The Surgery-First Orthognathic Approach: With discussion of occlusal plane-altering orthognathic surgery 9811575401, 9789811575402

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The Surgery-First Orthognathic Approach With discussion of occlusal plane-altering orthognathic surgery Jong-Woo Choi Jang Yeol Lee

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The Surgery-First Orthognathic Approach

Jong-Woo Choi • Jang Yeol Lee

The Surgery-First Orthognathic Approach With discussion of occlusal plane-­altering orthognathic surgery

Jong-Woo Choi Department of Plastic Surgery Asan Medical Center Seoul Korea (Republic of)

Jang Yeol Lee SmileAgain Orthodontic Center Seoul Korea (Republic of)

ISBN 978-981-15-7540-2    ISBN 978-981-15-7541-9 (eBook) https://doi.org/10.1007/978-981-15-7541-9 © Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are reserved 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 Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

The surgery-first approach (SFA) or the surgery-first orthognathic approach (SFOA) can be defined as an approach based on going directly to orthognathic surgery without presurgical orthodontic treatment, which used to be a pre-requisite for traditional orthognathic surgery. Therefore, SFA is a concept that is not only challenging the status quo but is also a new paradigm in craniomaxillofacial surgery. In the early 2000s, some Korean orthodontists started the modern concept of surgery-first approach under the name of functional orthognathic surgery which means that postsurgical orthodontic treatment could be more effective and functional compared to presurgical orthodontic treatment. And they had already published the surgery-first concept in The Korean Journal of Clinical Orthodontics. This article clearly addressed and described the surgery-first orthognathic approach without presurgical orthodontic treatment, which is the fundamental basic concept underlying our current surgery-first approach. I have cooperated with this orthodontic group since 2006 for the surgeryfirst approach and found out the surgery-first approach could work very well in many cases. Now that we could get the clinical results in our practice consistently for the last 15 years and have proved the efficacy and validity based on numerous SCI articles, I , JW Choi, and my partner orthodontist, JY Lee, thought that it is time for writing a book in order to share our clinical experiences and knowledge about our surgery-first approach. This book is the result of our hard work and essence of our collaboration for the last 2 years for completing this book. Regardless of the specialty, we hope this book will help the surgeon and orthodontist understand the modern surgery-first approach and be able to apply this concept to their clinical practice, which would be not only a very effective tool but also a paradigm shift in orthognathic surgery. Finally, as a surgeon, I am very grateful that my teachers, BY Park, DH Lew, and YO Kim, who guided me to the world of craniofacial surgery. In addition, I thank YR Chen, Philip Chen, LJ Lou, Sabine Girod, NC Gellrich, and Eduardo Rodriguez who helped me learn the updated techniques in craniofacial and orthognathic surgery. Lastly, I appreciate the consistent support of KS Koh and JP Hong as mentors in my life. Without all of them, I would not be what I am now. As an orthodontist, I am extending my sincere appreciation in memory of Dr. William R. Proffit’s enthusiasm for making the cornerstone of surgical orthodontics. And I would like to express my deep gratitude to Dr. HS Baik, v

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who has given me the philosophy of treating patients with surgery, and Dr. YC Park, who has played a pioneering role in TADs and taught me. Also, I am grateful to professors of the Department of Orthodontics at Yonsei University and Dr. KJ Kim and Dr. TK Kim. Seoul, Korea (Republic of)  Seoul, Korea (Republic of) 

Jong-Woo Choi Jang Yeol Lee

Abstract

Traditional orthognathic surgery, which consists of presurgical orthodontics, orthognathic surgery and postsurgical orthodontics, was introduced by Dr. Hugo Obwegeser in the 1960s. Since the early 2000s, we have actively applied a surgery-first orthognathic approach without presurgical orthodontic treatment, based on a novel presurgical simulation process using a dental model up until now. The surgery-first orthognathic approach, which is recently getting popularized worldwide, does not simply involve ‘skipping’ the presurgical orthodontic treatment. We believe it requires the modern diagnostic strategy and the sophisticated simulation methods followed by precise orthognathic surgery and preplanned postsurgical orthodontic treatment. For successful management of the various dentofacial deformities, the integrated consistent strategy throughout the whole process is essential. According to our 20 years’ experience and research in surgery-first orthognathic approach, it has proved very effective in treating many patients. In addition, the total treatment time was considerably less with the surgery-first orthognathic approach. Despite evidence that surgery-first approach is effective and has its advantages, the craniomaxillofacial surgeon employing the traditional orthognathic approach may find it difficult to change the methodology. To help the traditional orthognathic surgeon make sense of this new approach, this book addresses our concept, our novel simulation methods, orthognathic surgery itself, postsurgical orthodontic treatment and surgical outcomes based on our 20 years’ experience and investigations including the details. Now that we are convinced that surgery-first approach could be a paradigm shift, we hope this book could contribute to the advances of modern orthognathic surgery.

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Contents

1 History and Evolution of the Surgery-First Approach����������������   1 1.1 Definition and Evolution of SFA����������������������������������������������   6 1.2 Benefits and Drawbacks of SFA ����������������������������������������������   8 1.3 SFA Controversies��������������������������������������������������������������������   9 References������������������������������������������������������������������������������������������  18 2 Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach������������������������������������������������������  21 2.1 Communication Between Surgeons and Orthodontists in the Surgery-First Approach��������������������������������������������������  21 2.2 Surgery-First Approach Sequence��������������������������������������������  22 2.3 Establishment of the Surgical Treatment Objectives����������������  22 2.4 Surgical Treatment Objective (STO)—Paper Surgery in FOS ��������������������������������������������������������������������������������������  23 2.5 Surgery-First Approach Clinical Procedure������������������������������  23 References������������������������������������������������������������������������������������������  36 3 Model Surgery Setup in the Surgery-First Approach������������������  37 3.1 Model Setup Procedure������������������������������������������������������������  37 3.2 Virtual 3D Model SetUp ����������������������������������������������������������  44 References������������������������������������������������������������������������������������������  48 4 Postoperative Care of Patients Undergoing the Surgery-First Approach and Postoperative Orthodontics Involving Temporary Anchorage Devices��������������  49 4.1 Postoperative Care of Patients Undergoing the Surgery-First Approach������������������������������������������������������������  49 4.2 Postoperative Orthodontics Combined with the Use of Temporary Anchorage Devices ������������������������������������  50 4.3 Application of TADs in the Surgery-First Approach����������������  50 References������������������������������������������������������������������������������������������  69 5 Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective������������������������������������������������������������������  71 5.1 Orthognathic Surgery for Patients with Class II Malocclusions��������������������������������������������������������������  71 5.2 Surgical Treatment Objective for Class II Orthognathic Surgery��������������������������������������������������  71

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5.3 Vertical Position of the Maxilla in Mandibular Retrognathism (Type I) ������������������������������������������������������������  77 5.4 Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)������������������������������������������������������������  81 5.5 Vertical Position of the Maxilla in Mandibular Retrognathism (Type III)����������������������������������������������������������  89 5.6 Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)����������������������������������������������������������  89 5.7 Surgery-First Approach in Class II Surgeries ��������������������������  97 References������������������������������������������������������������������������������������������ 100 6 Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective������������������������������������������������������������ 101 6.1 Examination and Evaluation of Facial Asymmetry������������������ 101 6.2 Aspects of Mandibular Asymmetry: Vertical Versus Horizontal Asymmetry������������������������������������ 101 6.3 Surgery-First Approach for Facial Asymmetry������������������������ 102 References������������������������������������������������������������������������������������������ 111 7 Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus Osteotomy Versus Sagittal Split Ramus Osteotomy �������������������� 113 7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral Vertical Ramus Osteotomy (IVRO) Versus Sagittal Split Ramus Osteotomy (SSRO)���������������������� 113 7.2 Transverse Soft Tissue Changes Following the Surgery-First Approach������������������������������������������������������������ 141 References������������������������������������������������������������������������������������������ 148 8 Update on Orthognathic Surgical Techniques������������������������������ 149 8.1 Incision and Dissection ������������������������������������������������������������ 149 8.2 Osteotomy �������������������������������������������������������������������������������� 151 8.3 Fixation ������������������������������������������������������������������������������������ 155 References������������������������������������������������������������������������������������������ 158 9 Virtual Surgical Planning and Three-Dimensional Simulation in Orthognathic Surgery���������������������������������������������� 159 9.1 Introduction������������������������������������������������������������������������������ 159 9.2 Methods������������������������������������������������������������������������������������ 161 9.2.1 Data Acquisition����������������������������������������������������������� 161 9.2.2 Virtual Surgical Planning���������������������������������������������� 162 9.2.3 Template Design and Manufacture ������������������������������ 162 9.2.4 Surgical Intervention���������������������������������������������������� 162 9.3 Postoperative Analysis�������������������������������������������������������������� 164 9.3.1 Measurement Protocol�������������������������������������������������� 165 9.3.2 Statistical Analysis�������������������������������������������������������� 166 9.4 Results�������������������������������������������������������������������������������������� 166 9.5 Discussion �������������������������������������������������������������������������������� 168 9.6 Conclusion�������������������������������������������������������������������������������� 170 References������������������������������������������������������������������������������������������ 182

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10 Three-Dimensional Photogrammetric Analysis in Orthognathic Surgery���������������������������������������������������������������������� 185 10.1 Introduction���������������������������������������������������������������������������� 185 10.1.1 Two-Dimensional (2D) Versus Three-Dimensional (3D) Cameras���������������� 185 10.1.2 3D Photogrammetry in Orthognathic Surgery���������� 186 10.2 Methods���������������������������������������������������������������������������������� 191 10.2.1 Imaging Methods������������������������������������������������������ 191 10.2.2 Landmark Identification�������������������������������������������� 192 10.2.3 Measurement of Actual Distances and Surface Areas on the 3D Images������������������������������� 192 10.3 Results������������������������������������������������������������������������������������ 194 10.3.1 Cephalometric Changes�������������������������������������������� 194 10.3.2 Vertical Facial Proportions���������������������������������������� 194 10.3.3 Transverse Facial Proportions ���������������������������������� 195 10.3.4 Nose and Cheek Convexity��������������������������������������� 195 10.3.5 Lip Contour �������������������������������������������������������������� 195 10.3.6 Frontal Mid- and Lower-Third Facial Surface Areas������������������������������������������������������������ 195 10.3.7 Soft Tissue Landmarks Related to Facial Symmetry�������������������������������������������������������� 196 10.4 Discussion ������������������������������������������������������������������������������ 196 References������������������������������������������������������������������������������������������ 209 11 Clinical Application of Surgery-­First Orthognathic Surgery in Patients with Class III Dentofacial Deformities �������� 211 11.1 Introduction���������������������������������������������������������������������������� 211 11.2 Results (Figs. 11.7, 11.8, 11.9, 11.10)������������������������������������ 219 11.3 Summary �������������������������������������������������������������������������������� 220 References������������������������������������������������������������������������������������������ 232 12 Clinical Application of the Surgery-­First Approach in Patients with Class II Dentofacial Deformities������������������������������ 233 12.1 Counterclockwise Rotational Movement of the MMC in Patients with Class II Malocclusions Accompanied by OSA Without Maxillary Advancement������ 240 12.2 Preliminary Investigation�������������������������������������������������������� 244 12.3 Results������������������������������������������������������������������������������������ 246 12.4 Discussion ������������������������������������������������������������������������������ 247 12.5 Conclusion������������������������������������������������������������������������������ 252 References������������������������������������������������������������������������������������������ 266 13 Clinical Application of the Surgery-­First Approach to Facial Asymmetry���������������������������������������������������������������������������� 267 13.1 Facial Asymmetry Classification�������������������������������������������� 267 13.1.1 Pseudo Facial Asymmetry ���������������������������������������� 268 13.1.2 Developmental Facial Asymmetry���������������������������� 268 13.1.3 Overdevelopmental Facial Asymmetry �������������������� 269 13.1.4 Underdevelopmental Facial Asymmetry ������������������ 269 13.1.5 Craniofacial Asymmetry�������������������������������������������� 271

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13.2 New Classification of Facial Asymmetry and the Surgery-­First Approach (SFA)������������������������������������������ 272 13.3 Indications of SFA in Patients with Facial Asymmetry���������� 279 13.4 Relative Contraindications of SFA������������������������������������������ 279 13.5 Post-SFA Stability in Patients with Facial Asymmetry���������� 280 13.6 Summary �������������������������������������������������������������������������������� 295 References������������������������������������������������������������������������������������������ 295 14 Long-term Follow-up Following the Surgery-First Approach������ 297 14.1 Results������������������������������������������������������������������������������������ 297 14.2 Discussion ������������������������������������������������������������������������������ 306 References������������������������������������������������������������������������������������������ 319 15 Total Treatment Time in the Surgery-First Orthognathic Approach������������������������������������������������������������������ 321 15.1 Results������������������������������������������������������������������������������������ 339 15.2 Discussion ������������������������������������������������������������������������������ 341 15.3 Conclusions���������������������������������������������������������������������������� 343 References������������������������������������������������������������������������������������������ 343 16 Occlusal Plane-Altering Orthognathic Surgery (Jaw Rotational Orthognathic Surgery)���������������������������������������� 345 16.1 Concept of Occlusal Plane-Altering Orthognathic Surgery�������������������������������������������������������������� 345 16.2 Classification Of Occlusal Plane Altering Orthognathic Surgery�������������������������������������������������������������� 347 16.3 Surgical Techniques���������������������������������������������������������������� 358 16.4 Discussion ������������������������������������������������������������������������������ 361 References������������������������������������������������������������������������������������������ 364

About the Author

Jong-Woo  Choi, MD, PhD, MMM  Dr. JongWoo Choi (J.W. Choi) was born in 1970 and raised in Seoul, South Korea. He earned a MD degree from Yonsei University in 1996. He pursued Plastic and Reconstructive Surgery training at Severance Medical Center/Yonsei College of Medicine in Seoul and completed his residency. He continued on to the Medical College of Ulsan where he earned his PhD degree. He got the Master of Medical Management (MMM) degree in Marshall School of Business, University of Southern California (USC), US. He is a craniomaxillofacial surgeon and microsurgeon and professor & chair of plastic & reconstructive surgery in Seoul Asan Medical Center. His career goal is to contribute to restore the patients’ deformities and heal the patients with craniomaxillofacial surgery and microsurgery. To combine the craniofacial surgery and microsurgery has positioned himself to take on the most difficult reconstruction cases. He is recognized among international peers for his pioneering works on orthognathic surgery and craniofacial surgery such as surgery-first orthognathic surgery without presurgical orthodontic treatment, one-piece cranioplasty without Bandeau based on numerous SCI articles. In addition, he has also performed more than 1,200 cases of microsurgical head and neck reconstructions such as dynamic tongue and pharynx reconstruction using various perforator flaps. He also spends a great deal of time in research. His area of research is in bone regeneration using BMP-2, 3D printing scaffold and stem cells including computer simulation and 3D printing technology. He has participated in writing my books and the chapters including “Asian facial cosmetic surgery” of the new 1st, 2nd Edition Plastic Surgery Textbook authored by Peter Neligan. He has received numerous awards from the Korean Society of Plastic and Reconstructive Surgery (KSPRS). Between 2005 and 2010, he received the best paper awards 5 times from KSPRS. And he was selected as a “Young Plastic Surgeon of the Year” in 2008. He has been participating more than 10 international meetings a year as a lecturer. He was a international fellow of AOCMFS in Hanover, Germany under N.C. Gellrich and a visiting professor in department of plastic surgery in Stanford university, Shock Trauma Center, University of Maryland and MD xiii

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Anderson Medical Center between 2011 and 2012 with Sabine Girod, Eduardo Rodriguez and David Chang. He played a role as a Secretary General of International Society of Simulation Surgery (ISSIS). He is simultaneously serving and served as directors of scientific committees in 3 major societies of craniomaxillofacial surgery in Korea such as Korean society of Plastic and Reconstructive Sugeons (KSPRS), Korean Cleft palate and Craniofacial Associations (KCPCA) and Korean Society of Simulation Surgery (KSSIS). He is the current chair of Department of Plastic & Reconstructive surgery, Asan Medical Center, South Korea, which is the biggest hospital in South Korea. In addition, he is the editorial board in Plastic & Reconstructive Surgery, Annals of Plastic Surgery, Journal of Craniofacial surgery and Archives of Aesthetic plastic surgery. He is a current craniofacial section ­editor of Archives of Plastic Surgery. Jang Yeol Lee, DDS, MSD, PhD  Dr. Lee was born and raised in Seoul, South Korea, and he received his dental degree (DDS) from Yonsei University in Seoul, Korea, in 1995 and earned his master’s and PhD degrees in the same school. He completed internship and orthodontic residency at Yonsei University, Seoul, Korea, from 1995 to 1999. He is currently director of the Smileagain Orthodontic Center in Seoul, Korea, and Clinical Professor at the Department of Orthodontics of Yonsei University and Sungkyunkwan University, Seoul, Korea, and Clinical Professor at the Department of Plastic and Reconstructive Surgery, Seoul Asan Medical Center, Ulsan University, Seoul, Korea. He was an Associate Fellow of School of Dentistry at the University of Warwick, UK.  Dr. Lee is also a visiting scholar in the Department of Orthodontics, School of Dentistry at the University of North Carolina, USA, and University of California at Los Angeles, USA. Dr. Lee has treated many adult orthodontic patients focusing on aesthetics, and he is one of the pioneer clinicians of surgery-first approach having over 15 years’ clinical experience. Dr. Lee has been invited and has given many lectures on various topics about mini-screw orthodontics, surgical orthodontics with surgery-first approach, and lingual orthodontics over the last 15 years over the world. He has also organized clinical courses in many countries such as the USA, the UK, Germany, Japan, Australia, Mexico, Singapore, China, and Morocco. He has participated in writing SCI articles and chapters in textbooks. Since 2008, he has served as a member of the Board of Trustees of the Korean Association of Orthodontists. He has held a position of Secretary General of the World Implant Orthodontic Association (WIOA), and currently, he is advisory board member of WIOA.

