Imaging Techniques in Dental Radiology: Acquisition, Anatomic Analysis and Interpretation of Radiographic Images [1st ed.] 9783030413712, 9783030413729

Citation preview

Imaging Techniques in Dental Radiology Acquisition, Anatomic Analysis and Interpretation of Radiographic Images Ingrid Rozylo-Kalinowska

123

Imaging Techniques in Dental Radiology

Ingrid Rozylo-Kalinowska

Imaging Techniques in Dental Radiology Acquisition, Anatomic Analysis and Interpretation of Radiographic Images

Ingrid Rozylo-Kalinowska Department of Dentomaxillofacial Radiology Medical University of Lublin Lublin Poland

ISBN 978-3-030-41371-2    ISBN 978-3-030-41372-9 (eBook) https://doi.org/10.1007/978-3-030-41372-9 © Springer Nature Switzerland AG 2020 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 Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To my family for their support every day of my life and their enormous patience.

Foreword

Radiographic modalities in DMFR produces two- and three-dimensional information on the facial skeleton and teeth and is increasingly being used in many of the dental specialties, including periodontics, endodontics, orthodontics, orthognathic surgery, trauma and implantology. Being familiar with anatomy and pathology especially in periodontology and periapical lesions as well as endodontics/trauma patients would help professions to discover occult diseases and maxillofacial pathology cases especially that has refereed pain earlier. Treatment planning for maxillofacial pathologies involves gathering as much information as possible. Key tools to successful treatment planning are the appropriate radiographic techniques, allowing visualisation of a site in all three-dimensional aspect with less ionising radiation as possible. Moreover, aware of the systemic diseases and their appearances of the maxillofacial complex is crucial for appropriate diagnose and treatment. Throughout this book, aspects of radiographic modalities in DMFR including technical details and applications in various disciplines are being discussed. This book offers a comprehensive, detailed, up-to-date review of our current knowledge in the DMFR imaging. The eminently readable text is complemented by numerous and superb illustrations. As a result, this book offers a comprehensive review of imaging modalities in DMFR. I would like to congratulate the author for her superb efforts which have resulted in this excellent book. Faculty of Dentistry Ankara University Ankara, Turkey 2020

Kaan Orhan, DDS MSc MHM PHD BBAc

vii

Preface

Tempora mutantur et nos mutamur in illis—this Latin adage is the sign of the time which changes and people change with it. Since the dawn of radiography and radiology in the end of the nineteenth century, the face of dentomaxillofacial radiography has considerably changed. After the first presentation of the results of experiments carried out by Wilhelm Konrad Roentgen in November 1895, it was not long until the first dental exposure was registered by a German dentist by the name of Otto Walkhoff, and it was already done in January 1896. Radiographic imaging quickly become foundation of diagnostics in dentistry and maxillofacial surgery. During more than 120 years of history of radiography and radiology development has been immense. Although the basics of imaging techniques have remained unchanged for decades, and in case of bisecting angle intraoral technique for more than 110 years (Cieszyński’s rule of isometry published in 1907), advances in registration of radiographic image quickly followed. The development concerns both image receptors— now mostly digital—and radiographic equipment fitted with more advanced software, mechanics as well as devices aiding in positioning. Cone-beam computed tomography (CBCT) has first been described in 1990s, but in the recent decade number of installations of these diagnostic X-ray units in dental offices have peaked. Nowadays it is difficult to imagine dental imaging diagnostics without CBCT in almost all, if not all, disciplines of dentistry. However, CBCT is demanding due to necessity of analysis of numerous slices and transformation of perception from two-­ dimensional to three-dimensional. However, owing to that radiodiagnostics became more precise as teeth and tooth-bearing structures are three-dimensional objects thus traditional two-dimensional radiography is not sufficient to demonstrate all anatomic variations and pathological lesions. Nowadays the question keeps coming back whether Artificial Intelligence (AI), or rather Machine Learning, is only a hype or the future of radiology, does it pose a danger or provide advantage to the profession of radiologist? More time is needed to verify which of these approaches is correct, but it is likely that AI will not replace radiologists, including dentomaxillofacial ones, but will become one of the diagnostic tools in their box relieving them from more tedious tasks providing more time for in-depth evaluation of more complicated cases. However, until that stage of development of AI is reached, dentists and radiologist still have to rely mostly on their skills and abilities in reading dental radiographs. It is obvious that analysis of radiographic images is subjective and depends on knowledge and experience, but is also influenced by external factors ix

x

Preface

such as fatigue, hectic schedules, increasing workloads and patient bias. It is not possible to fully avoid diagnostic errors as humans are not machines, but in order to minimise mistakes, one must constantly learn and practice. So this is the aim of the present textbook—to provide concise information on dental radiography and basics of radiological interpretation which will serve as foundation for further professional development. The book is based on my textbook in Polish called “ABC of dental radiography and radiology” which had the same aim—to provide foundation for all beginners in this extraordinary field of dentistry and radiology.

