scheme to be utilized in the interim prosthesis has not been established in the literature [5]. There is no evidence to show that one occlusal scheme is superior to another, one type of tooth form is more efficient than another, or one type of occlusal scheme is preferred by patients. Most occlusal schemes advise on avoiding non-axial loading on implants. If we evaluate the recommendations critically, we become aware that axial loading of implants almost never occurs along the long axis of the implant. Instead, function occurs on various areas of the prosthesis with the development of complex bending moments within the restorative implant components and within the surrounding bone. Factors that affect distribution of occlusal forces include but are not limited to:

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(a) Number of implants involved. (b) Biomechanical design of the implant. (c) Nature of the bolus of food. (d) Design and fit of the prosthesis. (e) Nature of the opposing occlusion. (f) Deformation of the bone and the prosthesis. During the immediate load phase, management of the occlusion for force distribution and protection of the existing implants becomes very critical [5, 23, 24]. Unfortunately, an evidence base does not exist which guides the clinician in developing an occlusal scheme. The following are generalized guidelines when immediate loading in a patient with a class 1 incisor relationship: 1. Posterior cusps flattened to minimize bending and torsional forces. 2. Evaluation of the opposing occlusion: if the full-arch interim prosthesis opposes natural teeth, it may be feasible to adjust the natural teeth to minimize steep inclines and lateral forces. 3. Bilateral simultaneous contact. 4. Shallow protrusive disclusion. 5. Anterior group function. 6. Steep anterior disclusion is not recommended as this may create destructive deflective forces which may result in prosthesis fracture. 7. No cantilevers: Although no evidence-based consensus has been established regarding cantilevers, it is the overall recommendation that distal cantilevers are minimized or eliminated from the interim prosthesis. Cantilevers have been found to create greater risk in restoration fracture and implant failure, when utilized in the interim restoration [25–28]. 8. Definitive contacts on canine to canine with lighter contacts on posterior teeth. The rationale for the above is that the further posterior the tooth, the higher the occlusal forces. The implants in the posterior part of the mouth are also in the weakest quality bone. As clinicians, our goal in the immediate load phase is to minimize occlusal load on the implants that are more posteriorly positioned and in the poorest-quality bone.

9. Use of a night-time appliance. From a clinician’s perspective, one aspect that must be considered is the relationship between occlusion loading and mechanical complications. As resin fracture and tooth fracture are the most common types of prosthetic complication in these types of prostheses [5], the design and the rigidity of the interim hybrid prosthesis has been suggested to aid in the strength and resilience during the healing phase [29]. Furthermore, increased rigidity of the interim prosthesis is also suggested to aid in successful osseointegration by reducing loadinduced implant micro-­movement during healing [30–32]. The rigidity of the interim restoration is increased through dimensional thickness. Appropriate restorative space must be created by the surgeon to fulfil the biomechanical requirements of the specific restoration treatment planned. One of the main methods in which rigidity can be improved is through reinforcement of the interim hybrid prosthesis. Patient advantages include less breakage and a longer-lasting provisional restoration. Clinician advantages include fewer unscheduled visits and reduced chair time. One material that has shown to increase flexural strength is use of a fibre [31]. This material type has also been suggested to increase fracture toughness in provisional restorations [5, 30, 32] (Figs. 8.5, 8.6, 8.7, 8.8, and 8.9).

Fig. 8.5  Fibre reinforcement requires an indirect technique with impressions and tooth set up

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Fig. 8.6  Putty matrix of tooth position in relation to the temporary cylinders

Fig. 8.7  Fibre tied in a specific manner to provide support for the teeth, processed provisional

Fig. 8.8  Clinical delivery

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Fig. 8.9  Provisional restoration intra-orally, note minimum vertical overlap of anterior teeth

8.5 Optimal Number of Implants The number of implants needed to successfully and routinely rehabilitate an edentulous arch utilizing an immediate loading protocol has been debated for some time in the literature. Classically, the use of five mandibular implants for a full-arch rehabilitation has been advocated. However, recently, two to three implants have been advocated for the fixed rehabilitation of a dental arch utilizing an immediate loading protocol [33–35]. With the introduction of full-arch fixed rehabilitation on four implants [36, 37], the conceptual requirement of increased implant numbers for full-arch fixed rehabilitation was put into question. With continued research being conducted in this area, it can be stated that the use of four to six implants for fixed full-arch rehabilitation utilizing an immediate loading protocol is evidence based. When deciding the optimal number of implants, we must give the term optimal a broader definition. The clinician should consider not just the number of implants but where in the jaw they are placed and the quality of bone in which they are placed [38]. The magnitude of stresses that develop in the bone, the implant and the prosthesis, and the relationship of the stresses and strains to thresholds for damage to the bone and prosthetic components should also be given consideration. The treatment plan must be developed biomechanically. When looking at the literature in this arena, three types of study have been completed:

1. Mathematical models. 2. 3D finite element analyses 3. Intra-oral strain gauge studies. When attempting to predict forces on four, five, or six implants with the above studies, extrapolation becomes very difficult. What makes this problem difficult to solve is the fact that each implant is connected to both the bone and the prosthesis; computing the loads (and stresses and strains) in each part of the structure is a problem that is not solvable by statics alone but also requires data on the material properties of the implants, bone, and prosthesis as well as their stress-strain behaviours. Prosthesis rigidity, bone implant stiffness, and deformation of the mandible also come into consideration. The use of fewer implants to rehabilitate an edentulous patient has been established, and the need for reserve implants is no longer considered necessary.

8.6 Axial vs. Tilted Implants The introduction of a tilted implant protocol in full-arch fixed rehabilitation utilizing immediate loading put into question the need for universal axial implant placement. Since that time, these two implant positioning regimens have been compared throughout the literature [39–44]. However, it is clear that in many instances tilting of posterior implants in full-arch rehabilitations provide significant benefits (Table 8.1) [44].

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However, concerns about the consistency and clinical results using tilted implants continue to be present in the industry. Three general areas of concern are prevalent: 1. Titled implants exhibit more bone loss. 2. There is increased stress concentration around tilted implants. 3. Restorations with tilted implants experience greater prosthetic complications. It has now been thoroughly established that the use of tilted implants in an immediate loading protocol does not induce more bone loss compared to the use of an axially placed implant [47– 49]. Many studies have indicated that the inclination of implants, in a splinted structure, aids in decreasing the stress in the arch [40, 50– 52]. There is no evidence to demonstrate a higher prosthetic complication rate in restorations that encompass tilted implants [17, 27]. Table 8.1  Benefits of tilted posterior implants [39–49] 1. Implants are placed into more dense and better-­ quality bone. 2. Longer posterior implants can be utilized through tilting. 3. Tilting posterior implants allows for greater distribution of the implant connections. 4. Larger anterior-posterior spread of implants decreases cantilever lengths needed. 5. Marginal bone levels are maintained around tilted implants. 6. Similar success and survival rates when compared to axial implants. 7. Vital anatomical structures are avoided by tilting posterior implants. 8. Tilting posterior implants minimizes the need for grafting procedures (Fig. 8.10).

Fig. 8.10  Advantages of tilted implants

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The reasons why splinted restorations utilizing a tilted implant protocol perform so well include the following: 1. Rigidity of the prosthesis counteracts the relatively small bending moments applied to the tilted implants. 2. Enough micro-motion for function is not enough to prohibit osseointegration. 3. Off-axis loading is stabilized by cross-arch stability.

8.7 Vertical Cantilever Height: Crown-Implant Ratio In patients who have undergone severe resorption, there is obviously a limited amount of bone to place the implants and an obvious bulk of prosthetic structure and on occasion causing a tremendous prosthesis to implant ratio. The theory is that in these patients with unfavourable crown-implant ratios, the prosthesis acts as a lever causing a bending moment and transmits stress to the peri-implant crestal bone causing resorption. Multiple studies have shown that crown-­ implant ratio is not a factor that causes bone loss providing there is a good fit of the prosthesis to the implants and we are maintaining cross-arch stabilization [53–57].

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8.8 Medical Evaluation of the Patient A systematic review by the Academy of Osseointegration [58] evaluated the effects of various medical conditions and medications on bone remodelling. This section will highlight certain clinically relevant medical conditions, patient-related factors, the use of certain medications, and their recent consensus pertaining to immediate loading protocols. Clinician-related factors will also be discussed. The medical conditions that may influence immediate loading include but are not limited to: 1. Diabetes mellitus. 2. Patients on dialysis. 3. Osteoporosis. The medications of interest that may affect outcomes of immediate loading include: 1. Selective (SSRIs).

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Patient-related factors: 1. Bruxism. 2. Smoking. Clinician-related factors: 1. Experience. 2. Expertise.

8.9 Medical Conditions That May Impact Immediate Loading 8.9.1 Diabetes Mellitus Diabetes mellitus is a chronic metabolic disease classified by the World Health Organization as the sixth leading cause of death in the world [59, 60].

Diabetes mellitus presents in two forms. Type 1 (T1DM) is an autoimmune disorder with early onset in childhood where the body cannot produce insulin. Type 2 (T2DM) is a multifactorial disease with genetic and environmental factors, where the pancreas cannot produce insulin, and thus the body becomes insulin resistant [61, 62]. The four currently recommended diagnostic tests for diabetes (Classification of diabetes mellitus. Geneva: World Health Organization; 2019): 1. Fasting plasma glucose measurement ≥7.0 mmol/L (126 mg/dL). 2. A 2-hour (2-h) post-load plasma glucose after a 75 g oral glucose tolerance test (OGTT) ≥ 11.1 mmol/L (200 mg/dL). 3. HbA1c ≥ 6.5% (48 mmol/mol). 4. A random blood glucose ≥11.1 mmol/L (200 mg/dL) in the presence of signs and symptoms of diabetes.

8.9.1.1 How Does It Affect the Body? Diabetes mellitus is associated with poor wound healing, neuropathy, structural damage to blood vessels, poor micro-circulation, arterial hypertension, and unsatisfactory immune response [63]. It is also associated with increased dental implant failure due to poor osseous healing [64–66]. Patients with diabetes mellitus produce advanced glycation end products (AGEs) [67, 68].

8.10 How Does Diabetes Affect Implants and Immediate Loading? One of the preferred criteria for immediate loading and predictable osseointegration is the absence of systemic disease [69]. In T2DM patients, AGEs accumulate permanently in the vessel walls, altering the phenotype of important cells such as macrophages, polymorphonuclear cells, fibroblasts, and endothelial cells [68]. This leads to production of destructive inflammatory cytokines leading to bone resorption around immediately loaded implants [68, 70]. The diabetic patients are also associated with higher risk of osseointegration failure due to infection [71] and long-term bone and soft tissue complications [59].

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However, in controlled diabetics there is optimal osteoblast activity and minimal bone resorption. It is also associated with lower levels of AGEs [68, 72].

8.10.1 Does Literature Support Immediate Loading of Implants in Uncontrolled Diabetic Patient? The placement of dental implants in a diabetic patient is a topic of substantial debate in implant dentistry. In diabetic patients the clinician should proceed with caution. Various studies advocate that implants in patients with diabetes mellitus should be avoided [73, 74]. Studies also show that with proper glycaemic control (controlled diabetic), dental implants can osseointegrate and remain functionally stable like that in a non-­diabetic individual [75, 76]. Studies likewise show that immediate loading in a controlled diabetic can be safely done [77]. When it comes to immediate loading, a recent systematic review stated that there is no difference in the survival of immediately loaded dental implants among non-diabetic individuals when compared to type 2 diabetic individuals, even when not controlled [78].

8.10.1.1 Can Immediate Loading Be Done on Patients with Uncontrolled Diabetes Mellitus? Full-arch immediate loading is an advanced implant procedure which depends on multiple factors such as adequate primary stability (>35 N cm insertion torque), rigid cross-arch stabilization, density of bone, health of the bone bed, and lastly to an extent on the patient’s inherent healing potential. Although the current consensus points towards immediate loading even in uncontrolled diabetic individual, the clinician should follow prudence in proper case selection and follow certain protocols before and after the implant procedure.

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1. HbA1c levels should be evaluated before the procedure [70]. 2. Since diabetic patients are more prone to peri-­ implant infections [79], it becomes imperative that management of periodontal infection should be done before implant placement. 3. Pre-operative antibiotic coverage should be started as it helps in reducing the rate of implant failure from 13.4% to 2.9% in diabetic patients [80]. 4. Chlorhexidine mouthwash should also be started pre-operatively as studies have shown it helps to reduce the failure rates from 13.5% to 4.4% [80]. 5. In uncontrolled diabetic individuals with concomitant obesity and cardiovascular diseases, immediate loading should be avoided as there can be greater chances of failure [69]. 6. Periodic recalls of the patients after implant therapy for hygiene maintenance to avoid chances of peri mucositis and peri-implantitis in the long term. 7. Accessing the opposing dentition and parafunction. Low occlusal loads in a patient with a denture as an opposing dentition with no parafunction will categorize as a low-risk individual.

8.10.1.2 Alternatives to Immediate Loading in a Diabetic Individual The clinician has various alternate choices if the patient has uncontrolled diabetes and other comorbidities that would prevent him/her from opting for immediate loading. Complete Denture This is a very viable option, more so if the patient presents completely edentulous to the dental office. This is not the most preferred choice as the denture can cause uncontrolled loads on the implants during mastication. A soft tissue liner can be used to cushion the occlusal loads to a certain extent. However, this may still not prevent all the transfer of the loads and can cause failure of the implants. For the soft liner to be effective, the minimum thickness of the reliner should be at least 4 mm.

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Fig. 8.11 (a) Strategic abutments in place. (b) Teeth supported provisional

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Fig. 8.12 (a) Implants integrated. (b) Impression with teeth present

Strategic Abutments If the patient is partially edentulous and immediate loading cannot be attempted, the clinician may use existing teeth as strategic abutments. These teeth would hold a fixed provisional restoration while implants are placed in the edentulous sites between them. The advantage of this approach is that the patient has fixed restorations throughout, and the implants can heal undisturbed. The downside of this procedure is that the strategic abutments are of poor prognosis and may fail while the implants are integrating. Should this happen, the patient would be transitioned to a removable prosthesis. Once osseointegration has been confirmed, the strategic abutments can either be submerged if they are periodontally sound or can be extracted. Impressions can be made of the integrated implants and implant supported provisionals fabricated for insertion when the strategic abutments are extracted/submerged. The following patient was an uncontrolled diabetic who needed mandibular full-arch restoration. The patients’ request was to be transi-

tioned in a fixed restoration. Two mandibular anterior teeth and two premolars were retained to be used as strategic abutments (Fig. 8.11a, b). On implant integration, an open tray impression was fabricated to make an implant-supported prosthesis (Fig. 8.12a, b). The lab was instructed to make an implant-supported prosthesis, removing the teeth from the cast. Once the provisional was ready, the anterior teeth were extracted and the premolars were submerged (Fig. 8.13a, b). Provisional/Transitional Implants In this approach single one-piece smaller diameter implants are placed in between or palatal to the primary implants. These provisional implants can be used to restore the patient while the primary implants heal with a submerged approach. The provisional implants can be removed during the fabrication of definitive restoration (Fig. 8.14a, b).

8.10.1.3 Patients on Dialysis Chronic kidney disease (CKD) is a general term of heterogenous disorders affecting the structure

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Fig. 8.13 (a) Strategic abutments extracted. (b) Implant supported provisional

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Fig. 8.14 (a) Temporary implants. (b) Temporary implants between primary implants

and function of kidneys. It could be due to kidney damage (albuminuria) or decreased kidney function (glomerular filtration rate, GFR)  90 degrees

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Fig. 8.17 (a) Positive rake angle in regular drill. (b) Negative rake angle in Densah bur

such as Celexa, Paxil, Lexapro, Prozac, and Zoloft—are drugs designed to inhibit serotonin reuptake and boost its levels to treat depression [132]. Because of their unique effectiveness in depression treatment, SSRIs have become the

most widely used antidepressants worldwide [133]. Although serotonin is required for treating depression, it is also needed for the functioning of digestive, skeletal, and cardiovascular tissues [133].

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8.12 Patient-Related Factors 8.12.1 Bruxism

Fig. 8.18  Densah burs improve primary stability

Fig. 8.19  Osseodensified site

Serotonin regulates bone metabolism by acting on the bone receptors and serotonin transporters, resulting in complex signal transmission in osteoblasts and osteoclasts [133]. Thus, SSRIs block receptors on bone cells resulting in a direct negative effect on bone formation [134, 135] and metabolism [133] by increasing osteoclast differentiation [136] and decreasing osteoblast proliferation [133].

8.11.4.2 Can Immediate Loading Be Done in Patients Taking SSRIs? Since the bone in patients taking SSRIs is normal in structure and quality, it is easy to achieve primary stability and good rigid fixation to go for immediate loading. However, SSRIs are associated with not early but late failures due to mechanical loading. The failures caused by mechanical overloading usually occur after the loading time of 4 and 6  months [137]. So, it becomes prudent to carefully plan surgical treatment in SSRI users as there is a higher risk to implant survival [138].

Bruxism is defined as a movement disorder of the masticatory system that is characterized, among others, by teeth grinding and clenching, during sleep as well as wakefulness [139, 140]. Bruxism is frequently considered a causative factor for temporomandibular disorders (TMD), tooth wear (e.g., attrition), loss of periodontal support, and restoration failure. However, many conflicting pieces of evidence show that these are due to bruxism [141–144]. Psychosocial factors like stress and personality are also frequently mentioned in relation to bruxism. Bruxism seems to be mainly regulated centrally, not peripherally. Implant overloading due to bruxism can cause complications like occlusal surface wear, fracture, loosened screws or abutment, and implant fracture [145]. In fact, bruxism is considered a contraindication for implant treatment, although most evidence is usually based on clinical experience [146].

8.12.1.1 How to Diagnose a Bruxer? The diagnosis of bruxism includes a complaint of jaw muscle discomfort, fatigue, stiffness, occasional headaches, the presence of tooth wear, tooth sensitivity, muscle hypertrophy, TMJ clicking or jaw lock, and tongue indentation. The clinical diagnosis of bruxism is based on an orofacial examination and the patient and the partner’s report. Often, the patients are unaware of sleep bruxism, and even their partner may not know if they are deep sleepers [147]. This can lead to an incorrect diagnosis by the clinician [147]. Diagnosis becomes even more challenging if the patient reports to the office completely edentulous. The best way to diagnose bruxism is polysomnographic analysis [145], although that is considered complicated by some authors [148] and may not always be practically possible for all general clinicians in their day-to-day practice.

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8.12.1.2 What Are the Problems of Doing Immediate Loading in a Bruxer? The occlusal loads produced by a bruxer are considerably higher and can be termed as overload than that seen in a normal physiologic chewing cycle [146]. It is, therefore, not unlikely that forces applied to implants during bruxism are even larger than those exerted during mastication [149], making them more prone to occlusal overload and possible subsequent failure [146]. One of the most critical aspects of immediate loading is to keep the micromotions below the threshold value [105–108], as it is not immediate loading per se but deleterious macro-motions that increase the risk. Moreover, as the loads generated by bruxers are considerably higher, there are higher chances of early failure. The risk of failure is enhanced due to the absence of periodontal ligament and decreased proprioception.

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8.12.2 Can Immediate Loading Be Done in Bruxers? Immediate loading in bruxers is controversial in implantology, with multiple studies for both and against it. One of the problems is that many studies do not include bruxers in the inclusion criteria; hence, the results cannot be predictable. Multiple prospective studies show problems with implants in bruxers. Wannafors et al. [150] reported a significant relationship between bruxism and implant failure after the implants have been functional for a year. Likewise, Glauser et al. [151] found a higher percentage of implant loss in bruxists (41% vs. 12% after 1  year). Another review by Lazzara [152] and another study by Misch et al. [153] consider bruxism as a contraindication for immediate loading. However, counter studies show that immediate loading can be easily done in bruxers [153–157]. In conclusion, immediate loading in bruxers has inherent biomechanical risks ranging from breakage of provisional restoration (Fig.  8.20a) to implant loss (Fig.  8.20b) during the healing

Fig. 8.20 (a) Fracture of provisional. (b) Failure of implants

period. Multiple studies show that there are also greater chances of late failures in a bruxer. Considering that immediate loading by itself requires strict protocols to be followed, like adequate primary stability, rigid cross-arch fixation, etc., an inexperienced clinician (50 implants) may be able to attempt the same as studies show that they experience less failure as compared to inexperienced clinicians [158]. However, this should be tried only after thoroughly clarifying the risks and pitfalls of the procedure to the patient. This will avoid any future embarrassments and legal glitches for the clinician.

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8.12.3 Are There Any Practical Guidelines When Attempting Immediate Loading in a Bruxer?

6. Achieve the passivity of the temporary by doing the one screw test. An active prosthesis can exert loads on the implant leading to overloads on the prosthesis and the implants [167, 168] (Figs. 8.22 and 8.23). The following guidelines should be followed to 7. Occlusion has to be very carefully evaluated. prevent the chances of over loading in a bruxer: If the opposing dentition is implant-­ supported fixed restoration or natural denti 1. Multiple studies, including this retrospective tion, the following points must be study by Naiedermaier [159] and by Brunski considered: [160], show that a minimum of four implants (a) Simultaneous bilateral equal intensity is sufficient to restore an entire arch opticontact points in maximum intercuspamally. However, it makes more sense to tion with shallow anterior guidance increase the number of implants in a bruxer. (Fig. 8.24a, b). This means keeping a low ratio of the pros- (b) Flap cusps for flat linear pathways. No thetic unit to implants (PU/I). Studies have interference in lateral excursions shown that a low PU/I ratio improves the (Fig. 8.24c), even if the opposing dentilong-term prognosis of the implants [161– tion is a denture (Fig. 8.24d) 166]. This PU/I value works as a ‘safe side’ (c) Posterior disclusion in protrusion parameter (Fig. 8.21). (Fig. 8.24e). 2. Avoid cantilevers in the provisional and final 8. A rigid stabilization splint for nightly use restorations. (night guard) contributes to optimally dis 3. Though implant length is more relevant in tributing and vertically redirecting the forces immediate loading, an increased length and that go with nocturnal teeth grinding and width of the implant should be used for long-­ clenching [169–175] (Fig. 8.24f). Some cliterm favourable prognosis and reducing nicians prefer to put a layer of cold cure resin stress [167, 168]. over the occlusal surface and keep the inner 4. Tarnow et al. recommend metallic reinforcecore made of a softer material for better ment of the temporary to reduce the bending retention and for it to act like a dampening loads in the immediate loading protocol. effect (Fig. 8.24g). However, if the number of implants is 9. Although a night guard is given, the clinician increased, the rigid temporary can efficiently cannot prevent the patient in engaging in the counteract loads of occlusion [169]. habit. Nevertheless, the clinician may be able 5. Rigid metallic splint using the digital prototo reduce the deleterious loads on the col can act as additional protection to reduce implants [176]. the micro-motions and keep it below the threshold value (Fig. 8.13a, b).

Fig. 8.21  Low PU/I ratio

Fig. 8.22  Avoid cantilevers in immediate loading

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Fig. 8.24 (a, b) Simultaneous bilateral contacts. (c, d) No interferences in lateral excursions. (e) Posterior disclusion in protrusion. (f) Hard night guard. (g) Soft night guard with layer of resin. (h) Occlusal markings

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10. The nightguard should be given only for one arch. Giving night guards on both arches can increase the vertical dimension and cause discomfort. The arch selected should be the stable of the two and should interfere the least with occlusal excursions (Fig. 8.24h).

8.13 Case Report Infrequently, a clinician may fail to see the subtle signs of bruxism and may treat such a patient with an immediate loading protocol. This is especially true of patients that are edentulous. No amount of bone loss can be a predictive marker for bruxism. Bruxism may lead to consequences such as minor screw loosening and fracture of the provisional to failure of the implants in the critical healing period. The following case shows the management of a patient with possible bruxism. The term possible bruxism is used as the patient had minimum signs and no symptoms of bruxism. The possibility of bruxism was taken into consideration, once he had multiple breakage of the temporary during the healing phase. A 65-year-old male patient reported to the practice. He had been wearing a cast partial denture since a few years and was looking for a fixed option. Extra-oral examination in the frontal view showed that the patient’s horizontal reference lines (the eyebrow line, the inter pupillary line, and the commissural line) were almost parallel to each other and the patient had a straight facial midline. Because of the extremely low lip line, it could not be ascertained if both facial and dental midline coincided (Fig. 8.25a, b). His sagittal view showed a very minor concave profile (Fig. 8.25c). His vertical dimension was maintained due to the cast partial denture (Fig. 8.25d). On ­palpation, the muscles of mastication were not sore. The patient did not complain of any joint discomfort. However, the patient considered himself as having a stress taking mentality. He however admitted of grinding not during the examination phase

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but after he had multiple fractures of the temporary. The patient had a low lip line with more exposure of teeth on the right side and none of the left side of the face, indicating a minor asymmetry in the smile (Fig. 8.25e). The occlusal plane did not show any abnormality. Some old cervical facets were restored with composite resin and some minor wear was observed in the incisal edge (which did not seem pathological/excessive). However, considering phonetics and aesthetics as the parameter, the maxillary incisal edge position was correct and could be used as a reference plane for deciding the restorative space and the final prosthetic material. Intraoral examination is conducted after the dentures were removed, partial edentulism on both the arches. The extent of horizontal bone resorption was minimum (Fig.  8.25f, g). There was minor wear seen on the incisal edges of the mandibular anterior teeth (Fig. 8.25h). Radiographic evaluation showed there was minor pneumatization of the sinus. CBCT evaluation showed adequate bone to place three axial and two tilted implants in the upper arch (Fig.  8.25i). The lower arch required three implants. The tilted implant protocol was followed and the lower implants were placed in the same surgical appointment. Long, wide implants were placed to ensure high primary stability. Open tray impressions were made on the multi-unit abutments (MUAs), and a lab fabricated temporary with PMMA was fabricated. Adequate thickness of provisional was kept to avoid fractures in the healing period. The pickup technique was used to ensure passivity. The one screw test was positive (Fig. 8.25j–m). The lower arch was restored with partial denture with soft liner over the implants to restore function and maintain the posterior support in the interim healing period. The patient was asymptomatic for a period of 4  weeks. He then reported with a single tooth being dislodged to the office which was easily attached on the temporary. The occlusion was re-­ verified to rule out any heavy occlusal contact point on the said tooth. Anticipating that the

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Fig. 8.25 (a) Facial midline. (b) Harmony of horizontal reference planes. (c) Concave profile. (d) Vertical dimension-­maintained. (e) Low and asymmetric lip line. (f) Minimal horizontal resorption. (g) Few teeth remaining. (h) Minor wear on anterior teeth. (i) Radiographic evaluation. (j) Tilted implant with MUA. (k) Lab fabricated PMMA. (l) Implants placed. (m) Temporary prosthesis. (n) Temporary fractured. (o) Old cast to make

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temporary. (p) Digital impression. (q) Bite registered digitally. (r) Verification jig. (s) Teeth setting trial. (t) Second PMMA temporary fractured. (u) PMMA trial. (v) One screw test on PMMA. (w) Metal trial with hybrid design. (x) One screw test on metal trial. (y) Milled titanium framework with individual zirconia crowns. (z) Milled titanium framework with individual zirconia crowns

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patient may have higher occlusal forces, a night guard was fabricated at this stage and delivered to the patient. The patient then reported to the office after 4 weeks after the first incident with a broken temporary in the midline (Fig. 8.25n). A new temporary was made at this stage using the older cast that was preserved in the office (Fig. 8.25o). The patient was kept on the temporary for another 3 weeks. The patient had no complaints at this stage, and the fabrication of final prosthesis was commenced at this stage using the digital protocol. Digital impression was made with scan bodies on MUAs (Fig. 8.25p). Despite the digital protocol, a model was printed and a verification jig was made to verify the impression (Fig. 8.25r). Since the occlusion was correct, the bite was also recorded digitally (Fig. 8.25q). Teeth setting trial was done as the patient wants some minor changes in the aesthetics (Fig. 8.25s). At this stage, the patient again reported to the office with the second fractured temporary (Fig. 8.25t). The old temporary was not repaired, as the fabrication of the final prosthesis was being done.

PMMA trial was done and verified for aesthetics, function, phonetics, and passivity (Fig. 8.25u, v). Once the PMMA trial was done, the same PMMA trial was given as a third provisional to the patient. Milled titanium framework with provisions for individual zirconia crowns was fabricated. The passivity was verified again with one screw test (Fig.  8.25w, x). A full zirconia monolithic design was avoided to prevent the chances of fracture of the final prosthesis as higher occlusal bite forces was anticipated in this case. The final prosthesis with individual zirconia crowns was fabricated. The crowns were luted on the framework by the lab as all the access holes were palatal and occlusal (Fig.  8.25y, z). The design chosen provided both aesthetics and long-­ term favourable biomechanical prognosis for this case. The prosthesis was verified for passivity and occlusion. Mutually protective occlusal scheme was used for the final prosthesis (Fig. 8.26a–e). Considering that either the patient is a bruxer or has heavy occlusal bite forces, biomechanical principles were taken into consideration while

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Fig. 8.26 (a) Passivity of prosthesis. (b) Maximum intercuspation. (c) Protrusion. (d) Lateral excursions. (e) Acceptable aesthetics. (f) Minimal cantilever. (g) Hard nightguard

fabricating the final prosthesis. No excessive cantilevers were given and a milled passive prosthesis was delivered (Fig. 8.26f). A hard night guard was fabricated to avoid future excessive loads on the implants (Fig. 8.26g).

8.14 Smoking Smoking is one of the risk factors for placing dental implants. Most of the studies on immediate loading tend to exclude patients who are smokers. Lower success rates are reported in smokers

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than in non-smokers [177]. The rate of failures is four times higher in patients who smoke more than 20 cigarettes daily [178]. Smoking negatively affects bone metabolism by impeding normal function and proliferation of the alveolar bone marrow mesenchymal stem cells. A study by Zhao et al. revealed that these changes were also correlated with osseointegration disturbances and reduced implant stability among smokers from the third to sixth week after surgery [179].

8.14.1 What Are the Problems of Doing Immediate Loading in a Smoker? As discussed, one of the essential criteria for immediate loading is high primary stability or insertion torque. The implants are loaded within 1  week under physiological loads to keep the micro-movements below the threshold of 150  μm—the higher the primary stability, the lesser the micro-motions. However, as described by Raghvendra et al. [180], there is a dip in the primary stability between the second and fifth week, supported by other studies [181–183]. However, the problem with smokers is that the trough span (dip in stability) for the non-smoker group was relatively shorter, lasting for only 1 week, whereas that for the heavy smoker group lasted for approximately 10 weeks [184]. Longer trough spans mean more micro-movements, which could lead to failure in immediate loading protocols.

8.14.2 Can We Perform Immediate Loading in Smokers? Although multiple studies recommend against placing implants in smokers, some suggest

immediate loading can be done predictably in heavy smokers, provided certain criteria are met. A study shows that immediate loading in edentulous arches of heavy smokers seems successful when the primary implant stability is high, full-­ arch splinting is secure, and also, a soft diet minimizes the initial forces [185]. Of course, these patients should be made aware of the possible risks involved, including chances of infection, delayed healing, and loss of the implant. If possible, the patient should be advised to stop smoking 2  weeks before and 4–6 weeks after the surgery, which could help in the early healing period and reduce the failure chances. The study mentioned earlier [185] also concluded that better results are obtained if the abutment implant connection is not removed. Using MUAs would significantly help in such a scenario.

8.15 Case Report The following case shows the management of a case of a heavy smoker (15–20 cigarettes a day) with the immediate loading protocol. A 48-year-old male patient reported to the practice. He complained of pain and mobility of teeth and wanted a fixed replacement option. Extraoral examination in the frontal view showed that the patient’s horizontal reference lines (the eyebrow line, the inter pupillary line, and the commissural line) were parallel to each other and the patient’s dental and facial midline coincided (Fig. 8.27a, b). The sagittal view showed a straight profile with no loss of lip support (Fig. 8.27c). His vertical dimension seemed to be maintained. The patient had an average lip line with 3–4  mm of teeth visible, although the maxillary incisal edge position seemed to be shifted coronally (Fig. 8.27d).

Fig. 8.27 (a) Facial and dental midline coinciding. (b) Harmony in all three horizontal lines. (c) Straight sagittal profile. (d) Maxillary incisal edge shifted. (e, f) Terminal dentition. (g) Radiographic evaluation. (h) Maxillary flap raise. (i) Implants placed. (j) Pickup technique, passivity ensured. (k) Implant level open-tray impression. (l) MUA level open-tray impression. (m) Jig trial—upper. (n) Jig trial—lower. (o) Jaw relation. (p) Teeth setting trial. (q) PMMA trial. (r) PMMA trial. (s, t) Milled titanium framework with individual zirconia crowns. (u, v) Maximum intercuspation. (w) Protrusion. (x) Lateral excursion. (y, z) Oral hygiene instructions

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Intraoral examination showed aggressive periodontitis with grade III mobility in almost the entire dentition. The occlusal plane was not normal with migration of various teeth. Oral prophylaxis was done with antibiotic prophylaxis for a period of 5 days before the surgery. This ensured reduction in inflammation during the procedure.

The patient was asked to stop or reduce smoking for 2 weeks before the surgery (Fig. 8.27e, f). Radiographic evaluation showed there was minor pneumatization of the sinus. CBCT evaluation showed severe atrophy but adequate bone to place three axial and two tilted implants in the

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maxillary arch. The mandibular arch required axial implants placement (Fig. 8.27g). The flap was raised and the tilted implant protocol was followed for the maxillary arch, and

axial implants were placed in the mandibular jaw. Long, wide implants were placed to ensure high primary stability (Fig. 8.27h, i).

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Open tray impressions were made and a lab-­ fabricated acrylic temporaries were fabricated for both the jaws. Adequate thickness of provisional was kept to avoid fractures in the healing period. The pick-up technique was used to ensure passivity. The one screw test was positive (Fig. 8.27j). The patient was given hygiene and diet instructions and was asked to be on soft diet. The patient was asked to avoid smoking for the next 4–6 weeks. The patient followed the instructions and had uneventful healing. The process for final restoration was started after 4  months. The extended healing period was decided considering that the patient was a smoker. Open tray impressions were made (Fig. 8.27k, l) and jig trials for both the arches were done (Fig. 8.27m, n). Jaw relation and teeth setting trial were conducted (Fig. 8.27o, p). This was followed by PMMA trial. Once passivity was ensured, all the corrections needed were communicated to the lab (Fig. 8.27q, r). Milled titanium framework with provisions for individual zirconia crowns was fabricated. The passivity was verified again with one screw test (Fig. 8.27s, t). Mutually protected occlusal scheme was designed (Fig. 8.27u–x). Oral hygiene instructions were given to the patient to avoid chances of peri-implantitis, because not only was the patient a smoker but also had aggressive periodontitis as the causative factors for loss of dentition in first place (Fig. 8.27y, z). Stable bone levels were observed during the delivery of the final prosthesis (Fig. 8.28).

Fig. 8.28  Stable bone levels

8.16 Clinician Related Immediate loading protocol is an advanced surgical and prosthetic modality of treatment that a clinician can offer a patient. This involves a number of factors that come into play right from correct case selection, surgical and prosthetic planning to their correct execution. The entire modality can be stressful (especially if done in the free hand approach) for both the patient and the clinician. It has been in author’s experience that immediate loading protocol should be attempted by clinician who is a bit experienced as there is a learning curve to these procedures. This is supported by studies that show that there is a strong correlation between experience of the surgeon and the success of the procedure [158, 185]. An inexperienced surgeon may not be able to get high stability especially in the maxilla, may not create adequate restorative space, may end up perforating the buccal plate, and lastly may not get passivity of the framework. Unlike in the conventional approach, where the implants can be submerged, that freedom is not available in the immediate loading protocols. This can lead to severe embarrassment for the clinician if he fails to deliver to the patient what was initially promised. Lastly, early failures in the protocol in the initial few cases may dishearten the clinician who may stop adopting this technique completely, depriving his patients from such a life-changing treatment modality.