About the Author

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History and Evolution of the Surgery-First Approach

Orthodontic and orthognathic surgical treatments are provided to patients who suffer from dentofacial deformities. These deformities not only result in malocclusions but also affect the facial profile. Therefore, surgeons and orthodontists should simultaneously consider both the facial profile and the bite occlusion to achieve the ideal correction. They also must determine the best solution for each individual patient (Fig.  1.1). Although the restoration of bite occlusion should be the fundamental basis of orthognathic surgery and orthodontic treatment, there is also a current focus on the patient’s facial profile. Regarding the orthognathic profile, dentofacial deformity could be categorized into concave and convex profile. Then, its growth pattern could be subcategorized into anterior and posterior divergent profile. Based on the individual patient’s profile and occlusal status, the best option for the orthognathic surgery should be determined. The surgery-first approach (SFA) or the surgery-­ first orthognathic approach (SFOA) is defined as orthognathic surgery without the presurgical orthodontic treatment that was, traditionally, a prerequisite to orthognathic surgery. Therefore, SFA is a concept that not only challenges the status quo but also is a new paradigm in craniofacial surgery. Traditionally, to overcome postoperative occlusal instability, presurgical orthodontic treatment was deemed to be essential for achieving successful, long-term orthognathic procedure outcomes [1]. However, since the

original cause of the dentofacial d­ eformity is a skeletal discrepancy, orthognathic surgery should be used for correction. I agree with this expression by Dr. YuRay Chen about the concept of SFA. Thus, why would the skeletal discrepancy, the fundamental etiology of the dentofacial deformity, not be corrected first? Such an approach seems rational and logical. However, a question remains regarding how to overcome the postoperative occlusal instability. Generally, there are three approaches to solving this obstacle. First, South Korean groups often make use of the fact that the SFA direction is the same as the postsurgical orthodontic treatment [2]. Second, some Japanese groups depend on the active use of pre- and postoperative tooth management, including cusp grinding and mini screw use [3]. Third, Taiwanese groups have recommended SFA, based on the regional accelerated phenomenon (RAP), using corticotomies [4]. It seems like that each group developed the surgery first approach with a little different concept. Although there is some controversy regarding who first suggested the SFA concept, a literature search for the original paper suggests that South Korean authors wrote most of the early papers. In 2002, Korean orthodontists (the “Smile Again Orthodontic Group”) published the SFA in a “The Korean journal of clinical orthodontics”, calling the procedure “functional orthognathic surgery” (Fig.  1.2). In this article, the authors

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_1

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a

b

Fig. 1.1  Differential diagnosis of a dentofacial deformity, based on the facial profile as it relates to occlusion and the facial skeleton. (a) Not only maxillomandibular relationship but also anterior and posterior facial heights determine the facial divergence. (b) Occlusion directly influences facial profile. But, the degree of change in terms of facial profile could be camouflaged with the natu-

ral dental compensation. (c) Occlusal plane angle can also change the facial profile enormously while maintaining the same occlusal relationship. Therefore, the surgeon and orthodontist should observe not only the occlusion, but also the facial divergence including the occlusal plane. Each patient requires an individualized treatment planning

1  History and Evolution of the Surgery-First Approach

3

c

Fig. 1.1 (continued)

a 1

2

3

4

5

6

Fig. 1.2  A depiction of the fundamental concept behind the surgery-first orthognathic approach. This dental model shows the surgery-first concept, involving the separation of the teeth to mimic presurgical orthodontic treatment. The

dental model describes the surgery-first orthognathic approach without presurgical orthodontic treatment. CO Oh, HB Son. Functional Orthognathic Surgery (1). The Korean Journal of Clinical Orthodontics. 2002;1(1):32–39

1  History and Evolution of the Surgery-First Approach

4

b

Fig. 1.2 (continued)

1  History and Evolution of the Surgery-First Approach

c

Fig. 1.2 (continued)

5

1  History and Evolution of the Surgery-First Approach

6

d

Fig. 1.2 (continued)

clearly addressed and described SFA, without presurgical orthodontic treatment; this would be the fundamental concept behind modern SFA from my understanding. The authors of the 2002 study insisted that SFOA, without presurgical orthodontic treatment, was possible, based on the novel, mock dental surgery that included mimicking the presurgical orthodontic treatment process for separating the teeth. The article already showed several very successful surgical clinical outcomes using the SFA concept. Korean orthodontic groups, such as the Smile Again Orthodontic Center, started using SFA in 2001, and our institution, cooperating with the Smile Again Orthodontic Group, started using SFA in 2007. Our group has suggested SFA concepts and demonstrated clinical SFA outcomes, based on feasibility testing with mock SFA dental surgeries, in multiple publications.

This balance of this chapter will address the current SFA concept, discuss the controversial issues found in the current literature, and describe our 15 years of clinical experience with SFA.

1.1

Definition and Evolution of SFA

SFA is an orthognathic approach that consists of orthognathic surgery and postsurgical orthodontic treatment, in the absence of presurgical orthodontic treatment [5]. This procedure is regarded as a paradigm shift from the traditional orthognathic approach. In the past, some orthognathic surgeries were performed without proper presurgical orthodontic treatment (Fig.  1.3). This occurred before the establishment of the traditional protocol that involves 12–18  months of

1.1  Definition and Evolution of SFA

7

Fig. 1.3 The traditional orthognathic approach requires presurgical orthodontic treatment, such as leveling, decompensation, and arch coordination, as shown in the top series of panels. Unlike in the traditional approach, decompensation of the lower and upper teeth is not performed, preoperatively, in the surgery-first approach (SFA). Thus, SFA inevitably leads to a predesigned

malocclusion status that is corrected during the postsurgical orthodontic treatment. The direction of the natural dental compensation is the same as that in the postsurgical orthodontic treatment. The evolution of the use in the miniscrew plays an important role in the rapid and effective correction of the postoperative occlusal instability

presurgical orthodontic treatment, followed by the orthognathic surgery and 6–12  months of postsurgical orthodontic treatment [6]. However, this approach cannot be regarded as SFA in keeping with the modern SFA concept. Despite some controversies, the first paper describing SFA was published, in 2002, in the Korean

Journal of Clinical Orthodontics (1(1): 32–39, 2002). This article addressed the modern concept of SFA, referred to as “functional orthognathic surgery.” The procedure was described as consisting of orthognathic surgery followed by postsurgical orthodontic treatment, without any presurgical orthodontic treatment; the procedure

1  History and Evolution of the Surgery-First Approach

8

was based on novel laboratory work. When it comes to our concept of SFA, the laboratory work of ours does not mean the simple estimation of the occlusion with presurgical orthodontics, but includes the novel process where the each teeth, separated from the dental model, were simulated. The clinical cases included in the article involved separation of the teeth, using a dental model to simulate the immediate postsurgical occlusal status, without presurgical orthodontic treatment. The model simulation of the teeth allows the surgeon or orthodontist to recreate the surgery-first status and skip the traditional presurgical orthodontic treatment. This approach remains the fundamental basis of clinical SFA applications in our practice.

1.2

Benefits and Drawbacks of SFA (Fig. 1.5 and Fig. 1.6)

The starting point of the concept of surgery-first approach is the concept of correcting the skeletal abnormality that provides the cause first, and then correcting the positional abnormality of the tooth, which is a symptom of the skeletal abnormality. Therefore, the tooth movement after surgery is a fast and natural in the forward direction by adapting the teeth to the surrounding muscles or functions and the new corrected skeletal position. In addition, from the patient’s point of view, there is a great advantage in that it is possible to quickly return to social life by improving facial appearance earlier. However, since this technique requires a completely different preparation and process from the way we have been doing for a long time, additional efforts are required from the perspective of doctors. The advantage and disadvantage of surgery-first approach can be summarized as follows. 1. Advantages 1. Direction of the postsurgical orthodontics is the same as the natural compensation. 2. Possibility of reduced total treatment time.

3. No need for aggravated gross appearance during presurgical orthodontic period. 4. Minimal disturbance of patient’s social life. 5. Patient-oriented approach; early improvement of facial esthetics. 6. Efficient surgical-orthodontic timetable; sufficient postoperative time to manage skeletal and facial changes. 7. Early correction of sleep disorders.

The goals of preoperative orthodontics for orthognathic surgery patients are:

• Elimination or reduction of dental compensation due to skeletal discrepancies. • Horizontal and vertical positioning of the anterior teeth, canine, and posterior teeth. • Establishment of an arch form coordinating with each jaw. • Alignment for irregularities of the teeth.

Tooth movements during preoperative orthodontics occur in a direction opposite to the functional compensation and result in adverse effects to the surrounding soft tissue during decompensation; it can also prolong the period of preoperative orthodontic treatment. For the patient, the movement can worsen facial esthetics, increase patient discomfort, and worsen the functional disturbance, limiting dental compensation (Fig.  1.4). Conversely, during SFA, the direction of the postoperative dental decompensation is the same as in the dental and muscle adaptation to the new, surrounding skeletal structures. This is one of the main reasons for shortening the total SFA treatment time. Another factor affecting treatment time is the regional accelerated phenomenon (RAP), which can be maximized after surgery. This phenomenon might be controversial after a certain postoperative period; however, tooth movement can be accelerated during the early

1.3  SFA Controversies

Initial

9

5M Pre-op ortho.

10M Pre-op ortho.

After Surgery

Fig. 1.4  Changes in the facial profile of a patient with a Class III dentofacial deformity during traditional orthognathic surgery (presurgical orthodontic treatment, orthognathic surgery, and postsurgical orthodontic treatment). During the traditional approach, the patient inevitably suf-

fers an aggravated facial appearance during the presurgical orthodontic treatment that requires dental decompensation, such as a labial version of the lower incisor and a lingual version of the upper incisor

postoperative period. SFA also avoids aggravating the patient’s gross appearance during presurgical orthodontic treatment. Thus, this procedure can fulfill patient demands for early improvements in facial esthetics and can minimize social life disturbances. For orthodontist, the time to observe postoperative bone healing and bone segment changes are increased, providing more latitude for handling possible postoperative skeletal relapses.

Establishing of the surgical occlusion in surgeryfirst approach will be mentioned in the following chapters, but this requires a more detailed and elaborate process than the conventional surgicoorthodontic process. Therefore, these are tasks that take time before we get used to it. In addition, the process of predicting and reproducing possible tooth movement after surgery requires some skill and experience. In addition, bended surgical wires need to be manufactured, and the postoperative care process may take a little longer due to incomplete occlusion after surgery. Although there is a great advantage that the patient’s facial aesthetics improves immediately, the facial profile after these surgery is not perfect until dental decompensation is finished, and this should be sufficiently informed to the patient before surgery. The paradigm shift at this point is the beginning, not the completion. There is no doubt that future experiences, research and technological advances will make the surgery-first approach process more comfortable and accurate.

2. Disadvantages

1. Simulation of postsurgical occlusion is time consuming. 2. More delicate and complicated short-­ term orthodontic procedures. 3. Requires accurate and experienced decisions. 4. Complicated bending of the surgical arch wires. 5. No opportunity to extract third molars, preoperatively. 6. Needs possible extended intermaxillary bony fixation period. 7. Incomplete lip and facial profile immediately after surgery. 8. Chewing difficulties, immediately after surgery, due to incomplete occlusion.

1.3

SFA Controversies

1. Stability In general, good stability in both the horizontal and vertical planes has been observed, in our experi-

10

1  History and Evolution of the Surgery-First Approach

ence, with the mandible position showing the highest associated relapse rate. Horizontally, Ko et  al. reported a mean B-point relapse of 1.44  mm (12.46%) at the one-year follow-up [4]. When comparing SFA with the traditional treatment, Kim et al. found average anterior relapses of 1.6 mm in patients undergoing traditional treatment and 2.4 mm in the patients undergoing SFA; Liao et al. reported mild horizontal relapses in both groups [7, 8]. According to our studies, vertical and skeletal stabilities are generally maintained, and dental movement in patients undergoing SFA surpassed that in patients undergoing traditional treatment [9–11].

ment time for SFA is 14.2 months (range, 10.2– 19.4 months) and that for the traditional approach is 20.16 months (range, 15.7–22.5 months) [13]. This may be due to a synergistic effect between the postoperative orthodontic force and the newly established adaptive force from the lip and the tongue in the direction of tooth movement, decreasing the time to full compensation. The temporary (a few weeks) decrease in postoperative muscle activity, bite force, and occlusal pressure may also be a facilitating factor [14]. The orthodontic treatment associated with the traditional approach has been reported to last ­ 15–24 months, preoperatively, and 7–12 months, postoperatively, with the orthodontist being the key arbiter of the treatment duration [15]. Similarly, we have reported much shorter total treatment times for SFA than for the traditional orthodontic treatment approaches reported in the literature, especially for patients not requiring tooth extractions.

2. Total treatment time Some authors insist that RAP could play a role in accelerating tooth movement during the postsurgical period because osteoblasts and osteocytes are activated for several months, postoperatively [11]. Therefore, some surgeons perform a multiple corticotomies on the maxillary and mandibular bones to induce RAP. However, in our experience, we also observed dramatically shortened treatment times, despite not performing corticotomies [6]. Thus, in our opinion, the fact that the direction of the postsurgical orthodontic movement corresponds with natural tooth compensational movements plays a much more important role in reducing the overall treatment time than does RAP.  Because we overcame the temporary, postoperative occlusal instability, postsurgical orthodontic treatment should be much more effective than presurgical orthodontic treatment for directing tooth movement. In addition, our analysis of the factors influencing total treatment time showed that tooth extraction is the most influential. This analysis also indicated that, regardless of the orthognathic approach, if the orthodontist extracts a tooth, tooth mobilization might occur for some time. Therefore, to obtain the maximal reduction in total treatment duration associated with SFA, avoiding tooth extraction is the preferred treatment choice, if possible [12]. Despite the heterogeneity of extant SFA publications, a treatment time that is shorter than that associated with the traditional approach seems to be a consistent finding. Overall, the mean treat-

3. Indications and contraindications (a) SFA indications If the desired surgical occlusion, following SFA, has been modeled to simulate postoperative orthodontic movement, all surgical cases can be theoretically treated using SFA. Clinically, however, in several situations surgical correction involving SFA is inappropriate. Hence, understanding the contraindications for SFA is necessary to understand its indications. (b) SFA contraindications (i) Severe crowding of the upper anterior teeth A blocked upper lateral incisor, on the palatal side, may significantly interfere with surgical occlusion. (ii) Severely compensated, flared upper incisors In such cases, obtaining satisfactory esthetics, immediately after surgery, may be difficult due to excessive overjet.