Photograph of piece of art of Swedish artist Bertia Vallien from the cycle called “Thoughts”, which symbolises idiosyncrasy of radiology—technique, knowledge and skills, allows seeing what is inside human body without breach in integument

Lublin, Poland

Ingrid Rozylo-Kalinowska

About the Author

Prof. Ingrid Rozylo-Kalinowska, MD, PhD, DSc., graduated from the Faculty of Medicine of the Medical University of Lublin, Poland, in 1997. In the same year she started postgraduate studies in radiology. In the years 1998–2007 she worked in the 2nd Department of Medical Radiology of the Medical University of Lublin. In 1999 she was awarded Ph.D. degree with merits in the Medical University of Lublin and in 2004 the D.Sc. degree by the Medical University of Warsaw, Poland. In 2010 she was granted the Full Professor title by the President of Poland. In the years 2007–2011 she was working as an Assistant Professor in the Department of Dental and Maxillofacial Radiology of the Medical University of Lublin, in 2012 she became the head of the Independent Unit of Propedeutics of Dental and Maxillofacial Radiology of the Medical University of Lublin and in 2018 the Head of the Department of Dentomaxillofacial Radiology of this University. She is specialist in radiology and diagnostic imaging. Scientific work of Ingrid Rozylo-Kalinowska includes over 200 full papers and over 300 conference contributions. She is supervisor of 13 completed Ph.D. theses, 5 ongoing Ph.D. processes as well as of 11 M.Sc. dissertations. She completed six training periods abroad (France, Jordan, Spain, UK). Her didactic work includes dental radiography and radiology, maxillofacial radiology, medical radiology and diagnostic imaging for dentists, medical radiologists, radiographers as well as Polish and English Division students of dentistry, radiography and dental hygiene. She is the Immediate Past president of the European Academy of DentoMaxilloFacial Radiology. She will host the 18th European Congress of Dentomaxillofacial Radiology, in Lublin, Poland, in June 2022. She is the regional director of International Association of Dentomaxillofacial in Europe. She is the vice president of the Polish Dental Association. She is the chairman of the Section of DentoMaxillofacial Radiology of the Polish Medical Radiological Society. She is a member of the European Society of Radiology and Pierre Fauchard Academy, the Polish Section. She is a board member of the local division of the Polish Hygienic Society. She is the editor-in-chief of the Journal of Stomatology, journal of the Polish Dental Association. She belongs to the editorial boards of several scientific journals and serves as a reviewer of numerous manuscripts submitted to international scientific journal. xi

xii

About the Author

She is a co-editor and co-author of the book “Temporomandibular Joint Imaging” (Springer, 2018), five dentomaxillofacial radiology textbooks in Polish, chapters on dentomaxillofacial radiology in four Polish textbooks, as well as parts of the “English-Polish and Polish-English Dental Dictionary” (1999) and “Practical Dental Dictionary” (2016). She translated eight medical textbooks (including three on dental as well as head and neck radiology) from English or German to Polish.

Acknowledgements

I would like to thank Dr. Anna Michalska for aid in database search for new and interesting radiographs. The book would not be complete without the efforts of Dr. Leszek Szalewski, who apart from being a skilled dentist, is a dedicated photographer and was very helpful in taking photographs that I was unable to take myself, e.g. the one included in the Foreword. I would like to extend my gratitude and thankfulness to my models—my daughter Ewelina and my PhD student Dr. Katarzyna Portka. They both were extremely patient and dedicated although the task was tiresome and time-consuming. This book would never come to life without its predecessor published in Polish by the Editorial House “Czelej”—I am grateful to them for granting permission for using the materials as framework of the current book.

xiii

Contents

1 Introduction to Dental Radiography and Radiology������������������������������   1 2 Materials and Preparation for Dental Radiographs������������������������������   7 Suggested Reading��������������������������������������������������������������������������������������  12 3 Intraoral Radiography in Dentistry ��������������������������������������������������������  13 3.1 Taking a Periapical by Means of Paralleling Technique ��������������������  18 3.1.1 Introductory Steps������������������������������������������������������������������  18 3.1.2 Patient Preparation������������������������������������������������������������������  20 3.1.3 Assembling of Positioning Device������������������������������������������  21 3.1.4 Positioning������������������������������������������������������������������������������  23 3.1.5 Instructions for Patient������������������������������������������������������������  24 3.1.6 Exposure ��������������������������������������������������������������������������������  25 3.1.7 After Exposure������������������������������������������������������������������������  26 3.2 Taking a Periapical by Means of Bisected Angle Technique��������������  27 3.2.1 Introductory Steps������������������������������������������������������������������  27 3.2.2 Patient Positioning in Bisected Angle Technique ������������������  27 3.2.3 During and After Exposure ����������������������������������������������������  34 3.3 Taking a Bitewing Radiograph�����������������������������������������������������������  34 3.4 Taking an Occlusal Radiograph����������������������������������������������������������  36 3.5 Limitations of Taking Intraoral Radiographs��������������������������������������  40 Suggested Reading��������������������������������������������������������������������������������������  40 4 Panoramic Radiography in Dentistry������������������������������������������������������  43 4.1 Steps in Taking a Panoramic Radiograph ������������������������������������������  45 4.1.1 Introductory Steps������������������������������������������������������������������  45 4.1.2 Patient Preparation������������������������������������������������������������������  46 4.1.3 Patient Positioning������������������������������������������������������������������  46 4.1.4 Instruct the Patient������������������������������������������������������������������  50 4.1.5 X-ray Exposure ����������������������������������������������������������������������  51 4.1.6 After Exposure������������������������������������������������������������������������  52