8.17 Conclusion The biomechanical aspects of full-arch rehabilitation utilizing an immediately loading protocol are multi-faceted with many dynamic parts to consider. Careful planning and the amalgamation of surgical and restorative therapies is essential. However, it must be emphasized that this procedure, as with all implant therapy, is a restoratively driven treatment modality. Thus, restorative plan-

8  Scientific Basis of Immediate Loading and the Biomechanics of Graftless Solutions

ning must be completed prior to implant surgery to allow for proper implant placement, as well as the creation of adequate restorative space. Full-arch immediate loading is predictable when initial implant stability is attained. This is the main prerequisite for this type of therapy. The broad distribution of implants which can involve angled implant placement will be beneficial from both a biomechanical and restorative standpoint. This prerequisite when combined with a carefully designed cross-arch stabilized interim hybrid prosthesis with minimal cantilevers will provide the greatest chance for success of the immediately loaded implants. Attributes such as reinforcement of the interim hybrid prosthesis, as well as minimizing excessive restoration height, will aid in the force risk of the prosthesis. Finally, and most importantly, the occlusion on the interim hybrid prosthesis must be adjusted to minimize deflective occlusal forces. This combined with a soft diet during the healing phase will provide the best chance for success. A thorough evaluation of the patient’s medical history is of equal importance. It is an integral part of the entire treatment planning for the immediate loading concept. Immediate loading should only be suggested and executed when the patient is medically stable. Contrary to initial beliefs, immediate loading can be performed in bruxers, heavy smokers, and uncontrolled diabetics. However, these must be attempted by experienced clinicians who can follow the rigorous rules required for its success, like high primary stability, rigid cross-arch stabilization, and thorough instructions about the diet. Patients must be informed of the risk prior to commencing treatment.

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9

FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations Martin Wanendeya and Saj Jivraj

Abstract

Treatment planning of edentulous patients with fixed restorations on dental implants has undergone a paradigm shift since the introduction of graftless solutions. Minimally invasive full-arch implant dentistry adheres to concept of preserving and maintaining bone. Full-arch solutions should not adhere to a specific philosophy but rather to the defect the patient presents with. The patient may be missing teeth, gingiva, or bone, or all. Based on the defect, the clinician will plan the appropriate type of restoration. This chapter will discuss digital and analogue workflows for full-arch implant rehabilitation where the patient presents with teeth or presents with very minimal resorption.

M. Wanendeya (*) Ten Dental, London, UK e-mail: [email protected]

9.1 What Is an FP1? More and more patients are seeking full-arch solutions due to a combination of factors. These include an ageing population whose dentitions are failing and needing replacement; an awareness by both dentists and patients of the option to have fixed teeth as opposed to dentures; and dental implant companies marketing full-arch solutions to dentists and sometimes to patients directly. However, in all the marketing and training available, the main solution that is featured is an FP3 solution. Carl Misch [1] first proposed the classification system that we use today to classify the pink and white balance for partial and full-arch implant-­ supported restorations. Misch proposed three groups: FP1, FP2, and FP3. FP1 is the replacement of only the white tissues, i.e., only the teeth, in the implant restoration. FP2 replaces the crown and a portion of the root with white material and very little (if any) pink. FP3 is the prosthetic replacement of both the pink and white tissue, i.e., the teeth and the gums, when providing an implant restoration (Fig. 9.1). In this chapter we will be focusing on the FP1 approach to full-arch implant dentistry.

S. Jivraj Anacapa Dental Art Institute, Oxnard, CA, USA © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_9

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12 mm 4 mm

FP-1

FP-2

FP-3

FP-1

FP-2

FP-3

12 mm 18 mm

10 mm

4 mm

18 mm

10 mm

Fig. 9.1  Misch Classification

One of the questions that is often asked is how to assess an individual patient and decide on whether the most appropriate method of replacement is FP1 or FP3. It is important to recognise that the FP1 classification is a prosthetic classification and implant dentistry is a prosthetically guided discipline where we begin with the end in mind. Something that has changed in recent years regarding the provision of full-arch implantology is what clinicians are replacing. Traditionally, it was dentures being replaced, as well as terminal dentitions where dentures and implants were the only solution available. Today, there is far more data about the success rates of implants [2] and therefore more options available to the professional team. Now, there must be a discussion with the patient regarding whether it is prudent to keep terminal teeth until they have lost all their supporting hard and soft tissue structures or use the remaining bone for implant placement. Opting for implant treatment at this slightly earlier stage often allows an easier transition to an implant supported prosthesis, known to some as the “tertiary dentition”. In addition, many patients have had extensive crown and bridgework in the past, so as this starts to fail, it is important for the clinician to decide the best time for and type of intervention. As stated, many of the solutions and the courses currently available to dentists focus on

FP3 solutions. This is not helped by a perception within the profession that: 1. Very few patients are suitable for an FP1 restoration. 2. FP1 is difficult to conduct. 3. FP1 requires extensive hard and soft tissue reconstruction. 4. FP1 is not stable due to soft tissue recession. It is, therefore, important for practitioners to be able to accurately assess whether a case is suitable for FP1 restoration.

9.1.1 Stage 1: Data Capture An FP1 case should be planned in the same way that all full-arch treatments are planned—using a facially driven approach. Only once the facially guided wax up is produced should the type of restoration (FP1 or FP3) be determined. Facially driven planning [3] uses both photographs and video clips to look at the position of the three components of a patient’s smile [4] (Fig. 9.2a–c): • The teeth. • The lip framework. • The gingival scaffold.

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

a

b

Fig. 9.2  Smile photo showing lips, teeth, and gingival margins. (a) Smile photo showing lips, teeth, and gingival margins. (b) Smile photo showing lips, teeth, and gingival

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c

margins. (c) Smile photo showing lips, teeth, and gingival margins

Fig. 9.3  Extra oral photos with the RAW protocol

With this information in mind, a diagnostic wax-up can be proposed with the teeth in the ideal position, using guidelines that were originally designed for denture tooth setup [3, 5]. It is important that the photographs show the patient smiling, with lips at rest as well as with maximum lip movement. Some patients will naturally resist showing their full smile, and in these cases, video can be used to document the full range of lip movement. On some patients, there can be up to 2.5 mm more tooth display during a video, when they are not consciously restricting their lip movement [6] (Fig. 9.3). There are several factors that one can use to guide the decision-making process when establishing if a patient is suitable for an FP1 ­prosthesis. To ensure all areas are sufficiently covered, it’s important to carefully gather the required information for accurate diagnosis and

treatment planning. This requires the following images: 1. Facial photographs should include images of [7]: (a) Full face lateral with patient lips at rest. (b) Full face lateral with patient smiling. (c) Full face lateral with patient laughing/ grimacing. (d) Close-up frontal smiling. (e) Close-up lateral with patient smiling (Fig. 9.4). 2. Intraoral photographs should include: (a) Upper teeth only with contrastor in place. (b) Upper and lower occlusal photographs. (c) Lateral photographs showing the left and right occlusion. 3. An OPG radiograph. 4. Intraoral scan or impression. 5. Cone beam CT scan.

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a

b

c

Fig. 9.4  Extra oral photos with the RAW protocol. (a) Extra oral photos with the RAW protocol. (b) Intraoral lateral photo. (c) Lateral intra-oral view of presenting situation. (d) Smile photo. (e) Upper and lower occlusal photos

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d

f

e

Fig. 9.4 (continued)

9.1.2 Stage 2: Facially Driven Digital Wax-Up This information is then refined and used to create a facially driven, digital wax-up [3]. As part of this process, the following lines and curves should be drawn on the facial photograph to determine the position of the teeth, starting with the central incisors (Fig. 9.5a–d): 1. The interpupillary line. 2. The midline. 3. The smile curve. From these lines the smile is evaluated and the ideal tooth position determined, starting with the position of the central incisors [8]. The rest of the tooth shapes can be designed from here using the golden proportion [9], and the rest of the tooth shapes can be drawn, again guided by the facial features (Fig. 9.6a, b). Using the proposed tooth shapes and facial photographs, a digital wax-up should be produced. There are several software packages on

the market that facilitate this process, which include, but are not limited to, Smilecould, Digital Smile Design Lab, 3Shape Smile Design, Exocad, and Meshmixer. The steps from here are as follows (Fig. 9.7a, b): • Begin with an STL of the starting position of the teeth. • Superimpose the two-dimensional ideal tooth shapes onto a two-dimensional version of this STL. • Use the two-dimensional tooth shapes to position three-dimensional teeth onto the original STL. • Copy and modify any functional aspects as needed, increasing the vertical dimension if required. • Make a new wax-up where the gingival margins and incisal edges of the proposed teeth can be seen separately without the palate present. • Consider whether the papilla is curved [10] and if the positions of the papilla in the arch

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a

b

c

d

Fig. 9.5 (a) Upper arch photo with contrastor. (b) Interpupillary line. (c) Midline and interpupillary line. (d) Smile curve, midline, and interpupillary line

a

b

Fig. 9.6 (a) Tooth proportions, arch form, smile curve, midline and interpupillary line. (b) Midline, smile curve, and central incisor tooth forms in place

Fig. 9.7  Midline, smile curve, and upper tooth forms incisors in place

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

are ideal. Some software packages, such as Smilecloud (Dentcof, Romania), allow the papilla levels to be raised and lowered on the teeth, meaning these can be tailored to each individual case. Once the facially driven wax-up has been generated, the next stage of the diagnostic process can begin.

9.1.3 Stage 3: Superimposition of the Initial Situation, the Digital Wax-Up, and the CT Scan The final steps to confirm the restorative design involve superimposition of these three elements to check the position of the proposed gingival margin and the bone. This process has been described by several authors for single teeth [11] and multiple teeth [12]. The process involves looking at the relationship of the bone to the gingival margin of the proposed tooth and checking the distance in both the buccal and apical dimensions. The planning is then broken down into three steps: 1. Choosing individual implant positions. 2. Evaluating pontic sites. 3. An overall view of the case.

a

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9.1.3.1 Choosing Individual Implant Positions When planning for the three-dimensional implant placement, one needs to ensure the correct emergence profile for each tooth. This is achieved by considering the multi-unit abutment as part of the emergence profile shape. The implant depth is vital to allow the correct emergence profile, as well as the correct critical and subcritical contours [13–15], so this must be incorporated within the planning stage (Fig. 9.8a, b). To ensure the correct emergence profile, the gingival margin of the proposed tooth needs to be 2–3  mm above the collar of the abutment. The abutment should ideally have a concave profile from the implant with adequate room for soft tissue, and this tends to be achieved with abutment collar heights of 2 mm or more. So, depending on the system used and the abutment selected, the implant head will be 5 mm below the gingival margin on the proposed tooth. If this height is less, the emergence of the abutment tooth will need to be more acute (Fig. 9.9). The width of the proposed multi-unit abutment should also be a taken into consideration—software that allows the clinician to see both the implant and abutment position are helpful for this. A very wide abutment will make it difficult to create the emergence profile of a narrow tooth. However, if only a wider multi-unit abutment (greater than 4.5 mm) is available to the clinician, the implants should be

b

Fig. 9.8 (a) Smilecloud view showing smile curve and tooth form. (b) Simplant view with implants, abutments showing

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Emergence angle around 45 degrees. Low risk of food impaction. It may be more difficult to get ideal anterior aesthetics due to lack of soft tissue space

Emergence angle less than 45 degrees. Risk of food impaction. Implant should be placed deeper to avoid this

Ideal emergence angle for soft tissue volume around the implant and aesthetics and

Ideal emergence angle. This implant maybe a little deeper that the ideal position, but is still restorable with good aesthetics

Fig. 9.9  Abutment height and emergence profile

a

4.8 mm

b

Ø 3.6 mm

23

2.5

2.5 6.2 mm 5 mm

4.0 mm

1.5 mm

Fig. 9.10 (a) Narrow and wide multi-unit abutments> uni-abutment and multi-base abutments (Dentsply Sirona, Charlotte NC, USA. (b) Narrow multiunit abutments (Neodent)

ideally positioned to avoid narrow teeth such as lateral incisors and small premolars (Fig. 9.10). Depending on the material being considered for the final bridge, the distance between implants needs to be optimised too. For instance, when using a monolithic zirconia final bridge, manufacturer guidelines [16] for many materials state that there should be no more than two pontics between abutments and

that there should be no more than a 1-unit posterior cantilever. This, along with the bone availability, bone anatomy, and opposing dentitions, will guide the practitioner as to where the ideal implant positions within the arch should be. Due to anatomical constraints, if the implants can only be positioned in sites to be restored using a bridge with larger abutment span, a titanium-­reinforced zirconia bridge can

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations Fig. 9.11 (a) Metal reinforcement for final bridge. (b) Metal reinforcement for final bridge. Prosthetic shell for WeldOne protocol

a

be used in this case, as the titanium will provide adequate support for the zirconia (Fig. 9.11a, b).

9.1.3.2 Evaluating Pontic Sites Pontics are an important part of the biology and aesthetics of a case and should not be ignored. In planning the pontic, a distance of 4 mm [17] from the gingival margin to the bone is considered ideal to allow adequate soft tissue to form between the pontic and the bone. 9.1.3.3 An Overall View of the Case In order to evaluate the access options and therefore the feasibility of an FP1 prosthesis, the clinician must bear in mind that a minimum of four and maximum of eight implants are needed—and each implant site and pontic site need to be assessed individually. At the end of this process, an overview of the case with implant positions, pontic sites, and both the provisional and final bridge size should be planned.

9.1.4 Stage 4: Periodontal and Prosthetic Planning Once the implant positions are decided, each implant and pontic sites need to be optimised. The clinician must bear in mind that after extraction, the hard and soft tissue around the extraction socket will remodel [18], and where the aesthetics outcome is critical, some form of preservation or augmentation procedure will be needed. Healed sites and extraction sockets need to be evaluated while bearing in mind the inevitable

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b

changes in volume that will occur without any intervention: • Is there adequate hard tissue following implant placement to maintain aesthetics? • Is there adequate hard tissue for an aesthetic and self-cleansing pontic site? • Is there adequate soft tissue for aesthetics after implant placement? • Is there adequate soft tissue for pontic aesthetics? On each implant and pontic site, decisions will need to be made and strategies implemented to either: 1. Maintain the current hard and soft tissue volume around extraction sockets. 2. Augment the soft tissue around pontic sites. 3. Manipulate and augment the soft tissue, and suture this around the prosthesis at either the implant or pontic site. 4. Augment any hard tissue.

9.1.4.1 Maintain the Current Hard and Soft Tissue in an Extraction Socket There are three methods that can be used in an extraction socket to maintain the buccal volume following extraction: 1. Combination therapy [19]—where a connective tissue graft is used in conjunction with biomaterials within the socket to maintain volume. 2. Partial extraction therapy [20]—the most wellknown variant is socket shield where a small portion of the buccal root is left in place after extraction to maintain the buccal bundle bone.

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3. Immediate dentoalveolar restoration [21]— where tuberosity bone and soft tissue can be used to preserve alveolar bone, as well as repair larger bone and smaller soft tissue defects at the time of implant placement. 4. The IVAN [22] technique—which can be used to repair single-site hard and soft tissue defects.

9.1.4.2 Augment the Soft Tissue around Pontic Sites There are many different methods of soft tissue augmentation, and this has been the subject of many books, lectures, and manuals, especially when studied concomitant with immediate loading. These concepts include:

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often be the palate and the tuberosity. Occasionally, the ramus can be used instead. If, after the assessment, there are too many areas with defects that cannot be augmented or sites that cannot be preserved to give an aesthetic result, then the adoption of an FP3 approach— with the necessary amount of bone removal— may give a more predictable aesthetic result for the patient. An FP1 implant bridge is indicated where there are four to six implant sites, adequate soft tissue for augmentation, and a likely aesthetic outcome. In this situation, the next stages of planning should begin.

1. The Vista [23] technique, which can be used to tunnel soft tissue into pontic areas to increase the width and, to a limited extent, the height of soft tissue. 2. If a flap is raised, a connective tissue graft can be placed on the inside aspect of the flap in order to increase the width at the pontic site.

9.1.5 Stage 5: Implant Planning

9.1.4.3 Augment the Hard Tissue In sites where no implants are being placed, many methods of bone augmentation are possible with either particulate and autogenous bone, or combinations of these with or without resorbable membranes (which provide varying resorption times).

1. Placing the implants accurately. 2. Making a provisional restoration.

9.1.4.4 Manipulate and Augment the Soft Tissue to the Prosthesis at Either the Implant or Pontic Site This technique fabricates the ideal contours on the provisional restoration prior to surgery and then during surgery by adapting the soft tissue contour to the provisional restoration with sutures. Pozzi et al. [24] used a xerographic collagen matrix in their description of the digitally assisted soft tissue (DASS) technique, but the authors’ preferences were to use a connective tissue graft in a technique described by Carvalho as “prosthetically guided healing”. As part of this assessment, different donor sites can be considered—the most useful will

1. The multifunctional guide [25]. 2. The WeldOne Shell [26].

Once a treatment plan has been determined, including the implant positions and the treatment of each implant and pontic site, the next stage is to intimately intertwine the FP1 process. This involves:

There are many methods that can be used for this, and for the purpose of this textbook we will focus on two (Fig. 9.12a, b):

Both of these methods of transfer are made in the shape of the facially driven wax-up. The tooth position, shape, and occlusion are then transferred from the wax-up to the provisional restoration.

9.1.5.1 The Multifunctional Guide The multifunctional or Galluci guide, as described in his article, allows the fabrication of a guide that functions as: 1. A surgical guide to allow implant placement within the prosthetic envelope.

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b

Fig. 9.12 (a) Multifunctional guide. (b) Multifunctional guide

a

b

Ideal pontic shape to adapt the soft tissue around Palatal rest so that the guide can be positioned correctly

Correct interproximal contours

Hole to aid implant position

Correct pontic design Palatal rest so that the guide can be positioned correctly

c

d

Diagnostic wax up

Diagnostic wax up

Multifunctional guide

Multifunctional guide

Fig. 9.13 (a) Multifunctional guide. (b) Multifunctional guide. (c) Multifunctional guide and diagnostic wax-up. (d) Multifunctional guide and diagnostic wax-up

2. A surgical guide to allow placement of the implant at the correct depth, considering the multi-unit abutment. 3. A guide to look at the soft tissue profiles of the pontic sites and allow planning of any hard or soft tissue augmentation procedures. The emergence profiles of the pontic are built into the Gallucci guide to allow the correct prosthetic profile for the pontic, resulting in a multifunctional guide. This performs as both a surgical guide and a basis for the provisional prosthesis. Once the implants are placed, abutments are selected and placed, and temporary cylinders are attached, the

multifunctional guide is then picked up in the mouth and adapted to make a provisional restoration. During this process, a steel or titanium wire is placed into the prosthesis to reinforce it.

9.1.5.2 Pontic Design for the Multifunctional Guide Many authors have proposed different pontic designs. To achieve a truly cleansable and aesthetic provisional and final bridge, an ovate pontic design should be used. The pontics are designed in the Gallucci guide to ensure the ideal contour for hard tissue to adapt to and soft tissue to be sutured around the provisional restoration (Fig. 9.13a, b).

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a

Tooth shape and gingival margin follow the diagnostic wax up

Prosthetic space for the wire reinforcement

b

Intra Orally welded wire reinforcement

Prosthetic space for the wire reinforcement

Fig. 9.14 (a) Prosthetic shell. (b) Prosthetic shell and welded framework

9.1.5.3 The WeldOne Shell This approach was developed by Marco Degidi and Paulo Malo, who pre-fabricated a composite shell restoration (using Bredent composite) which was adapted at the time of surgery. With digital technology, a composite shell (NextDent) can be designed and printed based on the diagnostic wax-up. This shell is used to transfer the shape and level of the gingival margins of all the teeth from the wax-up, as well as the occlusal contacts that have been designed (Fig. 9.14). When using this method, implants are placed either freehand or using a separate guide, and once the abutments are placed, a specially designed cylinder is fitted onto these. This cylinder is thicker than most multi-unit temporary cylinders to allow it to resist the pressure and temperature generated by resistance welding. A titanium wire is bent to allow contact with multiple welding cylinders, and this wire is then welded intraorally using resistance welding. The framework is then sandblasted, anodised, primed, and picked up in the composite shell with dual-­ cure composite. The emergence profiles of both the abutments and pontic sites are fabricated by the dental technician. The main differences between the two techniques are as follows. Multifunctional/Gallucci guide Pontics fabricated before surgery Reinforcement wire not attached to the cylinders Occlusal anatomy removed during wire placement

WeldOne Shell Pontics fabricated after pick up Reinforcement wire attached to the cylinders Occlusal anatomy maintained

9.1.5.4 Guided Surgery Guided surgery can be used to place the implants, and studies show that implants placed using a tooth supported guide can be placed to within 0.22 ± 0.07 mm (with a 2 mm sleeve to bone distance) of the planned implant position [27]. The advantage of using a guide is that the clinician can get closer to the ideal implant position that has been planned with the abutment in mind. Pilot guides offer an alternative that still allows the clinician to control the initial osteotomy and then complete the drilling protocol and the implant placement with precision. 9.1.5.5 Stackable Guides Stackable guides allow the use of two or more guides, fabricated using the same planning software and implemented with pins, screws, or sometimes magnets to transfer information from one stage to another. These fixation/pins/magnets sometimes require a separate guide [28]. The different guides may include (Fig. 9.15a, b): • A “surgical” guide is supported by either the teeth or mucosa and is used to place implants. • A “bone reduction” guide can be used to shape the osseous anatomy. • A “prosthetic” guide can be used to position the provisional prosthesis in the correct position before pickup.

9.1.5.6 Freehand Placement Freehand placement is possible. If the hard and soft tissue contours of the socket match the contours of the proposed provisional restoration, the

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217

b

Fig. 9.15 (a) Stack guide from Pinaud Planification. (b) Stack Guide from SMOP

The patient should be placed on a soft diet for 12 weeks post-surgery, provided with a bite guard for the opposing arch and reviewed after 2 weeks. Any non-resorbable sutures should be removed at this point. Any resorbable sutures can be left in place for a longer period and removed as needed.

9.1.6 Stage 6: Fabricating the Final Restoration

Fig. 9.16  Implant position showing prosthesis, placement depth, and multiunit abutment

ideal position and depth of the implant are easier to visualise (Fig. 9.16). It is important to remember that the implant will need to be placed 5 mm (depending on the abutment height) below the gingival margin of the proposed tooth to allow an ideal emergence profile.

9.1.5.7 Fabrication of the Provisional Restoration The fabrication method of the provisional restoration when using a Gallucci guide or WeldOne Shell has been described in the paragraphs preceding this. The occlusal principles that are used for other methods of full-arch restoration are the same as for an FP1 prosthesis. The occlusal scheme used in all full-arch restorations should ensure even contact in centric relation (CR) and posterior disclusion on lateral guidance.

9.1.6.1 The Digital Workflow The fabrication of the final restoration can be completed using both analogue and digital workflows. This technique works best with a well-­ adjusted provisional restoration that has been aesthetically and functionally tested and approved by the patient. If this is not the case, a second provisional restoration will be needed with any changes made, and only once this has been approved should the final restoration be fabricated using the triple-scan technique and digital workflow. The digital workflow is often utilised over three separate appointments: 1. Digital impression using the triple-scan technique. 2. Try-in and verification. 3. Fit final prosthesis. Appointment 1: Digital Impression Using the Triple-Scan Technique The triple-scan technique involves taking three scans and using digital technology to marry them up in the software. The workflow is different for the various brands of scanner, but the principle is

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the same. This technique has been described in the literature [29] (Fig. 9.17a–c): 1. Scan the prosthesis in the mouth, the opposing arch, and the bite. 2. Connect scan bodies to the abutments and scan the scan bodies. 3. Scan the prosthesis outside the mouth, especially the fit surface so that the emergence profiles and pontic shapes can be copied from the provisional to the final restoration. When these three scans are combined, they give the essential information needed to move onto the next stages. These involve working on: • The shape of the prosthesis including tooth shapes, tooth positions, pontic shapes, and the emergence profile. • The vertical dimension and opposing arch. • The abutment positions. The next stage of this workflow is to make a try-in and to verify the digital information. A try­in is needed as the information from the initial scan is merged within the software and this can lead to positional changes. Another reason that the design may need to change between the provisional and the final restoration is due to the material choice for the final prosthetic. The dental technician may need to make minor changes during the CAD process, and these changes may have aesthetic and functional implications. If monolithic zirconia is being used for the final restoration, the design parameters, including the minimum layer and connector thickness [16], need to be incorporated into the PMMA try-in. a

b

This CAD and then CAM process may mean that the try-in is bulkier in some areas than the provisional restoration. It is important at this stage for the patient to test the try-in and the dentist to assess all aspects. Appointment 2: Try-in and Verification From the information that has been sent to the laboratory, the dental technician will design and manufacture the following: 1. Digital model with analogue models. 2. Printed/milled PMMA try-in with link abutments. 3. A printed verification device. During the next appointment, the provisional restoration should be removed and the PMMA try-in placed in the mouth so the fit and occlusion can be assessed. If the thickness of the restoration has increased between the provisional and the try-in, then phonetics should be checked as well. It is important that the pontic sites engage the soft tissue in a way that creates a mucosal seal and prevents food impaction in these areas. If there are pontic sites where there is no engagement between the try-in and the soft tissue, composite should be added to engage the soft tissue in these areas and create a mucosal seal. The quality and accuracy of the digital model may vary from laboratory to laboratory for many reasons [30], so it is important to check the precision of the model each time. This can be done in two ways (Fig. 9.18a, b): 1. Pickup method. 2. Printed verification jig. c

Fig. 9.17 (a) Scan of the provisional restoration. (b) Elos scan bodies in place. (c) Scan of the provisional restoration

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

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b

Fig. 9.18 (a) 3D-printed verification device. (b) 3D-printed verification device linked with composite

a

b

Fig. 9.19 (a) Temporary cylinders in place over abutments. (b) 3D verification jig picked up

a

b

c

Fig. 9.20 (a) 3D verification poured into stone index. (b) Stone index. (c) Final bridge verified on stone index

Pickup Method

The first method [31] involves using a printed verification device that has a small amount of space to accommodate the multi-unit pickup ­cylinders. These are attached in the mouth as the device is placed and everything is picked up with dual-cure composite or pattern resin (Figs. 9.19a, b and 9.20a–c). This device can be used in several ways:

2. If the printed model is not accurate, one or more of the analogue teeth can be repositioned in the model to make this accurate. 3. A plaster cast can be poured with analogue teeth in place from the verification device, and this can be used as the working cast. This can be scanned and incorporated into the CAD for the design of the final bridge. Printed Verification Jig

1. To verify the accuracy of the printed model in one of the clinically accepted ways [32].

Sinada and Papaspyridakos [33] describe a method where a digitally designed and milled

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PMMA jig is made using data acquired from photogrammetry. This is designed to fit directly onto the multi-unit abutments and assessed with a screw resistance test, before a stone index is cast. The final prosthesis is cemented to link abutments on this stone index. It is necessary to note that there is still some debate about the accuracy of digital impressions from an intraoral scanner for full-arch implant dentistry [34]. Some of the more recent papers have concluded that the accuracy of full-arch digital impressions taken with an IOS is within a clinically acceptable range [35]. However, not all the reviews in the literature support this conclusion, and not all the intraoral scanners used in the studies perform as accurately as one another [36]. This should be considered when utilising a digital approach. In addition, the first method mentioned for fabrication with the stone index gives dentists a hybrid approach where the CAD can be performed digitally and the model made using an analogue workflow. This is later digitised to make the final restoration and used to support the cementation of the link abutments. This hybrid technique may be preferable for some clinicians. Not all dentists and laboratories will have the necessary equipment for digital input, but it is possible to use an analogue workflow for fabrication of the final restoration instead.

9.1.6.2 Using an Analogue Workflow As the prosthesis will be made with milling equipment, the final part of the process involves scanning and digitising the verified model that has been created so far. In this workflow, the following impressions are initially taken at the first restorative appointment: 1. Impression of the prosthesis in the mouth. 2. Impression of the opposing arch. 3. Bite registration. 4. Facebow registration. 5. Abutment level impression with open-tray impression copings unsplinted.

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From these impressions the laboratory will then produce: 1. Mounted upper and lower models in occlusion. 2. Screw-retained bite block to record the vertical dimension. The vertical dimension from the existing prosthesis can be copied if the mounted models are cross-mounted before the screw-retained bite block is made. 3. An unsplinted verification jig. At the second appointment, the dentist will then: 1. Check and adjust the screw-retained bite block to ensure the correct vertical dimension of occlusion. 2. Capture the implant positions, by removing the provisional restoration and joining the verification jig with the pattern resin, which is then also removed once everything is joined. 3. Capture the soft tissue. This is best done as soon as the provisional is removed, so if the provisional restoration has been out for a long time, it may be worth replacing the provisional for 5  min to allow the soft tissue to settle. All contours can then be captured accurately before any major soft tissue change occurs, which is inevitable with the restoration not in place [37]. This information is then digitised in the laboratory, and a printed/milled PMMA try-in with link abutments is manufactured. At the following appointment, the try-in is checked and verified. As in the digital workflow, the design may need to change between the provisional and the final restoration due to the material choice for the final restoration. Once any necessary adjustments have been made, it is re-tried in the mouth. More material may need to be added to the fit surface if the try­in does not engage with the soft tissue in the same way as the provisional restoration. Once the final restoration is approved, it is then sent for manufacturing.

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

7. Seal the screw channels with thread tape.

10. Apply the ceramic primer restoration. Let it air dry or gently dry with oil free compressed air.

8. CLEARFILTM CERAMIC PRIMER PLUS and Panavia V5 paste from Kuraray Noritake.

9. Apply the ceramic primer on the hybrid base.

Panavia V5 paste is available in 5 different colors. The opaque paste is self-curing and the other four are double curing.

Let it air dry or gently dry with oil free compressed air.

11. Apply the bonding cement paste with a brush, making sure that all surfaces on the hybrid bases are covered with cement.

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12. Place the restoration on the hybrid bases covered with cement and amount on the model and apply pressure. Remove the excess cemet that has been pushed out between the hybrid bases and the restoration.

Fig. 9.21  Elos bonding protocol

9.1.6.3 Laboratory Bonding Protocol Although many studies are showing good medium-term success rates for monolithic zirconia restorations [38], one of the issues reported is the debond of the link abutments [39]. A careful and researched bonding protocol for the link abutments should be followed [40], including use of well-researched and documented materials (Fig. 9.21).

9.1.7 Stage 7: Fitting the Final Restoration The final restoration is fitted at the next appointment. During the fit of the final restoration, it is important that the pontic sites engage the soft tissue in a way that creates a mucosal seal and prevents food impaction in these areas [41]. The static and dynamic occlusion should be checked, with an OPG radiograph taken to confirm fit.

The screw access holes should be filled with PTFE and flowable composite or glass ionomer, and subsequent review and maintenance appointments should be scheduled.

9.1.7.1 Patient Cleaning and Maintenance One of the ways in which the cleaning around an FP1 bridge differs from an FP3 bridge is that it requires minimal maintenance by the patient. The recommended cleaning regime should involve cleaning with an electric toothbrush, and in areas where there is food impacted around the papilla, use of an interdental brush is recommended. It is not necessary for the patient to clean underneath the pontic areas if a mucosal seal has been achieved. However, in cases where this has not taken place, superfloss or X- floss can be used, with the understanding that a mucosal seal will not develop in these areas.

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Case 1 Patient 1 Age 84 MH patient is on warfarin Patient Expectation The patient attended the practice having been referred in looking for a solution to her failing dentition. She was told after the previous consultation that her upper teeth would need extensive rehabilitation. She had considered looking at a solution where we would maintain some of the remaining teeth and place implants into the spaces. Still, due to the cost and timeframe, she opted for a solution where the remaining upper teeth would be removed and replaced with an implant-supported restoration. History of Presenting Complaint The patient has a heavily restored dentition, with most of the upper teeth root treated, crowned, and restored. However, many of the remained crowns have decay underneath them, and the bridge on the upper right-hand side has failed due to decay. Extraoral (Figs. 9.22, 9.23, 9.24 and 9.25) and intraoral (Figs. 9.26, 9.27 and 9.28) photographs were taken as part of the initial assessment. These photographs showed that the patient had a very high smile line with very significant gingival display (Figs. 9.22, 9.23, 9.24 and 9.25). There were no abnormal findings with the extraoral and intraoral examinations. The current occlusal scheme of canine guidance on the left and right side and protrusion on the UL1 was adequate, and we chose to conform to this while conducting this rehabilitation.

Fig. 9.23  Photos taken as part of the RAW protocol

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The planning for the facially driven wax-up was started with the interpupillary line to determine the horizontal plane and the midline. The central incisors were positioned in the correct position from a facial perspective (), and a tooth shape was selected from the two-­ dimensional library (Figs. 9.29, 9.30, 9.31 and 9.32). The OPG provided by the referring dentist showed a failing upper dentition (Fig. 9.33).

Fig. 9.22  Extraoral front-facing smile photo taken with head level and teeth visible. This will be used in the smile design

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

Fig. 9.24  The 12 o’clock view

Fig. 9.25  Smile photo

Fig. 9.26  Frontal photo retracted view

Fig. 9.27  Lateral photo retracted view

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An intra-oral scan was taken, and the STL was uploaded to Smilecloud alongside the photographs. Teeth were selected from the Smilecloud library, and a functional wax-up was prepared (Figs. 9.34, 9.35, 9.36, 9.37, 9.38 and 9.39). The extraoral and intraoral photographs were taken and processed using Smilecloud to ideally position the teeth based on the face and, from there, generate a facially driven diagnostic wax­up (Figs. 9.35, 9.36, 9.37, 9.38 and 9.39). During this planning, particular care was taken to note the position of the transition line (Fig. 9.40). Treatment Options Options discussed with the patient were either: 1. Keep and try and restore as many teeth as possible and place implants in the spaces. 2. Extract the remaining upper teeth, conduct osteoplasty beyond the transitions zone, place four implants within the premaxilla, and accept a shortened dental arch with final restorations extending from UL5 to UR5 (Fig. 9.41). 3. Extract the remaining upper teeth, conduct osteoplasty beyond the transitions zone, place two implants within the premaxilla and two zygomatic implants, and have final restorations extending from UL6 to UR6. 4. Extract the upper teeth, and conduct the needed augmentation and preservation to restore the patient with an FP1 bridge held with six implants (Fig. 9.42). The facially driven diagnostic wax-up (Fig.  9.43) was then adjusted using the virtual

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articulator (Fig. 9.39). This wax was then altered digitally to make a prosthetic shell (Figs.  9.44, 9.45, 9.46, 9.47, 9.48, 9.49, 9.50, 9.51 and 9.52). This prosthetic shell was then printed in NextDent C&B MFH (Micro Filled Hybrid) (NextDent B.V.  Soesterberg, the Netherlands) (Figs. 9.47, 9.48, 9.49, 9.50, 9.51 and 9.52). The following digital files were then imported into SMOP software:

Fig. 9.28  Upper occlusal photo showing failing upper dentition

Fig. 9.29  Extraoral photo combined with intraoral photo. The interpupillary line and midline have been added to this

Fig. 9.30 Proposed tooth shaped superimposed over Fig. 9.8. The positions of the teeth are determined using facial landmarks

1. Initial model (STL 01). 2. CT scan. 3. Diagnostic wax-up (STL 02). 4. Prosthetic shell (STL 03). These files are linked in a way that allows them to be imported with their coordinates allowing all the positions of STL 01, 02, and 03 in the design to be linked together, and if STL 01 is matched with the CT scan, the wax-up and shell positions are known as well. At this stage, a site-by-site assessment is conducted on all the potential areas where implants can be placed. The same criteria for assessing individual sites for immediate implants are applied to each site to ensure adequate primary stability after either extraction or partial extraction. The sites chosen in this case are the UL1, UL3, or UL4 and the UL6 on the left-hand side, and UR1, UR3, or UR4 and UR6. Once the implant positions were chosen, the stackable guide was built, and to do this, the following steps were taken. 1. Anchor pins are placed away from either implants or tooth roots. 2. Teeth that are not implant sites (UR2 and UL2) are left on the initial model (STL 01a).