1.3  SFA Controversies

11

(iii) Excessively extruded upper second molars Severe mandibular prognathism causes excessive overeruption of the maxillary second molars because the maxillary and mandibular second molars do not occlude at all. If the amount of extrusion is excessive, interference with posterior surgical occlusion may compromise postoperative stability.

the tongue’s position falls, spacing occurs between the lower incisors. This may cause discordant upper and lower intercanine widths in the surgical occlusion, resulting in postoperative interference and bone instability.

(iv) Disharmony between the upper and lower intercanine widths

In cases of class II or III skeletal surgeries, partial anterior crossbite occurs. As a result, the postoperative functional adaptation of the incisors may be hindered, making postoperative orthodontic treatment very difficult.

Often mandibular prognathism results in functional displacement of the tongue; when

a

(v) Postoperative anterior crossbite

b

c

Fig. 1.5  Traditional orthognathic approach with presurgical orthodontic treatment. Traditional approach could provide us with the stable surgical outcomes. But, the total treatment time ranges from 18 month to 30 months. In

d

addition, the patient should endure the aggravated facial appearance during the presurgical orthodontic treatement period owing to the dental decompensation based on uncorrected skeletal locations

12

1  History and Evolution of the Surgery-First Approach

e

f

g

h

Fig. 1.5 (continued)

1.3  SFA Controversies

13

i

k

Fig. 1.5 (continued)

j

l

1  History and Evolution of the Surgery-First Approach

14

m

o

Fig. 1.5 (continued)

n

p

1.3  SFA Controversies

a

c

Fig. 1.6  Surgery first orthognathic approach without presurgical orthodontic treatment. My experiences for last15 years revealed that SFA turned out to be similar in terms of skeletal stability. In addition, the total treatment time decreased dramatically especially in non tooth extraction

15

b

d

cases. It could be regarded as a functional orthognathic surgery given the fact that the direction of the postsurgical orthodontic treatment is identical with that of the natural dental compensation

16

1  History and Evolution of the Surgery-First Approach

e

f

Fig. 1.6 (continued)

g

1.3  SFA Controversies

17

h

j

Fig. 1.6 (continued)

i

k

18

1  History and Evolution of the Surgery-First Approach

l

m

n

o

Fig. 1.6 (continued)

(vi) Asymmetric transverse dental compensation in facial asymmetry Severe horizontal asymmetries, in facial asymmetry patients, may result in asymmetric transverse compensation of the left and right posterior teeth. In such cases, SFA surgical occlusion may promote unilateral posterior occlusion or excessive lateral compensation of the canines, resulting in insufficient asymmetry correction.

References 1. Obwegeser HL.  Orthognathic surgery and a tale of how three procedures came to be: a letter to the next generations of surgeons. Clin Plast Surg. 2007;34(3):331–55. 2. Choi JW, Lee JY, Yang SJ, Koh KS.  The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity. Ann Plast Surg. 2015;74(3):333–41. 3. Sugawara J, Aymach Z, Nagasaka DH, Kawamura H, Nanda R. “Surgery first” orthognathics to correct a

skeletal class II malocclusion with an impinging bite. J Clin Orthod. 2010;44(7):429–38. 4. Ko EW, Lin SC, Chen YR, Huang CS.  Skeletal and dental variables related to the stability of orthognathic surgery in skeletal class III malocclusion with a surgery-first approach. J Oral Maxillofac Surg. 2013;71(5):e215–23. 5. Choi JW, Bradley JP.  Surgery first orthognathic approach without presurgical orthodontic treatment: questions and answers. J Craniofac Surg. 2017;28(5):1330–3. 6. Jeong WS, Choi JW, Kim DY, Lee JY, Kwon SM. Can a surgery-first orthognathic approach reduce the total treatment time? Int J Oral Maxillofac Surg. 2017;46(4):473–82. 7. Kim JY, Jung HD, Kim SY, Park HS, Jung YS.  Postoperative stability for surgery-first approach using intraoral vertical ramus osteotomy: 12-month follow-up. Br J Oral Maxillofac Surg. 2014;52(6):539–44. 8. Liao YF, Chen YF, Yao CF, Chen YA, Chen YR. Long-­ term outcomes of bimaxillary surgery for treatment of asymmetric skeletal class III deformity using surgery-first approach. Clin Oral Investig. 2019;23(4):1685–93. 9. Jeong WS, Lee JY, Choi JW.  Large-scale study of long-term anteroposterior stability in a surgery-first orthognathic approach without presurgical orthodontic treatment. J Craniofac Surg. 2017;28(8): 2016–20.

References

19

10. Jeong WS, Lee JY, Choi JW.  Large-scale study of 1 3. Peiro-Guijarro MA, Guijarro-Martinez R, Hernandez-­ Alfaro F.  Surgery first in orthognathic surgery: a long-term vertical skeletal stability in a surgery-­ systematic review of the literature. Am J Orthod first orthognathic approach without presurgical Dentofacial Orthop. 2016;149(4):448–62. orthodontic treatment: part II.  J Craniofac Surg. 14. Uribe F, Adabi S, Janakiraman N, Allareddy V, 2018;29(4):953–8. Steinbacher D, Shafer D, et  al. Treatment duration 11. Yaffe A, Fine N, Binderman I.  Regional acceland factors associated with the surgery-first approach: erated phenomenon in the mandible followa two-center study. Prog Orthod. 2015;16:29. ing mucoperiosteal flap surgery. J Periodontol. 15. Luther F, Morris DO, Hart C.  Orthodontic prepara1994;65(1):79–83. tion for orthognathic surgery: how long does it take 12. Jeong WS, Choi JW, Kim DY, Lee JY, Kwon and why? A retrospective study. Br J Oral Maxillofac SM.  Corrigendum to “Can a surgery-first orthognaSurg. 2003;41(6):401–6. thic approach reduce the total treatment time?”. Int J Oral Maxillofac Surg. 2017;46(9):1203.

2

Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

There are three main goals of orthognathic surgery (Fig. 2.1). The first is the functional recovery of normal oral and maxillofacial structures. This functional recovery includes the normal positioning of the jawbones, physiological positioning of the mandibular condyle, and creating the ideal occlusal relationship. The second is the recovery of aesthetics. Abnormal or asymmetrical disharmony of the jaw causes poor esthetics, and facial esthetics can be restored through orthognathic surgery; the restoration of esthetics is the most desired surgical goal for patients. Third is recovery from psychosocial problems. Poor facial esthetics, caused by long periods of jaw discomfort, can reduce individual self-­esteem. This makes the Fig. 2.1  The three main goals of orthognathic surgery: improved function, aesthetics, and psychosocial state

improved internal psychological state that results from orthognathic surgery a very meaningful goal [1–5]. Therefore, the surgical treatment objectives of orthognathic surgery patients should be determined with careful consideration of all three aspects.

2.1

Communication Between Surgeons and Orthodontists in the Surgery-First Approach

Communication and discussion between the attending maxillofacial surgeons and orthodontists are essential for the planning of orthognathic

3 Goals of Surgico-orthodontics

Aesthetics

Function

Functional occlusion Masticatory Swallowing TMJ Speech Stability

Dentofacial harmony Facial profile Proportion Individual preference Cultural trends

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_2

Psychosocial Aspects

Self-esteem Body image Social Functioning Mental Health Quality of Life

21

22

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

surgeries. In the past, the role sharing associated with conventional surgical correction involved orthodontists planning and implementing a preoperative orthodontic treatment that aimed to develop the ideal occlusion; the orthodontist determined when the preoperative orthodontic treatment was complete. During the orthognathic surgery period, the actual surgical plan was often determined by the surgeon who decided the appropriate location of the jawbones and determined the detailed surgical plan, based on the final surgical occlusion recommended by the orthodontist. However, Surgery-First Approach (SFA) requires a slightly different approach that involves the establishment of occlusion and the final positioning of the jawbones from the beginning of treatment. In other words, the ideal occlusion and the positioning of the jawbones should be determined at the same time, requiring detailed communication between the attending surgeon and the orthodontist. First, the clinicians need to determine whether SFA is appropriate. This may depend on whether the simulation of the final postoperative occlusion can be predicted accurately and easily, whether such predictions can be surgically achieved, and whether the simulated surgical occlusion can be managed adequately during postoperative bone segment healing and fixation. The final decision should be determined after considering whether the process interferes with postoperative stability, a determination largely made by orthodontists. Just like in the conventional orthognathic process, the actual occlusion setting process includes occlusal simulation and predictions performed mainly by the orthodontist, with the skeletal positioning reflecting the opinions of the surgeon. However, since this process should not be disjointed, a systematic communication process between the surgeons and the orthodontists need to be established at the beginning of the case.

2.2

Surgery-First Approach Sequence

In general, there are not any major differences between the procedures involved in traditional orthognathic surgery and SFA.  The biggest difference is that the preoperative orthodontic treatment is simulated outside the mouth, rather than being performed on the patient. Based on the modeling, surgical occlusion is established and reflected in the orthognathic surgery plan (Fig. 2.2).

2.3

Establishment of the Surgical Treatment Objectives

The surgical plan for orthognathic patients is mostly based on lateral cephalometric radiographs. There have been numerous attempts to establish a surgical plan using three-dimensional (3D) data, and this will become more common in the future; however, in this description, we will describe the traditional two-dimensional surgical planning method. Additionally, the application of 3D images in the treatment of orthognathic patients will be described in later chapters. The target of orthognathic surgery is not necessarily the pursuit of a “normal” outcome. For example, the “normal” locations of the maxilla and mandible differ among races and between genders. In some cases, the target depends on the individual patient. Therefore, we need to pay attention to the fact that the “normal” we refer to reflect mean values rather than a dichotomy between normal and abnormal. The following case will explain the throughout procedures establishing surgical treatment objectives for the SFA (Figs.  2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and 2.9).

2.4  Surgical Treatment Objective (STO)—Paper Surgery in FOS

23

Surgery-first approach; Differences in procedure

Conventional Orthognathic Surgery

Surgery-first approach

1.

Initial Diagnosis

1.

Initial diagnosis

2.

Surgical planning – STO

2.

Surgical planning – STO

3.

Pre-surgical orthodontic Tx

3.

Simulation of pre-surgical ortho. Tx

4.

Surgical arch wire

5.

Fabrication of wafer

4.

Simulation of orthognathic surgery

6.

Orthognathic surgery & post op. care

5.

Surgical arch wire

7.

Orthodontic re-diagnosis

6.

Fabrication of wafer

8.

Orthodontic treatment

7.

Orthognathic surgery & post-op. care

9.

Finishing

8.

Orthodontic re-diagnosis

9.

Orthodontic treatment

: Model mounting & Model set-up

10.

Finishing

Fig. 2.2  Differences in the sequence of steps between the conventional orthognathic approach and the surgery-first approach. The most notable difference is that the presurgi-

cal orthodontic treatment procedure (traditional approach) is replaced by a simulation of presurgical orthodontic treatment (SFA)

2.4

preoperative orthodontic planning, based on a paper surgery. First, set the FH plane, nasion-FH perpendicular line, FH-AB plane angle, FH-A′B′ plane angle, and FH occlusal plane as reference lines (Fig.  2.6). In Surgery-first approach method, additional procedure of intraarch adjustment of will be added before positioning of jaw bones. This procedure needs to be decided based on the setup model surgery procedure, which will be described in the next chapter.

Surgical Treatment Objective (STO)—Paper Surgery in FOS

1. General measurement and reference lines 2. Intra-arch adjustment; maxillary dentition 3. Intra-arch adjustment; mandibular dentition 4. Positioning of maxilla 5. Positioning of mandible 6. Genioplasty decision 7. Final profile adjustment and evaluation The following describes the Surgical Treatment Objective (STO) stages of

24

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

Fig. 2.3  A patient with typical skeletal Class III deformities, including a prognathic mandible and long face

2.4  Surgical Treatment Objective (STO)—Paper Surgery in FOS

Fig. 2.4  Lateral and frontal cephalometric radiographs. The patient’s chin deviates to the left

25

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

26

2.5

Surgery-First Approach Clinical Procedure

sion right after surgery. In general, after the intermaxillary fixation period, the start of postoperative orthodontic treatment is determined through an observation period of 4 to 8 weeks after surgery while part-time wearing a surgical wafer. In some cases, it may be possible to delay the start postoperative orthodontic treatment, unlike the conventional method.

The chart in Fig. 2.11 summarizes the SFA clinical process. Basically clinical process for SFA will not be different with conventional surgery process except the post-operative care needs to be emphasized more considering unstable occlu-

a

Dental

Skeletal Dental

b

1. Incisor Inclination

55 65

2. Position of Mx. Anterior area

U1 to Uop

55°

L1 to Lop

65°

Fig. 2.5  Cephalometric measurements for surgical treatment objective determinations. All measurement can varies depend on each ethnical norms and following numbers are based on Korean norms [6]. (a) Incisor inclination; parameter determining post-operative dental decompensation, (b) Positioning of maxillary anterior; anterior vertical position of maxilla needs to be determined with the verti-

A to NP

0 mm

U1 to STMu 2 mm

cal position of incisors and amount of incisor showing, (c) Inclination of occlusal plane and maxillomandibular inclination, (d) Chin position; determining genioplasty advancement, (e) Lower facial height; determining genioplasty reduction, (f, g) Thickness of soft tissue; related to determine both dental and skeletal anteroposterior position

2.5  Surgery-First Approach Clinical Procedure

c

27

d

Skeletal Dental

3. FH to Uop, FH to AB

Skeletal Soft Tissue

4. Chin position

14

45 %

81 • FH to Uop

14°

• FH to AB

81°

55 %

4mm

e

g

Skeletal Soft Tissue

SkeletalSoft Tissue

f 6. Thickness of Soft tissue

5. Lower facial Height

1

+5mm

2 (Female 1.8, Male 2.0)

+2.5mm - 4.5mm - 3mm

Skeletal Soft Tissue

7. Thickness of Soft tissue (Ratio)

FH to A’B’ 81° 4 2 2 1

Fig. 2.5 (continued)

28

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

Fig. 2.6 Basic reference lines for lateral cephalometric measurements

Reference lines

FH plane Nasion-FH perpendicular FH-AB plane angle FH-A’B’ plane angle FH Occlusal Plane Lower 1/3 ratio

a

Fig. 2.7  Surgical treatment objective procedure for the surgery-first approach, including paper surgery and model setup. Intra-arch adjustment will be done based on model

b

setup procedure (Chapter 3) and model setup chart is useful for communication with dental technician

2.5  Surgery-First Approach Clinical Procedure

c

Fig. 2.7 (continued)

29

30

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

d

e

f

g

h

Fig. 2.7 (continued)

2.5  Surgery-First Approach Clinical Procedure

31

a

b

Fig. 2.8  Throughout progress of orthodontic treatment and comparison of intraoral photos between initial state and final state after debonding

32

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

c

Fig. 2.8 (continued)

2.5  Surgery-First Approach Clinical Procedure

33

a

b Fig. 2.9  Comparison of extraoral photos between initial state, 8 weeks after surgery and final state after debonding

34

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

a

b

Fig. 2.10  Comparison and superimposition of lateral cephalometric radiographs between initial, post-op 2weeks, post-op 8weeks and debonding. Final lateral

cephalometric radiograph shows that it is almost identical to the originally planned STO

2.5  Surgery-First Approach Clinical Procedure

c

d

Fig. 2.10 (continued)

35

2  Surgical Treatment Objectives and the Clinical Procedure for the Surgery-First Approach

36

Flow chart and roles in Surgery-first approach Pre-op 4wks Initial exam, Records Pre-op 3wks Dx, Consultation Tentative STO Pre-op 2wks Basic pre-op exam Pre-op 1wks OMFS Surgeon

SAW, Final Records, Lab preparation for set-up

Set-up, Surgical Occlusion Pre-op Lab procedure Final STO, Wafers

Orthodontist

Post-op 0-2wks MMF, Post-op care Post-op 2-4wks Active PT, C-P every week Post-op 4-8wks Observation Post-op 8wks~ Post-op ortho. Tx

Deband~

Periodic F/U Every Year

Patient

Fig. 2.11  Surgery-first approach: flow chart and roles. Good communication between the orthodontist, surgeon, and patient ensures a successful outcome

References 1. Kiyak HA, Hohl T, West RA, McNeill RW.  Psychologic changes in orthognathic surgery patients: a 24-month follow up. J Oral Maxillofac Surg. 1984;42(8):506–12. 2. Kim SJ, Kim MR, Shin SW, Chun YS, Kim EJ. Evaluation on the psychosocial status of orthognathic surgery patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2009;108(6):828–32. 3. Liddle MJ, Baker SR, Smith KG, Thompson AR. Psychosocial outcomes in orthognathic surgery:

a review of the literature. Cleft Palate Craniofac J. 2015;52(4):458–70. 4. Zingler S, Hakim E, Finke D, et  al. Surgery-first approach in orthognathic surgery: psychological and biological aspects—a prospective cohort study. J Craniomaxillofac Surg. 2017;45(8):1293–301. 5. Jung MH.  Quality of life and self-esteem of female orthognathic surgery patients. J Oral Maxillofac Surg. 2016;74(6):1240.e1–7. 6. Yang SD, Suhr CH. F-H to AB plane angle (FABA) for assessment of anteroposterior jaw relationships. Angle Orthod. 1995;65(3):223–32.