xv

xvi

Contents

4.1.7 Taking a Tomographic Radiograph of Temporomandibular Joints (TMJs)������������������������������������  54 4.1.8 Example of Positioning for a Tomographic Radiograph of Temporomandibular Joints in Panoramic Machine������������������������������������������������������������  54 Suggested Reading��������������������������������������������������������������������������������������  56 5 Cephalometric Radiograph in Dentistry/Oral Health����������������������������  57 5.1 Steps in Taking a Cephalometric Radiograph������������������������������������  58 5.1.1 Introductory Steps������������������������������������������������������������������  58 5.1.2 Patient Preparation������������������������������������������������������������������  59 5.1.3 Patient Positioning������������������������������������������������������������������  60 5.1.4 Instruct the Patient������������������������������������������������������������������  63 5.1.5 X-ray Exposure ����������������������������������������������������������������������  63 5.1.6 After Exposure������������������������������������������������������������������������  63 Suggested Reading��������������������������������������������������������������������������������������  64 6 Dental Cone-Beam Computed Tomography (CBCT)����������������������������  65 6.1 Steps in Taking a Cone-Beam Computed Tomography Scan ������������  72 6.1.1 Introductory Steps������������������������������������������������������������������  72 6.1.2 Patient Preparation������������������������������������������������������������������  72 6.1.3 Patient Positioning������������������������������������������������������������������  72 6.1.4 Large FoV CBCT��������������������������������������������������������������������  73 6.1.5 Small FoV CBCT��������������������������������������������������������������������  73 6.1.6 Instruct the Patient������������������������������������������������������������������  74 6.1.7 X-ray Exposure ����������������������������������������������������������������������  75 6.1.8 After Exposure������������������������������������������������������������������������  76 Suggested Reading��������������������������������������������������������������������������������������  76 7 Technical Errors and Artefacts in Dental Radiography������������������������  79 7.1 Positioning Errors in Intraoral Techniques ����������������������������������������  80 7.2 Positioning Errors in Panoramic Radiography����������������������������������� 100 7.3 Positioning Errors in Lateral Cephalometric Radiography���������������� 112 7.4 Errors Resulting from Incorrect Settings of Radiographic Parameters���������������������������������������������������������������� 114 7.5 Errors Resulting from Incorrect Handling of X-ray Films in Analogue Radiography �������������������������������������������������������� 115 7.6 Errors Resulting from Incorrect Chemical Processing of X-ray Films in Analogue Radiography������������������������������������������ 117 7.7 Errors Resulting from Incorrect Read-out of Digital Radiographs���������������������������������������������������������������������������������������� 119 7.8 Errors and Artefacts in Cone-Beam Computed Tomography ������������ 121 Suggested Reading�������������������������������������������������������������������������������������� 124

Contents

xvii

8 Normal Anatomical Landmarks in Dental X-rays and CBCT�������������� 127 Suggested Reading�������������������������������������������������������������������������������������� 146 9 Analysis of Dental Radiographs and CBCT Studies������������������������������ 147 9.1 Calcifications and Other Radiopacities���������������������������������������������� 162 Suggested Reading�������������������������������������������������������������������������������������� 176 10 Safety Precautions for Dental Patient and Dental Staff Using X-Rays���������������������������������������������������������������������������������������������� 177 Suggested Reading�������������������������������������������������������������������������������������� 186

Abbreviations

AAOMR ARPNSA CBCT CT EADMFR EAO ESE FOV ICRP MRI MSCT PSP ROI SADMFR SPP TLD TMJ US

American Academy of Oral and Maxillofacial Radiology Australian Radiation Protection and Nuclear Safety Agency Cone-beam computed tomography Computed tomography European Academy of Dentomaxillofacial Radiology European Association of Osseointegration European Society of Endodontology Field of view International Commission on Radiological Protection Magnetic resonance imaging Multi-slice computed tomography Photostimulable storage phosphor Region of interest Swiss Association of Dentomaxillofacial Radiology Storage phosphor plate Thermoluminescent dosemeter Temporomandibular joint Ultrasound