Fig. 9.31  Alternative tooth shapes. These are from the original DSD Keynote

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Fig. 9.32  Facial landmarks and ideal proportions shown on facial, intraoral, and smile photos. Design by Smilecloud (Smilecloud, Timisoara, Romania)

Fig. 9.36  Intraoral scan of teeth at initial presentation

Fig. 9.33  Initial panoral radiograph supplied by referring dentist

Fig. 9.37  Facially driven digital wax-up

Fig. 9.34  Frontal view Fig. 9.38  Facially driven digital wax-up with incisal edge. Not needed

Fig. 9.35  Intraoral scan of teeth at initial presentation merged with frontal view

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Fig. 9.39  Digital articulation in Exocad (Exocad GmbH, Darmstadt, Germany). Design by Smilecloud (Dentcof, Romania)

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Fig. 9.43 Digital wax-up. Design by Smilecloud (Dentcof, Romania) Screenshot from Exocad (Exocad GmbH, Darmstadt, Germany)

Fig. 9.44  Digital wax-up adjusted in Exocad to make a prosthetic shell. Design by Steve Campbell at Nexus Dental Laboratory

Fig. 9.40 Transition line visible on high smile. Screenshot from Exocad (Exocad GmbH, Darmstadt, Germany)

Fig. 9.41  Proposed implant positions showing a shorter AP spread if bone reduction was conducted

Fig. 9.42  Proposed implant positions showing a good AP spread if no bone reduction conducted

Fig. 9.45  An alternative view of the prosthetic shell

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Fig. 9.47  The prosthetic shell 3D printed in NextDent C&B MFH (Micro Filled Hybrid) (NextDent B.V. Soesterberg, The Netherlands)

Fig. 9.46  An alternative view of the prosthetic shell Fig. 9.48 Adequate prosthetic space is left for the welded framework

Fig. 9.49  The tooth shapes on the prosthetic shell are derived from the facially driven wax-up Fig. 9.50  Surgical guide. Planning for this case has been conducted with SMOP (Swissmeda A,G Baar, Switzerland)

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Fig. 9.51  Location pins on the surgical guide. These will be used to give a reference point between the surgical and the prosthetic guide

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Fig. 9.54  On the day of surgery, frontal view

Fig. 9.55  On the day of surgery, occlusal view Fig. 9.52  The prosthetic guide. This will be used to seat the prosthetic shell in the correct position before the welded framework is picked up

Fig. 9.53  Upper photo retracted with contrastor in place

Fig. 9.56  Serial exactions are conducted and the teeth left in place are to support the surgical guide. Partial extraction therapy will be conducted before implants are placed

Two different guides are made: 1. One that has allowed placement of the anchor pins and the implants (STL 01a) (Fig. 9.53). 2. One that has the position of the prosthetic shell (STL 03) and the anchor pins (Fig. 9.29). This information was then sent to the laboratory, and the following were printed:

1. The surgical guide (Fig. 9.53). 2. The prosthetic guide (Fig. 9.29). 3. The prosthetic shell printed from composite. Before the day of surgery, the patient stopped the anticoagulants as advised by her general medical practitioner. Surgery (Figs.  9.54, 9.55, 9.56, 9.57, 9.58, 9.59, 9.60, 9.61, 9.62, 9.63, 9.64, 9.65, 9.66, 9.67, 9.68, 9.69 and 9.70).

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Fig. 9.57  Surgical guide in place

Fig. 9.58  Surgical guide in place

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Fig. 9.61  Pontic shield prepared for UL3

Fig. 9.62 Narrow multi-unit abutments have been placed, followed by the corresponding welding sleeves (Dentsply Sirona, Charlotte NC, USA)

Fig. 9.59  Implants in place Fig. 9.63  A 2 mm titanium wire has been bent and then welded to the welding sleeves to form a passive metal substructure that will be used to make the provisional restoration

The implants were placed on the day of surgery, and the restorative protocol first described by Dr. Marco Degidi (Weldone) was conducted.

Fig. 9.60  Implants in place. UR6 has been placed as an immediate implant into the palatal socket. Note the UL3 root has been sectioned

• The posterior teeth were extracted. • The anterior teeth were decoronated apart from the lateral incisors (Figs. 9.56 and 9.57). • The UL2, UL1, UR1, and UR3, were prepared for PET (Fig. 9.38).

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Fig. 9.64  Intraoral view of titanium wire bent around the temporary cylinders

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Fig. 9.67  During the pickup, the framework is secured on one implant and seated, and then picked up with combo.lign (Bredent, Senden, Germany) dual-cure composite inside the printed composite shell. An extra-long screw that is usually used for impression posts has been used to allow the framework to be removed easily

Fig. 9.65  The prosthetic shell is tried in the mouth and then checked if it seats without interference

Fig. 9.68  Frontal view of acrylic pick up

Fig. 9.66  The titanium frame will be picked up inside the printed shell Fig. 9.69  The metal framework and printed shell imme-

• 6 Ankylos C/X (Dentsply Sirona) implants diately after pickup were placed in the UL6, UL3, UL1, UR1, UR3, and UR6 positions using the surgical guide, and the primary stability of greater than • A 2  mm titanium wire was attached to the 25 Ncm was achieved in all sites. welding sleeves, and the wire was intraorally • After placement of the implants, six straight welded to form a metal framework linking the balance base narrow (Dentsply Sirona) multi-­ abutments (Fig. 9.63). unit abutments were placed. • The titanium wire is removed and trimmed to • Welding sleeves were attached to the multi-­unit fit into the shell and checked outside the abutments and torqued to 15 Ncm (Fig. 9.62). mouth.

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Fig. 9.70  Soft tissue grafting and socket preservation. A combination of techniques has been used. For the UL2 and UR2, rotated pedicle grafts have been used. Socket preservation has been conducted using a xenograft (Bioss, Geistlich Pharma Ag, Lucerne, Switzerland); PRFG has been used to contain some of the granules of xenograft

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Fig. 9.72 The provisional restoration matches the wax-up

Fig. 9.73 The provisional restoration in place. Cyanoacrylate (tissue glue) has been used to aid haemostasis on the palate Fig. 9.71  The provisional bridge is finalised. Work by Jamie Brain CDT from JB Denture Clinic

• The printed shell is tried in the mouth to check that it can be seated without interference (Fig. 9.65). • The titanium wire is sandblasted and anodised in preparation for intraoral pickup (Fig. 9.66). • The printed shell is primed in preparation for the pickup, and a hole is made in the area where a single screw will be used to hold the titanium wire in place during the pickup. • The titanium wire is picked up inside the shell with dual-cure composite. • Once the shell is picked up, this is given (Fig. 9.69) to the technician to finish and polish. As part of the finishing, the correct subgingival shape and emergence profile of the bridge abutments and the correct shape of the pontics are fabricated (Fig. 9.71). • While the technician was working on the bridge, soft tissue augmentation was con-

Fig. 9.74  The provisional restoration in place

ducted. Inverted pedicle grafts were placed on the UL2 and UR2 as these teeth need vertical augmentation. PRGF was placed in the sockets of the UR6 and UL6. Xenograft was placed on the sockets of the remaining teeth (Fig. 9.70). • The provisional bridge is fabricated with the correct pontic shapes and emergence profiles (Fig.  9.72), and the provisional bridge is a direct copy of the diagnostic wax-up. • This is torqued to 15  Ncm, and the bite is checked and adjusted, the occlusal scheme chosen in canine guidance on lateral excursions and protrusive on the upper central (Figs. 9.73 and 9.74).

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Final Restoration After a period of healing of 12  weeks, the patient returned for a review (Figs.  9.75, 9.76, 9.77, 9.78 and 9.79). At this point, the implant integration was checked, and the restoration process was started.

Fig. 9.79  Occlusal view

Fig. 9.75  The patient at the 4-week review

Fig. 9.80  Radiograph taken after placement and before final restoration

Fig. 9.76  Frontal view showing occlusion

Fig. 9.81  Provisional restoration in place

Fig. 9.77  Lateral view

Fig. 9.78  Lateral view

A panoral radiograph was taken at this stage (Fig.  9.80). The restoration process involves copying the soft tissue and occlusal contours while ensuring the final restoration will have adequate thickness and cross-sectional area to prevent the zirconia from fracturing. Therefore, the material change will mean thickness changes from the provisional to the final restoration. The provisional bridge (Fig. 9.81) is removed (Fig. 9.82), and having removed the provisional bridge, the soft tissue is checked, and the implant integration is checked (Fig. 9.83). At this point,

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Fig. 9.82  Provisional restoration removed

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Fig. 9.85  Elos scan bodies in place. Please note this image is taken after two of the scan bodies have been removed

Fig. 9.83  Provisional restoration removed

Fig. 9.86  Screenshot with Elos scan bodies in place. Scan taken with Trios Scanner (3Shape, Copenhagen, Denmark)

Fig. 9.84  Elos scan bodies are connected to the multi-­ unit abutment in place (Elos Medtech, Gorlose, Denmark)

Elos scan abutments are placed on the abutments and talked by hand (Figs.  9.84, 9.85 and 9.86). These were scanned with a Trios scanner, and three scans were taken. 1. A scan of this bridge provisional bridge in place (Fig. 9.87). 2. A scan of the opposing arch. 3. A scan of the bite (Fig. 9.88). 4. A scan of the scan bodies on the multi-unit abutments.

Fig. 9.87  Screenshot with Elos scan bodies and provisional superimposed. Taken with the triple-scan technique. Screenshot taken from Trios 3 scanner (3Shape, Copenhagen Denmark)

These were sent off to the laboratory (Uniqa Dental Lab), a model was printed with model analogues (Elos Medtech), and a verification jig was made.

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Fig. 9.91  Verification jig in place Fig. 9.88  Screenshot showing provisional restoration in occlusion. The tripe scan technique allows the capture of the abutment position, vertical dimension, shape of the provisional restoration, and soft tissue contours in the scans. Screenshot taken from Trios 3 scanner (3Shape, Copenhagen Denmark)

Fig. 9.92  Soft tissue contours before try-in inserted

Fig. 9.89  Milled PMMA try-in with link abutments

Fig. 9.93  Facial photo with try-in in place

Fig. 9.90  Digital model with verification jig in place

The lab was then instructed to make a PMMA try-in (Fig. 9.89) using the link abutments from the library, which was then tried in along with the verification jig made on the printed model (Fig. 9.90). Due to the inaccuracy of the printed models, it is essential not to take the printed model or the

verification jig as absolute verification of the implant position (Fig.  9.91). The provisional bridge is removed (Fig. 9.92). The try-in is used for an aesthetic evaluation. The patient is continuously put through the DSD process during this aesthetic evaluation, with the interpupillary line in the midline checked (Figs.  9.93, 9.94, 9.95, 9.96 and 9.97). Instructions were given to the laboratory for any final modifications to the final prosthesis,

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Fig. 9.97  Laboratory communication to request changes to the shape of the try-in Fig. 9.94  The try-in is put through the same digital smile design process. Final bridge design by Alina Roscoe at Uniqa dental laboratory

Fig. 9.95  Laboratory communication to request changes to the shape of the try-in

Fig. 9.96  Laboratory communication to request changes to the shape of the try-in

such as changes to the gingival margin, changes in tissue pressure, and spacing between the interdental areas. The laboratory then imports these photographs, which are taken with the try-in in the

mouth, and these are taken and then from and then put through the 3Shape design software (Figs.  9.98, 9.99, 9.100, 9.101, 9.102 and 9.103). The PMMA try-in is copied to form the final bridge, with special care taken to allow for the adequate thickness of the zirconia to be used. This final restoration is then milled in the relevant zirconia, hand-finished, stained with Miyo, and sent to the practice (Figs.  9.104, 9.105, 9.106, 9.107, 9.108, 9.109, 9.110 and 9.111). The final bridge is then picked up inside the mouth to pacify it, using the KAL (Kulzer abutment luting) technique. Once picked up inside the mouth and the occlusion checked, it is sent back to the laboratory for the final processing stages, and the link abutments are cemented. The process of replication from the wax-up to the shell temporary to the final restoration is shown in Fig. 9.112. The final bridge is fitted in the mouth, and a facial photograph (Fig. 9.113) and the final radiographs are taken (Figs. 9.114, 9.115, 9.116, 9.117, 9.118, 9.119, 9.120, 9.121, 9.122 and 9.123). Case 2 The patient presented with a failing upper dentition. The UR1, UR3, and UL2 were intact. However, the UL1 and UR2 are fractured at the gum level (Fig. 9.124a). A radiographic examination showed minor vertical bone deficiency in the posterior quadrants (Fig. 9.124b).

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Fig. 9.98  The photos with the try in are imported back into the milling and design software (3Shape dental system, 3Shape, Copenhagen, Denmark)

Fig. 9.99  The Final bridge is superimposed onto the two-­ dimensional photograph

Fig. 9.100  The design of the final bridge Fig. 9.101  The design of the final bridge

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Fig. 9.102  The design of the final bridge

Fig. 9.105  Milled zirconia bridge after removal from the milling machine

Fig. 9.103  The design of the final bridge. Final bridge design by Alina Roscoe at Uniqa dental laboratory

Fig. 9.106  Milled zirconia bridge after removal from the milling machine

Fig. 9.107  Staining process with Miyo Stain kit (Jensen Dental, North Haven, Connecticut). Final stain and finishing by Khristo Ivanov by at Uniqa dental laboratory Fig. 9.104  The final zirconia bridge ready to be milled

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Fig. 9.111  Final bridge Fig. 9.108  Staining process with Miyo Stain kit

Fig. 9.112  Printed model of diagnostic wax-up. Printed shell based on the wax-up. Final zirconia bridge. All of these show the same tooth shape and position that has been designed from the facially driven wax-up Fig. 9.109  After sintering and before final staining (this needs to be checked)

Fig. 9.110  Final bridge

Fig. 9.113  Smile photo of patient with final bridge in place

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Fig. 9.116  Final restoration in place

Fig. 9.114  After removal of the provisional restoration

Fig. 9.117  OPG of the final restoration in place

Fig. 9.115  Final restoration in place Fig. 9.118  Final bridge in place

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Fig. 9.119  Before and after photos side by side

Fig. 9.123  Smile at the start of treatment

a

Fig. 9.120  Start photo and screenshot of STL

b

Fig. 9.124 (a) Smile photo. (b) Initial panoral radiograph Fig. 9.121  Final photo and screenshot of wax up

Fig. 9.122  Smile with bridge in place

The patient presented with moderate tooth wear on the lower arch and a missing tooth on the lower right side. Lateral views show an edge-to-edge pint with incisal wear and chipping on both the left- and the right-hand side (Figs.  9.124, 9.125, 9.126, 9.127, 9.128, 9.129 and 9.130). As part of the process of rehabilitation and assessment, a digital impression was taken and sent to the laboratory (Fig.  9.131). A facially driven diagnostic wax-up was made from this digital impression.

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Fig. 9.125  Left lateral view retracted view

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Fig. 9.129  Upper photo retracted with contrastor in place

Fig. 9.126  Right lateral view retracted view Fig. 9.130  Frontal view of remaining teeth in occlusion

Fig. 9.127  Upper occlusal photo showing failing upper dentition

Fig. 9.131  Digital models for diagnostic work up

The diagnostic wax-up was combined with a CT scan and the initial situation described earlier in this chapter. A multifunctional guide was made with implants planned on the UL1, UL4, UL6, UR1, UR4, and UR6 areas (Figs.  9.132, 9.133, 9.134, 9.135, 9.136, 9.137, 9.138, 9.139, 9.140, 9.141 and 9.142). The implants were positioned using Simplant to the correct depth to allow the correct emergence profiles with the necessary multi-unit abutment (Fig. 9.140). Fig. 9.128  Lower occlusal photo

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Fig. 9.132  Upper STL file of presenting situation (STL 01). This is prepared in Simplant (Dentsply Sirona, Charlotte NC, USA)

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Fig. 9.136  STL 01 merged with STL 03

Fig. 9.137  STL 03 and CT scan Fig. 9.133  STL 01 merged with CT scan

Fig. 9.138  CT scan showing planned implant position Fig. 9.134  STL 01 merged with CT scan merged with facially driven wax-up (STL 02)

Fig. 9.135  STL 02 merged with multifunctional guide (STL 03)

Fig. 9.139  Multifunctional guide with planned implants and abutments in place. The multifunctional guide is printed with NextDent C&B MFH (Micro Filled Hybrid) (NextDent B.V. Soesterberg, the Netherlands)

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Fig. 9.140  Multifunctional guide with planned implants and abutments in place

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During the assessment process, the depth of implant placement was planned to allow the correct emergence of the multi-unit abutments and the correct emergence profile around each of the abutments and each of the pontics (Fig. 9.141). On the day of surgery, partial extraction therapy was conducted on the remaining anterior teeth (Fig. 9.143). A remote palatal incision was conducted on the maxilla’s upper left and right-­ hand sides (Fig. 9.144). The multifunctional guide was dried in as it was tried in the bony contours adjusted to allow the necessary 2 mm between the base of the pon-

Fig. 9.141  Planned implants and abutments in place. The depth of placement and the emergence profile can be planned

Fig. 9.142  Multifunctional guide in Exocad (Exocad GmbH, Darmstadt, Germany)

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Fig. 9.143  Day of surgery. Partial extraction therapy (PET) is being conducted on the remaining teeth and roots

Fig. 9.144  PET completed on UL1 and UR1. Incisions in the posterior sextants

Fig. 9.145  Multifunctional guide in place. This is being used to ensure that any osseous contouring is conducted where needed and to create the correct shape of the ridge

tic and the bone for an adequately designed pontic (Fig. 9.145). Six implants were placed in the correct positions with the aid of a pilot guide, multi-unit abutments were placed (Fig. 9.146), and temporary cylinders were attached to the implants and picked up in the multifunctional guide (Figs. 9.147 and 9.148).

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Fig. 9.146  Implants and abutments in place. Uni abutments from the EV system (Dentsply Sirona, Charlotte NC, USA)

Fig. 9.147  Pick-up cylinders in place

Fig. 9.148  Multifunctional guide picked up with combo. lign (Bredent, Senden, Germany)

Soft tissue was taken from the tuberosity area and placed in and around the upper posterior segments and the UL3 (Fig. 9.149). A provisional restoration was fabricated by the technician (Fig.  9.150). Suturing was conducted around the provisional restoration (Figs. 9.151 and 9.152). A panoral radiograph was taken of the implants in place after surgery (Fig. 9.153).

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Fig. 9.149  Soft tissue harvested from the tuberosity

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Fig. 9.153  Radiograph taken after placement

Fig. 9.154  Provisional restoration at 12 weeks Fig. 9.150  The provisional bridge is finalised. Work by Jamie Brain CDT from JB Denture Clinic

Fig. 9.155  Provisional restoration removed

Fig. 9.151  The provisional restoration in place

Fig. 9.152  The provisional restoration in place

After 12 weeks of healing, the patient returned for the impression appointment (Fig. 9.154). At this appointment, the provisional bridge was checked (Fig.  9.155) and removed (Fig.  9.156), and the pontic areas were checked to ensure adequate hygiene and engagement of the pontic into the soft tissue. Scan bodies for multi-unit abutments were placed onto the abutment and torqued by hand (Fig. 9.157). Temporary cylinders were placed onto the abutments (Fig. 9.158), scanned with a Primescan, and sent to the laboratory along with the copy of the scan bodies (Fig. 9.157) and scans of the pro-

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visional bridge inside and outside the mouth. Unfortunately, one of the abutments was loose and needed to be torqued again to 25 Ncm. This movement meant that the initial impression would not be accurate, meaning a second impression appointment would be required. The lab designed a 3D-printed pickup jig (Fig.  9.159) to be used at the next appointment and a PMMA try-in with the correct link abutments (Figs. 9.160 and 9.161). Fig. 9.156  Provisional restoration removed This try-in will have the same emergence profiles and pontic shapes from the provisional ­restoration but will have the dimensions necessary for the zirconia (Figs. 9.160 and 9.161). At the second impression appointment, the try-in was placed inside the mouth (Fig. 9.162). The pick-up jig was put into the mouth along with the temporary cylinders (Figs.  9.163 and 9.164). These were secured with composite and sent to the laboratory alongside new scans using the triple-scan technique (Figs. 9.165, 9.166 and 9.167). Fig. 9.157  Elos scan bodies are connected to the multi-­ Scan of the provisional inside the mouth unit abutment in place (Elos Medtech, Gorlose, Denmark). (scan 1). The triple-scan technique is being used Scan of the provisional outside the mouth (scan 2) (Fig. 9.167). Scan of the scan bodies attached to the abutments (scan 3). The final prosthesis was designed (Fig. 9.168), milled (Fig. 9.169), and processed (Fig. 9.170) in the laboratory, and Miyo staining was applied (Fig. 9.171). It is important to note that there will be a difference in the soft tissue profile which means ignoring the shape of the soft tissue on the scan that the laboratory receives and using the shapes copied from the provisional to make the final restoration (Figs. 9.172 and 9.173). Fig. 9.158  Pickup cylinders in place Fig. 9.159 3D-printed pickup jig has been designed to fit around the pickup cylinders

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Fig. 9.160  Design of the try-in. This is designed as a copy of the provisional restoration

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Fig. 9.163  Pickup jig in place. This is designed to ensure very small (0.5 mm) space between the jig and the cylinder and is placed in the mouth so that it sits passively. Printed in NextDent SG (surgical guide) (NextDent B.V. Soesterberg, the Netherlands)

Fig. 9.161  Design on the try-in

Fig. 9.164  Dual-cure low shrinkage composite is placed into the spaces and the jig is picked up

Fig. 9.162  PMMA try-in is checked in the mouth

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Fig. 9.165  At this appointment, the triple-scan technique is used to capture the occlusion, vertical dimension, abutment position, soft tissue contour, and the shape of either

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provisional restoration or the try-in. The scanner used here is the Primescan (Dentsply Sirona, Charlotte NC, USA)

where the smile line has changed after having more confidence in their smile.

Fig. 9.166  The captured files on the Primescan

Once the processing was complete, the final bridge was placed onto the stone index created by pouring a model from the pickup jig (Fig. 9.174), and the link apartments were cemented (Figs. 9.175 and 9.176). The bridge was placed inside the mouth, and the screws were torqued to 15 Ncm (Figs. 9.177, 9.178 and 9.179), and a final panoral radiograph was taken to verify the fit of the final prosthesis (Fig. 9.180). We can see the patient’s smile before treatment (Fig. 9.181) and after treatment (Fig. 9.182),

Case 3 Treatment planning should be based on a thorough diagnosis to culminate in an appropriate treatment plan for the patients presenting clinical situation. Unfortunately, the All-on-4™ concept has been used as a panacea for full-arch implant reconstruction, and often patients are treated dogmatically with this treatment protocol. Often, the bone is removed needlessly to satisfy a certain treatment philosophy. Minimally invasive full-arch implant dentistry adheres to the concept of preserving and maintaining bone. Bone reduction is virtually eliminated, and the patient maintains their own gingiva. Although four implants are considered standard, the placement of additional implants is considered advantageous. As a practicing clinician, implant failure is always a concern, and should one of four implants fails, the definitive restoration need to be remade at the restorative dentist’s cost. If more than four implants have

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Fig. 9.167  The provisional restoration is scanned inside and outside the mouth

Fig. 9.168  Design of the final restoration. Final bridge design by Alina Roscoe at Uniqa dental laboratory

Fig. 9.170  Staining process with Miyo Stain kit (Jensen Dental, North Haven, Connecticut). (Photo by Khristo Ivanov)

Fig. 9.171  Final zirconia bridge Fig. 9.169  Zirconia framework after milling and hand finishing. Final stain and finishing by Khristo Ivanov by at Uniqa dental laboratory. (Photo by Khristo Ivanov)

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Fig. 9.172  Design of undersurface of proposed zirconia restoration showing convex contours and its relationship to the tissue

Fig. 9.175  Final zirconia bridge on the plaster base

Fig. 9.173  Cross section of the final restoration design. We can check this to ensure we have adequate cross-­sectional thickness of the zirconia framework, and the soft tissue profile of the final is copied from the provisional restoration

Fig. 9.176  Final zirconia bridge on the plaster base

Fig. 9.177  About to seat the final

Fig. 9.174  The pickup jig is used to cast a plaster base. This will be used to verify the digital model and to cement the zirconia framework to the link abutments

Fig. 9.178  Final bridge in place

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

Fig. 9.179  Final bridge in place

Fig. 9.180  OPG of final zirconia bridge in place

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nician must be cognisant that for wider stress distribution and biomechanical integrity of the restoration, the implants must satisfy the requirement of a favourable anteroposterior spread. In many clinical situations, there is an abundance of bone where more than four implants can be placed, and bone reduction may not be required. It is the authors’ opinion that more than four implants are required when: 1. There is an abundance of bone and biomechanically cantilevers can be avoided. 2. The patient presents with a dentition that exhibits signs and symptoms of excessive force. 3. Patient has uncontrolled metabolic disease which compromises healing. 4. Poor-quality bone. The advantages and considerations of placing more implants and preserving bone include the following:

Fig. 9.181  Smile at the start of treatment

Fig. 9.182  Smile at the end of treatment. Please note that the increased confidence has meant the patient gingival display has increased significantly

been placed, then there are reserve implants to work with. These additional implants also help in distributing stress over a wider area. The cli-

1. There is the ability to segment the prosthesis and complication management becomes easier for the clinician. 2. If in the future an implant were to fail, there are enough implants where the patient may not have to undergo surgery again. 3. The thought process that making an impression on four implants is easier than making an impression on five or six does not hold merit. Today with advancements in digital technologies, analogue impression making may soon become obsolete at multi-unit abutment level. 4. When placing implants, the clinician must begin with the end in mind visualising the definitive restoration. Zirconia requires specific connector dimensions and requires appropriate distance between implants. Zirconia also requires specific thickness for biomechanical integrity. The implants together with the multi-unit abutments must be positioned three-dimensionally to allow for this. 5. Maintenance of bone in between the implants can be obtained by banking roots.

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6. If a catastrophic failure were to occur and all the implants were lost, then the clinician still has the opportunity to retreat the patient. The following patient presentation illustrates the philosophy of minimally invasive implant therapy for full-arch implant rehabilitation utilising digital technologies. A 62-year-old female presented seeking a solution to her failing maxillary dentition. Her teeth had been compromised due to periodontal disease. She also presented with a previous history of dental implant failure (Figs. 9.183, 9.184 and 9.185). On clinical and radiographic examination, her maxillary dentition was deemed to be of poor prognosis. She had inadequate amount of bone in

M. Wanendeya and S. Jivraj

the upper left quadrant due to bone loss and pneumatisation of the maxillary sinus. The patient was treatment planned for maxillary full-­ arch implant rehabilitation with sinus bone augmentation in her upper left quadrant. The patient’s concerns were the following: 1. She did not want to wear a removable appliance at any point during the treatment process. 2. She wanted the teeth to look and feel like her own. 3. She wanted teeth back to the second molar. Considerations in implementing care were the following:

Fig. 9.183  Preoperative radiographs

Fig. 9.184  Buccal view of patient showing minor crowding and deep vertical overlap

Fig. 9.185  Smile view of patient showing display of gingiva when smiling

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1. History of periodontal disease and previous implant failure. 2. History of diabetes. 3. Preservation of bone. 4. Being able to provide implant bridgework which resembles her existing dentition without pink ceramics. 5. Transitioning the patient with fixed restoration during the entire treatment process. The above considerations required a more cautious approach in treatment planning and execution. Immediate loading of the implants was eliminated in favour of healing and conventional load. Immediate loading of implants should only be done after a thorough evaluation of the risk factors involved and not performed dogmatically. Treatment Plan and Sequence 1. Intraoral scans were completed (Trios 3Shape technologies) and shell provisionals were milled (ProArt CAD Ivoclar Vivadent), utilising key strategic teeth which would anchor the restoration while implants were integrating (Figs. 9.186 and 9.187). 2. Sinus lift and bone augmentation were completed on patient’s upper left quadrant. Extraction of strategic teeth and placement of dental implants were conducted. Strategic teeth would be prepared to hold a provisional restoration so implants would not be loaded. This decision was made due to a history of failed implants and history of diabetes (Figs. 9.188 and 9.189).

Fig. 9.187  Printed tooth-supported surgical guides

Fig. 9.188  Day of surgery: strategic teeth have been extracted, implants placed, and bone allograft placed in extraction sockets. Shell provisionals relined

Fig. 9.189  Postoperative characterized provisional

Fig. 9.186 Digitally milled shell provisionals from PMMA puck (Ivoclar ProArt)

3. Placement of implants in the upper left quadrant. 4. On integration implant impressions would be made to fabricate an implant supported provisional. This would be segmented (Fig. 9.190). 5. Extraction of remaining teeth and grafting of extraction sites with a bone xenograft to maintain ridge height and width and delivery of segmented provisionals.

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Fig. 9.190  Strategic teeth have been extracted and milled and implant-supported provisional placed

M. Wanendeya and S. Jivraj

Fig. 9.192  Occlusal view of milled prototype showing segmentation of prosthesis and anteroposterior spread of implants

Fig. 9.191  Milled prototype from acrylic puck fabricated in three segments

6. Tissue maturation and stabilisation. 7. Fabrication of prototype to verify aesthetics, phonetics, and occlusion (Figs.  9.191, 9.192 and 9.193). 8. Fabrication of segmented zirconia restoration supported by implants (Figs.  9.194, 9.195, 9.196 and 9.197). 9. Maintenance.

Fig. 9.193  Intraoral adjustment of prototype

By completing the above sequence, the following objectives were met: 1. Transitioning the patient through fixed provisional restorations at all times. 2. Preservation of bone. 3. Eliminating the risk associated with immediate loading in a patient that has a history of previous implant failure. 4. Minimising risk in a patient who has periodontal disease and type 2 diabetes. 5. Placement of more than four implants and segmentation of the restoration. 6. Utilisation of technology to make treatment more efficient.

Fig. 9.194  Minimally layered zirconia prosthesis fabricated in three segments (ceramics by Artem Asemov)

Case 4 Often, patients refuse additional grafting procedures, and there is insufficient bone to be able to place more than four implants in each arch. In these clinical situations, the patient must be made aware

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

Fig. 9.195  Minimally layered zirconia prosthesis

Fig. 9.196  Intraoral view of minimally layered zirconia prosthesis

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of the advantages and disadvantages of such treatment protocols and must be fully aware of the clinical and financial consequences of implant failure. The following patient presentation illustrates the philosophy of minimally invasive implant therapy for full-arch implant rehabilitation utilising four implants in each arch and digital technologies. A 71-year-old female presented seeking a solution to her failing maxillary and mandibular dentition. A detail medical and dental evaluation was performed. Specific concerns in treatment planning were multiple medications that resulted in the patient being xerostomic. The patient’s teeth had been compromised due to caries and periodontal disease (Figs.  9.198, 9.199, 9.200 and 9.201). The following diagnoses were made: 1. Caries. 2. Periodontal disease. 3. Lack of posterior support. 4. Bimaxillary protrusion. On clinical and radiographic examination, her maxillary and mandibular dentition was deemed to be of poor prognosis. The following clinical issues required attention: 1. Lack of bone in the posterior maxilla. 2. Over-eruption of teeth compromising restorative space. 3. Flaring of teeth. 4. High smile line with excessive gingival display.

Fig. 9.197  Smile view of restoration in situ

Fig. 9.198 Preoperative clinical view of smile and retracted intraoral view

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The patient’s concerns were the following: 1. The patient did not want to wear a removable appliance at any point during the treatment process. 2. The patient wanted to address the bimaxillary protrusion. (a) The patient refused grafting procedures. Considerations in implementing care were the following:

Fig. 9.199  Full face

Fig. 9.200  Peri-apical radiographs

Fig. 9.201  Lateral view of smile showing over-eruption and flaring

1. Multiple medications causing the patient to be xerostomic. 2. The patient’s smile line exhibited excessive gingival display and a short lip. It is the authors’ opinion that bone reduction and use of pink prosthetics in these types of clinical situations are contraindicated (Fig. 9.202). 3. Preservation of bone. 4. Providing an FP1 prosthesis and addressing the bimaxillary protrusion. This would entail

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Fig. 9.202  White lines showing anticipated positioning of maxillary and mandibular incisal edge

Fig. 9.203  Milled provisional

palatal placement of dental implants and carefully selecting a pre-angled multi-unit abutment to ensure appropriate emergence profile. 5. Providing an anteroposterior spread that is optimal. Placement of implants that do not compromise connector size for the definitive restorations. 6. Minimal alveolar bone recontouring to lift the maxillary occlusal plane up and to lower the mandibular occlusal plane. 7. Transitioning the patient with fixed restoration during the entire treatment process. The above considerations required a more cautious approach in treatment planning and execution. Treatment Plan and Sequence 1. Intraoral scans were completed (Trios 3Shape technologies), and shell provisionals were milled (ProArt CAD Ivoclar Vivadent) (Fig. 9.203).

2. The patient was treated surgically and prosthetically in 1  day, utilising laboratory ­fabricated static surgical guides. No guided surgery was performed per se. The surgical guides were stabilised on retained teeth and osteotomies of the anterior implants were performed. Four implants were placed in the maxilla and four in the mandible. Multi-unit abutments were secured and soft tissue closure was achieved. Deep sedation with profound local anaesthesia was used to remove all teeth except ones needed for stability of bone reduction and surgical stent. A tooth-­ supported surgical guide was provided to ensure accurate three-dimensional placement of implants in the maxilla. This required careful depth placement so that a pre-angled multi-unit abutment could be selected with a minimum collar height. This would allow correction of the flaring of the teeth as well as an optimal emergence profile. Alveolectomy was completed in the mandible to provide appropriate restorative space and correct the mandibular incisal edge position. The mandibular bone was reduced minimally to create a platform for implant placement. The patient was informed that the mandible may require pink prosthetics. The patient’s provisional immediate load prosthesis was fabricated on same day as implant placement. The patient tolerated the procedure well and healed uneventfully. 3. A direct technique for immediate loading was employed. Vertical dimension, centric relation, and occlusal plane were verified. After

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protection of the surgical sites with rubber dam, temporary cylinders were first picked up in the maxillary prosthesis. Patient was guided into centric relation, and a similar pickup of temporary cylinders was performed in the mandibular provisional restoration. The prostheses were removed and transferred to the dental laboratory where the prostheses were processed and finished. The prostheses were adjusted to compress the tissue by 2 mm and to develop the pontic sites from the outset. Twelve teeth were provided in the maxilla and ten teeth in the mandible. Occlusion was adjusted for shimstock hold on anterior teeth and shimstock drag on the posterior teeth. Vertical dimension was verified on delivery of the restoration. Extraction of remaining teeth and grafting of extraction sites with a bone xenograft were conducted to maintain ridge height and width. Moreover, delivery of segmented provisionals was (Figs. 9.204, 9.205, 9.206 and 9.207).

Fig. 9.205  Smile view showing tooth display. Increased length can be adjusted in provisionals

Fig. 9.204  Immediate load provisional restorations in situ

Fig. 9.207  Lateral view of provisionals

Fig. 9.206  Milled prototype from acrylic puck fabricated in three segments

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations

4. Tissue maturation and stabilisation. 5. Post-integration and additional provisional restoration were fabricated to ensure verification of aesthetics, phonetics, and tissue compression (Fig. 9.208). 6. Splinted open-tray impressions, jaw relation records, and tooth try-ins were performed. Additional provisional restorations were fab-

ricated. Aesthetics, phonetics, and soft tissue contours were further developed in the provisional restoration. 7. Minimally layered zirconia restorations were fabricated for both maxilla and mandible. Occlusion was provided on polished zirconia. Tissue contacting surface was designed in polished zirconia (Figs.  9.209, 9.210, 9.211 and 9.212). 8. The prosthesis was delivered adjusting the undersurface to ensure positive pressure. Dynamic occlusion was adjusted for canine guidance. Static occlusion was adjusted to ensure shimstock hold on canines and pre-

Fig. 9.208  Second set of provisionals fabricated

Fig. 9.210  Layered restorations in situ Fig. 9.209  Minimally layered zirconia prosthesis

Fig. 9.211  Lateral view depicting change in occlusal plane, flaring and incisal edge positions

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molars. Shimstock drag on anterior teeth and no contact on the cantilevers (Fig. 9.213). 9. Screws were torqued according to the manufacturer’s instructions, and access holes were sealed using Teflon and composite resin. By completing the above sequence, the following objectives were met: 1. Transitioning the patient through fixed provisional restorations at all times. 2. Preservation of bone and fabrication of an FP1 prosthesis in the maxilla. 3. Restoration of posterior support. 4. Satisfying the patients’ aesthetic concerns and solving the issue of bimaxillary protrusion. 5. Utilisation of technology to make treatment more efficient prosthetically.

Fig. 9.212  Smile view of restoration in situ

Fig. 9.213  Pre- and postoperative views following rehabilitation. (Ceramics by Artem Asemov)

9  FP1 Concepts in Rehabilitating the Edentulous Patient with Implant-Supported Restorations Acknowledgements from Dr. Wanendaya Thanks especially to my family (Sarah, Felix, and Jasper) and friends for the trust and the support I get from you every day. Thank you to all the team and Ten Dental, but specific thanks to the team members directly involved with treatment of patients in this chapter: Violeta Maftei, Valeria Andrade, Agata Polak, Mihaela Simona, and Maria Ivan. Thank you to the dental technicians involved in cases 1 and 2: Steve Campbell, Jamie Brain, Alina Rosca, Khristo Ivanov, James Cox, Hugo Patrao, and Fabio Trindade. Thank you to the individuals who have always helped and supported me through this time: Nigel Jones, Tushar Patel, Will Murphy and Paul Swanson. A special thanks to Paulo Carvalho and Nik Sisodia for their clinical support in getting to this point on our ever-evolving FP1 journey. I would like to acknowledge Paulo as the inventor of the “prosthetically driven healing” technique that has made FP1 so much more accessible as a treatment modality. Thank you to Dr. Jonathan Gordon for the surgical expertise in case 3. Thank you to Dr. Hessam Siavesh for the surgical expertise in case 4. Ceramics in cases 3 and 4 were done by Artem Asemov, Digital Dental Arts laboratory Ventura, CA.