3

Model Surgery Setup in the Surgery-First Approach

3.1

Model Setup Procedure

1. Mounting procedure The Z4 dental articulator is a specially designed instrument that can be utilized for mounting dental casts for patients undergoing the surgery-first approach (SFA) (Fig. 3.1). The main components of this articulator are the detachable magnetic plates that hold the maxillary and mandibular models. The thin magnetic plates have a uniform thickness and can be stacked; the final models of the upper and lower arches are ultimately attached to a transparent acrylic plate, using conventional gypsum. Another characteristic part of this articulator is the throttling plate that allows three-dimensional (3D) control of the maxillary surgery. The regulator allows the desired surgical position of the maxilla to be simulated, without cutting the gypsum board. (a) Face-bow transfer Like mounting a conventional surgical patient on a dental articulator, a face-bow application is needed to view the 3D spatial location of the maxilla relative to the rest of the skull (Fig.  3.2). Clinically, careful attention is required to compare the extent of left and right canting of the maxilla. Based on the Frankfort

Fig. 3.1  A photograph of the Z4 Articulator

horizontal plane, the maxilla is positioned, and the bite fork is fixed. Often, when the vertical positions of the right and left external ear rods are different, the surgical plan may need to be calibrated. (b) Mounting models First, three pairs of models are mounted onto the Z4 Articulator, using the maxillary face-bow and bite occlusion information (Fig.  3.3). One model pair is set up to allow individual tooth movements (Fig.  3.4). The remaining pairs are

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_3

37

3  Model Surgery Setup in the Surgery-First Approach

38

Fig. 3.2  Clinical application of the face-bow transfer

Fig. 3.3  Mounting models for wafer creation

used to create an intermediate wafer, which will guide the later maxillary surgery, and a final wafer that will allow the final postoperative occlusion.

dicular to the mounting plate, for each reference tooth (Fig. 3.5).

2. Individual setup procedure

A centerline is drawn on each arch to allow a symmetry evaluation using an arch-form template.



(a) Drawing vertical and horizontal reference lines

Before moving teeth, a horizontal line is drawn parallel to the mounting plate to establish a baseline on the mounted model that allows for isolated tooth movements among three pairs of mounted models. In the same way, a vertical reference line is drawn, perpen-

(b) Drawing midlines and checking symmetry

(c) Basic linear measurements The next step is to record the basic, pre-setup information. Vertically, this involves measuring the vertical distance between the mounting plate and the anterior, premolar, and posterior cusps, and measuring the canine width, interdental width, and arch depth. Horizontally, the shortest

3.1 Model Setup Procedure

39

Fig. 3.4  Mounting the individually cut model

Fig. 3.5  Drawing of the vertical and horizontal reference lines

horizontal distance between the anterior teeth and the incisal pin is measured and recorded; this provides the standard when each tooth is later moved, as directed by the orthodontist (Fig. 3.6).

(e) Final measurements and record checks When the final setup is complete, the amount of individual tooth movement is recorded and the final occlusion is corrected and confirmed by the doctor.

(d) Individual tooth setup 3. Maxillary surgery The orthodontist will design and order the movement of each individual tooth to its designated position, based on the surgical treatment objective (STO), and indicate any transverse width changes. The use of a proper work instruction sheet facilitates smooth communication between the doctor and technician (Fig. 3.7).

The maxillary surgery procedure is totally based on the STO.  The front, back, and side screws of the maxillary surgical module, used to attach the model to the articulator are adjusted to position the model in the following directions (Fig. 3.8):

40

3  Model Surgery Setup in the Surgery-First Approach

Fig. 3.6  Basic, linear measurements

Fig. 3.7  Setup of the individual tooth locations, according to the orthodontist’s orders (please refer to Fig. 2.7 in Chap. 2)

Fig. 3.8  Fabricating the maxillary module, prior to maxillary surgery

(a) Posterior vertical—to revise the amount of maxillary posterior impaction (right and left) (b) Anterior vertical (c) A–P horizontal

(d) Yaw (e) Lateral—to establish the midline and arch symmetry

3.1 Model Setup Procedure

4. Intermediate wafer fabrication With the initial model mounted, the mandible is in its original position and the maxilla is ready to undergo surgery. The intermediate wafer is fabricated using the mounting shown in Fig. 3.9. 5. Mandibular surgery After the maxillary surgery has been performed, the initial models are replaced with the model created after the setup. At this point,

41

the upper and lower arches are engaged to produce the surgical module (Fig.  3.10). Once this occurs, the initial surgical planning can be rechecked to ensure that it has been successfully modeled. If the position of the mandible is not located at the planned position, there may have been an error in the setup process. Thus, the setup process must be corrected, and the possible errors found. 6. Final surgical occlusion and final wafer fabrication

Fig. 3.9  Intermediate wafer fabrication

Fig. 3.10  Mandibular surgery and creation of the surgical module from the setup model

42

3  Model Surgery Setup in the Surgery-First Approach

a

b

Fig. 3.11  Final surgical occlusion and final wafer fabrication. Setup models were switched to original initial models and incisal pin of articulator is opened due to the premature contact on the 2nd molars and premolars

If the final mandibular position is acceptable, the final surgical occlusion can be modeled after the setup model mounting has been replaced by the initial model, with the maxillary surgical module and mandibular module inserted. At this point, the final wafer is produced and used in the operating room (Fig. 3.11). Vertical prematurity can occur in many patients during this process, resulting in an open bite. In particular, the articulator’s incisal pin

may start to float, mostly due to occlusal interference by the second molar. This results in a backward and downward rotation of the mandible. However, this rotation of the mandible is not permanent, and it can return to its original position once the occlusal interference is removed during the postoperative orthodontic period. Therefore, this backward and downward rotation of the mandible is temporary and transient (Fig. 3.12).

3.1 Model Setup Procedure

43

a

b

Fig. 3.12  Mandibular opening on final surgical occlusion. This transient mandibular backward and downward rotation will be closed to the planned position of STO during post-operative orthodontic period

The amount of mandibular backward and downward rotation caused by occlusal ­interference can be calculated, but this is not clinically meaningful. Because the final, planned STO assumes the completion of the orthodontic treatment, it is expressed in the articulator using the setup model. Since the extent of the actual mandibular surgery is measured on the setup model, mounted on the articulator, the amount of postoperative mandibular backward and

downward rotation does not need to be measured. The mandible tends to move forward and upward as tooth movement begins during the bone fixation period or during the postoperative correction period. Such mandibular movement may be regarded as a postoperative relapse but, strictly speaking, this mandibular movement is not a relapse. This is because the final position of the mandible, which has moved forward and

44

3  Model Surgery Setup in the Surgery-First Approach

upward, is that originally planned in the STO.  Thus, this mandibular movement, following the removal of the vertical prematurity, is more accurately referred to as the predicted or planned mandibular seating.

and based on this, it is possible to simulate the 3D surgical planning and finally set the surgical occlusion (Fig. 3.13). The technical consideration is the convenience and accuracy of this virtual setup process. In order to make the final surgical occlusion from 3D digital data for surgery first approach, it is necessary to merge the virtual setup data using the scan data of the tooth model and CT data for the movement of the jaw. At the present time, the merging process using different programs is required, and this is a very time-consuming work (Fig. 3.14). Considering the pace of technological progress, it seems certain that we will soon meet a program that solves these problems. If more desired, in a near future, combined merging with 3D facial scan data as well as tooth surface scan data and CT data will make surgical preparation process for SFA more accurate and convenient for our clinicians.

3.2

Virtual 3D Model SetUp

For last two decades, various attempts have been tried to apply 3-dimensional CAD, CAM technology to orthognathic surgery. The scope of application is increasing, such as making surgical wafers based on CT data, simulating surgery, or printing surgical guides for bone fixation required in the operating room [1, 2]. This 3D digital application can be usefully applied to surgery-first approach, especially in the model setup process [3–5]. Through the virtual setup process, it is possible to simulate the preoperative orthodontic movement as described above,

3.2  Virtual 3D Model SetUp

45

a

b

Fig. 3.13  Virtual setup using combined tooth surface scan data and CT data (Korean J Orthod. 2014;44(6):330–41)

46

3  Model Surgery Setup in the Surgery-First Approach

a

b Fig. 3.14  Virtual set-up process and virtual surgery process with different programs for SFA (Autolign®, Diorco, Korea & Mimics® Materialise, Belgium)

3.2  Virtual 3D Model SetUp

47

c

d

Fig. 3.14 (continued)

48

3  Model Surgery Setup in the Surgery-First Approach

References

3. Im J, Kang SH, Lee JY, Kim MK, Kim JH. Surgery-­ first approach using a three-dimensional virtual setup and surgical simulation for skeletal class III correction. Korean J Orthod. 2014;44(6):330–41. 4. Kim JH, Park YC, Yu HS, Kim MK, Kang SH, Choi YJ. Accuracy of 3-dimensional virtual surgical simulation combined with digital teeth alignment: a pilot study. J Oral Maxillofac Surg. 2017;75(11):2441. e1–2441.e13. 5. Badiali G, Costabile E, Lovero E, et al. Virtual orthodontic surgical planning to improve the accuracy of the surgery-first approach: a prospective evaluation. J Oral Maxillofac Surg. 2019;77(10):2104–15.

1. Uribe F, Janakiraman N, Shafer D, Nanda R. Three-­ dimensional cone-beam computed tomographybased virtual treatment planning and fabrication of a surgical splint for asymmetric patients: surgery first approach. Am J Orthod Dentofac Orthop. 2013;144(5):748–58. 2. Kang SH, Kim MK, You TK, Lee JY. Modification of planned postoperative occlusion in orthognathic surgery, based on computer-aided design/computer-aided manufacturing-engineered preoperative surgical simulation. J Oral Maxillofac Surg. 2015;73(1):134–51.

4

Postoperative Care of Patients Undergoing the Surgery-First Approach and Postoperative Orthodontics Involving Temporary Anchorage Devices

4.1

Postoperative Care of Patients Undergoing the Surgery-First Approach

History of Orthognathic Surgery Since the introduction of the first mandibular surgery involving Blair’s ostectomy, in 1907 [1], two mandibular surgery methods, introduced in the 1950s, have been used (Fig. 4.1). The first is intraoral vertical ramus osteotomy (IVRO) and the second is sagittal split ramus osteotomy (SSRO) [2, 3]. Currently, both procedures are widely used; each has different features, advantages, and disadvantages. The following is a comparison of specific aspects of sagittal split ramus osteotomy and intraoral vertical ramus osteotomy (Table 4.1).

1. Postoperative care differences between SSRO and IVRO SSRO and IVRO have different areas for resecting bone segments and different muscles attached to each bone segment. In addition, as mentioned in the table above, because the mechanism of bone healing of segments is different, the postoperative fixation method is different, which leads to differences in the postoperative care. The following is a summary of the differences in the post-operative care method for each technique, and even in the case of surgery-first approach, the same principles and procedures are accompanied for post-operative care for each technique.

SSRO

IVRO

Fig. 4.1  Two major methods for mandibular setback surgery; sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO)

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_4

49

50

4  Postoperative Care of Patients Undergoing the Surgery-First Approach and Postoperative…

Table 4.1  Comparison of specific aspects of sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) [8] Osteotomy

Bone healing Bone fixation Condylar head Postop MMF Prognosis

SSRO Posteroanterior sagittal split Open procedure Along IANV Frequent exposure of IANV Contact on marrow to marrow Rigid internal fixation Original position None or shorter period Weakly dependent on PT

IVRO Lateromedial cut Blind procedure Rear to IANV No exposure to IANV Contact on cortex to cortex No fixation New equilibrated position Required (for 7–10 days) Strongly dependent on PT

IANV inferior alveolar neurovascular bundle, PT physiotherapy, MMF maxillomandibular fixation, SSRO sagittal split ramus osteotomy, IVRO transoral vertical ramus osteotomy

SSRO • Short-term intermaxillary fixation • Early distal segment stability • Requires fixation (plate, screws) –– Requires a second surgery • Inferior alveolar neurovascular bundle • Possible proximal segment displacement –– Sagging, torque (relapse), temporomandibular joint problems IVRO • Date of procedure to bone healing is about 6–8 weeks • 1–2 weeks of care by the surgeon • 3–8 weeks of care by the orthodontist • Depends on the mandibular position during the bone healing period Physiotherapy (PT) protocol for patients undergoing the surgery-first approach (IVRO) • Intermaxillary fixation with the final wafer –– 1–2 weeks • Active PT with the final wafer in position –– 2–4 weeks 1 hr of PT after each meal (3 h/day) Elastic fixation for the balance of the day and during sleep

–– 4–5 weeks 1 hr of PT after each meal (3 h/day) Elastic fixation during sleep –– 5–8 weeks Observation period; PT if necessary Elastic fixation only during sleep

4.2

Postoperative Orthodontics Combined with the Use of Temporary Anchorage Devices

History of Temporary Anchorage Devices (TADs) Use in Orthodontics In 1945, Gainsforth and Higley [4] first attempted to implant a vitalium implant into an animal’s bone and use it as an orthodontic anchor. In 1988, Creekmore and Eklund reported the surgical use of a vitalium screw below the anterior nasal spine, successfully permitting intrusion of the upper incisors [5]. The clinical use of skeletal anchorage was reported in a 1997 paper by Kamoni, using a small, titanium, surgical screw [6]. Umemori and Sugawara reported cases involving the surgical implantation of miniplates to correct open bites [7]. Since 2000s, various studies regarding the use of such skeletal anchors have been published, indicating that it is possible to secure tooth movement and achieve absolute anchorage, which were previously difficult tasks in the orthodontic field. Since 2002, the Asian Implant Orthodontic Conference has been held annually, in South Korea, Japan, and Taiwan, to discuss the clinical application of skeletal anchorage. Beginning in 2008, the conference has been expanded to become the World Implant Orthodontic Conference, which contributes to the development of skeletal anchorage in the orthodontic field.