xix

1

Introduction to Dental Radiography and Radiology

In contemporary dental practice it is utterly impossible to imagine diagnostic workflow without the benefits of radiology. Radiographs are the foundation of imaging diagnostics in dentistry as the main areas of interest in this field are hard tissues of teeth and tooth-bearing bone. Visualisation methods using ionising radiation are still the most suitable for imaging of dental and alveolar tissues as they are based on attenuation of X-rays by dense objects. Radiographic machines and cone-beam computed tomography (CBCT) are more and more frequently being installed and used in dental offices. In maxillofacial radiology the scope of imaging is wider encompassing also soft tissues, thus other imaging methods, some of which are not based on ionising radiation, are applied. These methods include ultrasonography (US), magnetic resonance imaging (MRI), fluoroscopy and multislice computed tomography (MSCT). However, such machines and facilities are mostly based in hospitals and large medical outpatient clinics, and so far have not been widely applied in dental practice, therefore they will not be discussed within the frames of this book. Before the onset of panoramic radiography, various X-ray projections have been in use in dentomaxillofacial radiology to demonstrate teeth and maxillofacial skeleton. Many of them have been replaced by panoramic radiography, but several types are still requested. The next change in dentomaxillofacial radiology was introduction of cone-beam computed tomography, and its popularity can be judged by number of brands offering such equipment as well as growing numbers of installations in dental offices, apart from hospitals and diagnostic imaging centres. It is CBCT that makes even more radiographic projections obsolete in dentomaxillofacial radiography, as instead of taking several two-dimensional radiographs one three-­ dimensional volume may solve diagnostic problem. Contemporary dental radiography comprises intraoral radiography, extraoral radiography and cone-beam computed tomography. Intraoral radiographs are all those taken with an image detector (called also image sensor or image receptor) placed inside patient’s oral cavity. On the contrary, all radiographs registered with image sensor outside patient’s cavity are called extraorals. All radiographs can be © Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_1

1

2

1  Introduction to Dental Radiography and Radiology

taken using digital sensors or analogue image detectors, i.e. radiographic films; however, recently radiographic films also become redundant following the transition from analogue to digital radiography owing to numerous benefits of digital image registration. Intraoral radiographs comprise periapical, bitewing and occlusal radiographs. The name “periapical” is related to visibility of periapical tissues of radiographed teeth which is a prerequisite of this kind of X-rays. Periapicals can be taken by means of two techniques—paralleling technique and bisected angle technique. The latter being historically older, and until recently quite heavily used, is at the same time encumbered with faults such as lack of repeatability of projection and susceptibility to geometrical errors depending on skills and abilities of an operator. Therefore paralleling technique is considered superior to the bisected angle one, but is not ideal, either. It is not possible to successfully practice this technique in patients with some anatomical conditions and pathological lesions, while a strong gagging reflex may be a handicap, too. There are numerous indications for taking periapical radiographs including dental caries, periapical lesions, endodontic treatment, dental trauma, periodontal bone disease, congenital dental anomalies, acquired dental lesions such as abrasion, attrition, erosion, follow-up of treatment, e.g. of implant placement. It has been estimated that periapicals belong to the most commonly prescribed radiographs in humans, especially in highly developed countries. During lifespan there is high chance that teeth (taking into consideration their relatively high amount) will require radiographs during dental treatment, and then follow-up, or even re-treatment. On the contrary to periapical radiographs, bitewings do not demonstrate periapical tissues at all. The purpose of taking bitewing radiographs is to show crowns of upper and lower teeth at the same time, in one view at the expense of cropping the images of root apices. Depending on orientation of image sensor (usually with long axis horizontal, less commonly vertical), bitewings will present a smaller or larger portion of dental roots in their coronal parts. The main aim of prescribing a bitewing is to detect early caries on approximal surfaces which may be inaccessible to clinical evaluation, to diagnose the so-called hidden caries, i.e. carietic lesions in dentine undermining clinically unchanged enamel thus invisible in inspection as well as to diagnose early periodontal bone disease. Finally, occlusal radiographs are the ones taken with image receptor placed in the oral cavity in the occlusal plane with X-ray tube aimed from below for mandibular projections and from the top for maxillary radiographs. Again, occlusal radiographs become less appreciated than before in the era of CBCT; however, their use still should be advocated. Some clinical problems may be solved by means of occlusals already in dental office without the necessity of referring a patient for additional examinations in a diagnostic imaging centre, and subjecting the patient to further, and possibly higher doses of ionising radiation. Indications for occlusal radiography include diagnostics of impacted, retained, supernumerary, and additional teeth, diagnostics of trauma, bone expansion in cysts and tumours, presence of periosteal new bone formation (especially in mandibular axial occlusal radiograph), shadows of salivary stones cast against radiolucent oral floor tissues (in the same type of radiograph). Occlusal radiograph may be an alternative to periapical radiography in patients who cannot support image receptors inside the oral cavity.