References 1. Misch CE. Dental implant prosthetics. St. Louis, MO: Elsevier Mosby; 2015a. 2. Yang Y, Hu H, Zeng M, et al. The survival rates and risk factors of implants in the early stage: a retrospective study. BMC Oral Health. 2021;21:293. https:// doi.org/10.1186/s12903-­021-­01651-­8. 3. Coachman C, Calamita MA, Sesma N. Dynamic documentation of the smile and the 2D/3D digital smile design process. Int J Periodontics Restorative Dent. 2017;37:183–93. 4. Garber DA, Salama MA. The aesthetic smile: diagnosis and treatment. Periodontology. 1996;2000(11):18–28. 5. Fradeani M.  Aesthetic analysis a systematic approach to prosthetic treatment, vol. 1. Chicago, IL: Quintessence Books; 2004. 6. Mahn E, Sampaio CS, Pereira da Silva B, Stanley K, Valdés AM, Gutierrez J, Coachman C. Comparing the use of static versus dynamic images to evaluate a smile. J Prosthet Dent. 2020;123(5):739–46. Epub 2019 Aug 2. https://doi.org/10.1016/j.prosdent.2019.02.023. 7. Duarte S Jr. Quintessence of dental technology. Chicago: Quintessence; 2010. 8. Fradeani M.  Réhabilitation esthétique en prothèse fixée. Tome 1: analyse esthétique. [aesthetic rehabilitation with fixed prostheses. Volume 1. ­ Aesthetic analysis]. Paris: Quintessence International; 2006.

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9. Levin EI. Dental esthetics and the golden proportion. J Prosthet Dent. 1978;40(3):244–52. 10. Chu SJ, Tarnow DP, Tan JH-P, Stappert CFJ. Papilla proportions in the maxillary anterior dentition. Int J Periodont Restor Dentistry. 2009;29(4):385–93. 11. Rojas-Vizcaya F.  Biological aspects as a rule for single implant placement. The 3A-2B rule: a clinical report. J Prosthodont. 2013;22(7):575–80. Epub 2013 Apr 1. https://doi.org/10.1111/jopr.12039. 12. Rojas Vizcayo F. Rehabilitation of the maxillary arch with implant-supported fixed restorations guided by the most apical buccal bone level in the esthetic zone: a clinical report. J Prosthet Dent. 2012;107(4):213– 20. https://doi.org/10.1016/S0022-­3913(12)00041-­8. 13. González-Martín O, Lee E, Weisgold A, Veltri M, Su H.  Contour management of implant restorations for optimal emergence profiles: guidelines for immediate and delayed provisional restorations. Int J Periodontics Restorative Dent. 2020;40(1):61–70. https://doi.org/10.11607/prd.4422. 14. Su H, Gonzalez-Martin O, Weisgold A, Lee E.  Considerations of implant abutment and crown contour: critical contour and subcritical contour. Int J Periodontics Restorative Dent. 2010;30(4):335–43. 15. Esquivel J, Meda RG, Blatz MB. The impact of 3D implant position on emergence profile design. Int J Periodontics Restorative Dent. 2021;41(1):79–86. https://doi.org/10.11607/prd.5126. 16. Ivoclar Zirconia Zircad Prime IFU. https://www.ivoclar.com/. 17. Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontol. 1992;63:995–6. 18. Araújo MG, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol. 2005;32(2):212–8. https://doi.org/10.1111/j.1600-­051X.2005.00642.x. 19. Tsuda H, Rungcharassaeng K, Kan JY, Roe P, Lozada JL, Zimmerman G. Peri-implant tissue response following connective tissue and bone grafting in conjunction with immediate single-tooth replacement in the esthetic zone: a case series. Int J Oral Maxillofac Implants. 2011;26(2):427–36. 20. Gluckman H, Salama M, Du Toit J. Partial extraction therapies (PET) part 1: maintaining alveolar ridge contour at pontic and immediate implant sites. Int J Periodontics Restorative Dent. 2016;36(5):681–7. https://doi.org/10.11607/prd.2783. 21. da Rosa JC, Rosa AC, da Rosa DM, Zardo CM.  Immediate dentoalveolar restoration of compromised sockets: a novel technique. J Esthet Dent. 2013;8(3):432–43. 22. Pohl S, Kurtzman GM.  The modified IVAN technique: hard and soft tissue augmentation at extraction for delayed implant placement. J Oral Implantol. 2019;45(1):65–72. https://doi.org/10.1563/ aaid-­joi-­D-­18-­00161. 23. Zadeh HH, Borzabadi-Farahani A, Fotovat M, Kim SH.  Vestibular incision subperiosteal tunnel access

262 (VISTA) for surgically facilitated orthodontic therapy (SFOT). Contemp Clin Dent. 2019;10(3):548–53. PMID: 32308335; PMCID: PMC7150560. https:// doi.org/10.4103/ccd.ccd_720_18. 24. Pozzi A, Arcuri L, Block M, Moy P. Digital assisted soft tissue sculpturing (DASS) technique for immediate loading pink free complete arch implant prosthesis. J Prosthodont Res. 2020;65:119. https://doi. org/10.2186/jpr.JPOR_2019_386. 25. Gallucci GO, Bernard JP, Bertosa M, Belser UC.  Immediate loading with fixed screw-retained provisional restorations in edentulous jaws: the pickup technique. Int J Oral Maxillofac Implants. 2004;19(4):524–33. 26. Degidi M, Nardi D, Piattelli A.  Immediate loading of the edentulous maxilla with a final restoration supported by an intraoral welded titanium bar: a case series of 20 consecutive cases. J Periodontol. 2008;79(11):2207–13. 27. Guentsch A, Sukhtankar L, An H, Luepke PG.  Precision and trueness of implant placement with and without static surgical guides: an in  vitro study. J Prosthet Dent. 2021;126(3):398– 404. Epub 2020 Sep 3. https://doi.org/10.1016/j. prosdent.2020.06.015. 28. Salama M, Pozzi A, Clark W, Tadros M, Hansson L, Adar P.  The “scalloped guide”: a proof-of-concept technique for a digitally streamlined, pink-free full-­ arch implant protocol. Int J Periodontics Restorative Dent. 2018;38:791–8. https://doi.org/10.11607/ prd.3778. 29. Monaco C, Ragazzini N, Scheda L, Evangelisti E. A fully digital approach to replicate functional and aesthetic parameters in implant-supported full-arch rehabilitation. J Prosthodont Res. 2018;62(3):383– 5. Epub 2017 Nov 27. https://doi.org/10.1016/j. jpor.2017.10.005. 30. Etemad-Shahidi Y, Qallandar OB, Evenden J, Alifui-­ Segbaya F, Ahmed KE. Accuracy of 3-dimensionally printed full-arch dental models: a systematic review. J Clin Med. 2020;9(10):3357. PMID: 33092047; PMCID: PMC7589154. https://doi.org/10.3390/ jcm9103357. 31. Mandelli F, Zaetta A, Cucchi A, Mangano FG. Solid index impression protocol:a hybrid workflow for high accuracy and passive fit of full-arch implant-supported restorations. Int J Comput Dent. 2020;23(2):161–81. 32. Kan JY, Rungcharassaeng K, Bohsali K, Goodacre CJ, Lang BR. Clinical methods for evaluating implant framework fit. J Prosthet Dent. 1999;81(1):7–13. https://doi.org/10.1016/s0022-­3913(99)70229-­5.

M. Wanendeya and S. Jivraj 33. Sinada N, Papaspyridakos P.  Digitally designed and milled verification jigs generated from photogrammetry data acquisition: a clinical report. J Prosthodont. 2021;30:651–5. https://doi.org/10.1111/jopr.13409. 34. Zhang Y-J, Shi J, Qian S, Qiao S-C, Lai H-C.  Accuracy of full-arch digital implant impressions taken using intraoral scanners and related variables: a systematic review. Int J Oral Implantol. 2021;14:157–79. 35. Revell G, Simon B, Mennito A, Evans ZP, Renne W, Ludlow M, Vág J.  Evaluation of complete-arch implant scanning with 5 different intraoral scanners in terms of trueness and operator experience. J Prosthet Dent. 2022;128(4):632–8. Epub 2021 Apr 6. https:// doi.org/10.1016/j.prosdent.2021.01.013. 36. Amornvit P, Rokaya D, Sanohkan S.  Comparison of accuracy of current ten intraoral scanners. Biomed Res Int. 2021;2021:2673040. PMID: 34552983; PMCID: PMC8452395. https://doi. org/10.1155/2021/2673040. 37. Li J, Chen Z, Wang M, Wang HL, Yu H.  Dynamic changes of peri-implant soft tissue after interim restoration removal during a digital intraoral scan. J Prosthet Dent. 2019;122(3):288–94. Epub 2019 Mar 15. https://doi.org/10.1016/j.prosdent.2018.07.020. 38. Pozzi A, Arcuri L, Fabbri G, Singer G, Londono J. Long-term survival and success of zirconia screw-­ retained implant-supported prostheses for up to 12 years: a retrospective multicenter study. J Prosthet Dent. 2023;129(1):96–108. Epub 2021 Jun 27. https:// doi.org/10.1016/j.prosdent.2021.04.026. 39. Koenig V, Wulfman C, Bekaert S, Dupont N, Le Goff S, Eldafrawy M, Vanheusden A, Mainjot A.  Clinical behavior of second-generation zirconia monolithic posterior restorations: two-year results of a prospective study with ex vivo analyses including patients with clinical signs of bruxism. J Dent. 2019;91:103229. Epub 2019 Nov 10. Erratum in: J Dent. 2021 Aug;111:103694. https://doi. org/10.1016/j.jdent.2019.103229. 40. Almquist ML, Jensen BR, Ingemann AB, Duus K, Rangstrup S, Andersen H, Andersen OZ.  Influence of cement gap size, surface preparation, cleaning agent and ageing on the retention of cemented single ceramic crowns, supported by Elos Accurate Hybrid Bases. Elos Medtech; 2021. https://elosdental.com/ files/document_archives/DEV-­02229_Study_cementation.pdf. 41. Zitzmann NU, Marinello CP, Berglundh T. The ovate pontic design: a histologic observation in humans. J Prosthet Dent. 2002;88(4):375–80. PMID: 12447213. https://doi.org/10.1067/mpr.2002.128758.

Graftless Surgical Protocol: Diagnosis to Delivery

10

Ana Ferro, Mariana Nunes, Diogo Santos, Armando Lopes, Filipe Melo, and Miguel de Araújo Nobre

Abstract

The All-on-4® treatment concept was developed in the 1990s as a surgical protocol to rehabilitate the total edentulous in immediate function, with implant insertion, abutment and prosthesis connection being performed on the same day as the surgery. The concept was developed in order to avoid graft techniques or any additional surgery (e.g. inferior alveolar nerve lateralisation), resulting in less chair time and less surgical complications (Maló et  al., Clin Implant Dent Relat Res 5:2–9, 2003). By placing four implants acting as ‘cornerstones’—two anterior implants in an axial position and two posterior implants tilted distally between 30° and 45°—a more distal implant position could be reached, reducing not only cantilever but also improving implant A. Ferro (*) · M. Nunes · D. Santos · A. Lopes Oral Surgery Department, Maló Clinic, Lisbon, Portugal e-mail: [email protected]; mnunes@ maloclinics.com; [email protected]; alopes@ maloclinics.com F. Melo Prosthodontics Department, Maló Clinic, Lisbon, Portugal e-mail: [email protected] M. de Araújo Nobre Research, Development and Education Department, Maló Clinic, Lisbon, Portugal e-mail: [email protected]

anchorage benefiting from inserting the implants in better bone quality regions (Maló et  al., Clin Implant Dent Relat Res 5:2–9, 2003; Maló et al., Clin Implant Dent Relat Res 7:S88–S94, 2005; Krekmanov et al., Int J Oral Maxillofac Implants 15:405–414, 2000; Aparicio et  al., Clin Implant Dent Relat Res 3:39–49, 2001). The All-on-4® surgical protocol can be performed in both arches (maxilla and mandible) either through free-hand flap surgery or guided surgery. These options will be further explored later on in this chapter.

10.1 All-on-Four™ Surgical Protocol The first cases described for the full-arch restoration of the mandible included four implants placed in interforaminal area. The results determined high cumulative survival rates even in chronical removable denture patients with severe resorptions. Immediate implant loading in the mandible was registered at that time stating both high success and survival rates in part because of good bone quality [1]. Nevertheless, the reduced bone density combined with scarce bone availability of the maxilla, particularly critical in the posterior regions, perceived immediate loading as a greater challenge. The use of implant tilting showed to be effective in the maxilla: by using the sinus or

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_10

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nasal fossae corticals for implant anchorage, it was possible to frequently achieve a high primary stability that allowed performing immediate function [2]. The challenge of soft bone leads to the addition of a new tool to the concept: a novel implant design [3]. This implant merged three significant features decisive to what is today All-on-4’s ­success: the implant’s macrodesign (the implant’s shape and threads) allowed to condense bone instead of cutting; the new apex design made it possible to engage the sinus or nasal fossae corticals allowing bicortical anchorage; and because it is fully threaded from the apex to the implant head, the whole implant aims to achieve higher primary stability.[4]. The All-on-4® concept has proven to be very effective even in more challenging cases where bone resorption did not allow the placement of conventional implants by combining standard and zygomatic implants (All-on-4® Hybrid) or extremely atrophic cases with two zygomatic implants placed bilaterally (All-on-4® Extramaxillary) [5]. This surgical protocol gained visibility thanks not only to the symbiosis between biological, anatomical and mechanical aspects, but also to the short-, medium- and long-term results [1–3, 6–10].

10.2 Treatment Planning The treatment planning of the All-on-4® surgical protocol starts with a review of the patients’ medical history, followed by detailed clinical and

A. Ferro et al.

radiographic examinations, intra- and extra-oral photographs and impressions. With these elements the surgeon should be able to determine the degree of difficulty of the All-on-4® rehabilitation.

10.2.1 Radiographic Evaluation The quantity and quality of bone between maxillary sinuses are the key to choosing the surgical All-on-4® approach: All-on-4® Standard, Hybrid or Extramaxilla. In the mandible, the anatomical limits are given by the inferior dental nerves (Figs. 10.1, 10.2, and 10.3). Both orthopantomography and cone beam computerised tomography (CBCT) are mandatory in this process. In the maxilla, the criteria to perform an All-on-4® Standard consider the patients’ bone volume/ridge between the canines to be at least 5 mm in width and ≥10 mm in height. Considering the All-on-4® Standard in the mandible, the criteria include the patients’ bone volume/ridge in the interforaminal region to be 5  mm in width and ≥8 mm in height. Furthermore, a Standard case is anticipated to have the implant prosthetic emergence between the second premolar and first molar [11]. In addition to bone availability, an aesthetic study is performed taking into account parameters such as the lip support (extra-oral soft tissue support), the smile line, the prosthetic space and the occlusal vertical dimension changes (Figs. 10.4 and 10.5).

Fig. 10.1  Preoperative orthopantomography

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Fig. 10.2  Preoperative cone beam computerised tomography

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Fig. 10.3  Type of rehabilitation procedure according to the available bone volume from a conventional full-arch rehabilitation with six implants to an All-on-4® double-zygoma protocol

10.3.1 Surgical Protocol: Step by Step

Fig. 10.4  Lip support evaluation

10.3 All-on-4 Standard: Non-­ guided Surgery As mentioned earlier, the All-on-4® surgical protocol can be performed either with free-hand or guided surgery (Figs. 10.6, 10.7, 10.8, and 10.9) [8, 12].

Before anaesthesia, two facial points are marked to check the onset of occlusion vertical dimension (OVD), one in the nose and the other in the chin, determining the vertical dimension baseline (Fig. 10.10). With this value it will be possible to achieve the optimal OVD for the immediate prosthesis placement. Subsequently and under local anaesthesia, the surgery starts with a crestal incision slightly ­palatal (3  mm), allowing us to preserve keratinised tissue in the buccal flap. Two vertical releasing incisions in the first molar region are made (Fig. 10.11). A mucoperiosteal (full thickness) flap is then raised until the anatomical limits (a) the nasal cavity floor in the anterior region of the maxilla and (b) the anterior wall of the sinus, laterally (Fig. 10.12). In the mandible, similar principles apply but the crestal incision is performed dividing the existent keratinised tissue and the anatomical limits being the mental foramens bilaterally (Fig.  10.13). No releasing incisions are performed, except in situations of severe resorption in which an incision in the midline can be executed to provide more flexibility to the flap. To create a regular ridge for implant placement and accounting in advance with all aesthetic parameters, a bone reduction is performed either with the rongeur, round bur or piezoelectric device (Figs.  10.14 and 10.15). The rongeur

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Fig. 10.5  Smile line evaluation Fig. 10.8  Implant planning software image of the maxilla with planned implants in position

Fig. 10.6 Implant planning software image of the maxilla

Fig. 10.9  Implant planning software image of the mandible with planned implants in position

Fig. 10.7 Implant planning software image of the mandible

Fig. 10.10  Measuring occlusion vertical dimension

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Fig. 10.11  Incision on maxilla

Fig. 10.12  Flap raising

Fig. 10.13  Incision on mandible

allows the surgeon to collect autogenous bone and use it in some bone defects if needed. Before the implant placement, the surgeon needs to 1. Place the All-on-4® guide: A midline osteotomy with the 2  mm drill, perpendicular to

Fig. 10.14  Bone reduction with rongeur

Fig. 10.15  Bone reduction with round bur

bipupilar line and checked through the pin-­ guide placement in order to correctly set the All-on-4® guide (Figs. 10.16 and 10.17). The All-on-4® guide is flexible and can be adapted to all jaw sizes and shapes. It also features 10  mm-long straight laser marks displayed with a 7  mm inter-mark distance, providing the surgeon with the possibility of placing 6 straight implants or, if not possible, to correctly angulate the posterior implants between 30° and 45° (Figs. 10.18 and 10.19). 2. Identify the anatomical structures: In order to identify/map the anterior sinus wall, a curve probe is introduced inside the sinus through a small window opening made with a round bur (Figs. 10.20 and 10.21). In the mandible, the mental foramen can be easily identified through careful flap elevation, and bone availability can be determined after checking the inferior alveolar nerve’s loop by inserting a periodontal probe in the foramen (Fig. 10.22).

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Fig. 10.16 Beginning the osteotomy to place the All-on-4® guide

Fig. 10.19  Placement of the All-on-4® guide in the mandible

Fig. 10.17  Osteotomy with the 2 mm drill to place the All-on-4® guide

Fig. 10.20  Opening the access of the anterior sinus wall of the maxilla

Fig. 10.18  Placement of the All-on-4® guide in the maxilla

Fig. 10.21 Probing the anterior sinus wall of the maxilla

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Fig. 10.22  Probing the mental foramen in order to evaluate the alveolar nerves’ loop

10.3.2 Implant Placement In the All-on-4® surgical protocol, the implant placement follows the same rule for both maxilla and mandible’s rehabilitation: the surgeon should first place the posterior tilted implants, thus determining the space available for the anterior implants with no risk of inter-implant interference. The drilling protocol was simplified to the use of three drills, aiming for under-preparation of the implant site, thereby managing drill depth (increasing or decreasing the preparation of the last two drills) according to bone density. As stated before, the implant design allows bone expansion, acting as an osteotome/final drill, providing maximum stability. The preparation starts either with the round bur or precision drill, followed by the 2 mm twist drill used full length, creating the implant’s site preparation. The 2  mm twist drill is the most important drill since it will provide the necessary information about the implants’ length and also the bone density. Based on the bone density information, the surgeon proceeds according to the type of bone density in order to place a Ø4mm regular platform (RP) implant: (a) in soft bone, the surgeon should use the 2 mm twist drill until the desired implants’ length (Figs.  10.23 and 10.24) and subsequent drills (2.4–2.8  mm step drill and 3.2–3.6 mm step drill) only on the cortical aspect (Figs. 10.25, 10.26, 10.27, and 10.28); (b) in medium bone, both 2 mm twist drill and 2.4–2.8 mm step drill are used until the desired

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implants’ length with the 3.2–3.6 mm step drill just on the cortical aspect; and (c) in dense bone, all the drills are used to full length of the implants’ size. The implant is then placed, aiming to achieve an insertion torque of at least 30 N cm in the final seating. The final seating of the implant’s head must be at bone level (Figs. 10.29 and 10.30). In the maxilla, the posterior implants are tilted, following the anterior sinus wall up to 45°. Once the implants are placed in the correct apical-­coronal position, a mechanical bone mill should be used to remove the bone around the head of the implant before placing the angled abutments. Implant angulation is then reduced after placing the 30° multi-unit angled abutments at 15 N cm, providing short or no cantilever with an emergence between the first molar and second premolar (Figs.  10.31 and 10.32). The angled abutments should be connected with the All-on-4® guide in place to orient prosthetically the screw exit of the future immediate provisional prosthesis (Figs. 10.33 and 10.34). The anterior implants’ preparation follows the same drilling protocol (Figs. 10.35, 10.36, 10.37, 10.38, 10.39, 10.40, 10.41, 10.42, 10.43, and 10.44). If the bone density is considered soft, the implant’s apex should engage the nasal cortical, thus achieving bicortical anchorage in order to create appropriate stability. These implants should be oriented by means of a pin guide alternatively to the All-on-4® guide. Usually, straight multi-unit abutments are connected at 35 N cm to the anterior implants. Before suturing, if needed, palatal soft tissue must be removed to avoid abutment covering or excess soft tissue which may cause multi-unit impression copings interference and hence prosthesis misadaptation. Buccal soft tissue should not be reduced; otherwise, it can result in insufficient keratinised tissue around the abutments. In the mandible, given the sparse quantity of keratinised tissue, soft tissue should not be reduced, but apically positioned instead. After suturing, open tray multi-unit impression copings are screwed to the abutments and splinted by means of steel wire and pattern resin

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Fig. 10.23  Initiating drill sequence after using precision drill in the maxilla: 2 mm twist drill (first drill)

Fig. 10.26  2.4–2.8 mm step drill in the mandible

Fig. 10.24  Initiating drill sequence after using precision drill in the mandible: 2 mm twist drill (first drill)

Fig. 10.27  3.2–3.6 mm step drill in the maxilla

Fig. 10.25  2.4–2.8 mm step drill in the maxilla

Fig. 10.28  3.2–3.6 mm step drill in the mandible

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Fig. 10.29  Posterior implant placement in the maxilla. Note the implant’s angulation to provide a more posterior emergence

Fig. 10.32  Bone mill to remove bone around the head of the mandibular distal implant

Fig. 10.30  Posterior implant placement in the mandible. Note the implant’s angulation to provide a more posterior emergence

Fig. 10.33  Connecting the angulated abutment to the maxillary implant with the help of All-on-4® guide

Fig. 10.31  Bone mill usage to remove bone around the head of the maxillary distal implant

Fig. 10.34  Connecting the angulated abutment to the mandibular implant with the help of All-on-4® guide

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Fig. 10.35  Drilling protocol and anterior implant placement. Initiating drill sequence using the precision drill in the maxilla

Fig. 10.38  Using the 2 mm twist drill (first drill) for the anterior mandibular implant

Fig. 10.36  Drilling protocol and anterior implant placement. Initiating drill sequence using the precision drill in the mandible

Fig. 10.39 Using the 2.4–2.8  mm step drill in the maxilla

Fig. 10.37  Using the 2 mm twist drill (first drill) for the anterior maxillary implant

Fig. 10.40 Using the 2.4–2.8  mm step drill in the mandible

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(Figs. 10.45 and 10.46). The impression is made only with putty consistency elastomer. Once the impressions are concluded, healing caps are screwed to the abutments to (Figs. 10.47 and 10.48) support the peri-implant mucosa during the fabrication of the prosthesis. The immediate provisional prosthesis is connected on the

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same day of surgery achieving immediate function (Figs. 10.49, 10.50, 10.51, and 10.52).

Fig. 10.44  Mandibular implants placed at bone level and abutments connected

Fig. 10.41  Anterior implant placement in the maxilla

Fig. 10.45  Impression coping screwed to the maxillary abutments and connect for an accurate impression

Fig. 10.42  Anterior implant placement in the mandible

Fig. 10.46  Impression coping screwed to mandibular abutments and connect for an accurate impression

Fig. 10.43  Maxillary implants placed at bone level and abutments connected

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Fig. 10.47  Healing caps connected to the maxillary abutments

Fig. 10.50  Immediate prosthesis

Fig. 10.48  Healing caps connected to the mandibular abutments

Fig. 10.51  Patient smiling with the immediate provisional maxillary prosthesis achieving immediate function

Fig. 10.49  Immediate maxillary provisional prosthesis

Fig. 10.52  Patient smiling with the immediate provisional mandibular prosthesis achieving immediate function

provisional

mandibular

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10.4 All-on-4 Standard: Guided Surgery The implant placement follows the same protocol of the standard All-on-4® technique, but it is performed with a flapless approach planned previously in a 3D software. This protocol can be used if patients have the following inclusion criteria: (a) Sufficient bone volume (defined in the previous point of the All-on-4 protocol). (b) Enough mouth-opening capability to accommodate the surgical tooling (>40 mm). (c) A low smile line or when bone recontouring is not necessary. (d) An almost edentulous jaw (so the remaining teeth do not interfere with the position and placement of the implants). Through guided surgery, a full-arch restoration can be performed with a minimally invasive approach, reduced postoperative discomfort and treatment time for the patient. Prior to the surgical procedure, a well-defined protocol with five stages has to be followed: (1) patient examination (previously executed), (2) preparation of the radiographic guide and CBCT scan, (3) computer planning, (4) laboratory work and (5) surgery.

10.4.1 Patient Examination A preoperative treatment planning appointment is performed to evaluate the patient’s medical history, extra-oral aesthetic measures (lip support, profile, occlusal vertical dimension according to the Thompson functional and the Willis aesthetic methods, smile line, phonetics [8, 12]) and intra-oral features (arch form and relation, jaw size, molar class, interocclusal space). Radiographically, both an orthopantomography and a CBCT are performed in order to accurately assess the bone’s anatomy (volume and height) and determine the exact location of the mental foramen and/or maxillary sinus. If the patient fulfils the inclusion criteria (sufficient bone volume, low smile line and mouth-­ opening capability over 40  mm) (Fig.  10.53), a

Fig. 10.53  Evaluation of the mouth-opening capability

full-arch rehabilitation according to the All-on-4® concept can be performed.

10.4.2 Preparation of the Radiographic Guide and CBCT Scan The first step consists of the evaluation of the removable prosthesis. If the patient’s prosthesis does not meet the functional and aesthetic requirements or it is not an all-acrylic resin, a new prosthesis must be fabricated, presenting optimal design with a correct representation of the teeth position and a perfect fit to the soft tissue (always maintaining the requirements of the surgical template in mind). In the new prosthesis, six gutta-percha markers on the buccal side and three markers on palatal side are made, and a CBCT is done (Figs. 10.54 and 10.55). The patient is scanned following the double scan technique: one CBCT scan of the patient with the prosthesis with gutta-percha markers and another CBTC scan taken just to the patients’ prosthesis.

10.4.3 Computer Planning After scanning and using an implant planning software, both CBCTS are matched and a precise 3D treatment planning of an All-on-4 surgery can be performed.

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Fig. 10.54  Intra-oral view (1/2) with the radiographic guide during CBCT

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Fig. 10.56  Implant planning software—maxilla

Fig. 10.55  Intra-oral view (2/2) with the radiographic guide during CBCT Fig. 10.57  Surgical template—maxilla

Implants and multi-unit non-engaging angled abutments are selected for the rehabilitation and placed tridimensionally in the software. The order file is sent to the manufacturing company requesting the surgical template (Figs. 10.56 and 10.57). The surgical template is used as a guide to obtain a stone cast and make all the laboratory work (Figs. 10.58 and 10.59). Before surgery, a surgical index is made with silicone and also all prosthetic procedures are performed (Fig. 10.60).

10.4.4 Surgery Protocol Prior to the insertion of the implants, the surgical template is stabilised through anchor pins. The surgical index helps us to position the surgical

template in place while the anchor pins osteotomies are performed (Figs. 10.61 and 10.62). The first step is the use of tissue punch to have access to the bone (Fig.  10.63). The surgery is performed following the standard free-hand All-on-4 protocol but with a surgical guide guiding the drilling according to the preplan on a computer (Figs.  10.64, 10.65, 10.66, 10.67, 10.68, 10.69, 10.70, 10.71, 10.72, and 10.73). The surgeon has to adopt an under-preparation protocol of the implant site in order to achieve good primary stability. Once the implants are placed, the surgical template is removed, and the bone mill is used to remove the bone around the implants’ head. Angled abutments are connected to the implants by means of a pre-made guide positioner. With this guide it is possible to transfer the position

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Fig. 10.58  Surgical index and guide to transfer the position of the angulated multi-unit abutments (1/2)

Fig. 10.61  Stabilisation of surgical template with anchor pins and surgical index (1/2)

Fig. 10.62  Stabilisation of surgical template with anchor pins and surgical index (2/2) Fig. 10.59  Surgical index and guide to transfer the position of the angulated multi-unit abutments (2/2)

Fig. 10.63  Tissue punch Fig. 10.60  Pre-surgically the maxillary removable denture is converted into a fixed screw-retained implant-­ supported prosthesis of acrylic resin

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Fig. 10.64  Anterior implant placement: twist drill 2 mm

Fig. 10.65 Anterior implant placement: twist drill 2.8 mm

Fig. 10.66 Anterior implant placement: twist drill 3.6 mm

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Fig. 10.67  Anterior insertion

implant

placement:

implant

Fig. 10.68  Posterior implant placement: twist drill 2 mm

Fig. 10.69 Posterior implant placement: twist drill 2.8 mm

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Fig. 10.70 Posterior implant placement: twist drill 3.6 mm

Fig. 10.71 Posterior insertion

implant

placement:

implant

Fig. 10.72  Occlusal view after implant placement with the surgical template

from the model to the mouth, allowing a passive fit of the provisional prosthesis (Figs. 10.74 and 10.75). Following this procedure, a pre-made denture converted into a fixed all-acrylic resin

Fig. 10.73  Occlusal view after implant placement without the surgical template

Fig. 10.74  Positioning of the non-engaging angulated abutment with the help of the abutment guide

Fig. 10.75  Abutments in place

implant-supported prosthesis is connected and the occlusal adjustments verified (Figs.  10.76, 10.77, and 10.78).

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Fig. 10.76  Frontal view of the provisional prosthesis

Fig. 10.77  Occlusal view of the provisional prosthesis

Fig. 10.78 Patient prosthesis

smiling

with

the

provisional

10.5 All-on-4 Standard: Navigated Surgery To improve accuracy and precision, surgeons have available guided computer-assisted surgical

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implant placement systems: static guidance and dynamic guidance (surgical navigation) [13]. The main difference between static guidance and surgical navigation is the placement of implants in a predetermined position without the possibility of changing the implant position or dimensions perioperatively, while for the surgical navigation system, the operator uses a triangulation setup provided by the computer to guide the implant placement, allowing changes during the surgery. Surgical navigation provides accurate spacing and angulation of the implants, decreasing the risk of damaging anatomic structures as maxillary sinus or inferior alveolar nerve. Moreover, virtual implant planning and navigation provides surgical and prosthetic collaboration for achieving a successful outcome through an exact and precise planning. The accuracy of this system is independent of CAD-CAM stents and the surgical field can be visualised live at any time. Additionally, dynamic navigation allows dental surgeons to scan, plan and execute navigated surgery on the same day and patients with limited mouth-opening capability can undergo dynamic navigation. However, dynamic navigation requires a team approach and a learning curve for developing predictability in implant placement. This may be related to the difficulty in keeping sight of the display during the surgical procedure. The present case illustrates the surgical workflow in a bimaxillary full-arch rehabilitation through the All-on-4 concept assisted by dynamic navigation. A 69-year-old male, non-smoker, healthy patient presented with the need for bimaxillary full-arch rehabilitation. Periodontal compromised teeth with mobility, gingival recessions and deep pocket depth were diagnosed as not viable in the mandible and maxilla. After clinical examinations, orthopantomography, cone beam computerised tomography (CBCT) scan and intra-oral scanner were performed (Figs.  10.79 and 10.80). The DTX Studio Implant software was used to evaluate the baseline clinical situation, access the bone reduction, study the best surgical and prosthetic solution and select the position and size of

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of the clip receptor, which contained fiducial markers, and read by two cameras, providing the instruments’ tridimensional position and displayed in the navigation system. The handpiece also holds an array that, when combined with the fiducial markers on the clip receptor, provided accurate navigation through triangulation. Three points in three different maxillary teeth were selected as distant as possible in the DTX Fig. 10.79  Preoperative orthopantomography Studio Implant software to have the most favourable distribution quality and registration refinement. The probe tool was then used to map the exact same points in the patient’s mouth and registered by the system (X-Mark) (Fig. 10.84). After this process, the precision drill was calibrated, and the planned bone reduction height was marked with three horizontal osteotomies preplanned on the DTX Studio Implant software (Figs.  10.85 and 10.86). The preparation of the implant osteotomy was made using the precision drill, 2.0, 2.4–2.8 and 3.2–3.6 mm drills (Nobel Biocare AB), always considering the spatial position according to the live navigation data. Four implants were inserted according to the All-on-4 concept, and all achieved 35  N/cm of primary stability: the posterior implants reaching an angulation of 30–45° in relation to the occlusal plane and the anterior implants were inserted in an axial position. Multi-Unit Plus abutments of 30° 4.5  mm were attached to the posterior implants; while Multi-Unit straight 2.5 mm abutments were attached to the anterior implants (Fig. 10.87). The protocol followed the same sequence for Fig. 10.80 (a, b) Preoperative intra-oral photographs the mandibular rehabilitation (Figs. 10.88, 10.89, exhibiting the occlusal aspect of the maxilla on the left- 10.90, and 10.91). All four implants achieved hand side and mandible on the right-hand side 35  N/cm of primary stability. Multi-Unit Plus abutments of 30° 4.5  mm and were attached to the implants (Fig.  10.81). The X-Guide clip the posterior implants; while Multi-Unit Plus receptor was directly fixated in the maxilla straight 2.5 mm abutments were attached to the through two screws, and the navigation surgery anterior implants. Two provisional pre-made, was initiated (Fig. 10.82). high-density, acrylic resin prostheses with ten The surgical staff followed the prompts in the teeth were connected on the day of surgery, X-Guide software (X-Nav Technologies, LLC, achieving immediate function (Figs.  10.92 and Lansdale, PA, USA). Instruments were calibrated 10.93). (handpiece tracker, chuck, probe tool and the The All-on-4 concept assisted by surgical navpreparation drills) as follows (Fig.  10.83): the igation provided a safe and predictable full-arch overhead blue lights were reflected by the arrays bimaxillary rehabilitation, allowing the implants

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Fig. 10.81  DTX Studio Implant software image exhibiting planned bone reduction and implants’ position, diameter and length, following the All-on-4 concept

Fig. 10.82  Perioperative photograph illustrating the fixation of the X-Guide clip receptor and array in the maxilla

a

Fig. 10.83 (a–d) Calibration of the handpiece, chuck and probe tool

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b

Fig. 10.83 (continued)

c

Fig. 10.83 (continued)

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d

Fig. 10.83 (continued)

a

Fig. 10.84 (a, b) X-Mark selection and registration refinement process (maxilla)

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Fig. 10.84 (continued)

Fig. 10.85  Spatial calibration of the precision drill using an array

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Fig. 10.86 (a, b) Planned bone reduction osteotomy before and after flap elevation (maxilla)

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Fig. 10.87 (a–d) Perioperative preparation of implant sites, implant placement using live navigation and intra-oral view of the All-on-4 maxilla

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Fig. 10.87 (continued) Fig. 10.88 Perioperative photograph illustrating the fixation of the X-Guide clip receptor and array in the mandible

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Fig. 10.89 (a, b) X-Mark selection and registration refinement process in the mandible

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Fig. 10.90  Bone reduction plane osteotomy before flap elevation in the mandible

Fig. 10.91 (a–e) Perioperative implant sites preparation, implant placement using live navigation and intra-oral view of the All-on-4 mandible

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Fig. 10.91 (continued)

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a

b

c

Fig. 10.92 (a–c) Intra-oral perioperative view with the immediate prosthesis connected in the maxilla and mandible

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10.6 Conclusions In 2019, two long-term studies were published on the All-on-4 treatment concept [9, 10], with data collected in a private practice (Malo Clinic, Lisbon, Portugal). The retrospective study in the Maxilla [9] with a follow-up of up to 13  years involved 1072 patients with 4288 maxillary implants. The implant success rates reported were 97.7% at 5  years, 95.6% at 10  years and 93.9% at 13 years. The mean marginal bone loss was 1.18 mm at 5 years and 1.67 mm at 10 years. Prosthetic survival rate was reported to be 99.2%. The retrospective study in the Mandible [10] with a follow-up to 18 years involved 471 patients with 1884 mandibular implants. The implant success rates reported were 95.9% at 10 years, 93.5% at 13 years and 91.7% at 18 years. The mean marginal bone loss was 1.72  mm at 10  years and 2.32 mm at 15 years. Prosthetic survival rate was reported to be 98.8%. Considering the high implant and prosthetic success rates and the low incidence of both biological and mechanical complications, the All-on-4 concept can be considered a viable treatment alternative for full-arch rehabilitation. In addition, the All-on-4 concept allows flexibility to be used with recent developments in implant dentistry such as surgical navigation.