4.3

Application of TADs in the Surgery-First Approach

The use of skeletal anchorage in the orthodontic field is a major paradigm shift. It is a huge change that teeth can be moved in a direction that was previously considered impossible, and this applies equally to patients with orthognathic surgery.

4.3  Application of TADs in the Surgery-First Approach

51

Even if the patient undergoes preoperative orthodontic treatment in the conventional method, it is possible to perform more efficient preoperative dental decompensation. The role of TADs in the surgery-first approach can be emphasized in two aspects. The first is that no matter which stage it is applied to, it can be selectively applied strategically, and it is possible to apply retractive and intrusive forces that can solve the horizontal and vertical compensation that are commonly seen in surgery-first approach. In addition, TADs implanted in the bone can be effectively applied to prevent skeletal relapse after surgery. The following cases show examples of TADs applied to patients with surgery-first approach in each stage and circumstance. Application of TADs according to the surgery stage

–– Active management of preoperative prematurity In patients with skeletal Class III deformations, sagittal dental compensation occurs in an anteroposterior direction; sagittal and transverse compensation can be observed. In patients with excessive mandibular vertical growth, vertical compensation could also be observed in the maxillary premolar area (Fig. 4.2). Such sagittal and vertical compensation may interfere with surgical occlusion in patients undergoing the surgery-first approach. This type of occlusal interference may be actively removed during the preoperative preparation procedures. Occlusal interference is removed by providing selective intrusion, using mini-screws that are applied mainly in the maxillary premolar area (Fig.  4.3). The mini-screws are often placed on the palatal side on premolar maxilla, but they can also be placed on the buccal side, particularly in patients with unilateral asymmetry (Fig. 4.4).

1. Before surgery: preparing for the surgery-­first approach

a

c

Fig. 4.2 (a) Sagittal compensation in a patient with a skeletal Class III deformity. (b) Sagittal and transverse compensation can be observed, as well as transverse compensation that is caused by the retro-positioned maxilla.

b

d

(c) In patients with excessive mandibular vertical growth, vertical compensation is apparent in the maxillary premolar and molar areas

4  Postoperative Care of Patients Undergoing the Surgery-First Approach and Postoperative…

52

a

b

Fig. 4.3  For patients with occlusal interference following the surgery-first approach, two mini-screws can be placed, and an intrusive force applied, to eliminate the interference

Fig. 4.4  This surgery-first patient had occlusal interference involving her right first premolar. One mini-screw was applied for selective intrusion, before surgery. This

type of proactive approach provides more stable postoperative occlusion

2. Immediately after surgery: during maxillomandibular fixation and bone healing

the transient bite opening, early application of TADs is helpful for intruding the upper second molars (Fig. 4.5). The method and duration of postoperative intermaxillary jaw fixation vary slightly between surgeons. However, tight intermillary fixation is usually performed for 2 weeks. After this period, the mini-screws may be used for the selective intrusion of the posterior second molar (Fig. 4.6).

During the surgery-first approach, the final surgical occlusion can be preoperatively visualized using simulated tooth setup procedures. For most final surgical occlusions, these procedures can be used to demonstrate the anticipated vertical prematurity and temporary bite opening. To manage

4.3  Application of TADs in the Surgery-First Approach

53

Fig. 4.5 A patient who underwent the surgery-first approach showed vertical occlusal interference involving her upper second molars. During the bone healing period,

temporary anchorage devices were used to control the vertical interference

a

b

Fig. 4.6  Most of the posterior part of the surgical wafer covering the second molar was cutoff and lingual buttons were bonded to the palatal side of the palatal cusps of the upper second molars; elastic chains were also connected to mini-screws. This patient underwent the surgery-first

approach and showed vertical occlusal interference involving her upper second molars. During the bone healing procedure, temporary anchorage devices were used to control the vertical interference, in addition to using intermaxillary fixation and physical therapy

54

4  Postoperative Care of Patients Undergoing the Surgery-First Approach and Postoperative…

The forward and upward counterclockwise rotation of the mandible, during this period, is described in Chap. 3. 3. After Surgery: postoperative Orthodontics In surgery-first approach, after 4 to 8 weeks of bone healing period, orthodontic brackets will be bonded for the postoperative orthodontic treatment. During the postoperative orthodontic period, TADs can be applied in various situations. Among patients with skeletal Class III deformations, those with large amounts of maxillary incisor sagittal compensation may require extraction of the upper premolars to provide the ­appropriate amount of postoperative maxillary incisor decompensation. The surgery-first approach in this type of patient may yield surgical occlusion that is associated with a large amount of horizontal overjet and unstable occlusion during the postoperative bone healing

p­ rocess. In such cases, the patient might adopt habitual mandibular protrusion, after surgery, while seeking better ways of chewing. Such habits increase the risk of early relapse, but TADs can be used to effectively manage this type of habitual mandibular movement. Intermaxillary elastics, hooked to the TAD and attached to the interseptal alveolar bone of the maxilla and mandible can generate horizontal vector forces and prevent the development of a protruding mandible habit. This intermaxillary force, exerted on each jaw, also generates a vertical force that may be advantageous for eliminating vertical occlusal prematurity. TADs can also be used as a method to compensate for insufficient surgical correction or error such as remained canting, midline deviation, lip protrusion after surgery. In addition, TADs are sometimes used for dental decompensation of upper dentition without extraction or for dealing with late relapse. Clinical cases according to each situation are as follows.

4.3  Application of TADs in the Surgery-First Approach

55

Case Report 4.1; Preventive management of early relapse 26Yrs, Female C.C. : Mn prognathism, Facial Asymmetry Method II 80.4 85.7*** 31.4*

-5.3>

G-Sn/Sn-Me'

1.07

Gonial Angle (Ar-Go-Gn) (deg) 129.55*

4.79* 15.18*** 120.52

92.70>>

-2.46 10.29

61.25**

6.14***

77.29**

88.34*

B-Pog (mm)

G-Pog'(//HP)

Fig. 5.7 (continued)

0.79 **

94.40

10.30

99.06

Mentolabial Sulcus (mm)

5.50

1.20

6.32

STMs-U1

2.00

1.20

1.07

Sn-STNs/STMi-Me

0.49

0.20

0.61

Nasolabial Angle (deg)

c

0.10

5.3  Vertical Position of the Maxilla in Mandibular Retrognathism (Type I)

79

d

e

Maxilla ANS–vertically maintained - Lt: 0.5mm impaction (cannie) 2.0mm impaction (1st molar) 5.0mm impaction (PNS) - Rt 0.5mm impaction (cannie) 2.0mm impaction (1st molar) 5.0mm impaction (PNS) - Incisal Tip position: horizontally 1.0mm retraction & vertically maintained - Center of Rotation: cement-enamel junction of upper incisor Midline: Maintained Mandible - Lt: SSRO advancement (1.0mm at 1st molar, 9.0mm at Mn. Border) - Rt: SSRO advancement (1.5mm at 1st molar, 10mm at Mn. Border) -B-point: 4.0mm advancement -Chinpoint: 9.0mm advancement -Genioplasty : Reduction 4mm, advancement 2mm

f

Fig. 5.7 (continued)

80

g

h Fig. 5.7 (continued)

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

5.4  Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)

81

i

Fig. 5.7 (continued)

5.4

Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)

In Type II malocclusions, the vertical position of the maxilla shows excessive growth of the anterior part and normal growth of the posterior part. This growth pattern involves hyperdivergent mandibular growth, with a deep occlusal plane. Excessive vertical growth of the anterior part results in a gummy smile and results in compensatory vertical extrusion of lower inci-

sors and a deep anterior overbite. In this case, the goal of preoperative orthodontic treatment will involve flattening the curve of Spee by intruding the lower incisors or extruding the lower premolars. The surgical plan involves the upward movement of the anterior part of the maxilla (anterior nasal spine impaction) and maintenance of the vertical position of the posterior part (posterior nasal spine). This adds the effect of forward mandibular movement due to spontaneous counterclockwise rotation of the mandible (Fig. 5.8).

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

82

a

Mx. Anterior

Mx. Posterior Normal

Type II

+ Excess

b

73.5** 67.2***

Method II

6.3** 98.6*

58.0>>

17.2**

N-A

0.90

3.20

-12.06 >

L1-MP (mm) U6-NF (mm)

43.20

2.50

50.80 ***

24.50

1.50

25.90

L6-MP (mm)

35.40

2.30

34.99

PNS-ANS (mm)

53.40

3.50

61.25 **

Ar-Go (mm)

50.40

4.00

42.42 *

Go-Pog (mm)

81.70

4.10

76.10 *

0118.10

5.10

127.25 *

U1-NF (mm)

107.2

127.4* 6.3***

38.4* 67.4

22.3>> 89.0***

109.8* -5.0

70.5***

13.8* 9.2 *** 93.7

Gonial Angle (Ar-Go-Gn) (deg)

0.95 58.33 **

B-Pog (mm)

6.90

1.60

5.77

OP-MP Angle (deg)

11.40

4.00

30.01 *

A-B U1-NF Angle (deg)

-2.80

2.50

115.40

6.00

L1-MP Angle (deg)

94.90

5.60

9.10

3.80

23.18 ***

6.20

3.50

4.45

G-Pog'(//HP)

2.20

5.90

34.46 >>

Sn-Gn'-C Angle (deg)

99.10

5.30

121.57 >>

G-Sn/Sn-Me'

1.12

0.10

97.80

10.30

0.99 * 107.18

Mentolabial Sulcus (mm)

4.80

1.00

4.65

STMs-U1

2.20

1.00

3.79 *

Sn-STNs/STMi-Me

0.46

0.20

0.82 *

G-Sn-Pog' Angle (deg) G-Sn(//HP) (mm)

Nasolabial Angle (deg)

Fig. 5.8  Surgical planning for a patient with a Type II skeletal Class II deformity. The surgical plan involves the upward movement of the anterior part of the maxilla

68.35

3.95 ** 111.94 86.33 *

(Anterior nasal spine impaction) and maintenance of the vertical position of the posterior part (posterior nasal spine). Thereby, the gummy smile is corrected after surgery

5.4  Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)

c

d Fig. 5.8 (continued)

83

84

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

e f

Maxilla - ANS impaction : 3 mm - Total setback : 2mm - Lt: 1.5mm impaction (canine) maintained (1st molar) Maintained (PNS) - Rt; 2.5mm impaction (canine) 1.5mm impaction(1st molar) Maintained (PNS) - Incisal Tip poition: horizontally maintained & vertically 3.0mm intrusion - Center of Rotation: 2nd molar area -midline : 0.5mm~1.0mm to right Mandible -Lt: SSRO advancement (7mm at 1st molar, 11.5mm at Mn. Border) -Rt; SSRO advancement (5mm at 1st molar; 8.5mm at Mn. Border) -B-point : 9.5mm advancement -Chinpoint : 14.0mm advancement -Genioplasty : advancement more than 5mm

Fig. 5.8 (continued)

5.4  Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)

g

h Fig. 5.8 (continued)

85

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

86

i

j Fig. 5.8 (continued)

5.4  Vertical Position of the Maxilla in Mandibular Retrognathism (Type II)

k

l Fig. 5.8 (continued)

87

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

88

m

n

Fig. 5.8 (continued)

5.6  Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)

Diagnostic points • Steep occlusal plane • Gummy smile • Deep overbite

5.5

Vertical Position of the Maxilla in Mandibular Retrognathism (Type III)

In Type III patients, the vertical position of the maxilla shows deficient growth of the posterior part and excessive growth of the anterior part. This growth pattern is usually associated with pathologic bony changes in the condyles (­ idiopathic condylar resorption, ICR [1, 2]). Because of a short ramus height, the patient has a short posterior face height and a steep mandibular plane angle. Adaptive vertical growth of the anterior part of the maxilla results in patients having gummy smiles. In these cases, stabilizing the position of the mandibular condyle takes time, and evaluating the mandibular position over a certain period during a preoperative orthodontic process is preferable to performing the surgery-­first approach. The surgical plan involves the upward movement of the anterior part of the maxilla (anterior nasal spine impaction) and vertical lowering of the posterior part (posterior nasal spine). The postoperative stability of this surgical technique might

89

be still controversial [3] and it could be combined with autogenous bone grafting or hydroxyapatite alloplastic grafting, if necessary (Fig. 5.9). Diagnostic points • Steep occlusal plane • Gummy smile –– Short ramus height –– Possible pathologic condyles

5.6

changes

of

the

Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)

In Type IV malocclusions, the vertical position of maxilla shows deficient growth of the posterior part and normal growth of the anterior part. In these patients, the growth pattern is usually associated with a pathologic bony change in the condyles (ICR). Because of the short ramus height, patients demonstrate short posterior face heights and steep mandibular plane angles. However, the anterior part of the maxilla remains vertically normal, which can complicate the surgical plan. The surgical plan involves vertical lowering of the posterior part of the maxilla (PNS), combined with autogenous bone grafting or hydroxyapatite

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

90

a Type III

Mx. Posterior

Mx. Anterior

- Deficiency

+ Excess

b 76.9* Method II

66.5>

N-A

0.90

3.20

-6.38 **

N-B

-3.30

5.10

-29.00

PNS-N (mm)

54.60

2.80

53.08

26.20

3.80

44.24 >>

17.3**

MP-FH Angle (deg) U1-NF (mm)

30.00

2.00

32.72 *

L1-MP (mm) U6-NF (mm)

43.20

2.50

48.11 *

24.50

1.50

18.61 ***

L6-MP (mm)

35.40

2.30

37.33

PNS-ANS (mm)

53.40

3.50

48.97 *

Ar-Go (mm) Go-Pog (mm)

50.40

4.00

41.48 **

81.70

4.10

54.00 >

6.90

1.60

4.27 *

116.40

4.00

26.67 ***

116.2* 48.6* 143.0>> 5.8*** 21.8>>

94.4>>

119.4*

-1.8 14.4**

65.5* 9.2*** 61.3>

6.20

3.50

0.20 *

2.20

5.90

31.14 >>

Sn-Gn'-C Angle (deg)

99.10

5.30

145.09 >>

1.12

0.10

1.13

G-Sn/Sn-Me' Nasolabial Angle (deg)

Fig. 5.9  Surgical planning for a Type III patient with skeletal Class II malocclusion. The surgical plan involves the upward movement of the anterior part of the maxilla (anterior nasal spine impaction) and vertical lowering of

97.80

10.30

116.18 *

Mentolabial Sulcus (mm) STMs-U1

4.80

1.00

1.70 ***

2.20

1.00

-0.68 **

Sn-STNs/STMi-Me

0.46

0.20

0.82 *

the posterior part (posterior nasal spine). This may be combined with autogenous bone grafting or hydroxyapatite alloplastic grafting, if necessary

5.6  Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)

c

d Fig. 5.9 (continued)

91

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

92

e

f Fig. 5.9 (continued)

5.6  Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)

g

Maxilla - ANS impaction ; 3mm Mx total setback 1.5mm( A-point AP maintained) - Lt: 1.0mm impaction (canine) 2.5mm downing (1st molar) 5.0mm downing (PNS) - Rt:1.0mm impaction (canine) 2.0mm downing (1st molar) 5.0mm downing (PNS) - Incisal Tip position: horizontally 4.0mm advancement & vertically 3mm intrusion - Center of Rotation: root apex of premolar - Midline : maintained Mandible - Lt: SSRO advancement (8.5mm at 1st molar, 16mm at mn. Border) - Rt; SSRO advancement (7.5mm at molar, 15mm at Mn. Border) - B-point : 12.0mm advancement - Chinpoint : 17.0mm advancement - Genioploasty : advancement 6mm

h

Fig. 5.9 (continued)

93

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

94

i

j

Fig. 5.9 (continued)

5.6  Vertical Position of the Maxilla in Mandibular Retrognathism (Type IV)

k

l Fig. 5.9 (continued)