1  Introduction to Dental Radiography and Radiology

3

The most commonly applied extraoral radiographs are panoramics, which are tomographic (layer) images of curved structures. Apart from teeth located in the imaged plane, called focal trough, these radiographs cover a large portion of maxillofacial skeleton. However due to tomographic character and rotational movement occurring during exposure, panoramic radiographs are prone to many errors and artefacts. Indications to panoramic radiography include the following: • Orthodontic assessment, including presence of teeth germs, stage of development of dentition, presence of supernumerary or retained and impacted teeth, • Impacted third molars, • Periodontal bone disease, offering simultaneous assessment of all teeth and the extent of periodontal bone defects, • Lesions like cysts, tumours and other bone diseases that are too large to be fully imaged by means of periapical radiographs, • Mandibular trauma, • Initial stages of implant planning, • Dental age estimation. Panoramic radiography is not the method of choice for imaging of dental caries, periapical lesions, dental trauma as well as in endodontic treatment. Visualisation of temporomandibular joints may be challenging, too, as whole condylar heads may not fit within the focal trough. Even if they are fully imaged within the focal plane, angulation of long axis of right and left condylar head may be different leading to differences in radiographic image not caused by actual pathology. Moreover, panoramic radiograph is taken in “tête-à-tête” position of incisors which influences location of condylar heads—neither in open nor closed mouth position. Thus it is difficult, if not impossible, to correctly estimate condylar movement basing solely on these radiographs. Midfacial fractures and diseases of maxillary sinuses cannot be reliably diagnosed on panoramic radiographs as only parts of midface fall within the focal trough and lesions placed outside the focal trough are blurred or even invisible in panoramic radiographs. This may lead to underdiagnosis and mistakes in decision on treatment plan. In some countries full mouth surveys including periapicals and bitewings are preferred to panoramic radiography. The reasons include wider availability of intraoral X-ray machines than panoramic ones, as well as higher image resolution and quality in intraoral radiography with far less artefacts and additional shadows than encountered in panoramic radiography. In orthodontics and orthognathic surgery cephalometric radiography is employed, usually in the form of true lateral cephalometric radiographs and also postero-­ anterior cephalometric radiographs and cephalometric axial skull views, otherwise called submento-vertex projection. A lot of panoramic machines are equipped with options allowing taking of tomographic radiographs other than panoramic, such as tomograms of temporomandibular joints, maxillary sinuses and cross-sectional images of alveolar processes. However, as mentioned before, growing availability of CBCT leads to loss of importance of these radiographic projections.

4

1  Introduction to Dental Radiography and Radiology

Even though dental radiographs are fairly frequently taken, they cannot be regarded “routine” or “survey” radiographs. For every X-ray exposure, even performed with a relatively low burden of ionising radiation, must be justified and optimised. Cone-beam computed tomography is also an imaging technique basing on the use of ionising radiation, but in the course of exposure hundreds of X-rays are taken that later form the so-called volume. Image processing leads to creation of numerous slices in different planes (axial, coronal, sagittal, tangential, cross-sectional as well as oblique and drawn along a line or curve). Image resolution is a derivative of voxel size, i.e. length of side of the smallest three-dimensional element in the recorded volume. Fields of view (FoV) in Cone Beam CT can be small (from 3 × 4 cm) through medium (encompassing both upper and lower dental arches) up till large ones (even 30 × 30 cm). Smaller volumes can be virtually “stitched” to form larger ones and this way capacity of smaller image receptors is enhanced, but at the same time it must be remembered that in stitching mode more than one X-ray exposure is required. CBCT also offers a choice of resolutions from very high, e.g. 0.05  mm (important in evaluation of root canals) to lower (in the range of 0.3–0.4  mm) applied in large FoV to demonstrate big structures like maxillary sinuses where thin slices are redundant for diagnosis. Finally, CBCT varies in doses depending on protocols used—from ultralow dose imaging via standard dose to high doses in bigger FoVs, and also in smaller FoVs with very high resolution dedicated to endodontics. Since the advent of CBCT over 20 years ago, numerous guidelines elaborated by different societies and associations have been published. The primary indication for CBCT which is the reason why this imaging method successfully entered dental offices was dental implant planning. But nowadays CBCT is advocated whenever correct diagnosis cannot be reached by two-dimensional radiography, in cases with non-specific or conflicting clinical signs and symptoms, and in all cases where medical CT had been used before, e.g. maxillofacial congenital anomalies, maxillofacial trauma, complicated cases of impacted and retained teeth, suspicion of close anatomical relationship between mandibular third molars and inferior alveolar nerve canal. Currently CBCT is not suitable for reliable diagnosis of soft tissues, and identification of carietic lesions is heavily influenced by the presence of image artefacts if present. CBCT is used not only for diagnosis but also for virtual implant planning, also in conjunction with 3D printing of surgical guides and in CAD/CAM solutions for simultaneous planning of implants and prosthetic crowns produced in milling units. CBCT machine can be fitted with cameras allowing capturing of three-dimensional photographs that can be merged with CBCT data on teeth and skeleton as well as images from intraoral scanners. Albeit X-ray machines are very popular in dental offices, unfortunately not always all pieces of information from the images are retrieved. The reason is multifactorial. In the first instance, maxillofacial anatomy is complex and without fundamental knowledge of normal radiographic anatomy it is impossible to distinguish normal from abnormal findings. Secondly, within maxillofacial area there are found