References

Fig. 10.93  Postoperative orthopantomography of rehabilitation through the All-on-4 concept using live navigation

to be inserted with precision considering the crestal position, angulation and depth.

1. Maló P, Rangert B, Nobre M. “All-on-4” immediate function concept with Branemark System implants for completely edentulous mandibles: a retrospective clinical study. Clin Implant Dent Relat Res. 2003;5(Suppl 1):2–9. 2. Maló P, Rangert B, Nobre M. “All-on-4” immediate function concept with Banemark System implants for completely edentulous maxilla: a 1-year retrospective clinical study. Clin Implant Dent Relat Res. 2005;7(Suppl 1):S88–94. 3. Maló P, de Araújo Nobre M, Lopes A, Ferro A, Gravito I.  Complete edentulous rehabilitation using an immediate function protocol and an implant design featuring a straight body, anodically oxidized surface, and narrow tip with engaging threads extending to the apex of the implant: a 5-year retrospective clinical study. Int J Oral Maxillofac Implants. 2016;7(1):153.

294 4. Maló P, Nobre M, Lopes A, Rodrigues R. Preliminary report on the outcome of tilted implants with longer lengths (20–25 mm) in low-density bone: one-year follow-up of a prospective cohort study. Clin Implant Dent Relat Res. 2013;19:217. https://doi.org/10.1111/ cid.12444. 5. Malo P, de Araújo Nobre M, Lopes A, Ferro A, Moss S.  Extramaxillary surgical technique: clinical outcome of 352 patients rehabilitated with 747 zygomatic implants with a follow-up between 6 months and 7 years. Clin Implant Dent Relat Res. 2013;17 Suppl 1:e153. https://doi.org/10.1111/cid.12147. 6. Patzelt SB, Bahat O, Reynolds MA, Strub JR. The all-­ on-­four treatment concept: a systematic review. Clin Implant Dent Relat Res. 2014;16(6):836–55. https:// doi.org/10.1111/cid.12068. 7. Soto-Penaloza D, Zaragozi-Alonso R, Penarrocha-­ Diago M, Penarrocha-Diago M. The all-on-four treatment concept: a systematic review. J Clin Exp Dent. 2017;9(3):e474–88. 8. Lopes A, Maló P, de Araújo NM, Sánchez-Fernández E, Gravito I. The NobelGuide® All-on-4® treatment concept for rehabilitation of edentulous jaws: 7-year clinical and 5-year radiographic retrospective. Clin Implant Dent Relat Res. 2016;19:233. https://doi. org/10.1111/cid.12456.

A. Ferro et al. 9. Maló P, de Araújo Nobre M, Lopes A, Ferro A, Nunes M.  The All-on-4 concept for full-arch rehabilitation of the edentulous maxillae: a longitudinal study with 5-13 years of follow-up. Clin Implant Relat Res. 2019;21:538–49. 10. Maló P, de Araújo Nobre M, Lopes A, Ferro A, Botto J. The All-on-4 treatment concept for the rehabilitation of the completely edentulous mandible: a longitudinal study with 10 to 18 years of follow-up. Clin. Implant Relat Res. 2019;21:565–77. 11. Maló P, Nobre M, Lopes A.  The rehabilitation of completely edentulous maxillae with different degrees of resorption with four or more immediately loaded implants: a 5 year retrospective study and a new classification. Eur J Oral Implantol. 2011;4(3):227–43. 12. Maló P, Nobre M, Lopes A.  The use of computer-­ guided flapless implant surgery and 4 implants placed in immediate function to support a fixed denture: preliminary results after a mean follow-up period of 13 months. J Prosthet Dent. 2007;97:S26–34. 13. Lopes A, Nobre M, Santos D. The workflow of a new dynamic navigation system for the insertion of dental implants in the rehabilitation of edentulous jaws: report of two cases. J Clin Med. 2020;9:421.

Surgical–Anatomical and Prosthetic–Biomechanical ZAGA Criteria to Determine the Zygomatic Implant Trajectory

11

Carlos Aparicio, Arnau Aparicio, and John Brunski

Abstract

In the late 1990s, we learned from the pioneers the use of zygomatic implants to anchor dental restorations. Due to the youth of the technique at that time, the knowledge transmitted was rather intuitive. The surgical prescription was applicable to all patients, and no criteria or protocols had been developed to adapt the intervention to the different situations that patients might present. The technique has evolved, and today, thanks to the ZAGA Concept, we have protocols based on defined criteria that are supported by evidence to guide us in the decision-making that the process requires. In this chapter we will give clear notions of how to identify the key zones in the path of the zygomatic implant and the transcendence that C. Aparicio (*) Indiana University School of Dentistry, Indianapolis, IN, USA Zygomatic Unit at Hepler Bone Clinic, ZAGA Center, Barcelona, Spain e-mail: [email protected] A. Aparicio ZAGA Center, Private Practice QDT Center, Houston, TX, USA J. Brunski Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University, Stanford, CA, USA e-mail: [email protected]

these zones will have in the long-term result of the rehabilitation. The reader will obtain biomechanical notions of the behaviour of an inclined implant versus one with axial direction to the occlusal plane, as well as the effect of the masticatory load on the zygoma in different surgical situations. Through the use of clear and reasoned criteria the reader will be able to understand the parameters used by the ZAGA Concept to determine the implant trajectory preventing late complications in a predictable way. Finally, the specific ORIS criteria for determining the success or failure of a zygomatic implant restoration will be described.

11.1 Introduction The original protocol published by PI Brånemark in 2004 [1] for zygomatic oral rehabilitation was designed for the placement of one implant in each zygoma following an intra-sinus path (Fig. 11.1). The starting point was located palatally to the first molar/second premolar area. Additionally two to four regular anterior implants were placed and connected to the final prosthesis. According to PI Brånemark [1], ‘the direction of zygoma fixation was selected to provide optimal stability over the prosthetic requirements’. To achieve an intra-sinus trajectory in the presence of a concave maxillary wall, the implant head was placed on the alveolar palatal side, resulting

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_11

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Fig. 11.2  Occlusal clinical photograph showing the distance from the osseous crest (green dashed line) to the palatal emergence of the implants (white arrows). Since the original intra-sinus technique was used, the abutments are not angled but the initial straight ‘standard’ type

Fig. 11.1  Clinical photograph showing the anterior maxillary wall where a ‘window’ osteotomy has been performed (white circle). Through the window we visualise the original twist drill proceeding (green arrows), but we do not see its tip cutting the bone. In other words, if the objective of the osteotomy is to control the drilling by visualising the point where the drill cuts, we can consider it as an ‘emotional osteotomy’ because although it tries to do so, it does not achieve its goal

in bulky prostheses (Fig.  11.2). Eventual difficulty in correct phonetics and hygiene maintenance are often associated with this palatally retained reconstruction. Several factors related to the proceeding of zygomatic implants through the palatal aspect of the alveolar bone into the maxillary sinus can induce rhinosinusitis and present with clinical or subclinical oroantral communication from the peri-implant sulcus. Factors mentioned may include discrepancy between the osteotomy and implant diameters; history of periodontitis; inad-

Fig. 11.3  The implant has been placed conservatively. However, it has a straight connection with the abutment. To correct the angulation and place the emergence of the prosthetic screw in a crestal position, the abutment– implant connection must be made in the ZICZ (white circle). The green arrows indicate the possible points where bacterial filtration will occur, which will produce chemotactic stimulation for the osteoclasts favouring the late appearance of an OAC. (Image taken from the Internet)

equate oral hygiene procedures, chemotactic stimuli due to bacterial leakage at an implant– abutment junction placed at the ZICZ (Fig. 11.3), peri-implant osteomyelitis due to hygiene difficulties, etc. The possibility of this event would be inversely related to the thickness of the sinus floor in the area where the implant crosses it. The inflammatory response of the sinus floor mani-

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fests with a few symptoms. It is sometimes accompanied by a sensation of perialveolar and/ or facial discomfort, without usually pain when the implant itself is loaded [2]. Antibiotic therapy temporarily eliminates the infection, which eventually recurs later. A recent multicentre randomised controlled study has compared the use of zygomatic implants placed in immediate loading with the use of bone augmentation procedures at 1  year [3] and 3 years [4]. Study results have reported significantly fewer prosthetic failures, implant failures and time to functional loading in the zygomatic implant group. On the other hand, the authors note a significantly higher number of complications at 3 years in the case of zygomatic implants due to an apparent increase in severe sinusitis over time. The authors do not explain the reasons for this large number of sinusitis, but from a detailed reading of the article it appears that in 78% of the implants the intra-sinus implant path with additional window osteotomy of the original technique was used. It would be reasonable to speculate that the cause of the large number of late sinusitis could be due to the loss of the palatal bone seal, for some reason, combined with the use of threaded implants with rough surface (TiUnite®). In this chapter, complementary to the previous one in which the ZAGA Concept [5] was explained, we will define and explain the criteria we use to determine the implant trajectory in order to prevent the aforementioned complications when zygomatic implants are used. To this end, and in order to better understand the origin of potential problems, we will complement the ZAGA anatomical classification [6] with a description of the main anatomical areas to which the implant trajectory relates. Obviously, it will be important to understand how these implants behave biomechanically before proceeding with the design of both the placement/distribution and the prosthesis itself. This applies especially to the immediate provisional prosthesis, which is a key piece in the treatment. Finally, we will explain the key points that a reader should look for when reading a report describing the use of zygomatic

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implants. To do so, we will describe the ORIS criteria [7], specific to zygomatic implant rehabilitation. By using them systematically, we will be able to determine the degree of success or failure and compare them with other reports.

11.2 The ZAGA Zones As explained in the previous chapter, the success of the ZAGA Concept for the rehabilitation of the atrophic maxilla through zygomatic implant-­ anchored rehabilitations is based on the identification of the anatomical characteristics of the patient. Specifically, the surgeon must be familiar with the characteristics, physiology and function(s) of the structures that the oblique plane of the planned osteotomy intersects. With a didactic intent, we are differentiating three main zones (Fig.  11.4) of the zygomatic implant trajectory [8]: –– The ‘zygomatic implant critical zone’ (ZICZ). –– The ‘antrostomy zone’ (AZ). –– The ‘zygomatic anchorage zone’ (ZAZ).

11.2.1 The Zygomatic Implant Critical Zone The ‘zygomatic implant critical zone’ (ZICZ) is formed by the complex formed by the maxillary bone, the soft tissues and the zygomatic implant at the coronal level where the first contact with the maxillary bone occurs (Figs. 11.4 and 11.5). The fundamentals for the correct position of the ZICZ are especially important in the ZAGA Concept and will be discussed later. Residual alveolar bone and soft tissue preservation or even augmentation at the coronal level of the zygomatic implant are critical to prevent late complications. In fact, maintenance of bone and soft tissue in the ZICZ should be one of the main goals of our surgical approach. In this regard, a series of protocols, tools, interventions and procedures are proposed to reach appropriate bone and soft tissue stability on the ZICZ (Table 11.1).

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Fig. 11.4  The DTX Studio Implant program allows us to visualise this screenshot where we visualise in the 3D image the plane through which the implant proceeds. The 2D image on the right represents the cut where the implant

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Fig. 11.5 (a) The minimally invasive ZAGA channel-­ type osteotomy has been prepared. The Straumann ZAGA implant has its tip placed in the ZICZ (white circle). Note the precise under-preparation of the osteotomy as well as the preservation of the integrity of the sinus membrane at this level. The green circle marks the AZ which is as far away as possible from the ZICZ. The white arrows highlight the flat surface of the implant on the buccal side which will contribute to decrease the pressure against the soft tissue and therefore reduce the possibility of dehiscence due to tissue anoxia. (b) The same implant in (a) is

proceeds and its relationship with the adjacent structures. The arrows and circles represent by colour the positions of the ZICZ (red), the AZ (green) and the ZAZ (yellow)

b

in its final position ready to disassemble its transporter. Note the perfect contact and sealing of the implant walls with the ‘single’ osteotomy. The white arrows highlight how the flat surface of the Straumann ZAGA Flat is at the level of the bony envelope. The implant–abutment connection is made above the ZICZ using an abutment of smaller diameter than the implant platform (platform shift), so we do not expect bacterial stimulation. The AZ (green circle) is far from the ZICZ, so no antrum contamination is expected through it. The yellow circle marks the ZAZ

11  Surgical–Anatomical and Prosthetic–Biomechanical ZAGA Criteria to Determine the Zygomatic… Table 11.1  Rationale for recommended tools and procedures to achieve and maintain adequate bone and soft tissue stability in the ZICZ (From Aparicio C.  Soft tissue management in zygomatic implant rehabilitation In Advanced Zygomatic Implants: The ZAGA Concept. Carlos Aparicio Ed. Quintessence Chicago 2023) [9] • Postpone any intervention until the soft tissue is fully healed. • Incision. As a general rule, use a palatal incision, displacing and augmenting the soft tissue buccally to the implant platform. • ZAGA rolling flap. This is recommended for ZAGA type 4 anatomy with implants that are expected to be externalised and when the thickness of the palatal soft tissue permits. For this, we will use a partial-thickness incision extending from the ridge about 10–12 mm towards the centre of the palate where it becomes full thickness. We will then roll the palatal connective tissue, ideally leaving the periosteum intact, and move it buccally towards the neck of the abutment. • ZAGA partial thickness flap (PTF). Its purpose is to maintain or facilitate soft tissue closure in cases of sinus floor or palatal discontinuity. • Perform an adequate osteotomy procedure by placing the implant head in relation to the ridge according to the ZAGA Concept. • se an appropriate implant section and design to match the osteotomy and maintain the bone in the ZICZ. • Consider using simple procedures such as L-PRF alone or in conjunction with bone grafting to enhance/ facilitate healing and sealing of soft and hard tissues after surgery. • If dehiscence is anticipated or considered likely and sufficient connective tissue is available, use the ZAGA scar graft. A scar graft is a pedicle connective tissue graft around the neck of the implant, with the goal of increasing the amount of buccal tissue. • If dehiscence is anticipated or considered likely and sufficient connective tissue is not available, use the buccal fat pad. • After implant surgery, consider the use of a definitive abutment with adequate height as important factors in maintaining the marginal bone level. • Position the implant–abutment junction as far away from the ZICZ as possible to maintain the marginal bone level avoiding bacterial leakage and subsequent bone resorption. The latter is of particular relevance if a straight 0° implant head design is used. • Consider suturing options, including the use of periosteal incisions or release flaps to obtain tension-­free primary wound closure. • Avoid implant micromotion under masticatory load by using a rigid framework, no extensions, good masticatory load distribution and soft diet in the provisional prosthesis. • Recommend proper hygiene and diagnostic procedures that do not compromise the hemi-­ desmosomal bond between titanium and soft tissue.

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11.2.2 The Antrostomy Zone The antrostomy zone (AZ) is the area where the drill penetrates into the maxillary sinus cavity (Figs. 11.4, 11.5 and 11.6). ZAGA recommends a minimally invasive osteotomy procedure intended to maximise BIC using an under-­ preparation of the designed implant trajectory. The recommended minimally invasive ZAGA osteotomy [10, 11] procedure is adapted to the implant shape by direct bone drilling in the three areas where the implant will contact (ZICZ, AZ and ZAZ). In other words, prior to implant placement no previous ‘window’ or ‘slot’ osteotomy/ antrostomy is performed nor required. Depending on the maxillary anatomy, the zygomatic antrostomy zone will be located either at the internal side of the remaining alveolar bone (tunnel osteotomy in ZAGA types 0 and 1) or apically from the ZICZ when there is not enough alveolar bone, and the osteotomy trajectory is buccally offset (channel osteotomy). As a rule of thumb, the antrostomy should be located as far away as possible from the ZICZ.  Excluding ZAGA types 0 and 1 when the ZI perforates the sinus floor (Fig.  11.6a), the AZ is usually located at the zygomatic process of the maxilla, below the zygomatico-maxillary suture (Fig. 11.6b). ZAGA Concept uses anatomic, prosthodontic, numerical and 3D implant design criteria to determine the ZICZ position. The location of the antrostomy will depend on the zygoma buttress curvature and on the position of the coronal entrance point.

11.2.3 The Zygomatic Anchorage Zone The zygomatic anchorage zone (ZAZ) is the section of the zygomatic bone where the implant reaches its maximum primary stability (Figs. 11.4 and 11.5b). The zygomatic bone is variable in quality and quantity among patients. Nkenke et  al. [12] described it in 2003 as a trabecular bone with unfavourable characteristics for implant placement if not properly utilised. Structural zygomatic stabilisation will be maximised when four cortices of the maxillary zygo-

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a

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Fig. 11.6  The diagram shows an example of the design of a ZAGA tunnel osteotomy (a) and at the bottom a second example (b) of the choice of a ZAGA channel oste-

Fig. 11.7  Image taken from the Internet visualising two zygomatic implants placed with an osteotomy determined by a wrong positioning for the AZ. The white arrows highlight how zygomatic bone has been removed in excess and inaccurately making the apical margins of the implant not correspond with the diameter of the osteotomy. The threads of both implants are exposed, potentially losing initial stability and zygomatic bone mass without achieving function

matic process and zygomatic bone are penetrated. Generally speaking, from a biomechanical point of view we should also try to drill also the anterosuperior cortex of the zygoma to ensure primary stability of the implant. The maximum anchorage is achieved by the partial or total irruption of the implant in the infratemporal fossa, its re-entry in the zygomatic bone with final exit through the superior anterior cortex of the zygoma. Since the patient’s problem is precisely severe maxillary

otomy. Both examples are real and show the pre- and postoperative radiographs, with the planning of the implant position and the final situation at 3 years

atrophy, we need to maximise primary stability. To achieve this, the ZAGA Concept uses a tangential zygomatic bone–implant intersection, increasing the bone–implant contact (BIC). In parallel to the above, we recommend using the minimally invasive ZAGA osteotomy because it does not remove bone in the form of a slot or window prior to implant placement (Fig.  11.7), which decreases the BICA and the strength of the maxilla or zygomatic bone. Obviously, we will be able to preserve and adapt better to the bone structure if we add to the type of osteotomy ­mentioned above the use of site-specific implants and narrow diameter drills such as StraumannZAGA zygomatic implants.

11.3 Biomechanics in the Context of Tilted Implants The successful use of tilted implants has been described as an alternative to maxillary grafting in cases where patients present advanced maxillary resorption by Mattson et  al. 1999 [13] and Kremanof et  al. in 2000 [14]. Aparicio et  al. in 2001 [15] defined a ‘tilted’ implant as an implant ‘placed with more than 15° deviation from perpendicular to the occlusal plane’. Implants anchored in the zygomatic bone are tilted.

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Stress is defined as a force divided by the area supporting the force, so its dimensions are force/ area; for example, a typical unit for stress in the metric system is the Pascal (Pa), which equals 1  N/m2, and 1 million Pa equals 1  MPa (MegaPascal). There can be different types of strain, such as tensile strain, compressive strain and shear strain. Strain is the amount of deformation experienced by a sample of material in the direction of the applied force, divided by the initial dimensions of the sample. Stress and strain are related by the stress–strain relationship of the material involved. All materials have failure limits described in terms of stress or strain. When any prosthesis is loaded by masticatory forces, its supporting implants are also loaded along with the surrounding bone. Mechanical principles dictate that these forces will produce resistance forces within the materials involved, and these internal resistance forces are related to stress. Similarly, stress in a material also causes deformation or strain, and as a general rule, the greater the stress and strain in any material, the greater the risk of failure [16]. We cannot determine conclusively when the stresses and strains that bone can withstand are too great. This is because different types of bone, that is, dense cortical bone, trabecular bone, immature bone healing around an implant, human bone versus bone of another species, etc., have different properties [17]. On the other hand, we must keep in mind the possibility of fatigue failure of bone, which is a type of material failure that occurs under cyclic loading conditions. Fatigue is especially insidious because it occurs under magnitudes of stress or strain substantially lower than those that cause failure in a single cycle. For example, the ultimate tensile strength of pure titanium is about 760  MPa, but the so-­ called fatigue strength limit for 10 million cycles is only 300 MPa [18]. The situation is similar in bone. For example, in the case of the implant tilted at 25°, the peak peri-implant bone strain can be substantially greater than the strain in bone around an axially loaded implant. In some cases, it is possible that bone may fatigue under cyclic loading since humans routinely exert about 100 chewing movements per day [19, 20], which

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means that many thousands of cycles can accumulate in 1 year. As defined by Aparicio et  al. in 2001 [15], zygomatic implants can clearly be classified as ‘tilted’, which raises the question ‘What is the functional difference between a vertical versus a tilted implant, in particular with respect to the peri-implant bone?’ According to Brunski and Aparicio in 2023 [21], one answer arises from the comparison of stress–strain states in the peri-implant bone around vertical implants versus tilted implants in identical bone and loaded by the same vertical force. A suitable method to perform this comparison is finite element (FE) modelling, where relevant factors (e.g. bone properties, implant geometry, implant loading, etc.) can be controlled in a systematic way to allow for a ‘fair’ comparison. Figure  11.8 illustrates the results of an FE study of the intraosseous strain distributions occurring around a bone-integrated implant tested in three different orientations with respect to the occlusal plane. In the FE models presented here, the implant is made of pure titanium and the bone is assigned the approximate properties of a mixture of dense and cancellous bone. The three implants—straight (Fig.  11.8a), angled 15° (Fig. 11.8b) and 25° (Fig. 11.8b)—are assumed to be connected to the bone (‘osseointegrated’) and loaded by the same downward vertically directed force. The conclusion is that other factors being equal, such as the force on the implant, the size and shape of the implant, the quality and quantity of surrounding bone, etc., increasing the inclination of an implant increases the stresses and strains in the peri-implant bone compared to the case of a vertical implant. Early in the development period of tilted implants, it was stated that one of the advantages of tilting an implant was that it would ‘make maximum use of available bone and result in a simpler, more predictable, less costly and less time-consuming treatment compared to bone grafting procedures in the maxillary sinus or augmentation techniques...’ [15]. We could explain the statement ‘making the most of the available bone’ from a biomechanical point of view with a simple geometrical

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a

b

c

Fig. 11.8 (a–c) Principal compressive strains in bone around implants with different inclinations subjected to the same force. (From Brunski J. B. Biomechanics in the

a

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context of tilted implants. In Advanced Zygomatic Implants: The ZAGA Concept. Carlos Aparicio Ed. Quintessence Chicago 2023) [21]

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Fig. 11.9  If the available bone has a thickness of 10 mm (a), the length of the vertical implant in the bone (b) may be 10  mm, whereas if the implant is tilted 25° (c), the length in the bone increases to 11  mm. (From Brunski

J.  B, Aparicio C.  Biomechanics in the context of tilted implants. In Advanced Zygomatic Implants: The ZAGA Concept. Carlos Aparicio Ed. Quintessence Chicago 2023) [21]

example. Let us assume that the thickness of the sinuses floor in an individual is 10  mm (Fig. 11.9a). Let us further assume that it is an edentulous area which, because of its width, would allow the placement of a vertical implant (Fig. 11.9b) or an inclined implant (Fig. 11.9c). A simple geometric calculation indicates that the length in bone of the vertical implant would be 10  mm, while for the inclined implant with an angle α = 25°, the length of the implant in bone would increase to the length of the inclined dotted line in Fig.  11.9a, which is 11  mm. For an applied inclination of about 35°, the bone-toimplant contact area (BICA) of the tilted implant

may be about 15% greater than that of a vertical implant. Thus, from the perspective of making the best use of available bone, an inclined implant is arguably superior because it has a greater effective length in bone and (potentially) more bone contact area than the vertical implant. This provides a better understanding of the biomechanics of tilted implants related to insertion technique. For example, the angle of attack of the implant with an intra-sinus path to the zygomatic bone is more perpendicular, so the BICA is lower than when the implant is placed with an extra-sinus path [22].

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The above provides insight into the biomechanics of tilted implants. Regardless of the surgical and prosthetic justification chosen, the same biomechanical design considerations arise with zygomatic implants, which are tilted by definition: How are implants loaded during masticatory function? What is the difference in load distribution between an implant anchored exclusively in zygomatic bone and one that is also supported by alveolar bone? What stress levels occur in the peri-implant alveolar bone? What stress levels occur in the peri-implant alveolar bone? What stress levels occur in the peri-implant alveolar bone and what stress levels occur in the zygomatic bone? Under what conditions can the applied stresses exceed the damage limits? What are the differences between the loading of an isolated zygomatic implant and one connected to other implants? What are the differences between the loading of an isolated zygomatic implant and one connected to other implants? Ujigawa [23] used a finite element model to investigate the distribution of forces along zygomatic implants in a model with regular anatomy. They simulated an occlusal force of 150 N and a lateral force of 50 N. Their model also incorporated a 300  N force, applied to the bone and zygomatic arch, to simulate the action of the masseter muscle. The study showed large von Mises stresses in the zygomatic bone and suggested that most of the occlusal force was transmitted to this area. Stresses in severely resorbed jaws with connected implants (one zygomatic implant and two regular implants) were not concentrated around the alveolar bone supporting the zygomatic implant. Stresses under vertical and lateral loads, when separate implants were present, tended to be generated in the zygomatic bone, in the middle part of the zygomatic implant and at the implant–abutment junction, thus indicating the possibility of complications related to marginal bone, loss around the implants and mechanical failure of the components. According to Ujigawa, stress due to occlusal forces is borne primarily by the zygomatic bone, is transferred predominantly through the infra-­ zygomatic ridge and is divided between the fron-

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tal and temporal processes of the zygomatic bone in different directions. Therefore, zygomatic implants in combination with at least two conventional implants can restrain rotational loads and distribute stresses from the fixed prosthesis to the zygomatic bone, but cannot restrain stresses at the implant–abutment joint under lateral loading. It is interesting to note that the model used in the Ujigawa study uses a remaining alveolar bone height of 6.3 mm, which almost negates the indication for placing zygomatic implants or, in any case, represents a more favourable situation than usual with respect to the amount of alveolar bone available in a severely atrophic maxilla. Finite element studies performed by Freedman’s group in 2013 [24] and 2015 [25] provide answers to the importance of the alveolar bone in supporting or modifying the masticatory load on zygomatic implants placed according to the original or externalised technique. In the 2013 study, the authors created a model of a fixed bridge supported by two zygomatic implants placed using the intra-sinus Brånemark original technique. Subsequently, the model was duplicated and the holes around both implants were widened as they advanced through the maxillary bone. The result was a 0.5 mm gap between the implants and the bone. Forces ranging from 50 to 600 N were used, with the idea that forces up to 600 N would exceed those recorded in vivo. The maximum stresses observed in the model with alveolar support were lower than those in the model without alveolar support, regardless of the direction in which the force was applied. Alveolar bone support had the greatest influence on von Mises peak stresses when occlusally directed forces were applied. This is clinically significant as most masticatory forces are occlusally directed. The results of this study suggest that the support provided by the alveolar bone is important for zygomatic implants. The explanation Freedman suggests is that although the portion of the implant supporting the alveolar bone is very small compared to that supporting the zygomatic bone, the alveolar zone is much closer to the force being applied to the implant. This would

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allow the masticatory forces to be distributed over the entire maxilla and facial skeleton rather than solely over the zygomatic bone. In contrast to the results of Ujigawa et al. [23], only small stresses were observed in the zygomatic bone. Instead, the forces were distributed throughout the maxilla and the entire facial skeleton. This suggests that less force is distributed in the zygomatic bone than suspected when alveolar support is present. One possible explanation for the difference in results is that the Ujigawa model also incorporated a 300  N force applied to the arch and zygomatic bone to simulate masseter action. The study showed large von Mises stresses in the zygomatic bone and suggested that most of the occlusal force was transmitted to this area. However, it is difficult to know what proportion of the stress observed in the zygomatic bone came from the occlusal force and not from the masseteric force. In a second study published in 2015, Freedman et al. [25] investigated the influence of the maxillary alveolar bone on the stress distribution of zygomatic implants in extra-sinus position. For this purpose, they modelled two zygomatic implants that were placed in an extra-sinus position with anchorage in the zygomatic bone and contact in the alveolar bone. The implants were connected by means of a fixed bridge. This model was duplicated and the area of the maxillary alveolar bone contacting the implants was eliminated. Forces ranging from 50 to 600 N were applied to each model individually in the molar area of the bridge at varying angles to the occlusal plane. As before, the magnitudes of the maximum stresses were systematically higher in the model without alveolar support, regardless of the direction of the applied force. It is interesting to note how apparently the influence of the alveolar contact is much more important when the implant is placed with the original intra-sinus technique than when the extra maxillary technique is used. In fact, according to figures published by Freedman’s group, when there is no alveolar contact in the original technique, the stress on the zygomatic bone is enhanced by approximately three times. Whereas in the externalised technique the forces increase

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approximately twice as much when there is no contact. Freedman does not report a previous reduction of the maxillary wall of the model in the form of window or slot osteotomy that would decrease the contact of the implant with the maxillary wall. Moreover, Corvello demonstrated in 2011 [22] that due to the tangential attack of the implant the contact area at zygomatic level is greater in the externalised technique than in the original intra-sinus. Therefore, the explanation for the fact that in Freedman’s studies the reduction of contact in the alveolar area has less effect in the externalised technique than in the original one could be in the greater contact area of the implant with the maxillary wall and the zygomatic bone that is achieved with a minimally invasive osteotomy as preached by the ZAGA Concept.

11.4 The ZAGA Criteria to Establish the Zygomatic Implant Trajectory In designing the zygomatic implant trajectory, the surgeon must have to be familiar with the following aspects related to the maxillary anatomy that will determine both the position of the entry and exit point of the implant [8, 26]: • Remnant alveolar bone or basal bone forming the floor of the maxillary sinuses or nose, in terms of height, width, geometry and quality. • Palatine bone proximal to the floor of the sinuses, in terms of thickness, quality, architecture or presence of anatomical incisions. • Maxillary wall in terms of shape of its curvature if present, thickness and/or presence of anatomical incidences (e.g. alveolar artery). • The zygoma itself in its morphology and architecture in general, as well as the thickness of its cortices and the possible prolongations of the sinuses inside it. It will be especially important to know the details of the architecture of the transition zone of the zygoma with the maxilla, especially if a double window osteotomy is planned.

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In the ZAGA Concept, the type of incision and the flap are also designed in relation to the patient’s anatomy. After planning, we will execute them until we release a flap that allows us to control the entire surgical area. For this purpose it is advisable to use a retractor placed in the angle formed by the temporal and frontal process of the zygomatic bone. Following situating the retractor, the choice of the trajectory of the implant, as well as the points where it interacts with the subject, is guided by the anatomy of the area following three steps: (a) Identify the ZICZ. (b) Establish the AZ. (c) Perform the antrostomy by joining the two points.

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therefore the prevention of late complications such as oro-antral communication or soft tissue recession, as well as the appearance of mechanical, prosthetic and/or aesthetic complications, largely depends on it. As described by Aparicio et al. [8, 11], the location of the ZICZ is governed by prosthetic, biomechanical and anatomical considerations. Depending on these factors, the oral preparation may begin in the form of a tunnel in the bony ridge itself, placing the entry point on the palatal side of the alveolar ridge; or in cases of severe resorption such as ZAGA type 4, have the form of a lateral channel running from the ridge along the buccal side of the maxillary wall.

11.4.2 Establish the AZ

The initial step in zygomatic implant placement is to identify and determine the first contact zone of the implant at the level of the alveolar ridge (Fig.  11.10). This point is known as the zygomatic implant critical zone (ZICZ) [8, 11]. Determining this zone where the implant first contacts the alveolar bone and subsequently the soft tissue is a key factor for the success of the zygomatic surgical procedure. In fact, the choice of the type of osteotomy to be performed and

To achieve rehabilitation of the atrophic maxilla by means of a prosthesis fixed to zygomatic implants, the apical part of the implant is anchored in the zygomatic bone with the aim of achieving primary stability, refraining from damaging adjacent structures such as the orbit, the infraorbital nerve, the infratemporal fossa or the zygomatic bone itself. Once the ZICZ has been determined, the next step will be to proceed to determine the point where the drill will penetrate the antrum: the antrostomy zone (AZ). In the ZAGA Concept, the position of the AZ is determined according to the patient’s anatomy, and

Fig. 11.10  Radiographic series showing on the left the preoperative planning of the implant trajectory in a ZAGA type 4 situation. Due to the scarce residual alveolar bone in the ZICZ (red circle) a ZAGA channel osteotomy is determined. In the centre we visualise how the minimally

invasive ZAGA osteotomy has maintained the integrity of the membrane in the ZICZ (white arrows) despite the small amount of bone. On the right, the tomographic section over the implant shows the excellent situation of the sinus 3 years later

11.4.1 Identify the ZICZ

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Fig. 11.11  The tomographic section over the implant shows the result of a ZAGA tunnel osteotomy. The red arrows indicate the position of the ZICZ and entry of the implant into the residual alveolar bone. The green arrows indicate the point of the AZ, just on the other side of the tunnel

Fig. 11.12  The composition shows in the upper perimeter the tomographic slices corresponding to the plans for the zygomatic implants in second premolar/first molar positions. In the centre the clinical image with the ZAGA Flat implants placed in minimally invasive ZAGA channel

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more specifically according to the type of osteotomy previously chosen. If, due to the amount of bone remaining at the alveolar level, a tunnel-­ type osteotomy has been chosen, the antrostomy will be approximately 5  mm away on the other side of the alveolar perforation (Fig. 11.11). If, on the other hand, due to the scarcity of bone, an externalised channel osteotomy is chosen, the site of the antrostomy (AZ) will be located far away from the near ZICZ or in the zygomatic bone (Fig. 11.12). The decision of the location of the entry zone, trajectory and length of the implant at the level of the zygomatic bone will be determined according to the following criteria: numerical, relative to the number of implants to be placed; implant design in terms of its pattern and especially its thickness; and anatomical/structural relative to the architecture of the zygomatic bone and its relationship/transition with the maxillary wall. As explained more fully in Chap. 5 of The ZAGA Concept book [11], in the cases of ZAGA 2, 3 and 4, the point of penetration of the drill bit into the antral cavity corresponds to the point of

osteotomies. The double arrows highlight the distance between the AZ and the ZICZ. In the lower perimeter the radiological images taken 3  years after placement show the state of the maxillary sinuses. The white arrows point to the AZs

11  Surgical–Anatomical and Prosthetic–Biomechanical ZAGA Criteria to Determine the Zygomatic…

penetration of the drill bit into the antral cavity approximately to the point of entry into the zygomatic bone through its inferior facial cortex (close to the maxillo-zygomatico suture). In ZAGA 0 and some ZAGA type 1 cases, the entry point into the antral cavity is located just across the perforation of the remaining alveolar bone. In these cases, the apical entry point into the zygomatic bone is located on its inner side and does not correspond to the AZ. In order to achieve the longest possible intraosseous path, taking advantage of its sinuous shape and looking for an entry point in the zygomatic bone that crosses as many cortices as possible is recommended [12]. While seeking the maximum possible anchorage, the zygomatic osteotomy must ensure that the zygoma itself does not fracture. To this end, we must refrain from tangential drilling too close to the facial cortex, leaving little bone thickness between the implant and the outer surface of the cortex. We should also refrain from using exaggerated implant diameters that require major and unnecessary osteotomies that facilitate total or partial fracture of the zygoma (Fig. 11.13). This consideration will be especially important when placing two zygomatic implants in the same zygoma.