95

96

m

n

o Fig. 5.9 (continued)

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

5.7  Surgery-First Approach in Class II Surgeries

97

p

Fig. 5.9 (continued)

alloplastic grafting, if necessary (Fig.  5.10). To secure sufficient mandibular advancement, moving the maxilla forward may be necessary, in some cases. Additionally, improving the lip ­profile by extracting the upper and lower premolars may be necessary. In Type IV mandibular retrognathism, evaluation of the mandibular position for a period during the preoperative orthodontic process is preferable to the surgery-first approach. Diagnostic points • Steep occlusal plane • Normal incisal display –– Short ramus height –– Possible pathologic condyles

5.7

Surgery-First Approach in Class II Surgeries

Even in Class II surgery, if surgical occlusion of the surgery-first approach is achieved through model setup of the postoperative orthodontic movement, the surgery-first approach can be performed. However, the surgery-first approach should be performed cautiously in patients with Class II malocclusions and the following circumstances: 1. Unstable condylar position

changes

of

the

Patients with skeletal Class II malocclusions have a habitual tendency to move the mandible forward to obtain better occlusion. If such a long-­

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

98

a Type IV

Mx. Posterior

Mx. Anterior

- Deficiency

Normal

b

Maxilla 83.1 Method II

72.6** 10.4>>

38.6* 112.0 17.5**

102.7

114.3 38.6**

8.4*** 24.8>>

75.7

95.8***

91.4***

3.0* 18.0**

69.1***

- ANS–vertically maintained - Lt: 0.5mm downing (cannie) 4.0mm downing (1st molar) 6.0mm impaction (PNS) - Rt 0.5mm downing (cannie) 4.0mm downing (1st molar) 6.0mm impaction (PNS) - Incisal Tip position: horizontally 3 mm advance & vertically maintained - Center of Rotation: cervical point of upper incisor - Midline: Maintained Mandible

15.0>> 113.6**

Fig. 5.10  Surgical planning for a Type IV patient with skeletal Class II malocclusion. The surgical plan involves vertical lowering of the posterior part of the maxilla (pos-

- Lt: SSRO advancement (6mm at 1st molar, 15.0mm at Mn. Border) - Rt; SSRO advancement (6.5mm at 1st molar, 15.5mm at Mn. Border) -B-point: 11.0mm advancement -Chinpoint: 17.0mm advancement -Genioplasty : advancement more than 6mm

terior nasal spine), combined with autogenous bone grafting or hydroxyapatite alloplastic grafting, if necessary

5.7  Surgery-First Approach in Class II Surgeries

c

d

Fig. 5.10 (continued)

99

100

5  Treatment Strategy for Class II Orthognathic Surgery: Orthodontic Perspective

term habit persists, the patient may develop a dual bite. Often, such a dual bite may not be recognized preoperatively, which may lead to a postoperative backward relapse of the mandible. If the patient undergoes a preoperative orthodontic process, the adapted dual bite may be blocked and a relatively stable neutral occlusion may be obtained, preoperatively. As mentioned above, determining if the pathological resorption of the mandibular condyle has been stopped or is still ongoing is often difficult. Therefore, the duration of the preoperative orthodontic treatment provides an opportunity to observe whether the pathological resorption of the mandibular condyle will persist. 2. Anterior crossbite after surgery-first approach If surgical occlusion is set up for the surgery-­first approach, after simulating the postoperative tooth positions, surgical occlusion may result in a postoperative anterior crossbite. This anterior crossbite can be resolved through postoperative orthodontic treatment after bone fixation, with or without premolar extractions. However, resolving anterior crossbites can often be difficult because

the maxillary incisors are forced to the lingual surface of the lower incisors and because the force of the postoperative mandibular backward movement is transmitted to the lingual surfaces of the lower incisors. This generates a flaring force on the lingual surfaces of the lower incisors.

References 1. Arnett GW, Milam SB, Gottesman L.  Progressive mandibular retrusion—idiopathic condylar resorption. Part I.  Am J Orthod Dentofacial Orthop. 1996;110(1):8–15. 2. Arnett GW, Milam SB, Gottesman L.  Progressive mandibular retrusion—idiopathic condylar resorption. Part II.  Am J Orthod Dentofacial Orthop. 1996;110(2):117–27. 3. Esteves LS, Castro V, Prado R, de Moraes e Silva CÁ, do Prado CJ, Trindade Neto AI.  Assessment of skeletal stability after counterclockwise rotation of the maxillomandibular complex in patients with long-face pattern subjected to orthognathic surgery. J Craniofac Surg. 2014;25(2):432–6. 4. Kim JS, Kim JK, Hong SC, Cho JH. Changes in the upper airway after counterclockwise maxillomandibular advancement in young Korean women with class II malocclusion deformity. J Oral Maxillofac Surg. 2013;71(9):1603.e1–6.

6

Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

6.1

Examination and Evaluation of Facial Asymmetry

In recent decades, the development of various diagnostic techniques has facilitated accurate assessments of facial asymmetry. In particular, the development of three-dimensional (3D) diagnostic tools has enabled the identification of more asymmetry details than were possible using the two-dimensional plane, allowing these details to be reflected in the surgical plan [1–3]. In particular, facial scanners, capable of 3D evaluations of soft and hard tissues, have been used to assist surgical planning by clinicians (Fig. 6.1) [4]. Nevertheless, the surgeon’s clinical evaluation of the patient’s face is especially important in the surgical planning for cases of facial asymmetry. To establish a more accurate surgical plan, both a static evaluation of a facial photograph and an evaluation of the dynamic state are necessary (Fig. 6.2). In some cases, diagnosing facial asymmetry in a dynamic state is more reliable than using static diagnostic data. Directly checking from the frontal side of the patient allows assessment of intercanthal line canting, nose tip projection, philtrum projection, lip line canting, occlusal plane canting, upper denture midline to FM, lower denture midline to FM, chin point deviation, chin border canting, and dentition from above (Fig.  6.3). In addition, evaluating the smile in the dynamic

state and checking the maxillary central incisor exposure during posed and unposed smiles are important. This can be an important indicator for determining the vertical position of the anterior part of the maxilla, prior to surgery.

6.2

Aspects of Mandibular Asymmetry: Vertical Versus Horizontal Asymmetry

The growth area of the mandible can be divided into two parts, and accordingly, asymmetry may appear differently in different patients. If the difference in growth is mainly associated with the mandibular condyle or ramus, it can be clinically considered as vertical mandible asymmetry. These patients often demonstrate a vertical growth pattern, with different heights of mandibular gonial angles, unilateral compensatory vertical growth of the maxilla, and canting of the maxilla. Another form of asymmetry involves the horizontal asymmetry of the mandible. In patients with this type of asymmetry, the vertical position differences in the mandible gonial angles are relatively small and show small amounts of maxillary canting (Fig. 6.4). Of course, this mandibular asymmetry does not show only one pattern in one patient, and in most patients, two patterns may be combined at the same time.

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_6

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102

6  Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

a

b

c

Fig. 6.1  Various diagnostic data used for surgery plan- cone-beam computed tomography data, and three-­ ning in cases of facial asymmetry. Traditional two-­ dimensional facial scan data are useful for surgical dimensional cephalometric radiographs, three-dimensional planning

6.3

Surgery-First Approach for Facial Asymmetry

Most patients with skeletal Class II and Class III dentofacial deformities who require orthognathic surgery have some degree of facial asymmetry and patients with surgery-first approach also often demonstrate facial asymmetry. The surgical plan of SFA for facial asymmetry patients is not different, if the treatment protocol mentioned in the pre-

vious chapter is followed. If the degree of asymmetry is very severe or the degree of dental compensation is severe, it may not be suitable to perform surgery-first approach. To be more specific, if the asymmetrical aspect of the mandible has more vertical aspects, it is easier to establish the surgical occlusion for SFA. Basically, in these patients, the amount of left and right lateral transverse compensation is similar, and the displacement of the upper denture midline and lower

6.3 Surgery-First Approach for Facial Asymmetry

103

Fig. 6.2  Extraoral clinical photographs for surgical planning of a patient with facial asymmetry. Floss is used to set the facial midline prior to taking a frontal photo with

the patient smiling. A tongue blade is applied to see the canting of the maxilla; the patient was instructed to tilt his neck back (90°) to show the mandibular body asymmetry

Fig. 6.3  Preoperative extraoral clinical examination. The photographs allow surgical planning for cases of facial asymmetry by clinically assessing intercanthal line canting, nose tip projection, philtrum projection, lip line cant-

ing, occlusal plane canting, upper denture midline to FM, lower denture midline to FM, chin point deviation, and chin border canting

104

6  Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

denture midline is small, so most of the asymmetry is reflected in the skeleton itself. This means that most of the improvement should be corrected through a surgical procedure, and the range of post-operative orthodontic movement after surgery could be minimal (Fig. 6.5). On the contrary, for the patients having more horizontal asymmetry of the mandible, there could be large difference in the amount of lateral transverse compensation of the maxillary and mandibular dentition, which may make it more difficult to establish surgical

occlusion for SFA. In some cases, a unilateral crossbite can be obtained after surgery, which can impairs the stability of the bony segments after surgery, and also interferes with the direction of post-operative orthodontic movement (Fig.  6.6), so pre-operative orthodontic treatment before surgery is sometimes more desirable. Surgery-first approach for vertical mandible asymmetry Surgery-first approach for horizontal mandible asymmetry

Dental Compensation in Vertical Asymmetry

a

Dental Compensation in Vertical Asymmetry

b

Fig. 6.4  Different features of dental compensation in two types of mandibular asymmetry; vertical mandibular asymmetry and horizontal mandibular asymmetry. In the case of vertical asymmetry, the compensation of the maxillary and mandibular dentition shows similar patterns in

both left and right sides. On the other hand, in the case of horizontal asymmetry, the amount and angulation of transverse compensation is different in left and right sides, which makes the preparation of surgery-first approach more difficult

6.3 Surgery-First Approach for Facial Asymmetry Dental Compensation in Horizontal Asymmetry

c

Dental Compensation in Horizontal Asymmetry

d

Fig. 6.4 (continued)

105

106

6  Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

a

b Fig. 6.5  Surgery-first approach for vertical mandible asymmetry. Surgical occlusion was established using a model setup and, after removing the occlusal interference

throughout the postoperative orthodontic period, stable results were obtained

6.3 Surgery-First Approach for Facial Asymmetry

c

d Fig. 6.5 (continued)

107

108

e

f Fig. 6.5 (continued)

6  Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

6.3 Surgery-First Approach for Facial Asymmetry

g

h

i Fig. 6.5 (continued)

109

110

6  Treatment Strategy for Facial Asymmetry: An Orthodontic Perspective

a

b Fig. 6.6  Surgery-first approach for horizontal mandibular asymmetry. Unilatral crossbite is shown on the patent’s right side after surgery

References

References 1. Baek C, Paeng JY, Lee JS, Hong J. Morphologic evaluation and classification of facial asymmetry using 3-dimensional computed tomography. J Oral Maxillofac Surg. 2012;70(5):1161–9. 2. Leung MY, Leung YY. Three-dimensional evaluation of mandibular asymmetry: a new classification and three-dimensional cephalometric analysis. Int J Oral Maxillofac Surg. 2018;47(8):1043–51.

111 3. Oh MH, Hwang HS, Lee KM, Cho JH. Cone-beam computed tomography evaluation on the condylar displacement following sagittal split ramus osteotomy in asymmetric setback patients: Comparison between conventional approach and surgery-first approach. Angle Orthod. 2017;87(5):733–8. 4. Cintra O, Grybauskas S, Vogel CJ, Latkauskiene D, Gama NA Jr. Digital platform for planning facial asymmetry orthodontic-surgical treatment preparation. Dental Press J Orthod. 2018;23(3):80–93.

7

Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus Osteotomy Versus Sagittal Split Ramus Osteotomy

7.1

Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral Vertical Ramus Osteotomy (IVRO) Versus Sagittal Split Ramus Osteotomy (SSRO)

Since the introduction of Intraoral Vertical Ramus Osteotomy (IVRO) and Sagittal Split Ramus Osteotomy (SSRO) as mandibular setback surgery methods in the 1950s, extensive research on their postoperative stability has been conducted. Since the 1990s, several studies have shown that SSRO is prone to both anterior and upward relapses, after initial mandibular setback, and in the same direction for late relapse. In the case of IVRO, there are some differences among the studies, but initial relapses show posterior mandibular movement of mandible. In cases of late relapse, anterior and upward movement of the mandible is observed, similar to the aspect after SSRO (Fig. 7.1). However, the values are clinically acceptable and both procedures show very stable results [1–3].

How does the stability achieved after the surgery-­first approach differ from that of conventional mandibular setback surgery? In the early postoperative period, the segmental changes initiated by the dislocation of proximal and distal segments mostly affect initial relapses. These are caused by an imbalance of forces generated by the stomatognathic system associated with the distal segments. Intraoperative distal and lateral displacement of the proximal segments can cause this type of imbalance. At the late stage, the proximal and distal segments are mostly joined and the mandibular movement is generated from the muscles of the pterygomasseteric sling responding to a single united segment. In the surgery-first approach, there is the possibility of another stage between the early and the late stages; this stage is called the middle postoperative orthodontic stage. During this stage, how much does the incomplete occlusion affect the surgical stability? A study comparing the postoperative mandibular relapse patterns after conventional orthognathic surgery and those following the surgery-first approach showed that the mandibular forward

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_7

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

relapse was slightly larger following the surgery-­ first approach [4–7]. This was common for both the SSRO and the IVRO groups (Fig.  7.2) [8]. This was likely the case because, in the surgeryfirst approach patients, surgical occlusion may have induced transient temporary bite openings due to premature contact with the posterior teeth.

As mentioned in the previous chapter, this is because the position of the mandible, which has been moved forward and upward, is the position that was initially planned in the surgical treatment objective. Therefore, these mandibular movements would be more appropriately called predicted or planned mandibular seating [7].

Fig. 7.1  Comparison of relapses, after mandibular setback, following sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO). Previous

studies have shown diffrent directions of relapse according to time after surgery and stable overall results in both techniques

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral… IVRO

SSRO

19

18

-11.5mm

-9.3mm

a N Setback(B) T2-T1 Horz.1 yr(B);

0.6mm

2.2mm

Ver.1 yr(B);

-1.9mm

-3.3mm

B(x)

B(y) 125.0

80.0

Vertical position of point B (mm)

Horizontal position of point B (mm)

85.0

75.0 70.0 65.0 60.0 55.0 SSRO IVRO

50.0 T1

b

115

T2 Time

T3

Fig. 7.2  Comparison of relapses, after mandibular setback using the surgery-first approach, following sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO); J Craniomaxillofac Surg. 2016;44(9):1209–15. T1, 1 month before surgery; T2, 2

120.0

115.0

110.0

105.0 SSRO IVRO

100.0 T1

T2 Time

T3

weeks after surgery; and T3, 12 months after surgery. Considering the amount of mandibular closure, the pattern of relapse is similar to the conventional method in both SSRO group and IVRO group

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

Case Report 7.1: 20 years 9 months old female patient having complaints of mandibular prognathism, long face and facial asymmetry. Two-jaw surgery was planned and performed with surgery-first approach. The superimposition of lateral cephalometric radiographs shows relatively good stability after 39 months of surgery

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

117

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

119

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

123

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

125

Case Report 7.2: 19 years 8 months old female patient having complaints of mandibular prognathism and long face. Two-jaw surgery was planned and performed with surgery-first approach. TADs were actively applied during MMF(maxillomandibular fixation) period. It shows very stable result in 103 months after surgery

126

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

127

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

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7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

135

Case Report 7.3: 29 years 9 months old female patient having complaints of mandibular prognathism and long face. One-jaw surgery was planned and performed with surgery-first approach. Two bicuspids were extracted during post-operative orthodontic period to achive enough dental decompensation of upper arch. Please note vertical mandibluar change during post-operative orthodontic period. It moved to the position initially planned in the surgical treatment objective

136

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

137

138

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.1 Relapses Following the Surgery-First Approach for Patients with Class III Malocclusions: Intraoral…

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

7.2 Transverse Soft Tissue Changes Following the Surgery-First Approach

7.2

Transverse Soft Tissue Changes Following the Surgery-First Approach

Previous studies have shown that transverse changes in the mandibular gonial angle area, after mandibular surgery, are similar for both SSRO and IVRO.  Immediately after the operation, the intergonial width of the mandible

141

increases and then decreases, gradually [9–11]. After 1 year, the mandibular width decreased to less than its preoperative width. The width changes for the associated hard and soft tissues were greater for the soft tissues than for the hard tissues. Such transverse changes also occur in patients undergoing the surgery-first approach (Figs. 7.3 and 7.4) and it is important to inform patients of these changes, before surgery.