1  Introduction to Dental Radiography and Radiology

5

not only lesions which are specific for this region, mostly related to teeth and toothbearing structures, and also diseases which affect maxillofacial skeleton the same way they affect the rest of the axial skeleton as well as the appendicular skeleton. While diagnosis of dental-related diseases is fairly easy to a dentist, bone diseases are problematic as they are infrequent in basic dental care and when encountered may be missed or misdiagnosed, e.g. osteomyelitis or fibrous dysplasia. The latter diseases are on the other hand easy to be diagnosed by a radiologist, but at the same time medical radiologists usually possess little or even no knowledge on odontogenic lesions. There are not too many countries where dentomaxillofacial radiology is recognised as a specialty, and even in those where it is often the numbers of specialists are low. Depending on the quality of pregraduate training, dentists are with varying degrees prepared for reporting of dentomaxillofacial radiographs. Finally, not in every country it is mandatory to prepare a written report on a dental radiograph or even a CBCT volume. Therefore many dental radiographs are used only for the main purpose of the examination and other lesions are not reported or even missed. In case of the so-called incidental findings, their importance may be lower (like that of tonsilloliths), but when, for example, odontogenic tumour or oral cancer infiltration are not noted, they will progress and patient’s prognosis deteriorate. In conclusion, dentist should know how to take dental radiographs and CBCT volumes, how errors in radiographic technique can affect the resultant images and compromise diagnosis, how to differentiate normal anatomic landmarks and finally how to interpret radiographic images. Detailed knowledge on every single rare odontogenic tumour reported in literature in just a few cases is not mandatory for a general dentist, but it is essential to be able to identify a lesion in radiograph. If a dentist is not capable of reading and reporting of radiographs, he or she should either continue postgraduate education in this field, or establish cooperation with a knowledgeable specialist such as dentomaxillofacial radiologist, head and neck radiologist or another dentist appropriately trained in reading of dentomaxillofacial radiographic images and CBCT volumes.

2

Materials and Preparation for Dental Radiographs

Materials and machines necessary to take a dental radiograph, intraoral or panoramic: • • • • • • • • • • •

Intraoral (Fig. 2.1a) or panoramic X-ray machine (Fig. 2.1b), Digital image receptor (Figs. 2.2 and 2.3), dedicated scanner for indirect digital image sensors (Fig. 2.4), Whenever mandatory according to local legal provisions, a thyroid collar or shield (Fig. 2.4a) or a lead apron (Fig. 2.4b, c), Single-use plastic envelopes (Fig. 2.3b) or sleeves for image sensors, as well as for bite pieces in panoramic radiography and ear rods in cephalometric radiography, If intraoral radiograph is not taken in a dental chair, then special chair for dental X-rays with adjustable head support is recommended (Fig. 2.1), positioners for paralleling technique and bitewing radiographs (Fig. 2.1), Autoclave for sterilisation of multiple-use positioners, Disinfectant solutions or wipes PC with dedicated software (Fig. 2.5) Examination gloves. Digital image sensors:

–– In general they can be divided into direct and indirect receptors (Fig. 2.2), both are multiple-use types. –– Direct digital sensors include charge-coupled devices (CCD) and complementary metal oxide semiconductor (CMOS). These detectors are also called “solid-­ state” sensors. –– CCD device is a matrix of photostimulable elements registering electric signal proportional to inciding light from scintillator. –– CMOS is a system of photosensitive elements made of transistors built from metal, oxide and semiconductor.

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_2

7

8

2  Materials and Preparation for Dental Radiographs

a

b

Fig. 2.1  X-ray machines. (a) Intraoral with a dedicated chair for dental X-rays. (b) Panoramic with cephalometric appliance and two digital image detectors

a

b

Fig. 2.2  Digital image sensors for intraoral radiography—rigid sensor with a wire and a photostimulable storage phosphor plate (a) tube side and (b) lateral aspect

–– Photostimulable storage phosphor plates (PSP or SPP)—are covered with photostimulable storage phosphor materials that store absorbed energy of the X-ray beam (hence the name storage) in the form of a latent image. When they are subjected to laser energy (HeNe) in a dedicated scanner, the stored energy is released as light photons. This luminescence is detected by a photomultiplier tube which produces an electronic signal. The obtained signal is then converted

2  Materials and Preparation for Dental Radiographs Fig. 2.3  PSP plates in different sizes: 0— paediatric, 2—adult, 4—occlusal. (a) Rear view. (b) Wrapped in protective plastic envelopes

9

a

b

Fig. 2.4  Laser scanner for intraoral indirect digital radiography

to a digital image on screen. After read out in the scanner, the latent image is wiped out and the plate is used for the next exposure. –– Image intensifiers are used in some cephalometric machines, the “one-shot” type. They transform photons of X-rays (electromagnetic radiation) to a stream of electrons which are cast on a screen and produce luminescence.

10

2  Materials and Preparation for Dental Radiographs

Fig. 2.5  Example of digital radiography software

Features of direct digital systems (Figs. 2.1b and 2.2): • Image sensor must be directly linked with a computer by means of a wire or WiFi router. • Directly after exposure image is shown on screen in intraoral radiography, and shortly after exposure in panoramic and other extraoral radiographic techniques once data is uploaded from X-ray machine to a linked computer or server. • In some extraoral machines image preview appears on screen already during exposure which is helpful in case patient movement is noted or major positioning error occurred. Then preview helps in taking a decision on terminating the exposure before it ends as the faulty radiograph will have to be retaken. • Obtained radiograph automatically is diverted to an open patient’s file without further actions from the operator. • Intraoral solid-state sensors are less comfortable to patient and more demanding for the operator to manipulate in the oral cavity as these image detectors are rigid and thicker than PSP plates or analogue film packets. Moreover a wire protrudes from the rear side of the sensor making it even thicker in this area and the whole image detector more bulky. This may produce more intense discomfort to a patient and more severe gagging reflex. Positioning devices for direct digital sensors are different from the ones used for PSP plates and film packets as they must accommodate thicker detectors of variable sizes.