11.4.3 Perform the Antrostomy The final implant trajectory is determined by joining the coronal and apical points previously determined in steps A and B. To do so, a sequential osteotomy joining the points previously determined in steps A and B is performed. To under-prepare the bone of the trajectory, the future diameter of the planned implant is considered. Ideally the obtained bed will be fully sealed with an implant whose design corresponds to the morphology of the prepared osteotomy. As we have already pointed out, the ZAGA Concept uses only one osteotomy. Therefore, there is no need to waste bone from the patient’s maxillary wall by performing an ‘emotional’ osteotomy, in the form of a ‘window’ or ‘slot’, prior to the osteotomy really necessary for the implant placement.

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Fig. 11.13  The tomographic section shows the trajectory of the implant and the state of the adjacent structures. The double green arrow indicates that in order to refrain from unwanted fractures or unproductive removal of the zygomatic bone, the AZ should be placed at an approximate distance of at least 5  mm from the external zone of the superior external cortex of the zygoma

11.5 Interim Prostheses In zygomatic implant treatment, the immediate provisional prosthesis design and function is extremely important. First of all because a well-­ made immediate prosthesis reinforces the initial stability of the loaded implants by rigidly splinting all the implants and thus refraining excessive micromovement. In addition, provisional prostheses serve multiple functions such as providing acceptable aesthetics as well as masticatory and phonetic function during the healing process. As a provisional prosthesis, it will also be useful as a test to check the position, occlusion and ­aesthetics of the teeth as well as the soft tissue substitutes [27, 28]. As mentioned above, the prosthesis utilises one of the key principles of orthopaedics to provide supplemental rigidity to allow for neo-­ vascularisation and subsequent bone healing. Thus, in orthopaedics, a cast, a metal plate or, in the case of implants, a fixed prosthesis that rig-

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idly splints all implants will prevent their relative movement and allow healing. In the case of zygomatic implants, this concept of rigid splinting to refrain or control micromovement is even more important than in regular implants. Even if primary or secondary stability has been achieved in its apical anchorage zone, an eventual excessive micromovement would be facilitated by three possible factors: the first is the great lever length of a very long implant supported only at its apical end; the second is that the anatomical variations of the zygomatic bone are very large and in certain cases with less density or quantity of cortical bone it can increase its elasticity, favouring the movement of the implant; and thirdly, the eventual placement of the implant without total contact with the alveolar or palatal bone remnant. The ZAGA Concept pays special attention to the importance of the contact of the externally placed implant with the alveolar bone remnant in addition to the zygomatic anchorage. Regardless of whether the implant is placed through the ­palatal bone or externalised, it is essential that the implant has intimate contact with the alveolar or palatal bone. In fact, Becktor et al. in 2005 [29], using the original technique in 16 consecutive patients, had infectious complications in several of their patients due to oro sinus communications. The authors attributed the origin of the bone destruction to uncontrolled coronal peri-­ implant micromovement. The construction of the provisional prosthesis begins at surgery. During implant placement, the surgeon must ensure that the implant is correctly tilted towards the antagonist dentition. Ideally the surgeon will have a prosthetic guide to relate the emergence of the implants to the antagonist dentition and provide the implant head with an appropriate abutment type in length and angulation (Fig. 11.14). For the choice of the abutment length it will be important to have photographs of the patient in the operating room in different smile intensities without prosthesis as well as analyse the quantity and biotype of the soft tissue surrounding the implant to estimate its final height after healing.

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Fig. 11.14  Occlusal view of a prosthetic guide for checking the direction of the prosthetic screw Table 11.2 General rules for a full-arch immediate prosthesis • Maximum accuracy in impression taking, whether digital or analogue • Rigid initial splinting of all implants with transverse stabilisation of the arch • Dentition/occlusal surface/shortened to the limit marked by the emergence of the distal implants • Flat or convex but never concave prosthetic mucosal interface • Use of Henry Beyron’s principles for an optimal occlusion adapted to an implant-anchored prosthetic situation [28] • Soft diet for 3 months

The immediate screw-retained immediate prosthesis on zygomatic implants does not have specific components. For an implant-anchored provisional prosthesis, the general rules detailed in Table  11.2 are recommended. The structure should be rigid and accurately constructed for better load distribution. If the prosthesis is not sufficiently rigid, deformation and deflection of the zygomatic implant can lead to poor distribution of masticatory loads and facilitate micromovements that impede osseointegration, peri-implant bone loss or screw loosening. To optimise force distribution, rigid stabilisation will be of the full arch and will include all implants (Fig.  11.15). It will be essential to reduce or eliminate buccal/distal lever arms. Forces that cause bending moments are known to be the most unfavourable.

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speech and facial expression. It was chosen as a mnemonic tool because it somehow covers all four specific criteria expressing the long-term status of a single zygomatic implant.

Fig. 11.15  Frontal/gingival view of a temporary prosthesis. Note the good AP distribution of the implants and the perfect design of the mucosal prosthesis interface that will allow the patient to maintain hygiene. (Image courtesy of Dr. Fadi Yasmine)

11.6 The ORIS Criteria to Evaluate the Results of the Zygoma Anchored Oral Rehabilitation There is a tendency to validate, and subsequently use, the same diagnostic methods to assess the condition of teeth and oral implants. Similarly, there is a tendency to consider and evaluate a zygomatic implant in the same way as a conventional implant. However, zygomatic implants differ from traditional implants in their biomechanics, clinical procedures, anatomical sites to which they relate and possible complications. In other words, zygomatic implants are different from normal implants and to consistently evaluate the success of treatment with zygomatic implants the same parameters cannot be used as when evaluating conventional implants. Moreover, the current zygomatic approach is relatively new, especially if the head of the zygomatic implant is located in an extra maxillary area with interrupted alveolar bone around its perimeter. To compare in fine and thus improve the quality of the evaluation procedure, specific success criteria for zygomatic implants have been proposed in the literature [7, 26, 30]. In the aforementioned works, ORIS is the acronym for offset, rhinosinusitis, infection and stability. ORIS is also a term of Latin origins with a broad meaning covering the face, the mouth, pronunciation,

• Offset: Evaluation of prosthetic success based on the final position of the zygomatic implant with respect to the centre of the alveolar ridge. • Rhino-sinuses status: Adopting clinical and radiological criteria widely accepted in the ENT literature. Specifically, the Lanza– Kennedy clinical test [31] and the modified Lund–Mackay radiological test [32] are used to compare the sinus status by analysing the pre-­ surgical and post-surgical CBCT. • Infection-related soft tissue dehiscence: An evaluation of signs of infection or soft tissue dehiscence on a grading scale based on the reference photographs obtained. • Stability report: Accepting as success criteria a certain mobility without signs of rotational dis-osseointegration or apical pain. Based on these criteria, five possible conditions may be assessed when evaluating zygomatic implants [7]: • Success condition I: represents the optimal stage. • Success condition II: represents an alteration of routine without clinical impact. • Success condition III: represents a borderline situation with alterations that are clinically manifested but are still possible to successfully treat. • Success condition IV: would represent the surviving implant that supports the prosthesis but has not been measured according to the proposed criteria • Success condition V: reflects implant failure. Specific criteria to describe success/survival of zygomatic implants are necessary, both to write and read scientific literature related to zygomatic implant–based oral rehabilitations. Given that the success criteria we use to evaluate conventional implants (i.e. assessment of mar-

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tal implant origin. Treatment and prevention with bone morphogenetic protein-2/absorbable collagen sponge sinus grafting. Int J Oral Maxillofac Implants. 2013;28:e512–20. 3. Davó R, Felice P, Pistilli R, Barausse C, Marti-Pages C, Ferrer-Fuertes A, et al. Immediately loaded zygomatic implants vs conventional dental implants in augmented atrophic maxillae: 1-year post-loading 11.7 Conclusions results from a multicentre randomized controlled trial. Eur J Oral Implantol. 2018;11:145–61. 4. Felice P, Barausse C, Davó R, Pistilli R, Marti-Pages The ZAGA Concept is a natural evolution of the C, Ferrer-Fuertes A, et al. Immediately loaded zygooriginal zygomatic implant process originated by matic implants versus conventional dental implants in Branemark. augmented atrophic maxillae: three-year post-loading results from a multicentre randomised controlled trial. Unlike the previously described systems that Clin Trials Dentistry. 2020;2:5–25. promote a surgical technique that is applied to all 5. Aparicio C, editor. Zygomatic implants: the anatomy-­ patients in a similar manner, the ZAGA Concept guided approach. 1st ed. Chicago: Quintessence; promotes a patient-specific therapy that is tai2012. 6. Aparicio C. A proposed classification for zygomatic lored to each patient’s anatomy. It provides implant patients based on the zygoma anatomy guided patients with advanced maxillary atrophy the approach (ZAGA): a cross-sectional survey. Eur J opportunity to regain masticatory and aesthetic Oral Implantol. 2011;4:269–75. function achieving more anatomical prostheses 7. Aparicio C, López-Piriz R, Albrektsson T.  ORIS criteria of success for the zygoma-related rehabilitawhile minimising the risk of oroantral communition: the (revisited) zygoma success code. Int J Oral cations and sinus infections. Maxillofac Implants. 2020;35:366–78. The ZAGA Concept includes prosthetic–bio8. Aparicio C, Lopez-Piriz R, Peñarrocha mechanical and surgical–anatomical criteria that M.  Preoperative evaluation and treatment planning. Zygomatic implant critical zone (ZICZ) location. In: guide the decision-making in determining the Quimby A, Salam S, editors. Perspectives on zygoimplant trajectory, the type of osteotomy and also matic implants. Fernandes RP, Consul. Ed. Atlas the choice of the most appropriate implant design. of the oral and maxillofacial surg clinics of North The use of ZAGA achieves success by adaptAmerica. Amsterdam: Elsevier; 2021. p. 185–202. 9. Aparicio C. Soft tissue management in zygoing technologies, criteria and tools to the patient’s matic implant rehabilitation. In: Aparicio C, editor. anatomy, rather than adopting a rigid one-size-­ Advanced zygomatic implants: the ZAGA concept. fits-all approach. Chicago: Quintessence; 2023; in press. The results of using the combination of the 10. Aparicio C, Polido WP, Chow J, David L, Davo R, De Moraes EJ, Fibishenko A, Ando M, Mclellan G, ZAGA Concept, along with more individualised Nicolopoulos C, Pikos MA, Zarrinkelk H, Balshi instrumentation, including the new ZAGA TJ, Peñarrocha M. Identification of the pathway and implant designs proposed by the authors, show a appropriate use of four zygomatic implants in the consistently less traumatic osteotomy, increased atrophic maxilla: a cross-sectional study. Int J Oral Maxillofac Implants. 2021;36:807–17. https://doi. implant stability, improved bone-to-implant conorg/10.11607/jomi.8603. tact, bone sealing and bed adaptation. 11. Aparicio C. The ZAGA concept as patient-specific zygomatic therapy. Parameters for decision-making on the implant trajectory. In: Aparicio C, editor. Advanced zygomatic implants: the ZAGA concept. References Chicago: Quintessence; 2023; in press. 12. Nkenke E, Hahn M, Lell M, Wiltfang J, Schultze-­ 1. Brånemark P-I, Gröndahl K, Ohrnell L-O, Nilsson Mosgau S, Stech B, et  al. Anatomic site evaluation P, Petruson B, Svensson B, et  al. Zygoma fixture in of the zygomatic bone for dental implant placement. the management of advanced atrophy of the maxClin Oral Implants Res. 2003;14:72–9. https://doi. illa: technique and long-term results. Scand J Plast org/10.1034/j.1600-­0501.2003.140110.x. Reconstr Surg Hand Surg. 2004;38:70–85. 13. Mattsson T, Köndell PA, Gynther GW, Fredholm 2. Jensen OT, Adams M, Cottam JR, Ringeman J. Occult U, Bolin A.  Implant treatment without bone graftperi-implant oroantral fistulae: posterior maxiling in severely resorbed edentulous maxillae. J Oral lary peri-implantitis/sinusitis of zygomatic or denMaxillofac Surg. 1999;57:281–7.

ginal bone height over time) cannot be used, the implementation of ORIS success criteria as a follow-up tool is key to assessing the long-term multi-aspect success of the treatment.

11  Surgical–Anatomical and Prosthetic–Biomechanical ZAGA Criteria to Determine the Zygomatic… 14. Krekmanov L, Kahn M, Rangert B, Lindstrom H.  Tilting of posterior mandibular and maxillary implants for im- proved prosthesis support. Int J Oral Maxillofac Implants. 2000;15:405–14. 15. Aparicio C, Perales P, Rangert B. Tilted implants as an alternative to maxillary sinus grafting: a clinical, radiologic, and periotest study. Clin Implant Dent Relat Res. 2001;3(1):39–49. 16. Brunski JB. In: Aparicio C, editor. Biomechanical aspects of tilted regular and zygoma implants. Zygomatic implants: the anatomy-guided approach. London: Quintessence; 2012. p. 25–45. 17. Carter DR, Caler WE, Spengler DM, Frankel DM.  Fatigue behavior of adult cortical bone: the influence of mean strain and strain range. Acta Orthop Scand. 1981;52(5):481–90. 18. Brunski JB. In: Ratner ASHBD, Schoen FJ, Lemons JE, editors. Metals: basic principles. Biomaterials science: an introduction to materials in medicine. 3rd ed. Waltham, MA: Elsevier; 2013. p. 111–9. 19. Harrison A.  Methods of assessing visual acuity in young children. Am Orthopt J. 1975;25:109–14. 20. Harrison A, Lewis TT. The development of an abrasion testing machine for dental materials. J Biomed Mater Res. 1975;9(3):341–53. 21. Brunski JB, Aparicio C. Biomechanics in the context of tilted implants. In: Aparicio C, editor. Advanced zygomatic implants: the ZAGA concept. Chicago: Quintessence; 2023; in press. 22. Corvello PC, Montagner A, Batista FC, Smidt R, Shinkai RS. Length of the drilling holes of zygomatic implants inserted with the standard technique or a revised method: a comparative study in dry skulls. J Craniomaxillofac Surg. 2011;39(2):119–23. 23. Ujigawa K, Kato Y, Kizu Y, Tonogi M, Yamane GY.  Three-dimensional finite elemental analysis of zygomatic implants in craniofacial structures. Int J Oral Maxillofac Surg. 2007;36:620–5.

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24. Freedman M, Ring M, Stassen LFA.  Effect of alveolar bone support on zygomatic implants: a finite element analysis study. Int J Oral Maxillofac Surg. 2013;42:671–6. 25. Freedman M, Ring M, Stassen LFA. Effect of alveolar bone support on zygomatic implants in an extra-sinus position--a finite element analysis study. Int J Oral Maxillofac Surg 2015;44:785–790. 26. Aparicio C, Manresa C, Francisco K, Claros P, Alández J, González-Martín O, et  al. Zygomatic implants: indications, techniques and outcomes, and the zygomatic success code. Periodontol 2000. 2014;66:41–58. 27. Aparicio A, Aparicio C.  Prosthodontics aspects of the zygoma rehabilitation. In: Aparicio C, editor. Zygomatic implants: the anatomy-guided approach. 1st ed. Chicago: Quintessence; 2012. 28. Aparicio A, Aparicio C. Prosthetic rehabilitation. In: Aparicio C, editor. Advanced zygomatic implants. The ZAGA Concept. Chicago: Quintessence; 2023; in press. 29. Becktor JP, Isaksson S, Abrahamsson P, Sennerby L. Evaluation of 31 zygomatic implants and 74 regular dental implants used in 16 patients for prosthetic reconstruction of the atrophic maxilla with cross-­ arch fixed bridges. Clin Implant Dent Relat Res. 2005;7:159–65. 30. Aparicio C, Manresa C, Francisco K, Aparicio A, Nunes J, Claros P, et  al. Zygomatic implants placed using the zygomatic anatomy-guided approach versus the classical technique: a proposed system to report rhinosinusitis diagnosis. Clin Implant Dent Relat Res. 2014;16:627–42. 31. Lanza DC, Kennedy DW. Adult rhinosinusitis defined. Otolaryngol Head Neck Surg. 1997;117:s1–7. 32. Lund VJ, Mackay IS.  Staging in rhinosinusitis. Rhinology. 1993;31:183–4.

Clinical Techniques for Immediate Loading

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Stephanie Yeung and Saj Jivraj

Abstract

Patient factors and implant biomechanics influence the rationale, requirements and techniques for the immediate loading procedure. Proper patient selection, treatment planning and operation method will lead to a predictable, expeditious outcome for re-establishing a patient’s comfort and function. There are multiple subjective and objective patient and surgical factors to consider. Additionally, there are multiple approaches to completing the immediate loading clinical procedure itself, with the most common being direct, direct–indirect or the indirect technique. Each technique bears technical and patient-related advantages and disadvantages. This section will review the general requirements for patient selection and describe the three methods of completing an immediate loading procedure for full-arch fixed implant-supported restorations.

S. Yeung Private Practice, Los Angeles, CA, USA S. Jivraj (*) Anacapa Dental Art Institute, Oxnard, CA, USA

12.1 Rationale for Immediate Loading Immediate loading is defined as the prosthetic loading of dental implants within the first week of loading [1]. From a biomechanical standpoint, immediate loading can result in success and survival rates comparable to conventionally loaded dental implants [2]. Additionally, overall treatment time is decreased and the patient’s functional abilities are sooner established [3, 4]. Completing this procedure yields the potential for increased patient satisfaction predictably and efficiently. From a biomechanical standpoint, the success underlying immediate loading is derived from the allowance of 50–150 μm of micromotion—and the ability of a well-designed splinted restoration to limit it [3, 5]. Factors that may influence micromotion and restorative outcome include surgical planning, implant positions, patient biology and prosthetic design [6]. For the most predictable outcome, it is imperative to select the best procedural course with consideration to practicality and any clinical restraints. There are a variety of methods for fabricating a splinted full-arch restoration within the first week of implant placement. There are positive

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_12

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and negative attributes to each method. Restorations inserted within the day of implant surgery will minimise the patient’s exposure to anaesthesia and the restoration can precede postoperative soft tissue swelling. Delaying insertion by a few days may allow the patient time to rest. However, the patient would also be subject to repeated anaesthesia, in addition to considering the risk of tissue expansion over healing abutments. The fabrication and insertion method selected for immediate loading involves a series of objective and subjective variables. Objective determinants include surgical planning, restorative design and procedure timing. Subjective variables include personal preference, patient selection and patient preferences.

12.2 Requirements for Immediate Loading 12.2.1 Patient Selection There are multiple factors to consider in determining whether a patient is an ideal candidate for immediate loading. Medical history, such as bisphosphonates use, irradiation or immunosuppression, generally has a more difficult time with wound healing and has higher implant failure rates; thus, immediate loading may not be a good option [7]. However, tobacco use and well-­ controlled diabetes may not necessarily pose a risk [7, 8]. In addition to medical factors, there are behavioural and dental factors to consider. A history of periodontitis or parafunctional habits may not be immediate contraindications [8, 9]. However, surgical factors related to implant stability, such as position, bone quality and force distribution, can contribute negative impacts [10]. Therefore, prosthetic design must also be factored in for optimal rigidity of the prosthesis in conjunction to occlusal design for function [11]. Postoperative patient compliance to a soft diet and dental hygiene maintenance

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are also influential components for a successful outcome [ 12–14].

12.2.2 Surgical Considerations Placement of an adequate number of implants in well-dispersed positions is necessary for successful immediate loading. The goal in implant numbering and positioning is to limit micromotion and allow even distribution of occlusal forces. The number and position of implants may also be influenced by bone quality, insertion torque at the time of surgery or even implant length [8, 15, 16]. The accepted minimum number is four implants in the mandible and four to six implants in the maxilla; fewer implants may yield unpredictable results [3, 16–18]. If the distance between implants is too great, prosthetic failure may occur as a result of a large cantilever; conversely, too little distance may decrease resin bulk, thus leading to a weaker prosthesis [19].

12.2.3 Restorative Considerations The ideal prosthesis used in full-arch immediate loading is hygienic, rigid, aesthetic and allows for an even distribution of forces. To avoid interfering with healing processes, restorations should be convex for ease of hygiene maintenance. Additionally, screw retention is recommended to avoid cement-related irritation as well as excessive pull-out forces [20]. Aesthetics, rigidity and force distribution can be managed through occlusal design and allocation of sufficient space for teeth and acrylic bulk [8]. The importance of force distribution is paramount, considering that survival rates are generally improved when immediately loaded prostheses opposing natural dentition have higher success rates relative to opposing implants [21]. If occlusal forces are a potential concern, flattening cusps for balance and narrowing of occlusal surfaces should decrease occlusal forces [3].

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12.3 Immediate Loading: Clinical Methods Regardless of loading method, there are pertinent diagnostic details that need to be available prior to proceeding with the procedure itself. Preoperative information, such as radiographs, diagnostic casts, clinical charting and photos, should be made to aid surgical and restorative planning. Radiographs should include a full-arch cone beam computed tomography (CBCT) to help determine implant positioning and any adjunctive surgeries. Diagnostic casts can either be made using conventional impression materials or scanned intraorally. Preoperative photos should include frontal, profile and smile views to help determine tooth positioning and any disharmonies that can be surgically accounted for, such as the transition zone from prosthesis to gingiva. If necessary, a tooth setup should be made to establish vertical dimension, phonetics, aesthetics and occlusal plane. Upon completion of implant placement, seating of multi-unit abutments is recommended to elevate the fixture levels to or above gingival height for clinical access, altering implant trajectories if needed, passivity of the prosthesis and hygienic access. There are scenarios in which using multi-unit abutments is unfeasible, such as situations involving limited restorative space. Additionally, healing caps or healing abutments should be used to maintain access to restorative platforms while the fixed prosthesis is being converted or fabricated.

12.3.1 Direct Technique: Direct Denture Pick-Up and Conversion

Fig. 12.1  Intaglio of removable denture featuring well-­ extended flanges, full palatal coverage and ideal tooth positioning over the crest of the alveolar ridge

positioning within the prosthesis, which could result in a difference in chair time and comparably improved strength of the resulting immediate load prosthesis. Regardless of approach, both require the fabrication of a denture or indexed removable prosthesis prior to surgery. The removable prosthesis is used to pick up temporary cylinders fixed to the dental implants intraorally, and then converted into a fixed prosthesis extraorally. In the conventional method, it is important to identify any anatomical landmarks available to properly orient the prosthesis prior to any attempt at conversion; landmarks may include the palate, remaining teeth, pre-existing implants or even unaltered ridge areas (Fig. 12.1). For the digital method, the removable prosthesis must seat perfectly into the anchored guide.

12.3.1.1 Conventional Approach Using the removable prosthesis, a rapid-set silicone impression is made to identify the implant locations. The following images depict a comThe direct technique differs from others in that it plete denture containing a polyvinyl siloxane bite almost exclusively functions as a same-day post-­ registration material demarcating the implant surgery solution. Ideally, there should be an sites. The removable prosthesis should be relieved acceptable opposing arch with occlusion in this around these marked sites to allow a passive seatprocedure. Currently, there are two main meth- ing of the prosthesis relative to the anatomical ods of the direct technique: conventional and indices (Figs. 12.2, 12.3, and 12.4). digital. The main difference between the two Temporary cylinders are to be seated at this main methods is the predictability of implant point. Radiographs should be taken to verify

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Fig. 12.5  Seating of initial temporary abutment Fig. 12.2  Frontal view of denture used for conversion

Fig. 12.6  Seating with denture to check for passivity and verify sufficient clearance for pick-up resin Fig. 12.3  Rigid polyvinyl siloxane material indexing location of healing abutments

Fig. 12.4  Relief of denture at sites marked by PVS material

seating if at implant level. Parallelism between the temporary cylinders should be visually checked and any multi-unit abutments necessitating repositioning should be completed. Once par-

allelism is deemed acceptable, the removable prosthesis may be tried for passivity while indexed to the selected anatomical reference(s). The removable prosthesis should be tried over one temporary cylinder at a time to ensure that the trajectory of any single cylinder does not interfere with seating of the prosthesis. Temporary cylinders should not be in contact with any surfaces of the removable prosthesis; if contact is visible, further relief of the prosthesis is necessary. It is imperative that there is sufficient relief around the temporary cylinders to ensure that there is no interference in seating and that there will be sufficient space for pick-up resin to flow (Figs. 12.5, 12.6, 12.7, 12.8, 12.9, and 12.10). Prior to using any pick-up resin, measures must be taken to avoid allowing resin to flow into undesired areas. A rubber dam or rubber dam pieces should be adapted around all temporary cylinders to prevent resin from flowing onto

12  Clinical Techniques for Immediate Loading

Fig. 12.7  Seating of denture over two temporary abutments to verify passivity sufficient clearance for pick-up resin

Fig. 12.8  Intraoral view of two temporary abutments. Note: angulation is slightly off-angle, which may interfere with passivity of denture upon insertion

Fig. 12.9  Seating of denture over four temporary abutments to verify passivity sufficient clearance for pick-up resin. Note: angulations are slightly off-angle, which may interfere with passivity of denture upon insertion. All implant accesses should be clearly visible from the occlusal view. This denture required additional relief for the implant in the upper-left region

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Fig. 12.10  Intraoral view of four temporary abutments. Note: angulation is slightly off-angle, which may interfere with passivity of denture upon insertion

Fig. 12.11  Preparation for intraoral pick-up with rubber dam isolation

sutures or into the surgical site. To prevent potential screwdriver access issues, temporary ­ cylinder access holes should also be plugged with removable block-out material, such as rapid-set silicone or Teflon. The removable appliance should be placed ensuring that it is seated in the palate area (Figs. 12.11, 12.12, and 12.13). Autopolymerising acrylic resin can be used to carefully pick up the temporary cylinders. It is recommended that temporary cylinders be indexed into the prosthesis individually to maintain passivity and ensure sufficient resin is used to secure the position. Once one cylinder has been secured the patient must be viewed for accurate tooth position and occlusal plane. Once this is deemed satisfactory the remaining cylinders can be attached. Once all temporary cylinders have been indexed into the denture and the resin has been allowed to sufficiently set, it may

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Fig. 12.12  Placement of protective material to prevent ingress of excess material into implant access holes in temporary abutment

Fig. 12.13  Frontal view of removable denture in situ as pick-up resin is setting

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Fig. 12.15  Occlusal view of maxilla upon removal of converted prosthesis

Fig. 12.16  Intaglio view of converted prosthesis prior to finishing

finishing the implant fixture contact surfaces. Flanges should be reduced to allow direct visibility of the analogue abutment collars from a lateral view; this will aid in fabricating a hygienic, convex gingival surface. Additional acrylic resin can then be added to firmly fixate the temporary cylinders, provide resin bulk and finalise the shape of the fixed restoration. Temporary cylinders should also be adjusted to remove occlusal or contour interferences (Figs.  12.17, 12.18, 12.19, and 12.20). Upon insertion of the finished converted prosthesis, passivity should be verified by tactile senFig. 12.14  Occlusal view of removable as pick-up matesation when tightening screws and seating rial is setting verified with radiographs, followed by occlusal be removed from the mouth for finishing proce- adjustment. Care should be taken to verify a fair dures (Figs. 12.14, 12.15, and 12.16). distribution of occlusal forces, especially if there Once the prosthesis is detached from the are any cantilevers. There should be no active patient, polishing protectors should be connected gingival blanching or tissue pressure (Figs. 12.20 to the temporary cylinders to prevent over-­ and 12.21).

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Fig. 12.20  Posterior and intaglio view of immediate load prosthesis

Fig. 12.17  Intaglio view of converted prosthesis after adding resin to create convex or more hygienic contours

Fig. 12.21  Immediate load prosthesis in situ

Fig. 12.18  Removal of sharp edges and excess material on cameo surface of converted prosthesis

The restorative dentist must work diligently with the surgeon and laboratory technician to determine approximately the amount of bone reduction that is required, and this must be approximately replicated on the casts.

12.3.1.2 Technique for the Mandible The following are necessary for an optimal outcome:

Fig. 12.19  Frontal view of finished immediate load prosthesis

The mandibular arch is much more challenging to load utilising the direct technique. When a significant amount of bone reduction has been done, the prosthesis is usually not very stable and obtaining adequate centric relation records can be difficult. This is compounded by the numbness of the patient post surgery.

1. Approximation of bone reduction on casts. 2. Fabrication of a bone reduction guide with a reference from which the surgeon can measure. 3. Fully extended denture. The following illustrates the clinical sequence: (a) A silicone bite registration is placed in the intaglio of the denture and the denture is placed intraorally over the healing caps. (b) The patient is guided into maximal intercuspal/CR position. This can be attained with the use of a silicone index also.

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(c) This position is verified for repeatability. (d) A section of the silicone material is removed in the anterior area of the denture and a temporary cylinder placed intraorally. A hole is made in the intaglio of the denture corresponding to the marking of healing cap. The denture is seated over the temporary cylinder intraorally. (e) Self-cured acrylic resin is used to pick up the temporary cylinder. (f) The denture with attached temporary cylinder is removed. (g) The adjacent section of silicone is removed from the intaglio of the denture and a temporary cylinder is placed intraorally. A second hole is made in the intaglio of the denture corresponding to the position of the second temporary cylinder. (h) The denture is placed back into the mouth screw retained by the first picked up cylinder. The rigid silicone material in the posterior aspect provides anteroposterior stability. The second temporary cylinder should not interfere with the seating of the denture. The temporary cylinder is picked up with self-cured acrylic resin. (i) A similar sequence is followed to attach the third and then the fourth temporary cylinders. (j) Once all temporary cylinders are picked up the prosthesis is removed and taken to the laboratory for finishing and processing (Figs.  12.22, 12.23, 12.24, 12.25, 12.26, 12.27, 12.28, 12.29, 12.30, 12.31, 12.32, 12.33, 12.34, 12.35, 12.36, 12.37, 12.38, and 12.39).

12.3.1.3 Digital Method The digital method of direct immediate loading removes a significant amount of uncertainty from the conventional workflow. The aid of bone-­ anchoring devices bypasses potential issues associated with stability and orientation of the removable prosthesis during the conversion process. In the digital approach, many factors are predetermined in the surgical planning process, including implant position and multi-unit abutment angulations. In some systems, when the

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Fig. 12.22  Frontal view of mandibular removable denture indexing implant healing abutments with aid of opposing occlusion

Fig. 12.23  Intaglio view of mandibular removable denture with rigid polyvinyl siloxane index demarcating implant healing abutment positions

Fig. 12.24  Selective sectioning of PVS index and clearance of area surrounding one implant position

fully guided surgical sequence is executed perfectly, many of the steps found in the conventional approach can be bypassed. In the event that a fully guided surgery cannot be executed to the

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Fig. 12.25  Intraoral frontal view of single temporary abutment to be picked up first

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Fig. 12.28  Occlusal view of first temporary abutment pick-up with aid of opposing occlusion and remaining PVS index to maintain position

Fig. 12.26  Intraoral occlusal view of denture seating to check for passivity and verify sufficient clearance for pick-up resin

Fig. 12.29  Intaglio view of first temporary abutment after resin has set

Fig. 12.27  Frontal view of first temporary abutment pick-up with aid of opposing occlusion and remaining PVS index to maintain position

Fig. 12.30  Intaglio view of conversion prosthesis as second section of index is removed for pick-up of second temporary abutment

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Fig. 12.31  Intraoral view of temporary abutment in situ

Fig. 12.32  Intraoral occlusal view of pick-up of second temporary abutment

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Fig. 12.34  Drilling of initial holes through index to create clearance for two more temporary abutments

Fig. 12.35  Intaglio view of conversion prosthesis after holes have been sufficiently widened to create clearance for passivity of fit and space for material to flow around remaining temporary abutments

Fig. 12.33  Intaglio view of two temporary abutments after resin has set Fig. 12.36  Intraoral frontal view of last two temporary abutments

12  Clinical Techniques for Immediate Loading

Fig. 12.37  Intraoral occlusal view of one temporary abutment being picked up

Fig. 12.38 Lateral view of finished immediate load prosthesis

Fig. 12.39  Intraoral frontal view of finished immediate load prosthesis in situ

original plan, the removable prosthesis may still be usable for immediate loading using the conventional approach. Additionally, some digital workflows still rely entirely on the conventional approach to immediate loading the removable prosthesis.

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12.3.1.4 This Is a Sample Workflow Care must be taken to verify that the removable prosthesis fully engages the anchored guide without any interferences. This must be checked prior to and after seating temporary cylinders. If any interference is detected, the removable prosthesis should be adjusted to allow passivity. It is imperative that there is sufficient relief around the temporary cylinders to ensure that there is no interference in seating and that there will be sufficient space for pick-up resin to flow. Additionally, radiographs should be taken to verify seating of temporary cylinders (Figs.  12.40 and 12.41). Prior to using any pick-up resin, measures must be taken to avoid allowing resin to flow into undesired areas. A rubber dam or rubber dam pieces should be adapted around all temporary cylinders to prevent resin from flowing onto sutures or into the surgical site. To prevent potential screwdriver access issues, temporary cylinder access holes should also be plugged with removable block-out material, such as rapid-set silicone or Teflon (Figs. 12.42 and 12.43). Autopolymerising acrylic resin can be used to carefully pick up the temporary cylinders. It is recommended that temporary cylinders be indexed into the prosthesis individually to maintain passivity and ensure sufficient resin is used to secure the position. Once one cylinder has been secured the patient must be viewed for accurate tooth position and occlusal plane. Once this is deemed satisfactory the remaining cylinders can be attached. Once all temporary cylinders have been indexed into the denture and the resin has been allowed to sufficiently set, it may be removed from the mouth for finishing procedures (Fig. 12.44). Once the prosthesis is detached from the patient, polishing protectors should be connected to the temporary cylinders to prevent over-­ finishing the implant fixture contact surfaces. Additional extensions should be reduced to allow direct visibility of the analogue abutment collars from a lateral view; this will aid in fabricating a hygienic, convex gingival surface. Additional acrylic resin can then be added to firmly fixate the temporary cylinders, provide resin bulk and

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Fig. 12.40  Intraoral view of multi-unit abutments after completion of fully guided surgery

Fig. 12.43  Intraoral view of index for seating immediate load prosthesis

Fig. 12.41  Intraoral view of temporary abutments seated on multi-unit abutments

Fig. 12.44  Intraoral view of immediate load prosthesis with pick-up resin

Fig. 12.42  Intraoral view of temporary block-out material placed in temporary abutments to prevent ingress of excess resin during pick-up procedure

Fig. 12.45  Intraoral view of immediate load prosthesis upon removal of excess material to verify seat within index

finalise the shape of the fixed restoration. Temporary cylinders should also be adjusted to remove occlusal or contour interferences (Fig. 12.45).

Upon insertion of the finished converted prosthesis, passivity should be verified by tactile sensation when tightening screws and seating verified with radiographs, followed by occlusal adjustment. Care should be taken to verify a fair

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ing temporary abutments and holes in prosthesis. (e) Rubber dam (or similar material for block-­ out) is attached to the temporary cylinders to prevent material ingress into surgical site. (f) Autopolymerising resin is used to pick up the temporary cylinders, one at a time. (g) Once all temporary cylinders are picked up, the prosthesis is removed and taken to the laboratory for finishing and processing. Fig. 12.46  Frontal view of finished immediate load prosthesis in situ

distribution of occlusal forces, especially if there are any cantilevers. There should be no active gingival blanching or tissue pressure (Fig. 12.46).