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

142

a

b Fig. 7.3  Transverse soft tissue changes following the surgery-first approach: SSRO. Please note transverse bone remodeling of priximal segments made the width of gonion decreased

7.2 Transverse Soft Tissue Changes Following the Surgery-First Approach

c

d Fig. 7.3 (continued)

143

144

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

e

f Fig. 7.3 (continued)

7.2 Transverse Soft Tissue Changes Following the Surgery-First Approach

145

a

b Fig. 7.4  Transverse soft tissue changes following the surgery-first approach: IVRO. After debonding in 17 months of surgery, intergonial width decreased by 2 mm compared to the initial

146

7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

c

d Fig. 7.4 (continued)

7.2 Transverse Soft Tissue Changes Following the Surgery-First Approach

e

f

g Fig. 7.4 (continued)

147

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7  Relapses and Soft Tissue Changes following the Surgery-First Approach: Intraoral Vertical Ramus…

References 1. Yoshioka I, Khanal A, Tominaga K, Horie A, Furuta N, Fukuda J. Vertical ramus versus sagittal split osteotomies: comparison of stability after mandibular setback. J Oral Maxillofac Surg. 2008;66(6):1138–44. 2. Kitahara T, Nakasima A, Kurahara S, Shiratsuchi Y. Hard and soft tissue stability of orthognathic surgery. Angle Orthod. 2009;79(1):158–65. 3. Al-Moraissi EA, Ellis E 3rd. Is There a Difference in Stability or Neurosensory Function Between Bilateral Sagittal Split Ramus Osteotomy and Intraoral Vertical Ramus Osteotomy for Mandibular Setback?. J Oral Maxillofac Surg. 2015;73(7):1360–71. 4. Choi JW, Lee JY, Yang SJ, Koh KS. The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity. Ann Plast Surg. 2015;74(3):333–41. 5. Kim CS, Lee SC, Kyung HM, Park HS, Kwon TG. Stability of mandibular setback surgery with and without presurgical orthodontics. J Oral Maxillofac Surg. 2014;72(4):779–87. 6. Park HM, Yang IH, Choi JY, Lee JH, Kim MJ, Baek SH. Postsurgical Relapse in Class III Patients Treated

With Two-Jaw Surgery: Conventional Three-Stage Method Versus Surgery-First Approach. J Craniofac Surg. 2015;26(8):2357–63. 7. Choi SH, Hwang CJ, Baik HS, Jung YS, Lee KJ. Stability of Pre-Orthodontic Orthognathic Surgery Using Intraoral Vertical Ramus Osteotomy Versus Conventional Treatment. J Oral Maxillofac Surg. 2016;74(3):610–9. 8. Choi SH, Yoo HJ, Lee JY, Jung YS, Choi JW, Lee KJ. Stability of pre-orthodontic orthognathic surgery depending on mandibular surgical techniques: SSRO vs IVRO. J Craniomaxillofac Surg. 2016;44(9):1209–15. 9. Choi HS, Rebellato J, Yoon HJ, Lund BA. Effect of mandibular setback via bilateral sagittal split ramus osteotomy on transverse displacement of the proximal segment. J Oral Maxillofac Surg. 2005;63(7):908–16. 10. Amano K, Yagi T, Iida S, et al. Facial frontal morphological changes related to mandibular setback osteotomy using cephalograms. J Craniomaxillofac Surg. 2009;37(7):412–6. 11. Jung YS, Kim SY, Park SY, Choi YD, Park HS. Changes of transverse mandibular width after intraoral vertical ramus osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;110(1):25–31.

8

Update on Orthognathic Surgical Techniques

8.1

Incision and Dissection

Although some technical modifications were made since H.L. Obwegeser introduced the combined maxilla and mandibular osteotomy techniques for orthognathic surgery in 1960s, the fundamental concepts of H.L. Obwegeser did not seem like changed [1]. The sequence of the orthognathic surgery varies according to the preference of the surgeons. Personally, I prefer the maxilla-first approach for patients with Class III deformities and facial asymmetry while I mostly do the mandible-first approach in patients with Class II deformities. I am sure that the orthognathic surgical procedures chould be completed effectively without complications if the surgeon was aware of the surgical anatomy and basic concept of this technique. Regarding the issue whether the mandible first or maxilla first would be better, I decide this based on the vector of the maxilla. If I plan to perform the maxillary impaction on ANS or PNS, I prefer the maxillary first approach because the location of the condyle will not be changed after the fixation of the maxilla. On the contrary, in the case where the maxillary lengthening on ANS or PNS, I prefer the mandibular first approach because the condyle sag will be followed after the fixation of the maxilla. However, I always incise and dissect the mandible, first, and then start the maxilla. I start with the mandible to minimize bleeding and maintain the operative field relatively blood free.

After the mandibular dissection, I pack the area with gauze and start dissection of the maxilla. During the dissection of the maxilla, bone bleeding can be controlled. After finishing the dissections of the mandible and maxilla, I start the mandibular osteotomy before completing the separation of the mandible. Then, I start a LeFort I osteotomy, followed by a sagittal split of the mandible. I believe my sequence is helpful for minimizing any bone bleeding that may occur during orthognathic surgery. However, the specific sequence may vary according to the situation, such as for patients with Class II dentofacial deformities where I initially perform mandiblefirst orthognathic surgery [2] (Fig. 8.1). 1. Mandible Subperiosteal inflation, with local anesthetics, is usually performed before draping. After nasotracheal intubation, a cutaneous injection of local anesthetic and epinephrine is administered in the subperiosteal plane of the ramus of the bilateral mandible. This local injection is very helpful as a part of the blood-free, subperiosteal dissection of the mandible. A traditional buccogingival incision is made, using the cutting mode of a Bovie coagulator, down to the periosteum; a number 15 blade can also be used to achieve the same result. The lateral subperiosteal dissection is made using a round ­ curved elevator, which facilitates the elevation of the

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_8

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8  Update on Orthognathic Surgical Techniques

Fig. 8.1 Basic approach for Orthognathic surgery. Buccogingial incision for LeFort I osteotomy, SSOR, and genioplasty. Incision and dissection of the mandible, followed by the maxilla. The reason for starting with the

mandible dissection is to minimize bleeding and maintain a relatively blood-free operative field. After dissection of the mandible, I pack the area with gauze and start dissection of the maxilla

periosteum and pterygomasseteric sling in a single plane; without dissection of the pterygomasseteric sling, a single-plane periosteal dissection is not possible. Then, I start elevation of the periosteum of the posterior and inferior borders of the mandible with 45° and 90° angled elevators; a U-shaped elevator is used to finalize the periosteal elevation. For the medial dissection, determining the exact subperiosteal plane is crucial. I start to incise the bony periosteum using a Bovie coagulator or a number 15 blade, ensuring dissection of the subperiosteal plane. Using a curved elevator, I start the dissection of the medial parts of the mandible to locate the position of the horizontal osteotomy. Generally, the horizontal osteotomy line should be located between the sigmoid and lingual notches. A deep dissection should be made, to the posterior ramus (Fig. 8.1). Then, I temporarily fill the dissection space with radio-opaque cotton and gauze to minimize bone bleeding.

mandible portion of the surgery. A buccogingival incision is made from the lateral border of the maxilla to the contralateral border, using the cutting mode of a Bovie coagulator. After the mucosal incision, the facial muscles are retracted and the incision is extended to the periosteum. This approach helps with the dissection of unnecessary structures. Subperiosteal dissection is performed using a round periosteal elevator, in a single plane. The infraorbital neurovascular bundle should be preserved. I try to minimize dissection of the zygomatico cutaneous ligaments, which could cause drooping of the cheek soft tissue. The nasal floor and medial walls of the maxilla are then dissected. A curved elevator is inserted into the inferiolateral parts of the pyriform apertures, which are the easiest points for starting a subperiosteal dissection. Then, the side and floor of the maxilla are dissected. One step that is a somewhat difficult part of the subperiosteal dissection is at the vomer–septal junction. To avoid tearing the mucoperiosteum on the septum, precise elevation of the subperiosteal plane needs to occur. Finally, the lateral part of the maxilla is deeply dissected, to the pterygomaxillary junction. Because the posterior wall of the maxilla is not very thick, this dissection must be

2. Maxilla (Fig. 8.2) An injection of local anesthetic and epinephrine is usually made before the draping, as for the

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a

b

c

d

Fig. 8.2 (a) Incision marking on maxilla, (b) exposure of the maxilla including the ANS (anterior nasal spine). (c) complete subperiosteal dissection allows the surgeon to

do the surgery with minimal bleeding. (d) LeFort I osteotomy design was made by pencil. asymmetric anterior maxilla correction is planned

done carefully. If you feel the pterygomaxillary junction, the dissection needs to be extended slightly upward or downward. Personally, I try to locate the vertical part of the lower lateral buttress of the maxilla and dissect the vertical portion of the pterygomaxillary junction, as well; this is the crucial part of the LeFort I pterygomaxillary dysjunction. After dissecting the maxilla, I temporarily fill the dissection space with radio-opaque cotton and gauze to minimize bone bleeding.

preserving the mental nerve, a subperiosteal dissection is performed. For proper retraction, I prefer a Tessier retractor that allows me to visualize the deeper portion of the dissection better than does the Army–Navy retractor.

3. Chin

Before performing the LeFort I osteotomy, a precise osteotomy line should be drawn, using a pencil and based on caliper measurements, according to the surgical treatment objective. Keeping in mind that orthognathic surgery requires an accuracy of at least 0.5 mm, I do not believe in using the burring effect of the reciprocating or oscillating saw during bony resection. Because small bony protrusions can hinder the precise approximation of the bony segments, I resect the planned bony sections while ignoring the burring that occurs during sawing (Fig. 8.3). The lateral parts of the maxilla are cut to their full depth, including the anterior, lateral, and posterior walls of the maxilla, while protecting the surrounding soft tissue using Tessier retractors. However, the

If I am unsure whether I will perform genioplasty, despite the preoperative planning, I do not usually make a buccogingical incision for a potential genioplasty. If genioplasty is ultimately necessary, after finishing the LeFort I and sagittal split ramus osteotomy, I make an incision for the genioplasty on the buccal mucosa. Such an incision should be precisely made on the sulcus. If the incision is made too close to the attached gingiva, postoperative closure might be complicated by multiple scar bands on the mucosal incision. A subperiosteal dissection is made using a round elevator and the inferior border of the mandible is dissected with a curved elevator. While

8.2

Osteotomy

1. LeFort I osteotomy

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a

b

c

d

Sphenopalatine artery

Internal maxillary artery Artery of the pterygoid canal Sphenopalatine artery Infracrbital artery

Posterior descending palatine artery

Posterior superior alveolar artery

Masseteric artery

Descending palatine artery

Maxillary artery

Buccal artery

Posterior auricular artery Facial artery

Sphenopalatine artery

External carotid artery Inferior alveolar artery

Vidian artery Infraorbital artery Descending pharyngeal artery

Fig. 8.3 (a, b, c) Horizontal osteotomy on anterior and lateral wall of maxilla is done by reciprocating saw for LeFort I osteotomy while preserving the posterior wall of

Greater, lesser palatine artery Posterior superior alveolar artery Internal maxillary artery

maxilla. Surgeon should consider the vascular anatomy. (d) Septal osteotome is used for the separation of the septum

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Fig. 8.4  A medial cut should be made while preserving the descending palatine neurovascular bundle and the lateral cut is extended to its full depth. The endpoint of the

osteotomy cut on the medial part is determined based on a change in sound; the sound becomes dull when the pterygoid plate is touched. This is the endpoint of the medial cut

medial half of the maxilla should only be partially cut. If the medial portion of maxilla is cut to its full depth, the descending palatine neurovascular bundle would be injured (Fig. 8.4). The posterior part of the medial half of the maxilla should be managed using an osteotome and manual down fracturing. For the pterygomaxillary dysjunction, I prefer a Kawamoto osteotome, which involves a curved, 1-cm wide blade. I do not use the counter-finger technique as I perform a full cut of the pterygomaxillary dysjunction. At this stage, I focus on the separation of the vertical part of lower half of the pterygomaxillary fissure, which is the thicker and stronger part; this part should be completely separated to facilitate the dysjunction. After the septal osteotomy, the LeFort I segment can be easily and manually down-fractured. I use Rowe forceps to release the soft tissue and check for the completely free movement of the LeFort I segment. If massive bleeding occurs before the LeFort I down fracturing, I try to quickly finish the LeFort I down-fracture. After the LeFort I down-fracture, bleeding can be mostly controlled. In cases where the pterygomaxillary venous plexus has been injured, I prefer using gauze packing for at least 20 minutes. In most cases, I can preserve both descending palatine neurovascular bundles, which enables me to finish the orthognathic surgery without major bleeding.

structures; I use medial and lateral ramus retractors. The deepest posterior ramus should be visualized both medially and laterally. Inserting a 4 × 4-inch gauze below the inferior and posterior border is very helpful for minimizing unexpected injuries to neurovascular structures, such as the facial nerve, facial artery or vein, and retromandibular vein. The number of gauzes used should be counted to ensure that they are removed after the procedure. Determining the ideal horizontal osteotomy line is crucial; I determine the line position using a panoramic radiograph or computed tomography scan. The horizontal osteotomy line is usually made 1.0 or 1.5 cm above the occlusal plane of the mandible, despite individual patient differences. Using a burr drill, the triangular part of the medial ramus is burred out. The burring should be done posterior to the lingula to prevent unexpected, short sagittal splitting (Fig. 8.5). Then, a vertical cut is made with a reciprocating saw, in a proximal to distal direction. To prevent nerve damage during the vertical cut of the anterior osteotomy, during SSRO, I continue using a reciprocating sawing between the sagittal and vertical parts, moving the saw outwards when finishing the vertical osteotomy. An osteotome is used to finalize the sagittal split. Personally, I prefer the use of curved osteotome along the external cortex of the mandible. It allows me not only to finalize the sagittal split without the damage to the inferior alveolar nerve, but also to make the short ligual split easier. Although many surgeons prefer the spreading method for safe sagittal splitting, stepby-step out-overlapping of the osteotomes is also

2. Sagittal split osteotomy (Fig. 8.5) The sagittal split osteotomy starts with applying protection to the major nerve and vascular

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a

b

c

d

Fig. 8.5  Sagittal split osteotomy. (a) incision for SSRO. (b) sagittal split osteotomy starts with protecting the major nerve and vascular structures; I use medial and lateral ramus retractors. The horizontal osteotomy line is usually made 1.0 or 1.5 cm above the occlusal plane of the

mandible, despite individual patient differences. Using a burr drill, the triangular part of the medial ramus is burred out. (c, d) A reciprocating saw and osteotome are then used, allowing sagittal splitting (using spreaders) to gradually expose the medulla

helpful for avoiding injury to the mandibular nerve (Fig. 8.6). Sagittal splitting, using spreaders, gradually exposes the medulla. Once the neurovascular bundle has been identified, the medial pterygoid muscle and pterygomasseteric sling can be released from the medial surface of the proximal segment, using a freer. Sometimes, smoothing of the inner aspect of the proximal segment should be performed to reduce the risk of nerve impingement. For the setback, the proximal bone segments are resected while folding the proximal bony segments using bone forceps [3]. There are many ways to sagittal splitting. My preferable method is to use the curved sharp osteotome along the outer cortex of the mandible. This method allows me not only to avoid the damage of the inferior alveolar nerve, but also to perform the short lingual split easier. The out-overlapping method relies on the multiple osteotomes to separate the mandible.