2  Materials and Preparation for Dental Radiographs

11

• Active area of a direct digital image sensor is smaller than the whole device, and also smaller than a PSP plate active area as well as of a conventional film packet. • Solid-state image sensor is not sensitive to light, so it can be exposed to natural or external sources of light without threat of wiping out information on X-ray attenuation. Features of indirect digital systems (Figs. 2.2, 2.3, and 2.4): • Apart from image sensors, a dedicated laser scanner must be purchased. • Time from the exposure to obtaining the radiographs on screen is slightly longer than in direct digital radiography due to the need of performing the read out in the scanner. • Exposed PSP plates do not differ from the unexposed ones, so if attention is not paid to separating used and ready for use PSP plates, they can be confused— e.g. one already exposed can be applied for the second exposure (see— Fig. 7.26). • One scanner can be used for multiple X-ray tubes installed at different dental chairs or in separate X-ray labs. • PSP plates are available in several sizes, from paediatric to occlusal. • Active area of a PSP plate is comparable to that of an analogue film package and is larger than for a solid-state receptor. • PSP plate is thin and somewhat flexible which makes it easier for positioning in oral cavity and reduces patient discomfort during intraoral radiography. • PSP plates are more prone to mechanical damage than solid-state detectors as the layer of storage phosphor can be easily scratched with a nail, prosthesis attachment, sharp margin of a tooth and even slot of positioning device. • Use of PSP in extraoral radiography requires larger scanners, so in dental radiography PSPs are nowadays less frequently used for panoramics and cephalometric radiographs than solid-state sensors. • PSP plate is not as sensitive to light as a conventional film, therefore darkroom conditions are not required for processing of image from a plate. However, prolonged exposure to light (natural or artificial) can cause decrease of image quality after some time, and even lead to overall loss of the latent image. Advantages of digital radiography in comparison with analogue radiography: • Considerable reduction in time between exposure and ready radiograph, especially in direct digital systems. • Decrease in exposure dose from radiography. • Elimination of chemical film processing resulting in environmental protection as well as no need to supervise quality of film processing systems. • Image postprocessing options—image contrast and brightness adjustments, application of image filters.

12

2  Materials and Preparation for Dental Radiographs

• After calibration precise linear and angular measurements can be carried out, especially in intraoral paralleling technique periapicals. • Digital archive of radiographs—less physical storage space needed, easy retrieval of previously taken radiographs for comparison, possibility of generation of multiple copies of every radiograph without loss of image quality. • Teleradiology—image transfer and reporting done via secure picture archiving and communication systems (PACS). • High image resolution. • Wider dynamic range of X-ray which means that digital image receptors react to X-ray exposure and produce data in a wider range of X-ray exposure values. Disadvantages of digital radiography in comparison with conventional X-ray film: • One-time higher cost of implementation of the digital system. • Necessity of protection of stored sensitive patient’s data according to the General Data Protection Regulation (GDPR) in the European Union and similar local legal provisions in other areas of the world. • Some inconveniences in positioning of intraoral solid-state detectors. • Lack of control over radiographs of inferior quality—too many retakes are performed which ironically leads to increase in overall exposure dose to a patient, although a single exposure dose in digital radiography is lower than that for film radiography. • Possibility of tampering of digital radiographic image owing to computer image processing software. • Hardware malfunction and lack of Internet connection makes it impossible to take radiographs and retrieve images from digital archive. Dedicated technical support must be provided. Materials and preparation for analogue dental X-rays will not be discussed as the technique becomes obsolete, and information on analogue radiography can be found in many older sources.

Suggested Reading 1. Farman AG, editor. editor. Panoramic radiology. Seminars on maxillofacial imaging and interpretation. Berlin: Springer; 2007. 2. Langlais RP. Excercises in oral radiology and interpretation. 5th ed. St Louis: Saunders; 2016. 3. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. 4. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. 5. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014.

3

Intraoral Radiography in Dentistry

Intraoral radiographs are X-rays taken with image receptor placed within the oral cavity. Basics of intraoral radiography are the same for digital sensors and analogue films, while positioning may be slightly compromised in direct digital radiography due to a smaller size of active area of receptor in comparison with a PSP plate and conventional film packet. The following intraoral radiographs are available: • Periapical (taken by means of paralleling technique or bisected angle technique). • Bitewing. • Occlusal—maxillary and mandibular, standard, lateral and axial. Periapical radiographs: • Are commonly prescribed and belong to the most frequently taken X-ray images in humans; • Allow one-time demonstration of both teeth and their periapical tissues (hence the name periapicals), • Correctly taken periapical radiograph using digital sensor or film size 2 should demonstrate the whole tooth and about 5 mm of periapical tissues. Techniques of taking periapicals: • Paralleling technique—recommended due to repeatability. • Bisected angle technique—less reliable, but still used in some patients in whom paralleling technique is compromised. Features of paralleling technique: • Requires use of dedicated positioning devices available in sets (including also positioners for bite-wing radiographs) (Fig. 3.1 and Table 3.2); • Maybe more time-consuming than bisected angle technique, especially in initial phases of use before mastering;