12.3.2 Direct–Indirect Technique: Impression with Denture for Conversion

In the direct–indirect technique, a conventional denture or similarly indexed removable prosthe12.3.1.5 Technique sis is made prior to the surgery. This prosthesis The restorative dentist must work diligently with is used to capture impression copings attached the surgeon and laboratory technician to deter- to the dental implants/multi-unit abutments in a mine approximately the amount of bone reduc- full-arch silicone impression intraorally, and tion that is required, and this must be subsequently converted into a prosthesis extraapproximately replicated on the casts. orally. This procedure works best with existing The following are necessary for an optimal articulated study models since it allows for more outcome: accurate jaw relation records and occlusal adjustments during finishing procedures 1. Digital planning for fully guided surgery and (Fig. 12.47). removable prosthesis. This procedure differs from the direct tech 2. Fabrication of a bone-anchored guide, which nique in that a more accurate model depicting the adapts perfectly to an alveolar reduction guide gingival architecture is made; additionally, it and implant osteotomy/placement sleeves. maintains the benefits of using anatomical land 3. Removable prosthesis that adapts to bone-­ marks for transferring implant positions. An anchored guide or for conventional loading. additional advantage is if the immediate load provisional were to break the clinician has a model The following illustrates a sample clinical on which repairs can be performed. sequence: Using the removable prosthesis, a rapid-set silicone impression is made to generally identify (a) Implant surgery is completed using bone-­ the implant locations (Fig. 12.48). (Figures 12.49 anchored guide. and 12.50 depict a complete denture containing a (b) Removable prosthesis is tried to visually ver- polyvinyl siloxane bite registration material ify that clearance is available around demarcating the implant sites. The removable implants. prosthesis should be relieved around these (c) Temporary abutments are placed. marked sites to allow a proper seating of the prosRadiographs are taken to verify seat as thesis based on identified anatomical indices.) needed. Upon passive seating of the denture over the (d) Removable prosthesis is again tried to verify healing caps or abutments and any minor adjustpassivity and clearance between the protrud- ments necessary to account for occlusion or verti-

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Fig. 12.47  Occlusal view of implants with multi-unit abutments and healing abutments in situ

Fig. 12.48  Intaglio view of removable denture with rigid polyvinyl siloxane material indexing positioning of healing abutments

Fig. 12.49  Cameo view of removable denture with relief provided for passivity around pick-up impression components

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cal dimension, a jaw relation can be obtained to allow mounting of the poured model. Pick-up impression copings may be seated at this point. Radiographs should be taken to verify seating. Subsequently, the removable prosthesis should be tried for passivity while indexed to the selected anatomical reference(s). Impression copings should not be in contact with any surfaces of the removable prosthesis; if contact is visible or detected otherwise, further relief of the prosthesis is necessary. It is imperative that there is sufficient relief around the temporary cylinders to ensure that there is no interference in seating, in addition to allowing sufficient space for impression material to flow (Figs. 12.51, 12.52,

Fig. 12.50  Intraoral occlusal view of pick-up impression copings on abutments

Fig. 12.51  Occlusal view of removable denture with impression material surrounding critical components and anatomical landmarks

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Fig. 12.52 Frontal view of removable denture with impression material surrounding critical components and anatomical landmarks

Fig. 12.53  Intaglio view of removable denture with impression containing pick-up impression components

and 12.53). As an added method of security, self-­ curing resin may be used to splint impression copings and minimise any distortion upon removal of the impression. Analogues should be attached to the impression copings prior to pouring the gypsum model. The denture extensions should be lightly indexed into the poured gypsum to allow ease of indexing during subsequent finishing procedures; care should be taken to avoid engaging any undercuts in the flanges. Upon setting the gypsum, the impression may be separated from the model. At this point, the impression material and impression copings should be removed from the prosthesis. Without the impression copings, the removable prosthesis can be indexed to the model and articulated (Figs. 12.54, 12.55, and 12.56).

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Fig. 12.54 Frontal view of removable denture with impression containing pick-up impression components and corresponding lab analogues

Fig. 12.55  Pouring of gypsum into removable denture with impression material, pick-up impression components and corresponding lab analogues

Fig. 12.56  Lateral view of mounted removable denture with impression material, pick-up impression components and corresponding lab analogues. Note: occlusal index for mounting

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After mounting the indexed removable prosthesis, it can once again be removed from the impression to allow attachment of temporary cylinders to the implant analogues. Once again, there should be a passive, non-contacting relationship between the removable prosthesis and the temporary prosthesis. At this stage, temporary cylinders should be adhered to the indexed removable prosthesis with self-curing resin (Figs. 12.57, 12.58, 12.59, and 12.60). After successful attachment of all temporary cylinders, flanges should be reduced to allow direct visibility of the analogue abutment collars from a lateral view; this will aid in fabricating a hygienic, convex gingival surface (Figs.  12.60, 12.61, 12.62, and 12.63).

Fig. 12.57  Occlusal view of gypsum model with impression copings

Fig. 12.58  Lateral view of mounted gypsum model with temporary abutments seated on lab analogues

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Fig. 12.59  Occlusal view of removable denture seated on mounted model, relieved to fit passively around temporary abutments. Note: impression material has been removed, and temporary block-out material has been placed in implant access holes to prevent ingress of excess resin

Fig. 12.60  Placement of resin to adapt removable denture to temporary abutments, while seated on gypsum model

Fig. 12.61  Intaglio view of resin added to removable denture, prior to finishing

12  Clinical Techniques for Immediate Loading

Fig. 12.62  Occlusal view of cameo surface of finished immediate load prosthesis

Fig. 12.63  Intraoral lateral view of finished immediate load prosthesis in situ

With the prosthesis fixed into the model, additional acrylic resin can be added to rigidly attach the temporary cylinders, provide resin bulk for strength and finalise the shape of the fixed restoration. Temporary cylinders should be trimmed to eliminate any interferences. Occlusion may be adjusted on the articulator. Upon insertion of the finished converted prosthesis, passivity should be verified by tactile sensation when tightening screws and seating verified with radiographs, followed by occlusal adjustment. Care should be taken to verify a fair distribution of occlusal forces, especially if there are any cantilevers. There should be no visible gingival blanching or tissue pressure (Figs. 12.64 and 12.65).

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Fig. 12.64  Frontal view of finished immediate load prosthesis in situ

Fig. 12.65  Frontal view of maxillary and mandibular wax try-in ready for conversion

12.3.3 Indirect Technique: Pick-Up Impression with Extraoral Conversion Theoretically, an immediate-load fixed implant-­ supported restoration fabricated using the indirect technique should be the strongest since it avoids relieving larger holes into a removable prosthesis for intraoral pick-ups. Additionally, it is the least reliant on an existing denture for establishing jaw relations. The procedure is time consuming but does result in the most favourable strength, aesthetics and fit. There are two divergent methods for this approach: conventional and digital. Both methods involve planning and processing of diagnostic information, as well as impressions on the day of surgery.

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In the conventional method, the equivalent of impressions, jaw relation records and a wax try­in, is completed on the day of surgery. In the digital method, diagnostic information is used to generate a digital denture tooth setup, which is adapted to the digital impressions immediately after surgery.

12.3.3.1 Conventional Method On the day of surgery, there are multiple steps taken. It involves PVS impressions of splinted impression copings, jaw relation records and a wax try-in for fit. The information is then all uti-

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lised to process the immediate load prosthesis. To obtain maximum strength the acrylic resin can be reinforced with a silane-coated fibre, which chemically bonds to the poly methyl methacrylate resin (FIBERFORCE CST Canada). A putty matrix is made of the tooth setup and temporary cylinders are placed on the master cast and opaqued. Fibre is wrapped around the temporary cylinders in a specific manner. The denture wax up is processed utilising injection processing for minimal shrinkage and maximum strength (Figs.  12.66, 12.67, 12.68, 12.69, and 12.70).

Fig. 12.66 Gypsum model made from intraoral pick-up impression. Putty matrix of wax try-in verifies sufficient clearance for temporary abutments and acrylic materials

Fig. 12.67  Temporary abutments are reinforced with fibre prior to addition of denture teeth and acrylic. After processing and finishing, restoration is significantly more hygienic compared to direct immediate load prosthesis

Fig. 12.68  Frontal and lateral view of maxillary and mandibular wax try-in

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12.3.3.2 Digital Method There are three key components for the digital approach to fabricating an indirect immediate load restoration: patient selection, extraoral scanning and computer-aided design and manufacturing. For this method, repeatable landmarks, such as remaining teeth, must be identifiable in the patient’s mouth. Additionally, an extraoral scanner for identifying implant positioning is strongly advised due to the intrinsic distortion associated with intraoral scanning [22]. Lastly, none of this can be completed without access to ­computer-­aided design and manufacturing. The greatest shortcoming of this method is the time required for manufacturing the prosthesis, which may require several hours of laboratory fabrication time. Prior to the day of surgery, intraoral and extraoral photos, and intraoral diagnostic scans with jaw relationship information are obtained. This information is used to design a digital mock-up of tooth positioning, which will be confirmed upon integrating post-surgery extraoral scan data. Upon completion of surgery, the protocol for the extra-

oral scanner used is executed. Flags are seated on the multi-unit abutments upon confirming angulation, and the scan is completed. An intraoral scan or impression of the post-surgery soft tissue is subsequently made. This information is then integrated with the digital tooth setup to manufacture a provisional using either additive or subtractive manufacturing processes (Figs.  12.65, 12.66, 12.67, 12.68, 12.69, 12.70, 12.71, 12.72, 12.73, 12.74, 12.75, 12.76, 12.77, and 12.78).

Fig. 12.69  Finished prosthesis in situ

Fig. 12.71  Lateral view of patient prior to surgery

Fig. 12.70 Finished prosthesis in situ

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Fig. 12.72  Frontal view of patient prior to surgery. Floss marks midline, and selective teeth are used to aid digital design of provisional implant prosthesis

Fig. 12.73  Intraoral frontal view of digital markers for extraoral scanning in situ

Fig. 12.74  Intraoral frontal view of implant scan bodies for intraoral tissue scan in situ

12.3.4 Direct Pick-Up Tooth-Only Immediate Load Restoration Bone preservation is considered a requirement in more contemporary approaches to full-arch implant rehabilitation. The above digital

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Fig. 12.75 Digital markers from extraoral scanning combined with original diagnostic scan in design software

Fig. 12.76 Digital markers from extraoral scanning, intraoral tissue scan with scan bodies and original diagnostic scan in design software

Fig. 12.77  Digital design of provisional implant prosthesis with precise implant positioning

method outlined an indirect digital method to fabricate a full-arch immediate load provisional replacing a tooth-only defect. Aesthetics requires sculpting of the soft tissue to mimic papilla. The following patient case presentation will outline a direct pick-up approach for a tooth-only defect.

12  Clinical Techniques for Immediate Loading

The patient presented with a terminal dentition and was treatment planned for a tooth-only maxillary restoration and a mandibular restoration that would require pink prosthetics (Fig. 12.79).

Fig. 12.78  Intraoral frontal view of provisional implant prosthesis Fig. 12.79 Preoperative clinical situation who has been treatment planned for a maxillary tooth-only zirconia-­ based restorations and mandibular acrylic resin prosthesis

Fig. 12.80 Analogue-­ fabricated tooth-­ supported guides for surgical accuracy

Fig. 12.81 Milled acrylic provisional for chair-side pick-up

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Impressions were made and a tooth-supported surgical guide was fabricated for the maxilla. Tooth-supported guides allow stability during surgery and allow the surgeon to place dental implants in an ideal three-dimensional position. The surgeon uses the free gingival margin of the guide for depth of implant placement and orientation of the multi-unit abutment (Fig. 12.80). Provisional restorations can be either milled or conventionally processed (Fig. 12.81). Once surgery is completed and tissues sutured, a direct pick up of the provisional is done utilising the following process: 1. Protect the back of the throat. 2. Index the provisional on the caps of the multiunit abutments. 3. Make holes with an acrylic bur.

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4. Position the two anterior temporary cylinders on the multi-unit abutments and try the provisional. The palatal portion of the prosthesis should be flush with the palate. The temporary cylinders should not interfere with the seating of the provisional. 5. Place temporary cylinders on the posterior multi-unit abutments one by one and ensure the provisional seats without interference from the temporary cylinders (Fig. 12.82). 6. The surgical site should be protected with a rubber dam. 7. Teflon should be placed in the access holes of the temporary cylinders. 8. Cold-cured acrylic resin should be used to pick up the temporary cylinders within the confines of the prosthesis. Fig. 12.82  Pick-up of temporary cylinders chair side

Fig. 12.83 Acrylic restorations after conversion. Restoration can also be fibre re-enforced

Fig. 12.84  Day of delivery of maxillary and mandibular acrylic-based restorations. Day of delivery and 1 week post op. See tissue moulding

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9. The prosthesis should be removed, and healing caps replaced. 10. Ensure all temporary cylinders are stable within the provisional. 11. Inject self-cured tooth-coloured acrylic around the temporary cylinders to fill in the defects. 12. The pontic areas should be built up to extend into the extraction sockets by 2 mm. 13. Finish and polish and remove cantilevers. A silane-coated fibre may be used to reinforce the prosthesis (Fig. 12.83). 14. On delivery the provisional should compress the soft tissue and pontics should extend within the extraction sockets and support the tissue (Figs.  12.84 and 12.85).

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Fig. 12.85 Definitive zirconia restoration after tissue sculpting

References 1. Esposito M, Grusovin M, Willings M, Coulthard P, Worthington H.  The effectiveness of immediate, early, and conventional loading of dental implants: a Cochrane systematic review of randomized controlled clinical trials. Int J Oral Maxillofac Implants. 2007;22:893–904. 2. Papaspyridakos P, Chen C, Chuang S, Weber H. Implant loading protocols for edentulous patients with fixed prostheses: a systematic review and meta-­ analysis. Int J Oral Maxillofac Implants. 2014;29 Suppl:256–70. 3. Bruyn HD, Raes S, Ostman P, Cosyn J.  Immediate loading in partially and completely edentulous jaws: a review of the literature with clinical guidelines. Periodontol 2000. 2014;66(1):153–87. 4. Maló P, Nobre MA, Lopes A, Francischone C, Rigolizzo M. “All-on-4” immediate-function concept for completely edentulous maxillae: a clinical report on the medium (3 years) and long-term (5 years) ­outcomes. Clin Implant Dent Relat Res. 2012;14(Suppl 1):e139–50. 5. Szmukler-Moncler S, Salama H, Reingewirtz Y, Dubruille J.  Timing of loading and effect of micromotion on bone-dental implant interface: review of experimental literature. J Biomed Mater Res. 1998;43(2):192–203. 6. Kern J, Kern T, Wolfart S, Heussen N. A systematic review and meta-analysis of removable and fixed implant-supported prostheses in edentulous jaws: post-loading implant loss. Clin Oral Implants Res. 2016;27(2):174–95. 7. Niedermaier R, Stelzle F, Riemann M, Bolz W, Schuh P, Wachtel H. Implant-supported immediately loaded fixed full-arch dentures: evaluation of implant survival rates in a case cohort of up to 7 years. Clin Implant Dent Relat Res. 2016;19(1):4–19. 8. Peñarrocha-Oltra D, Covani U, Peñarrocha-Diago M, Peñarrocha-Diago M.  Immediate loading with fixed full-arch prostheses in the maxilla: review of the literature. Med Oral Patol Oral Cir Bucal. 2014;19(1):e512–7. 9. Li S, Di P, Zhang Y, Lin Y.  Immediate implant and rehabilitation based on All-on-4 concept in patients with generalized aggressive periodontitis: a medium-­

term prospective study. Clin Implant Dent Relat Res. 2017;19(3):559–71. 10. Bahat O, Sullivan R.  Parameters for successful implant integration revisited part II: algorithm for immediate loading diagnostic factors. Clin Implant Dent Relat Res. 2010;12 Suppl 1:e13–22. 11. Yamaguchi K, Ishiura Y, Tanaka S, Baba K. Influence of the rigidity of a provisional restoration supported on four immediately loaded implants in the edentulous maxilla on biomechanical bone-implant interactions under simulated bruxism conditions: a three-­ dimensional finite element analysis. Int J Prosthodont. 2014;27(5):442–50. 12. Romanos G, Nentwig G.  Immediate versus delayed functional loading of implants in the posterior mandible: a 2-year prospective clinical study of 12 consecutive cases. Int J Periodontics Restorative Dent. 2006;26(5):459–69. 13. Romanos G, Nentwig G. Immediate loading of endosseous implants in the posterior area of the mandible. Animal and clinical studies. Int J Oral Maxillofac Implants. 2008;23(3):513–9. 14. Balshi T, Wolfinger G.  Immediate loading of Brånemark implants in edentulous mandibles: a preliminary report. Implant Dent. 1997;6(2):83–8. 15. Lekholm U, Zarb G. Patient selection and preparation. In: Tissue integrated prostheses: osseointegration in clinical dentistry. Chicago: Quintessence; 1985. p. 199–209. 16. Chiapasco M.  Early and immediate restoration and loading of implants in completely edentulous patients. Int J Oral Maxillofac Implants. 1997;19(7):76–91. 17. Heydecke G, Zwahlen M, Nicol A, Nisand D, Payer M, Renouard F, et  al. What is the optimal number of implants for fixed reconstructions: a systematic review. Clin Oral Implants Res. 2012;23(Suppl 6):217–28. 18. Mericske-Stern R, Worni A.  Optimal number of oral implants for fixed reconstructions: a review of the literature. Eur J Oral Implantol. 2014;7(2):S133–53. 19. Drago C.  Cantilever lengths and anteriorposterior spreads of interim, acrylic resin, full-arch screw-­retained prostheses and their relationship to prosthetic complications. J Prosthodont. 2016;26:502–7.

336 20. Tarnow D, Emtiaz S, Classi A.  Immediate loading of threaded implants at stage 1 surgery in edentulous arches: ten consecutive case reports with 1- to 5-year data. Int J Oral Maxillofac Implants. 1997;12(3):319–24. 21. Suarez-Feito J, Sicilia A, Angulo J, Banerji S, Cuesta I, Millar B.  Clinical performance of provisional

S. Yeung and S. Jivraj screw-retained metal-free acrylic restorations in an immediate loading implant protocol: a 242 consecutive patients’ report. Clin Oral Implants Res. 2010;21(12):1360–9. 22. Treesh JC, et al. Complete-arch accuracy of intraoral scanners. J Prosthet Dent. 2018;120:382–8.

Material Considerations for Full-­Arch Implant-Supported Restorations

13

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of prosthodontics has advanced to newer heights and has enjoyed a great deal of innovation and There are various materials to choose from progressive development in recent years. This is a when designing full-arch fixed implant-­ tremendous benefit to today’s patients who have supported restorations. Material choices high expectations, and providing functional and include a traditional acryl resin titanium proscomfortable restorations alone may not be suffithesis to monolithic milled zirconia. As techcient to satisfy many of them. Patients have addinological advancements occur, newer tional desires in today’s therapy such as high materials and manufacturing processes are aesthetic demands, shorter treatment times, fewer being introduced into these therapies; howvisits and minimal maintenance issues. One treatever, clear guidelines on design and material ment option offered to these motivated patients is selection are lacking. The purpose of this the ability to rehabilitate the terminal or missing chapter is to look at specific areas, including dentition with a full-arch fixed implant-supported screw access, restorative space, opposing denrestoration. tition, aesthetics, framework design and fabriToday there are various materials to choose cation processes, to create guidelines to aid from when designing full-arch fixed implant-­ clinicians in making relevant and predictable supported restorations. Unfortunately, when decisions with respect to therapy for patients looking at the literature for guidance it is not supwith fixed implant-supported restorations. portive of a true evidence base in terms of an ideal material to utilise. There is no evidence to The clinical replacement of teeth by osseointe- show one design is superior to another or one grated implants has represented one of the most combination of materials is superior to another. significant advances in restorative dentistry. Most articles are case reports, which follow a Coupled with digital planning, digital impres- limited number of patients over a limited period sions and CAD/CAM technology, the speciality of time [1]. Although these reports do provide us with useful information, they cannot be classified as true evidence. The reality is that CAD/CAM S. Jivraj (*) technology is evolving, and by the time clinicians Anacapa Dental Art Institute, Oxnard, CA, USA have completed studies on a group of materials S. Rawal and followed them for a period of time, those Implant Support Services, Aspen Dental, materials become obsolete and newer improved Chicago, IL, USA materials or designs become available. Abstract

The Digital Dentistry Institute, Orlando, FL, USA

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_13

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Despite technological advances, certain principles remain the same. The purpose of this chapter will be to give the reader clinical guidelines on how to design a framework and the various combination of materials that are available. Design considerations in fabrication of the prosthesis include but are not limited to. 1. Screw access trajectory. 2. Restorative space. 3. Nature of opposing dentition. 4. Aesthetic demands. 5. Framework cross-sectional area for cantilevers and around screw channels. 6. Ease of fabrication and passivity.



(e) Managing complications of the dental fixtures—access for dealing with implant failure, peri-implant issues, infection, etc., is more readily available.

It can be seen from the above that designing a screw-retained restoration has a significant safety factor with regard to long-term maintenance of these prosthetics. More and more often clinical situations present where screw access trajectory is often in an unfavourable position. In this scenario, the clinician has two options:

1. Use of pre-angled abutments—pre-angled abutments do come with specific collar heights and this must be considered to maxi13.1 Screw Access Trajectory mise aesthetic outcomes. 2. Use of a two-part restoration with a primary When designing a splinted full-arch implant-­ framework that corrects implant trajectory supported restoration, screw retention has disand a secondary screw retained suprastructure tinct advantages [2]. Among these advantages are (Figs. 13.1, 13.2, 13.3, 13.4, and 13.5). the following: 1. The precision of fit of screw-retained restorations can be verified with radiographs using a single screw test [3]. 2. Delivering a screw-retained restoration also involves less time with no cement clean-up required [4]. 3. Screw-retained restorations have total retrievability, which is advantageous for the following reasons: (a) Periodic maintenance—it is a relatively simple procedure to remove the prosthesis if necessary for access to fixtures and intermediary abutments. (b) Dealing with loosened screws—access to screws is typically direct. (c) Fracture of the prosthesis—the prosthesis can easily be removed for repair. (d) Modification of the prosthesis—can accommodate issues such as continued tissue remodelling.

Fig. 13.1  Emergence profile inadequate. Note ledge as restoration emerges from implant

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Fig. 13.2  Trajectory of implants have been accommodated in fabricating prosthesis. Pre-angled abutments should be selected to correct trajectory of dental implants

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Fig. 13.5  Definitive restorations with correct emergence profile

13.2 Restorative Space Lack of restorative space is one of the most common occurrences that can compromise a restoration [5]. Inadequate restorative space will result in two scenarios:

Fig. 13.3  Diagnostic wax tooth try-in with corrected emergence profile

(a) Restorative complications such as material failure leading to repair or replacement of the veneering materials or complete framework fracture leading to failure of the entire prosthetic restoration. (b) Changing the treatment plan from one restoration type to another to accommodate the space requirements. Neither of the above scenarios is ideal and can be avoided by good communication between the surgical and restorative team prior to implementation of the therapy. The clinician must evaluate whether the patient exhibits minimal, moderate or advanced resorption to determine the available restorative space and therefore the ideal type of prosthesis to be fabricated. General guidelines for space requirements are the following:

Fig. 13.4  Provisional restoration fabricated to test aesthetics and phonetics

(a) Monolithic full-contour zirconia-fixed restorations require 10 mm or more of space from

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the head of the implant to the opposing dentition. (b) Porcelain fused to metal/zirconia-fixed restorations require 12 mm or more of space from the head of the implant to the opposing dentition. (c) Acrylic resin bonded to titanium-fixed restorations will require 15 mm or more from the head of the implant to the opposing dentition. (d) Implant-supported over-dentures will require 16 mm or more of space from the implant to the opposing dentition [6].

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Fig. 13.6  Milling titanium occlusals can maintain the vertical dimension

conducted to evaluate the clinical validity of using a full-contour zirconia occlusal surface. This study compared zirconia’s wear capacity to that of feldspathic porcelain, and it was reported Patients with implant-supported restorations that the antagonistic tooth wear was less in zircohave a reduced amount of proprioception, and as nia than feldspathic porcelain, suggesting that a result these restorations have been subject to zirconia may be more beneficial for antagonistic greater forces [7]. With this in mind, there have tooth wear [10]. The data on this subject is limbeen studies looking at various restorative mate- ited and further studies are required. rials and their effects not only on the implant-­ One clinical situation where the nature of the supported prosthesis, but on the opposing opposing dentition is of note is when designing dentition as well. One such clinical study investi- fully implant-supported prostheses for the maxilgated the maintenance requirements in patients lary and mandibular arches together. It has been with implant-supported restorations vs. implant-­ advocated to restore the maxillary arch with a supported restorations, implant-supported resto- zirconia-based ceramic prosthesis and an acrylic rations vs. natural dentitions and resin bonded to titanium prosthesis for the manimplant-supported restorations vs. complete den- dibular arch [11]. Advantages of using this ture wearers [8]. This study reported that the opposing arch design include the following: patients with implant vs. implant occlusions suffered a higher degree of fracture and greater wear (a) Maximum aesthetics with minimal staining of the occlusion (Fig. 13.6). over time with use of ceramics in the Another study focused on occlusal surface maxilla. design using noble metals, feldspathic porcelain (b) Absence of reported, ‘clicking’ by patients and acrylic [9]. For stability of occlusal contact, with opposing ceramic surfaces. clinicians have preferred a gold occlusal surface (c) Flexibility and resiliency in the system. rather than porcelain and acrylic; however due to (d) Reduced costs (Fig. 13.7). aesthetic concerns, patients often favour ­tooth-­coloured materials. Historically feldspathic One disadvantage would be increased wear of porcelain has been the material of choice, but the mandibular acrylic-based restorations. This more recently clinicians have utilised zirconia on can be considered a controlled failure, and the the occluding surface of the restoration. One con- patient must be made aware that the acrylic resin cern of clinicians has been the effect of zirconia teeth will most likely need to be replaced every on the opposing dentition. An in vitro study was 5–7 years.

13.3 Nature of Opposing Dentition

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Fig. 13.7  Use of zirconia in the maxilla and acrylic resin titanium in the mandible has many advantages

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Fig. 13.8  Inadequate thickness of zirconia around screw access hole will result in fracture of the zirconia framework

13.4 Aesthetic Demands Talented ceramists can produce high-level aesthetic results using both traditional noble metal alloy and zirconia frameworks. In regards to light transmission, both noble metal alloys and zirconia have been shown to be opaque [12]. Anecdotally many laboratory technicians report superior aesthetic results with zirconia frameworks due to the ability to be able to colour the zirconia and be able to have a tooth-coloured framework rather than an opaque grey-coloured framework which is usual with traditional high noble metal alloy frameworks. From an aesthetic perspective, ceramic-based restorations with either high noble alloy or zirconia frameworks are less likely to stain over time and result in superior stable long-term aesthetic results compared to acrylic resin bonded to titanium restorations. As mentioned above, ceramics should be considered for maxillary restorations and acrylic resin titanium in the mandible when full mouth implant rehabilitation is completed.

13.5 Cantilevers 13.5.1 Framework Cross-Sectional Area for Cantilevers and Around Screw Channels Specific attention needs to be paid to dimensions of the framework in the cantilever area and around screw access channels (Figs.  13.8 and

13.9). Specifically, the cross-sectional area of the chosen material must be sufficient enough to have strength and rigidity to perform in the intraoral environment. For screw channels, this is typically most important when considering the lingual or palatal cross-sectional area of the material. When focusing on cantilevers, connector size is critical for traditional noble metal alloys, titanium and zirconia frameworks. While there is no specific data on the minimum dimensions required for these frameworks, if space is extremely limited the authors prefer traditional noble metal frameworks. However, for the typical implant-supported restoration, patients who have undergone moderate to advanced resorption will have plenty of room to provide robust connectors with sufficient cross-sectional area. Literature on tooth-supported zirconia-based restorations recommended a minimal connector size of 4 mm × 4 mm, and it is the authors’ preference to respect this 16  mm2 area for implant frameworks as well as in the area of channels or connectors [13]. There are few studies to guide clinicians on the length of cantilever in the maxilla, especially when utilising the more contemporary materials such as zirconia. The length of the cantilever has a significant effect on the failure of these types of restorations, and in a meta-analysis it has been shown that the length of cantilever is more significant than the number of implants [14]. Deflection of the cantilever is related to its length; so minute increases in length have a significant

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ous procedure, which is not only time consuming but can add additional costs to treatment. With the increasing costs of gold, clinicians have moved away from traditional techniques and have begun to employ more contemporary techniques using CAD/CAM technology and materials such as zirconia and titanium. These techniques also require a high degree of skill but are less time consuming in the manufacturing process and due to the efficiencies gained from Fig. 13.9  Cantilevers should also be minimised in zirco- these techniques tend to be less costly than connia as this may result in fracture ventional fabrication procedures. Passivity in an implant framework has been impact on the fracture complications of restora- notoriously difficult to achieve when utilising tions. Lab-based studies on zirconia have shown screw-retained splinted restorations. Inaccuracies that in implant frameworks are the result of multiple variables, which include machining tolerances of (a) The longer the cantilever the lower the load components, distortion in the impression mateto failure. rial, setting expansion of the die stone, expansion (b) The smaller the connector size the less load and contraction of alloy and wax and distortion to failure. of the framework during heat treatment and (c) Failure usually occurred in the distal abut- application of porcelain [17]. ment wall [15]. Common solutions to provide a passive framework have been sectioning and soldering or fabriRecommendations for the cantilever include cating cement-retained restorations. Although cement-retained restorations have become (a) Limit distal cantilever. increasingly accepted, they still have the disad (b) Limit buccal cantilever. vantage that they are not readily retrievable and (c) Increase thickness of the framework in the studies have also shown that despite a clinician’s cantilever section distal to the most distal best efforts, excess cement is often left behind implant. which can result in biological complications [18]. (d) Limit occlusion on the cantilever. Another approach to achieve a passive screw-­ retained framework has been the use of the adhesive-­ corrected implant frameworks where 13.5.2 Ease of Fabrication individual cylinders were cemented within the and Passivity framework after it had been cast (KAL technique). This approach has merit in that it elimiTraditional techniques in fabricating full-arch nates many of the current prosthetic and implant frameworks involve waxing casting and laboratory inaccuracies associated with tradiapplication of a veneering material such as tional techniques [19]. acrylic or porcelain. This approach has been With the utilisation of CAD/CAM technology, adopted for many years and is considered the a lot of the variables have been eliminated and gold standard for fabrication of implant-­ frameworks can be produced with high precision supported restorations. The results achieved with [20] providing the operator has taken care in prothese techniques have been predictable and suc- ducing an accurate impression either from a cessful [16]. Traditional techniques do require a material-based approach or optically, and the high degree of skill and problems inherent with laboratory technician has exercised care in repliwaxing and casting can lead to it being a labori- cating it into either an analogue cast or has cre-

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ated a digital file. Furthermore, due to the elimination of potential errors the overall workflow has been simplified by utilisation of CAD/ CAM, which allows frameworks to be produced in fewer clinical steps with less labour in the dental laboratory [21]. There are several different materials that can be used to fabricate these CAD/CAM frameworks for implant-supported restorations, and these materials include but are not limited to

including the intaglio surface. One advantage is that it can be relined, but little is known about its longevity in terms of biomechanics. Anecdotally, numerous colleagues have experienced fractures of this type of framework. Failures may be due to excessive cantilever or inadequate bar shape, and further studies need to explore these issues. The second type of framework may include I- or L-shaped bar designs to maximise rigidity. One advantage of this design is that due to the shape of the titanium framework requiring less bulk of 1. Acrylic resin bonded or milled to titanium. material in any one dimension, adequate space 2. High-performance polymers: PEEK. and retention for acrylic resin can be achieved 3. Milled cobalt chromium. which maximises thickness in the cantilever area. 4. Zirconia – monolithic. The evidence base is also lacking in this design. –– Minimally layered. Although these frameworks have served many –– Hybrid design with zirconia frameworks patients well, particularly in the edentulous manand individually cemented crowns (lithium dible, success in the mandible does not automatidisilicate or zirconia). cally translate to success in the maxilla (Figs. 13.10, 13.11, and 13.12). The authors have had clinical experience with 13.6 Acrylic Resin Bonded or repeated fracture of teeth, acrylic resin delaminaMilled to Titanium tion and denture teeth wearing in the anterior maxilla (Fig. 13.13). One possible factor for this Framework designs for a full-arch, one-piece, clinical presentation could be the nature of force implant-supported acrylic resin and titanium-­ application in the maxillary anterior region, based restoration have changed significantly which is typically tensile in nature as opposed to since the transition from gold frameworks to tita- the posterior maxillary region and the mandibular nium [22]. Different manufacturers have differ- arch, which is mainly compressive in nature. This ent designs available, and despite technological problem is exacerbated in patients who present advances, frameworks still do not replicate the with signs of bruxism. These patients are prone to characteristics familiar to gold frameworks. With accelerated wear of posterior teeth which will titanium frameworks a few key parameters eventually lead to increased force and potential become important: overload of the anterior teeth and result in fractures. In order to avoid premature damage to (a) Bulk for strength. maxillary anterior denture teeth, one possible (b) Adequate access to oral hygiene. option is to extend the metal framework onto the (c) Minimal display of metal. (d) Retention for acrylic. (e) Adequate space for acrylic resin. (f) Adequate strength in the cantilever section. (g) Attention to cross-sectional area. When considering these parameters, there are mainly two types of framework designs to support acrylic resin teeth. One of these designs is the “minimalist” framework where acrylic is wrapped around the bar and encompasses it 360°,

Fig. 13.10  Original characteristics of gold frameworks

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Fig. 13.11  Titanium frameworks with similar characteristics to original gold frameworks

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type of restoration may eliminate many of the potential complications of traditional denture teeth bonded to titanium with processed acrylic such as delamination of teeth and fracture of acrylic veneering materials. The evidence base is lacking with these newer technologies, and ­further research needs to be conducted in these areas. These various designs and technologies can be used in high- and low-force situations. As noted previously, in high-force situations the teeth will wear much more quickly and will potentially need to be replaced as part of long-term maintenance. Although it is possible to make attractive restorations with denture teeth, the pink acrylic does lose its sheen over time and can accumulate greater amounts of stain compared to ceramic.

13.7 High-Performance Polymers: PEEK Fig. 13.12 Examples of wraparound and L-shaped frameworks

Fig. 13.13  Fracture of acrylic resin tooth from titanium framework

occlusal surfaces. The fabrication of prototypes with selective and controlled cutback procedures will allow accurate copy milling and incorporating metal posterior occlusal surfaces into the framework. Another possible option is to utilise new processes in the manufacturing of acrylic to titanium restorations such as milling acrylic around an embedded titanium framework utilising polychromatic monolithic acrylic [23]. This

The reason for the recent enthusiasm surrounding PEEK has been its potential for use as a metal alternative. Perhaps the most interesting property of PEEK for use as a framework material is its Young’s elastic modulus (4  GPa), which allows the PEEK substructure to more closely match the biomechanical characteristics of the jaw’s natural bone (2–12 GPa). Unusually, PEEK is well positioned in that it is strong and resistant to repetitive cyclical loading cycles, yet is slightly elastic, lightweight, and able to dissipate stress forces placed on it. It is these ‘bone-like’ properties that offer PEEK as a more biomechanically engineered substructure material [24]. It is postulated that the shock-absorbing properties of this material may result in less stress being transferred to the bone–implant interface. There is no evidence to support such a claim although theoretically it may seem reasonable. The Young’s elastic modulus of PEEK (4  GPa) is similar to the acrylics (2  GPa) and being a lot lower than titanium (100 GPa), but still retaining sufficient stiffness for rigidity of structure. However, unlike acrylic, PEEK also has sufficient strength (120 MPa flexural strength vs. 40 MPa for acrylic) and excel-

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lent flexural fatigue resistance to cyclical loads that make it fit for the purpose of long-term restorations. PEEK’s resistance to failure from flexural fatigue may be of interest to potentially address some of the technical complications associated with cantilever design, and lab-based tests have been published that show resistance to failure with distal cantilevers of up to 19  mm length [25]. PEEK as a permanent framework material has become an option in recent times through the availability of CADCAM forms. However, clinical data is typically limited at present to case studies [26–28] although the first formal clinical studies are starting to become available [29].

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Fig. 13.14  Milled cobalt chromium framework

13.8 Milled Cobalt Chromium Cobalt chromium frameworks have had a major resurgence in recent years. All of the traditional problems with fit, bonding and corrosion related to cast designs have been eliminated with the inception of milled framework designs [29]. These frameworks are then veneered with porcelains to create traditional porcelain fused to metal restorations. From an aesthetic point of view, metal ceramic prostheses can be created in a way that is more tooth-like than frameworks veneered with acrylics, especially after some years of function in the oral cavity (Figs. 13.14, 13.15, 13.16, and 13.17). CAD-CAM designs allow better control of ceramic thickness, passive frameworks, predictable ceramic bonding and less bending than high noble frameworks, especially in cantilevers. Cobalt chrome frameworks are particularly advantageous when less than 15  mm of restorative space is available and a posterior cantilever is present. The restoration can withstand occlusal forces even at minimal thickness [29]. The main attraction, however, seems to be the cost compared to gold-based frameworks. The main disadvantages are laboratory based as an industrial milling and sintering machine is required, with a skilled dental technician to utilise these newer technologies.

Fig. 13.15  Opaque must be applied appropriately to mask grey color of metal

Fig. 13.16  Completed ceramics on cobalt chromium framework

Fig. 13.17  Intraoral view of mandibular restoration in Fig. 13.16

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13.9 Zirconia Zirconia frameworks have evolved significantly over the last ten years and have become hugely popular as a restorative material for fully implant-­ supported restorations. The primary advantage of zirconia is that it is biocompatible, aesthetic and has great material strength [30]. The tooth-like colour of zirconia makes it beneficial in aesthetic areas of the oral cavity, and the excellent wear Fig. 13.18  Monolithic zirconia framework with staining characteristics make it advantageous in the posterior areas as well. These properties have resulted in the increased use of zirconia in the fabrication of these restorations. Clinical reports have evaluated restorations with a zirconia structure supported by implants and have provided some insight [31]. Zirconia has a high flexural strength, which makes it suitable as a framework in veneered or full-contour reconstructions. Some technical complications are likely to occur; these include but are not limited to 1. Chipping of the veneering ceramic. 2. Debonding of the titanium inserts. 3. Catastrophic failure of the framework. To reduce the risk of complication, there are a myriad of details the clinician and laboratory technician must respect. Zirconia frameworks can be designed according to the following parameters: 1. Monolithic zirconia. 2. Minimally cutback zirconia with ceramic layering. 3. Hybrid designs with individual lithium disilicate or zirconia crowns. 4. Hybrid designs with a primary titanium bar with overlying zirconia framework which may be layered or monolithic utilising intraoral scanning and CADCAM protocols.