After inserting the first osteotome, another osteotome is used to outwardly overlap the first. However, the final separation should be done using spreaders. 3. Genioplasty Although genioplasty is the easiest step, care should still be taken. The excessively deep insertion of the reciprocating saw may cause unexpected major bleeding from the submental musculature. To prevent this problem, I place a fingertip under the medial cortex area when sawing. This allows me to feel the tip of the reciprocating saw when performing the osteotomy, during genioplasty. In addition, the mental nerve should be protected. As the mandibular nerve is known to pass 5-mm below the mental foramen, the ideal genioplasty line should be planned at least 5-mm below the mental foramen.

8.3 Fixation

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Fig. 8.6  Sagittal split osteotomy. (a) After making the groove 1–2 cm above the occlusal plane using the burr, I start the sagittal split ramus osteotomy using a reciprocating saw, followed by a curved osteotome on the vertical ramus, and a straight Dotri osteotome for the lateral cortex. (b, c) Finally, sagittal splitting can be achieved, using Spreaders, to expose the medulla gradually. Surgeon should be aware of the vascular anatomy around the mandible. The-innercortex-and-lingual-periosteum-of-themandible-and-floor-of-the-mouth-are illustrated. The major nerve and vessels should be avoided during osteotomy Facial a. Mylohyoid branch Lingual branch Deep lingual arteries

Mylohyoid m. External carotid a. Facial a. Submental a. Branches to submandibular gland Mental branch inferior alveolar a. Lingual branch Deep lingual a. Mylohyoid m.

Inferior alveolar a. Mental banch

8.3

Fixation

Fixation is crucial in orthognathic surgery. However, appropriate management of the bone segments is a pre-requisite for ideal fixation (Fig.  8.7). Any bony hindrance should be removed in advance of fixation. In my practice,

fixation of the LeFort I segments is performed using 4 miniplates and 6-mm screws. For the upper parts of the maxilla, I prefer self-tapping screws because of the thickness of the maxillary bone. Generally, I employ drilling and screw fixation on to the alveolar bone for complete fixation of the LeFort I segment.

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a

b

c

d

Fig. 8.7  Fixation of the LeFort I segments is performed using 4 miniplates and 6-mm screws. This case was done with the patient specific 3D printing guide for LeFort I and SSRO. (a) the view after appying the 3D printing

occlusal splint. (b) 3D printing guide with LeFort I osteotomy guide. (c) 4 miniplates were fixed on the maxilla after the LeFort I osteotomy. (d) The view after the maxilla fixation

For mandible fixation, I prefer semirigid fixation. In patients with Class III dentofacial deformities where the distal segments should be setback, I use one 4-hole miniplate and 6-mm screws, on each side, in a semirigid manner. I do not feel there is a difference between using monocortical or bicortical fixation, based on the lag screw. However, for patients with Class II dentofacial deformities, I always use two miniplates, on each side, to prevent rotation of the distal mandibular

segments caused by the retraction force of the submental muscles (Figs. 8.8 and 8.9). Regarding the use of the biodegradable plate and screw systems, I prefer the titanium plate and screw systems in orthoganthic surgery. Although the literature says the biodegradable plate and screw systems can provide us with the similar results, I believe that the titanium plate and screw systems could provide the patients with the earlier mobilization of the jaws based on the stronger fixation forces.

8.3 Fixation

e

Fig. 8.8  For patients with Class III dentofacial deformities, where the distal segments should be setback, I use one 4-hole miniplate and 6-mm screws, on each side, in a

157

f

semirigid fashion. However, for patients with Class II dentofacial deformities, I always use two miniplates on each side

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Intraoperative biomechanical effects of orthognathic surgery

1. Stripping periosteum of the ramus

2. Splitting mandible

3. Condylar mobilization

4. Fixation resulting in flaring of mandible

Postoperative biomechanical effects of orthognathic surgery

5. Altered position of condyle

6. Altered tension of pterygomasseteric sling

Fig. 8.9 (a) Intraoperative biomechanical effects of orthognathic surgery. During the mobilization and fixations of the bony segments, the changes of the condyles

References 1. Obwegeser HL.  Orthognathic surgery and a tale of how three procedures came to be: a letter to the next generations of surgeons. Clin Plast Surg. 2007;34(3):331–55.

7. Postoperative orthodontic forces

should be considered. (b) Postoperative biomechanical effects of orthognathic surgery. The postoperative muscular vector should be kept in mind

2. Proffit WR, Turvey TA, Phillips C. Orthognathic surgery: a hierarchy of stability. Int J Adult Orthodon Orthognath Surg. 1996;11(3):191–204. 3. Choi SH, Yoo HJ, Lee JY, Jung YS, Choi JW, Lee KJ.  Stability of pre-orthodontic orthognathic surgery depending on mandibular surgical techniques: SSRO vs IVRO. J Craniomaxillofac Surg. 2016;44(9):1209–15.

9

Virtual Surgical Planning and Three-Dimensional Simulation in Orthognathic Surgery

9.1

Introduction

We are working in the era of the fourth industrial revolution, which includes three-dimensional (3D) computer simulation, computer-aided design– computer-aided manufacturing technology, 3D printing technology, artificial intelligence, augmented reality, virtual reality, and navigation. Some doctors may believe that these technologies are mostly used in industry; however, 3D technology is already a reality in medicine. Craniofacial surgeons, in particular, are pioneers in the clinical application of these technologies, with 3D computer simulations, computer modelling, and 3D printing technology having been applied since the late 1990s. Since the 2000s, the rapid prototype model has been commonly used in craniofacial surgical planning. Since the 2010s, 3D printing technology has become a daily routine in many craniofacial practices [1–4] (Fig. 9.1). Do you use a navigation system when you drive? I do, most of the time. Of course, without using a navigation system, I could arrive at my destination (Fig. 9.2). However, using such a system makes me more comfortable while driving. I believe that the adoption of the new 3D technologies will allow us, in a manner analogous to our automobile navigation systems, to reach our desired destination quickly, precisely, and reproducibly. This is the role of 3D simulation and 3D printing technology in medicine.

In orthognathic surgery, the traditional dental model setup is a typical example of presurgical simulation, and the occlusal splint or wafer provides a very good example of a surgical guide that connects the simulation with the real surgery. Now that orthodontists and maxillofacial surgeons have used these simulation processes for a long time, they can adopt the brand-new 3D technologies more easily, in my opinion. Simulation-guided orthognathic surgery (SGOS) is the process of using 3D patient data to create a stepwise guide for making an accurate diagnosis, creating 3D cephalometric measurements, virtually planning the surgical steps, and predicting the consequences of these steps on the dentoskeletal complex and soft tissue envelope. I adopted 3D simulation and 3D printing technology for orthognathic surgeries in 2012. Prior to that, even without 3D simulation and 3D printing, orthognathic surgeries were successfully performed, in my practice. However, the adoption of these 3D technologies has allowed me to prepare for the surgery more intensively, more precisely perform operations, and more objectively evaluate the surgical outcomes. Several reports have recently aimed to establish the basics of this domain. Thus, the broad lines of the technique (starting with data acquisition and passing through segmentation, surgical step simulation, and plan-transport template designs) are now widely accepted [4–6]. Furthermore, the development of simulation soft-

© Springer Nature Singapore Pte Ltd. 2021 J.-W. Choi, J. Y. Lee, The Surgery-First Orthognathic Approach, https://doi.org/10.1007/978-981-15-7541-9_9

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Fig. 9.1  Since the 2000s, the rapid prototype model has been commonly used in craniofacial surgical planning, including for orthognathic surgeries. A three-dimensional printing

model provides surgeons with tactile, hands-on planning experiences as well as the ability to check bony anatomies and bony interferences in advance of actual surgeries

Fig. 9.2  If we adopt the new three-dimensional (3D) technologies, they will help us reach our final destinations quickly, precisely, and reproducibly. This is the role of 3D simulation and 3D printing technology in medicine

ware has allowed prediction of soft tissue responses and provided the aesthetic standards for different populations (aesthetic-centered virtual planning) [7–9]. Studies on the efficacy of using virtual surgical planning (VSP) reported higher osteotomy and repositioning accuracies and greater timesaving during the planning and surgical stages than conventional methods [10–13]. As expected, the increased popularity of these techniques has drawn attention to measuring outcome accuracies and comparing them with conventional methods, as well as comparing different techniques [14–16]. However, measuring SGOS accuracy has two considerations. The first is the applicability of comparing VSP to real surgery, as

VSP should be measured as a separate entity with its own controlling factors, regardless of its utility in planning the accuracy of surgical techniques (Fig.  9.1). The second is that the absolute difference between measurements mainly depends on large travel distances. Therefore, another method for detecting the accuracy of small movement achievements should be used to investigate the factors affecting VSP applicability accurately. For the understanding of the readers, I introduce how to apply the 3D computer simulation and patient-specific 3D printing technology to the orthognathic surgery. Then I will share my outcomes of my investigation related to simulation guided orthognathic surgery.

9.2 Methods

9.2

161

Methods [17, 18]

obtained in a Digital Imaging and Communications in Medicine (DICOM) file and (2) a 3D file of the 9.2.1 Data Acquisition external facial appearance, created using a special 3D scanner (Morpheus 3D; Dental Solution MDS, Two forms of data are acquired before the simula- Seoul, South Korea) designed to acquire a rich 3D tion process: (1) radiographic data from cone-­ file that is used in the simulation process (soft tisbeam computed tomography (CT; 1-mm thick) are sue 3D file) (Fig. 9.3).

Fig. 9.3  An example of typical vertical facial asymmetry. Digital Imaging and Communications in Medicine data are taken from a computed tomography scan (1-mm thickness) to create three-dimensional volume rendering images

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9  Virtual Surgical Planning and Three-Dimensional Simulation in Orthognathic Surgery

Fig. 9.4  Three-dimensional computer modelling is done by combining data from the dental scan with those from the segmentation of each axial scan in the Digital Imaging and Communications in Medicine data

Subsequently, the two sets of data are introduced to the simulation and aligned using a semiautomatic process. In cases where dental landmarks are unclear, an additional data file containing scanned dental arches is merged with the skeletal 3D file. We use two types of software during the study: the Mimics program (version 19, Materialise-NV, Leuven, Belgium) is mainly used for bone segmentation and cephalometric analyses and the Morpheus 3D program (Dental Solution MDS, Seoul, South Korea) is used for soft tissue simulation; both are used in VSP.

9.2.2 Virtual Surgical Planning Using the simulation tools, the planned osteotomies are performed for both jawbones, including the Le Forte 1 osteotomy in the maxilla and the bilateral sagittal split osteotomy and genioplasty in the mandible. Afterward, the bone segments are moved, in a scaled manner, relative to the XYZ axes. These movements are performed under the guidance of the orthodontic plan, which was previously introduced into the software, and the average aesthetic measurements of the Korean population, which are integrated into the program database in

the form of reference anthropometric measurements (Fig. 9.4).

9.2.3 Template Design and Manufacture The surgical templates are designed as intermediate and final wafers, along with repositioning guides (Fig.  9.5). The designs are made using 3matic (version 11, Materialise-NV) and are based on the simulation results. Subsequently, the templates are 3D printed, using liquid-based techniques (stereolithography), to prepare them for intraoperative use.

9.2.4 Surgical Intervention These templates undergo preoperative, low-­ temperature plasma sterilization to avoid any risk of deformation. After the LeFort I osteotomy has been performed, the intermediate wafer and maxillary repositioning template are used to guide the maxillary movement in 3D patterns. Similarly, after mandibular osteotomies, the final wafer and mandibular repositioning template are used for mandibular repositioning (Fig. 9.6).

9.2 Methods

Fig. 9.5  While traditional orthognathic surgery uses the location of the mandible for fixation of the maxilla, three-­ dimensional technology allows the maxilla to be fixed based on the location of the maxilla, itself, using a three-­

163

dimensionally printed osteotomy guide and occlusal wafer. This figure also shows the three-dimensional printing guide that is used to stabilize the proximal segments of the mandible

Fig. 9.6  Clinical applications of a three-dimensional printing guide for orthognathic surgery, including a maxillary fixation guide and a three-dimensionally printed guide for stabilizing the proximal mandibular segments

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9.3

9  Virtual Surgical Planning and Three-Dimensional Simulation in Orthognathic Surgery

Postoperative Analysis

I introduce one of my investigations regarding the postoperative analysis in the clinical application of 3D technology to orthognathic surgery [18]. This retrospective study included patients with dentofacial deformities who underwent 3D simulation-guided two-jaw surgeries between June 2015 and February 2017  in the Plastic

Surgery Department of Asan Medical Center (Seoul, South Korea). The study inclusion criteria required the patients to be ≥16  years old, undergo two-jaw orthognathic surgery with 3D VSP guidance, and using digitally designed plantransporting templates. After excluding patients with previous orthognathic surgeries, 35 participants were included. 3D CT data was combined with 3D camera data (Fig. 9.7).

Fig. 9.7  A patient with facial asymmetry and increased facial height undergoing three-dimensional, simulation-­guided twojaw surgery. (a) Preoperative appearance. (b) Postoperative

appearance. (c) Analysis of esthetic facial measurements and proportions, relative to Korean population standards. (d) Soft tissue response to bony segment repositioning

9.3 Postoperative Analysis

165

CT was performed within the first 3 postoperative weeks; the DICOM file was uploaded into the simulation software to create the early postoperative 3D model.

9.3.1 Measurement Protocol (Fig. 9.8) The preoperative, post-simulation, and postoperative 3D models undergo similar measure-

ments by recording certain point positions, including, the upper canine, right upper canine, left upper molar 1, right upper molar 1, left upper incisor-­ anterior nasal spine (ANS), ANS-posterior nasal spine (PNS) positions for the maxilla, and the lower molar 1, right-lower molar 1, left B-point-­pogonion positions for the mandible. These points are measured relative to 3 fixed planes (Frankfort horizontal, coronal, and sagittal planes) that are perpendicular to each other at the Sella point.

Pre-Operative

Planned Travel distance (Tp)

Virtual Surgical Planning

Post-Simulation

Actual Travel Distance (Ta) Surgical Applicability

Early Post-Operative

Simulation-Guided Orthognathic Surgery

Stability

Late Post-Operative

Fig. 9.8  The simulation-guided orthognathic surgery process. The virtual surgical plan is connected with the real orthognathic surgery via the 3D printing guide

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Subsequently, the travel distances are calculated as positional differences for each point, relative to the XYZ axes. This was done by the planned travel distances (Tp) being used to represent the movement from the preoperative to post-simulation positions and the actual travel distances (Ta) being represented by the preoperative to early postoperative positions



2  ab ( Ta − Tp ) ( Ta − Tp )  r1MAI = and rMAI =  Tp Tp 

9.3.2 Statistical Analysis After calculating the previously described indices for each point, we used the Kolmogorov– Smirnov and Shapiro–Wilk tests to determine distribution normalcy. Subsequently, the MAI values for the mandibular and maxillary points were compared using the Mann–Whitney U-test. Moreover, the Pearson correlation coefficient test was used to analyze the correlation between the different MAI and Tp formulas.

9.4

(Fig.  9.1). Each point is measured twice, and the mean of both measurements is approximated to the nearest 0.01-mm value. To calculate the applicability, we measure the absolute difference between Ta and Tp to determine the absolute misapplication index (abMAI) and two other equations used to determine the relative MAI (rMAI):

Results (Fig. 9.9)

All patients had satisfactory functional and aesthetic outcomes, without major complications. The patients ranged in age from 16 to 40 (mean, 22.9) years; 54% were females. After excluding travel distances