Fig. 13.19  Clinical picture of monolithic zirconia with pink ceramic layering in situ

13.10 Monolithic From an evidence-based perspective, long-term data (10  years plus) to support monolithic full-­ contour frameworks at this time is lacking. This statement should not be considered a deterrent, but caution must be exercised during case selection (Figs. 13.18 and 13.19).

13.11 Minimally Layered It is possible to achieve strength and maximum aesthetics by minimal layering zirconia frameworks with veneering porcelain [32]. However, a few clinical studies show that unsupported

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veneered ceramic has a higher risk of chipping [33]. To take advantage of both the strength of zirconia and ideal aesthetics, it is recommended that frameworks be designed such that occlusal contact areas are in monolithic zirconia with minimal layering on the buccal surfaces in aesthetic areas. One caveat is that all veneered porcelain must be appropriately supported, with anatomically shaped design to the underlying zirconia framework [34]. When focusing on this issue, questions often arise in regards to the flexural strength of full-contour zirconia alone and the flexural strength of porcelain fused to zirconia systems. Clinicians have concerns about potential chipping and fracture of the veneering porcelain. Most studies will report that the veneering porcelain is the weak point in any multilayer system, including traditional PFM techniques [35]. Regardless of whether a noble metal or zirconia framework is being used, the overlying porcelain must be well supported [36]. Shear bond strength of porcelain to zirconia has also been investigated; studies show differences in bond strength depending on the veneering porcelain used and if the zirconia substructure is coloured or uncoloured [36]. It is the authors’ recommendation that when using a zirconia substructure compatible veneering porcelains ­ should be used and the heating and cooling cycles must be carefully controlled. Limiting the veneering porcelain and having a full-contour zirconia framework with zirconia occlusion is advantageous in this regard (Figs.  13.20, 13.21, 13.22, 13.23, 13.24, 13.25, and 13.26). One important design consideration with these zirconia restorations is the incorporation of cantilevers. Cantilevers in implant dentistry are valuable for sites where anatomic structures such as the maxillary sinuses exclude the ideal placement of dental implants, and are being used more often for graft-less procedures. They may, however, negatively affect the biomechanics of implant restorations and may result in mechanical and/or biological problems. Presently, evidence is limited concerning the breakage of cantilevered zirconia implant frameworks. This evidence is mainly limited to anecdotal and expert clinical reports. Well-designed, clinically relevant labora-

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Fig. 13.20  Acrylic prototype is tried intraorally to verify occlusion and contours

Fig. 13.21  Minimal cutback in acrylic

Fig. 13.22 Acrylic prototype scanned and milled in zirconia

tory studies are needed to establish the mechanical properties of zirconia cantilever frameworks. When designing zirconia-based implant frameworks, the following should be considered: 1. Maximise connector dimensions, buccal-­ lingually and occlusal-gingivally. 2. Minimise distal cantilever length. 3. Minimise buccal cantilever.

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Fig. 13.23  Note occlusion entirely in zirconia

Fig. 13.24  Minimally applied ceramics (lab work by Kenji Mizuno CDT)

Fig. 13.25 Maxillary restoration

minimally

layered

zirconia

4. Ensure very light occlusal contacts in the cantilever region. 5. Thicken the chimney around the most distal implant and thicken the buccal and lingual walls around the chimney of the implant. 6. Ensure monolithic zirconia is well polished. Studies have shown it to be kind to the opposing occlusion. 7. Minimal post-sintering adjustment. This will also help with preserving the strength of the material and avoiding accelerated ageing failures in the presence of saliva. 8. Design for retrievability. This allows simple detachment of the appliance and the chance to service the restoration or treat any implant-­ related problems. With proper implant placement, this can be achieved in most situations when treating the edentulous arch. 9. If restoring to the head of the fixture, the literature supports the use of a titanium insert. This increases the maximum load-bearing capacity of the restoration. It also compensates for the three-dimensional distortion that occurs post sintering. Zirconia abutments have been designed with a titanium ­component that has been fused or cemented to the zirconia. The unique design feature is that it permits titanium-to-titanium contact at the abutment implant interface and results in the same high degree of predictability associated with conventional metal abutment–implant connections [37].

13.12 Hybrid Designs with Individual Ceramic Crowns These types of restorations provide many advantages: (a) Maximal aesthetics since there are individual restorations especially with aesthetics in the interproximal areas.

Fig. 13.26  Maxillary and mandibular zirconia-based restorations in situ

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(b) Stress distribution due to underlying splinting and cross-arch stabilisation of the implants. (c) Ease of dealing with restorative complications—if a single crown were to fracture it can be replaced individually (Figs.  13.27, 13.28, 13.29, 13.30, and 13.31). Ideally they should be designed with the screw access trajectories in a favourable position so that the restoration can be readily serviced at hygiene appointments. However, despite the clinician’s best intentions, anatomic limitations may not allow screw-retained implant placement in the anterior maxilla, even after correction with angled abutments. In these situations a ‘hybrid’ between a monolithic design and individual cemented restoration may solve a challenging problem created by anterior implant trajectory [38].

Fig. 13.29  Framework try-in intraorally

Fig. 13.30  Maxillary hybrid zirconia restoration opposed by acrylic titanium restoration

Fig. 13.27  Hybrid design; when screw access holes are not ideally located, individual crowns can be made and luted

Fig. 13.31  Smile view of restorations in Fig. 13.30

Fig. 13.28  Individual crowns in zirconia replacing maxillary anterior teeth

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13.13 Hybrid Designs with a Primary Titanium Bar and Overlying Zirconia Framework Utilising Intraoral Scanning and CADCAM Protocols The delivery of full-arch implant-supported restorations has been significantly advanced by the rapid introduction of innovative digital technologies into clinical practice. These technologies allow for greater ease, cost efficiencies, and improved workflows. Intraoral scanning is one of these technologies that has significantly improved the acquisition of diagnostic data and clinical information required for the definitive restoration. It enables the clinician to execute a complex implant rehabilitation in a fewer number of visits. Intraoral scanning for single-tooth implant restorations has been shown to be just as accurate as analogue techniques. Full-arch scans have not been as reliable and consistent. It was shown that the precision of full-arch scans decreases as the distance between the scanning abutments increases. This inaccuracy can be a result of scanning protocols, scan abutment designs and the different technologies associated with different types of scanners. Recently scan gauges have been introduced that standardise the scanning procedure (Osteon Technologies). Scanning for full-arch implant restorations on multi-unit abutments has become a clinical reality. The protocols to scan include but are not limited to. 1. A more controlled path for the scanner to follow reduces the amount of scan head movements. 2. Allowing more than one scannable feature on the gauge to be deleted if tolerance of scan captured is less than the known gauge measurement. 3. Inclusion of an alignment procedure where the scan information is analysed using an increased point cloud data set for its reference to the planes present in the gauge design.

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The manufacturing process has also benefited from technology with laboratories now able to complete the definitive restorations utilising a full digital workflow. Fabrication of full-arch zirconia restoration supported by a titanium substructure can be completed by utilising a full digital workflow. These types of full-arch restorations may provide the following benefits: 1. Ease of fabrication—CADCAM technology. 2. Passivity of the framework—Utilising scan gauges and AI technology frameworks can be fabricated with a true digital model-less workflow. This can result in a clinically acceptable passive framework. 3. Implant/abutment interface—A titanium-to-­ titanium interface was used to minimise wear on the head of the implant. There is no zirconia touching the head of the fixture or even the multi-unit abutment. The clinician is also able to torque the prosthesis without creating undue stress in the zirconia framework. 4. Occlusion/wear—The framework can be created with full-contour zirconia with minimal cutback or full-contour zirconia and stain. The occlusion is designed in zirconia for stability of occlusal contacts. 5. Strength of framework/veneering porcelain— The zirconia is supported by a titanium substructure which biomechanically enhances the restoration. Care must be taken to ensure the thickness of zirconia is adequate. 6. Aesthetics—Is improved by minimal cutback and layering. 7. Delivery/retrievability—The entire restoration is screw retained and designed with retrievability in mind. The clinician must provide the following information to the laboratory: 1. Intraoral scanning of gauges in specific pathways. 2. Scanning of the tissues intraorally. 3. Scanning of the provisional restorations with gauges extraorally and scanning maximum intercuspation intraorally.

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4. Clinical photographs. 5. Prescription of the desired changes. The clinical information is systematically organised and manipulated in CAD software to propose a design for the prosthesis. This design can be previewed, and corrections made. The clinician may choose to go directly to the definitive restorations in one visit if the provisional restorations satisfy the requirements of aesthetics, contour and phonetics. It is recommended however that a clinical try­in of a printed resin prosthesis be done prior to definitive delivery to verify the clinician’s requirements. The definitive restorations are fabricated via a CADCAM process where the framework is digitally designed and milled from a blank of commercially pure titanium via a computer numeric-controlled machine. Such a process has shown to be efficient in producing accurate, customisable and durable frameworks. Today even the suprastructure is fabricated through a CADCAM process to produce the veneering acrylic or zirconia prosthesis. The following patient presentation will illustrate the digital workflow. The patient presented with a terminal dentition and was treatment planned for a maxillary and mandibular implant-supported restoration (Fig. 13.32). Bilateral sinus lifts were performed in the maxilla, and seven root-form implants were placed in the maxilla and six in the mandible (Paltop Dynamic, Keystone Dental Group)

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(Fig. 13.33). Provisional restorations were fabricated to optimise aesthetics, form and function (Fig.  13.34). The advantages of a full digital workflow include but are not limited to. 1. No impressions. 2. Clinician can complete the definitive restoration in two visits post integration. 3. Aesthetics can be verified with a 3D-printed try-in and modifications can be made. 4. No sophisticated equipment is required. The practitioner can utilise their existing intraoral scanner to capture all the data required (Fig. 13.35). The following data is required: 1. Proprietary scan gauges are placed and scanned (Osteon Technologies) (Fig. 13.36). 2. The soft tissue is scanned (Fig. 13.37). 3. The undersurface of the provisional is scanned (Fig. 13.38). 4. The patient is asked to occlude into maximum intercuspation and a right and left bite scan is performed (Fig. 13.39). The following photos are also submitted with the scans: 1. Provisionals in the mouth. 2. Smile. 3. Full face (Fig. 13.40).

Fig. 13.32  Preoperative situation of a terminal dentition has been treatment planned for maxillary and mandibular implant-supported restorations

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Fig. 13.33 After bilateral sinus lifts seven Paltop Dynamic implants placed in the maxilla and six in the mandible

Fig. 13.34  Provisional restorations fabricated

Fig. 13.35  Advantages of a digital workflow

Fig. 13.36  An example of scan gauges scanned in the mouth (Osteon Technologies)

Fig. 13.37  An example of soft tissue scan

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Fig. 13.38  An example of scanning of a provisional restoration undersurface

Fig. 13.39  An example of scanning the prosthesis in the mouth and recording occlusal relationships

Fig. 13.40  Photos submitted to Osteon

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All the data are uploaded to CAD software and a proposed design is created for approval by the clinician (Figs. 13.41 and 13.42). Once approved, a primary titanium substructure is milled to support an overlying zirconia framework. These two materials are bonded together utilising a resin cement (Fig. 13.43). The undersurface of the restoration and contours is convex and cleansable (Fig. 13.44). The definitive restorations are delivered and screws torqued to the manufacturer’s recommendations (Fig. 13.45).

Clinically these types of restorations have been reported (personal communication) to have less complications than monolithic and minimally layered restorations. With that said they do not have as long a clinical track record and a like-­ to-­like comparison cannot be made. They have been advocated for use in situations when minimal bone reduction is performed and the clinician is planning for an FP1 type of restoration (Figs.  13.46, 13.47, 13.48, 13.49, 13.50, 13.51, 13.52, 13.53, and 13.54).

Fig. 13.41  CAD design

Fig. 13.42  Restoration proposals of both sub structure and suprastructure

13  Material Considerations for Full-Arch Implant-Supported Restorations

Fig. 13.43  Combination titanium/zirconia restoration

Fig. 13.44  Undersurface or restoration illustrating convex cleansable surface

Fig. 13.45  Definitive restorations delivered

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Fig. 13.49  FP1-type prosthesis designed to compress tissue (ceramics by Artem Asemov)

Fig. 13.46  Zirconia overlay

Fig. 13.47  Milled titanium substructure

Fig. 13.48  Titanium is bonded to the zirconia overlay with a resin cement

Fig. 13.50  Occlusion in polished zirconia

Fig. 13.51  Undersurface of restoration

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facturing processes utilised and clinical parameters are just a few of these considerations, and this chapter attempts to give guidelines to aid in making relevant decisions for these prostheses. While some basic parameters have been stated, further studies need to be conducted to look into specific areas in greater detail to be able to make more predictable decisions with respect to these therapies.

Fig. 13.52  Lateral view showing compression against tissue

Fig. 13.53  Intraoral view of FP1 restoration in the maxilla and FP3 in mandible

Fig. 13.54  Smile view

13.14 Conclusion It is readily evident that material selection for full-arch implant-supported restorations is multi-­ factorial with a wide range of considerations for clinical success. Design of frameworks, manu-

References 1. Rojas-Vizcaya F.  Full zirconia fixed detachable implant-retained restorations manufactured from monolithic zirconia: clinical report after two years in service. J Prosthodont. 2011;20:570–6. 2. Chee W, Felton D, Johnson P, Sullivan D. Cemented versus screw-retained implant prostheses: which is better? Int J Oral Maxillofac Implants. 1999;14(1):137. 3. Chee W, Jivraj S. Screw versus cemented implant supported restorations. In: Treatment planning in implant dentistry. Lowestoft: British Dental Journal; 2007. p. 81–7. 4. Sailer I, Muhlemann S, Zwahlen M, Hammerle CH, Schneider D.  Cemented and screw-retained implant reconstructions: a systematic review of the survival and complication rates. Clin Oral Implants Res. 2012;23(Suppl 6):163–201. 5. Jivraj S, Chee WWL, Corrado P. Treatment Planning of the Edentulous Maxilla. Br Dent J. 2006;201(5):699. 6. Wicks RA.  A systematic approach to definitive planning for osseointegrated implant prostheses. J Prosthodont. 1994;3:237–42. 7. Jacobs R, Van Steenberghe D.  Comparative evaluation of the oral tactile function by means of teeth or implant supported prostheses. Clin Oral Implants Res. 1991;2:75–80. 8. Davis DM, Packer ME, Watson RM.  Maintenance requirements of implant supported fixed prosthesis opposed by implant supported fixed prosthesis, natural teeth, or complete dentures. A five year retrospective study. Int J Prosthodont. 2003;16:521–3. 9. Yip KH, Smales RJ, Kaidonis JA. Differential wear of teeth and restorative materials: clinical implications. Int J Prosthodont. 2004;17(3):350–6. 10. Jung YS, Lee JW, Choi YJ, et al. A study on the in-­ vitro wear of the natural tooth structure by opposing zirconia or dental porcelain. J Adv Prosthodont. 2010;2:111–5. 11. Chang PC, Henegbarth EA, Lang LA.  Maxillary zirconia implant fixed partial dentures opposing an acrylic resin implant fixed complete denture. A 2 year clinical report. J Prosthet Dent. 2007;97(6):321–30. 12. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, Haselton DR, Stanford CM, Vargas MA.  Relative

358 translucency of six all-ceramic systems. Part I: core materials. J Prosthet Dent. 2002;88(1):4–9. 13. Larsson C, Wennerberg A.  The clinical success of zirconia-based crowns: a systematic review. Int J Prosthodont. 2014;27(1):33–43. 14. Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications in fixed Prosthodontics. J Prosthet Dent. 2003;90:31–41. 15. Chong KK, Palamara J, Wong RH, Judge RB. Fracture force of cantilevered zirconia frameworks an in vitro study. J Prosthet Dent. 2014;1112:849–56. 16. Zarb GA, Jansson T. Laboratory procedures and protocol. In: Branemark PI, Zarb G, Albrektsson T, editors. Tissue integrated prostheses: osseointegration in clinical dentistry. Chicago: Quintessence; 1985. p. 303. 17. Jemt T.  Three-dimensional distortion of gold alloy castings and welded titanium frameworks. Measurements of the precision of fit between completed implant prostheses and the master casts in routine edentulous situations. J Oral Rehabil. 1995;22:557–64. 18. Korsch M, Walther W.  Peri-implantitis associated with type of cement: a retrospective analysis of different types of cement and their clinical correlation to the peri-implant tissue. Clin Implant Dent Relat Res. 2014;17:e434. https://doi.org/10.1111/cid.12265. 19. Voitik AJ.  The Kulzer abutment luting; Kal technique. A direct assembly framework method for osseointegrated implant prostheses. Implant Soc. 1991;2(1):11–4. 20. Almasri R, Drago C, Siegel S, et  al. Volumetric misfit in CAD/CAM and Cast implant frameworks: a university laboratory study. J Prosthodont. 2011;20:267–74. 21. Drago C, Howell K. Concepts for designing and fabricating metal implant frameworks for hybrid implant prostheses. J Prosthodont. 2012;21(5):413–24. https://doi.org/10.1111/j.1532-­849X.2012.00835.x. Epub 2012 Mar 13. 22. Drago C.  Ratios of cantilever lengths and anterior-­ posterior spreads of definitive hybrid full-arch, screw-retained prostheses: results of a clinical study. J Prosthodont. 2018;27:402. https://doi.org/10.1111/ jopr.12519. 23. Kattadiyil MT, Goodacre CJ, Baba NZ.  CAD/CAM complete dentures: a review of two commercial fabrication systems. Calif Dent Assoc. 2013;41(6):407–16. 24. Najeeb S, Zafar MS, Khurshid Z, Siddiqui F.  Applications of polyetheretherketone (PEEK) in oral implantology and prosthodontics. J Prosthodont Res. 2016;60(1):12–9. https://doi.org/10.1016/j. jpor.2015.10.001. 25. Sereno N, Rosentritt M, Jarman-smith M, Lang R, Kolbeck C.  In-vitro performance evaluation of polyetheretherketone (PEEK) implant prosthetics

S. Jivraj and S. Rawal with a cantilever design. Clin Oral Implants Res. 2015;26(S12):296. 26. Tipton P, Siewert B. High performance polymers part 3. Private Dentistry UK; 2016. 27. Siewert B, Parra M. A new group of material in dentistry. PEEK as a framework material used in 12-piece implant-supported bridges. Z Zahnärztl Implantol. 2013;29:148–59. 28. Moura GC.  New possibilities for high performance polymers in the MALO clinic protocol. In: British Association of Restorative Dentistry conference, 4–6 June 2016. 29. Abduo J. Fit of CADCAM implant frameworks: a comprehensive review. J Oral Implantol. 2014;40:758–66. 30. Larsson C, Vult Von Steyern P. Implant supported full arch zirconia based mandibular fixed dental prostheses. Eight year results from a clinical pilot study. Acy Odontol Scand. 2013;71:1118–22. 31. Puri S, Parciak EC, Kattadiyil MT. Complete mouth reconstruction with implant supported fixed partial dental prosthesis fabricated with zirconia frameworks: a 4 year clinical follow up. J Prosthet Dent. 2014;112:397–401. 32. Cheng CW, Chien CH, Chen CJ, Papaspyridakos P.  Complete mouth rehabilitation with modified monolithic zirconia implant supported fixed dental prosthesis and an immediate loading protocol: a clinical report. J Prosthet Dent. 2013;109:347–52. 33. Guess PC, Bonfante EA, Silva NR, Coelho PG, Thompson VP.  Effect of core design and veneering technique on damage and reliability of Y-TZP-­ supported crowns. Dent Mater. 2013;29:307–16. 34. Miyazaki T, Nakamura T, Matsumura H, Ban S, Kobayashi T. Current status of zirconia restorations. J Prosthodont Res. 2013;57(4):236–61. https://doi. org/10.1016/j.jpor.2013.09.001. Epub 2013 Oct 18. 35. Preis V, Letsch C, Handel G, Behr M, Schneider-­ Feyrer S, Rosentritt M.  Influence of substructure design, veneer application technique, and firing regime on the in vitro performance of molar zirconia crowns. Dent Mater. 2013;29:e113–21. 36. Mosharraf R, Rismanchian M, Savabi O, Ashtiani AH.  Influence of surface modification techniques on shear bond strength between different zirconia cores and veneering ceramics. J Adv Prosthodont. 2011;3(4):221–8. https://doi.org/10.4047/ jap.2011.3.4.221. 37. Kim JS, Raigrodski AJ, Flinn BD, Rubenstein JE, Chung KH.  Mancl LA in  vitro assessment of three types of zirconia implant abutments under static load. J Prosthet Dent. 2013;109(4):255–63. https://doi. org/10.1016/S0022-­3913(13)60054-­2. 38. Pozzi A, Tallarico M, Barlattani A. Monolithic lithium disilicate full contour crowns bonded on CADCAM zirconia complete arch implant bridges with 3-5 years of follow up. J Oral Implantol. 2015;41(4):450–8.

Clinical Steps for Fabrication of a Full-Arch Implant-Supported Restoration

14

Udatta Kher and Ali Tunkiwala

Abstract

14.1 Section I: Introduction

The ultimate goal in prosthetic rehabilitation of edentulous patients is the long-term fulfilment of their functional and aesthetic requirements. The fabrication of such prostheses is an exacting process and needs meticulous attention towards several clinical and laboratory steps. Each step is executed only after the proceeding step is verified so that the prostheses in the end will have a passive fit and superior accuracy. The need for effective communication with the dental laboratory is the bedrock of all prosthetic work. This chapter summarises the conventional techniques and prosthetic workflow for fabrication of full-arch fixed implant prostheses. In Sect. 14.2, a novel fast-tracking protocol has been devised, wherein from impression to delivery, the entire workflow can be carried out in one or two appointments.

The final design planning and material choice for the definitive fixed prosthesis should be accomplished before the surgical placement of the implants following the principles of prosthetically driven implant dentistry. The actual clinical steps will begin after the implants have osseointegrated. Whilst the rehabilitation of each arch can be carried out one at a time, it is possible to address both arches together with meticulous attention to detail. A well-designed functional and aesthetic provisional prosthesis is imperative for the smooth transition to a definitive one as it aids tremendously in lab communication at all stages. For the full-arch fixed implant prostheses, the number of clinical prosthetic steps needed in fabricating the definitive restorations has been depicted in Flowchart 14.1.

14.1.1 Step 1: Impressions

U. Kher · A. Tunkiwala (*) Private practice, Mumbai, India

Impressions for definitive prostheses can be done at the implant level or abutment level, based on the initial prosthetic plan (Flowchart 14.2). The implant-level approach entails using components that directly connect to the implant platform. The abutment-level approach utilises a multi-unit abutment that is torqued on the implant, and all the following prosthetic steps are performed over

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Jivraj (ed.), Graftless Solutions for the Edentulous Patient, BDJ Clinician’s Guides, https://doi.org/10.1007/978-3-031-32847-3_14

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Flowchart 14.1  Conventional sequence and appointments for full arch implant rehabilitation

the abutments. Working at abutment level allows the restorative margin to be taken further away from the crestal bone, and thus, it is biologically a better option, provided there is sufficient restorative space to accommodate the extra height of the multi-unit abutments. Moreover, working at abutment level will make all the subsequent prosthetic steps, like verification of fit, easier and thereby helps minimising errors. Lastly, as the abutment can allow implant trajectories to be straightened out and get screw accesses to the desirable positions, it reduces overall distortions in the impressions. The basic technique and principles of impression-making at implant or abut-

ment level will remain the same, although the componentry for each will be different. The impression must accurately represent the exact three-dimensional, implant/abutment positions and the surrounding soft tissue contours. Having a well-healed soft tissue around the implants is desirable as inflamed, unhealed tissues may bleed during impression procedures and affect the setting time and dimensional accuracy of the materials [1]. If a provisional restoration has been designed to shape the gingival tissue architecture to achieve a positive emergence profile, it must be copied in the impression procedure [2–5].

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Flowchart 14.2  Analogue and Digital Workflow for Implant impressions/scans

14.1.1.1 Impression Techniques Closed Tray Technique The closed tray or indirect transfer technique is suited only when the implants are placed parallel to each other. The closed tray copings are attached to the implant or the multi-unit abutment and an impression taken with elastomeric materials. After the retrieval and disinfection of the impression, the implant or abutment replica as applicable is attached to the impression coping and reinserted within the impression (Fig. 14.1). The key to a successful closed tray impression lies in this step of relocating the coping-replica assembly within the impression. For maximum accuracy the height of the coping that is captured above the tissues must be sufficient and the system should have designed the impression coping that facilitates accurate indexation within the impression. Some systems have a plastic cap over the copings that gets picked up with the impres-

sion material and allows for a definitive seat of the coping-replica assembly within the impression (Fig. 14.2). The closed tray technique, however simple, is contraindicated for non-parallel implant trajectories as there will be distortion in the set material during retrieval from the mouth due to the mismatch in their paths of withdrawal (Figs. 14.3, 14.4, 14.5, 14.6, and 14.7). Open Tray Technique The open tray impressions are preferred in cases where implants are placed deeper or have a thick band of soft tissue over them (Fig.  14.8). Moreover, this is the technique of choice when implants are not parallel to each other [6]. Full-­ arch impressions for implant-supported restorations require a high degree of accuracy for which the open tray or direct pick-up technique in a rigid custom tray is preferred [2–5]. The open tray copings may be engaging (hexed) or non-engaging (non-hexed) (Figs. 14.8

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Fig. 14.1  Closed tray impression coping

Fig. 14.3  Upper full-arch implants. Closed tray technique is used here as the parallelism between the implants is within the acceptable range

U. Kher and A. Tunkiwala

Fig. 14.2  Closed tray impression coping with plastic transfer cap

Fig. 14.4  Upper full-arch implants impression using the closed tray technique

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Fig. 14.5  Snap impression copings

Fig. 14.6  Lower implants with multi-unit abutments

Fig. 14.8  Hexed open tray coping for single-implant restorations

Fig. 14.7  Closed tray copings for multi-unit abutments

and 14.9). The former is used only for single implants and the latter for multiple implants as would be the case for full-arch cases. These copings are designed with undercuts on them and a long screw that will protrude beyond the selected tray. After the impression material has set, the long screw is disengaged completely

and the tray retrieved with the impression coping embedded within the material securely. The implant or abutment replica, as applicable, is fixed to the impression coping. At this point, the clinician must not use uncontrolled force to fixate the replica as that can lead to rotation of the coping within the elastomeric impression and thereby lead to a flaw. To overcome this potential error, it is advisable to splint the open tray copings to each other with a rigid material, intraorally [7–9]. Literature supports the use of splinted impression copings with a rigid material with low-­ dimensional change [6–10]. Several techniques have been used for splinting of the impression copings such as autopolymerising resin, dual-­ cured resins, plaster and prefabricated resin bars

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Fig. 14.10  Open tray copings that have not been splinted

Fig. 14.11  Upper-arch implants ready for impressions

Fig. 14.9 Non-hexed copings for multiple-implant restoration

(Figs. 14.10 and 14.11). The splinting of copings with autopolymerising resin which is sectioned and reconnected after setting are considered to provide maximum accuracy and are thus preferred [7, 11, 12]. The necessity to section the splints connecting the copings and reconnecting them intraorally arises due to the polymerisation shrinkage of the material that can lead to a certain amount of pressure between all copings, thereby leading to an invisible flaw in the impression. The splinting of the copings could be performed intraorally in one step or could be done on a primary model and splinted extraorally. Both these techniques will need the copings to be sectioned and reconnected with fast-setting resin intraorally (Figs. 14.12, 14.13, 14.14, 14.15, and 14.16).

Fig. 14.12  Floss tied to the open tray copings to act as scaffold for resin splinting

Fig. 14.13  Open tray copings splinted with pattern resin

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Fig. 14.14  Splinted open tray impression done with polyether on custom tray

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Fig. 14.17  Stock tray with plastic inserts for open tray technique

However, stock trays designed especially for the open tray technique could also be used (Fig. 14.17).

14.1.2 Step 2: Verification Jig

Fig. 14.15  Lower multi-unit abutments

Fig. 14.16  Open tray copings for multi-unit abutments

14.1.1.2 Impression Materials Polyvinyl siloxane or polyether impression materials are the preferred options for making impressions due to their higher level of accuracy and dimensional stability [8, 13, 14]. A custom tray coated with an appropriate tray adhesive is preferred for making the impressions [15, 16].

The verification jig is fabricated on the master model. These jigs are generally made using temporary titanium cylinders that have been splinted with each other on the master cast. The clinician will try these in the next appointment with the one screw (Sheffield) test. The jig is screwed onto the distal-most implant and must not lift up from the contralateral implant. A distortion-free radiograph may be done to verify the same. In case the verification jig fits perfectly, the impression is deemed to be correct and the next step of jaw relation may be undertaken at the same appointment. However, if the verification jig is not seating accurately or passively, it must be sectioned between the offending implants and rejoined intraorally with fast-setting resin. The lab must be informed of this act so that they can relocate the implant or abutment replica in its correct position within the stone model and make an altered master cast with accurate positions of all implants/abutment replicas. The verification jig may be made in acrylic resin (Figs. 14.18 and 14.19). These need to be thick so that the flexion of the resin during seating of the jig does not give a false negative result, thereby misleading the clinician to think that the jig is accurate or passive. To avoid such errors, an alternative rec-

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14.1.3 Step 3: Interocclusal Records [16, 17]

Fig. 14.18  Plaster verification jig

Fig. 14.19  When resin verification jig lacks passivity or accuracy, it must be sectioned and individual cylinders left on each implant

Accurate interocclusal records are required to enable the lab to mount the upper and lower ­master casts in accurate relation with each other. In cases where both arches are being restored together, the upper arch is mounted with an aesthetically accurate face bow record, such as a dentofacial analyser. The lower cast will be mounted in centric relation with regard to the upper cast, and this should be accomplished at the desired vertical dimension of occlusion (Fig. 14.21). The steps would be as follows: (a) Upper rim adjustment keeping parallelism with the inter-pupillary line and the Camper’s plane. (b) Vertical dimension of occlusion determination using the freeway space as a guideline. (c) Centric relation record. In full-arch cases, these interocclusal records can be done in four ways: 1. Conventional complete denture bases on residual ridge. 2. Screw-retained complete denture bases (Figs. 14.22, 14.23, 14.24, and 14.25). 3. Two-piece screw-retained bases (Figs.  14.26 and 14.27). 4. Using Aluwax on healing abutments/final abutments (Fig. 14.28).

Fig. 14.20  New resin can be used to join the cylinders intraorally and lab informed

ommendation is to make the verification jigs with impression plaster (Fig. 14.20). The brittle plaster will break if the screw is forced in due to lack of passivity, thereby preventing a potential impression error to go through to the next step. Fig. 14.21  Conventional record bases for jaw relation

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Fig. 14.25  Several other lines marked to help select the right size of teeth in the lab Fig. 14.22  Screw-retained record base for jaw relation

Fig. 14.23  CR recorded on fixed screw-retained bases

Fig. 14.24 Midline transfer along with cuspid line marked on rim

Fig. 14.26  The fixed screw-retained part of the two-­ piece record base

Fig. 14.27  The second part of the record base with wax rim

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Fig. 14.28  Aluwax records the JR on stock abutments

In most cases of full-arch prosthodontics, at least two interocclusal records are recommended at two different stages during the treatment.

14.1.3.1 Conventional Complete Denture Bases on Residual Ridge This is done on movable record base just like in complete denture prosthodontics. Pros It is an easy technique and can be done without any additional lab steps or componentry. Cons (a) Record bases may be unstable, leading to an error in CR records. (b) The entire movable base feels bulky to most patients. (c) Presence of flanges may create confusion with lip support.

14.1.3.2 Screw-Retained Complete Denture Bases Pros The record bases are fixed to the implants and thus the accuracy of the record is much higher. Cons (a) Record bases need to be lab fabricated. (b) The long temporary cylinders used in the record bases can be a nuisance during adjustment of the height of the wax rim as they will interfere and will need to be shortened repeatedly.

U. Kher and A. Tunkiwala

14.1.3.3 Two-Piece Screw-Retained Bases Record bases are made in two parts per arch that fit into each other. The first part is screwed onto the implants, thereby providing stability, and the second part is snapped onto the first one. The second part has the wax rim and can be easily removed from the mouth to adjust the same and snapped back to check the height and the arch form. Pros Prevents repeated unscrewing as with the case of single screw-retained base. Cons (a) Needs lab fabrication and additional componentry. (b) Needs sufficient restorative space.

14.1.3.4 Using Aluwax on Healing Abutments/Final Abutments This is with stable components like tall healing abutments or stock abutments on implants, but needs a lot of calculations. The nose-chin points should be marked with approved provisional in place, and then the vertical dimension is reproduced for the CR record using wax to record the abutments. Pros (a) Records done on stable components. (b) No bulky record bases in the mouth. Cons (a) You will need extra set of all same abutments. (b) Chances of error in VDO high as there is no anterior stop.

14.1.4 Step 4: Teeth Set for Try-In The goal of this step is to verify the teeth arrangement from an aesthetic and functional standpoint. Two types of trials can be done after the jaw relation is taken.

14  Clinical Steps for Fabrication of a Full-Arch Implant-Supported Restoration

(a) Complete denture try-in on record bases. In cases where there is no fixed provisional restoration made and the incisal position of upper incisors is not approved from the facial aspect, it is prudent to carry out a denture trial (Figs.  14.29 and 14.30). This trial must be preferably screw-retained on some temporary cylinders or can be a conventional complete denture trial on record bases. An important aspect here is that the denture should not have a labial flange so that the lip support or the lack of it can be judged by the patient and the clinician during the trial. All aspects of aesthetics, phonetics, vertical dimension and occlusion in harmony with CR must be judged and, if needed, corrected at this stage. (b) Resin prototype screwed-in trial. This trial is the key step, an important milestone in the full-arch implant reconstruction workflow. The goal is to give the

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patient a trial that will feel and look exactly like the final prostheses as far as the overall design is concerned (Figs.  14.31, 14.32, 14.33, 14.34, and 14.35). This trial is a prototype of the final prostheses and can be made in resin. The most common method of fabrication for such trials is to

Fig. 14.31  Complete denture try-in on screw-retained base

Fig. 14.29  Complete denture try-in on movable base

Fig. 14.32  Resin prototype

Fig. 14.30  Complete denture try-in on movable base

Fig. 14.33  Resin prototype

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Fig. 14.34  Resin prototype being tested intraorally

Fig. 14.36  Bisque trial

Fig. 14.35  New bite records on resin prototype

mill them with polymethyl methacrylate (PMMA), and these can be shaped, stained and coloured as needed to meet the patients’ aesthetic requirements (Figs. 14.36 and 14.37). In cases where a complete denture (CD) trial was carried out and approved, it can serve as a template for designing these PMMA prototypes. The technician will scan these approved CD trials and design the PMMA prototype in a software (Exocad) and will share the view of the final aspects. Once approved by the clinician, the milling can be carried out in resin with temporary cylinders fixed to the prototype. The staining and polishing are then carried out, and the resin prototype delivered to the clinician. At the time of PMMA prototype clinical trials, it is crucial to check all aspects of the final prostheses. A checklist as follows may be used: (a) Passivity (one-screw test). (b) Incisal edge position. (c) Pink–white junction (within the prototype). (d) Pink–pink junction (between the prototype and the tissues). (e) Occlusion. (f) Phonetics and vertical dimension of occlusion.

Fig. 14.37  New CR record on Bisque trial to fine-tune the occlusion in the lab

(g) Shape of intaglio. (h) Overall look and feel of the prostheses must be acceptable. The aesthetic aspects such as midline, axial inclinations, presence of adequate labial corridor, and proportions of the teeth must be evaluated and corrected if needed. The upper plane must be critically evaluated and corrected to meet aesthetic requirements by staying parallel to the inter-pupillary line. In full smile position (Duchene smile), the proportion of pink to white on the prototype must be assessed with photographs or videography. The teeth must appear in correct proportion to the face and sufficient zone of pink must remain. In cases where the pink aspect of the prostheses is too narrow (