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_3

13

14

a

3  Intraoral Radiography in Dentistry

b

Fig. 3.1  Sets of positioning devices for periapicals and bitewings. (a) For PSP plates and film packets. (b) For digital sensors

• Radiographs obtained by means of this technique are repeatable which is of utmost importance in follow-up, measurements and digital subtraction radiography; • Potential drawback is slightly enlarged radiographic image in some cases when due to anatomical conditions it is not possible to place image receptor close to radiographed teeth; • Is preferred to bisected angle technique and should be used whenever possible depending on availability of positioning devices, anatomical relationships in the mouth, patient cooperation, etc.; • Not in every patient it is possible to obtain radiograph by means of this technique, e.g. in patients with shallow hard palate or severe gagging reflex. Features of bisected angle technique (by Cieszyński): • Apparently is more simple than paralleling technique as does not require dedicated positioning devices although certain types of holders are available, but not widespread (Fig. 3.2); • Requires a lot of patient cooperation in supporting image detector; • Is prone to technical errors (see Chap. 7); • The outcome is very dependent on skills of operator; • Radiographs are not repeatable; • When meticulus positioning is carried out and anatomical conditions are favourable, the length of radiographic image of tooth equals real tooth length. Theoretical fundamentals of paralleling technique: • For anterior radiographs long axis of image detector must be vertical and for posterior radiographs—horizontal (Fig. 3.3); • Plane of image receptor is placed in parallel position to long axis of examined tooth;

3  Intraoral Radiography in Dentistry

15

Fig. 3.2  Set of positioning devices for bisected angle technique

Fig. 3.3  Diagram of positioning of image receptor in oral cavity for periapicals of anterior and posterior teeth

• Central X-ray beam falls at right angle to both long axis of image detector and long axis of examined tooth (Fig. 3.4); • Correct spatial relationships between image receptor, examined tooth and X-ray beam are provided by means of a dedicated positioning device (Fig.  3.5 and Table 3.1); • Once patient closes the mouth on the bite piece, image detector changes position to parallel to long axis of examined tooth; ring of positioning device placed close to skin surface aids in aiming X-ray beam at right angle to long axis of radiographed tooth and long axis of image detector, and at the same time at right angle to tangent to dental arch in the area of examined tooth (orthoradial projection) (Fig. 3.4); • Image receptor should be as close as possible to radiographed tooth in order to avoid image magnification; however, in clinical practice it is mostly possible only in case of posterior teeth in mandible; in maxillary posterior teeth positioning to a great extent depends on shape of hard palate—when high, “gothic”, it is easy to ideally position image receptor, but a shallow, flat hard palate forces distance between image detector and radiographed teeth; in case of anterior teeth it is mandatory to place image receptor further inside oral cavity (Fig. 3.6).

16 Fig. 3.4 Paralleling technique—diagram of positioning of image receptor and cone of X-ray tube in relationship to examined tooth. (a) Ideal positioning—image receptor close to long axis of radiographed tooth. (b) Compromised positioning—image receptor parallel to long axis of radiographed tooth, but due to anatomical conditions it is placed at some distance to radiographed tooth

3  Intraoral Radiography in Dentistry

a

Cone

X-ray tube

Image receptor

b X-ray tube Cone

Image receptor

Theoretical fundamentals of bisected angle technique: • Just like in paralleling technique, for anterior radiographs long axis of image detector must be vertical and for posterior radiographs—horizontal; • Central X-ray beam is aimed at radiographed tooth at a certain vertical and horizontal angle; • The rule of isometry (published by Cieszyński in 1906) is used in order to determine correct vertical angulation of X-ray tube cone; • According to this rule long axis of image detector and long axis of radiographed tooth form sides of an angle, which is divided into two by a theoretical line called bisecting line (bisector) (Fig. 3.7); • This way two similar triangles are obtained, having one common side and two identical acute angles, which means that opposite sides of these two triangles are equal; • According to this rule in ideal conditions when central X-ray beam falls at right angle to the bisector, the length of radiographic image of tooth should be equal to real length of tooth; • Bisecting line is theoretical and there are no laser lights to aid in its determination therefore in practice vertical angulation of X-ray tube is based on values of angles derived from Table 3.2, which must be modified according to patient’s anatomy; it must be underlined that the values are only guidelines and can also vary between different educational resources, so it is necessary to individually

3  Intraoral Radiography in Dentistry

17

a

b

c

d

e

f

g

h

Fig. 3.5  Correct assembly of positioning devices. (a, b) Paralleling technique anterior maxilla. (c, d) Paralleling technique posterior maxilla. (e, f) Paralleling technique anterior mandible. (g, h) Paralleling technique posterior mandible. (i, j) Bitewing

18

3  Intraoral Radiography in Dentistry

i

j

Fig. 3.5 (continued) Table 3.1  Positioners for paralleling technique and for bitewings • There are many sets of positioning devices available in the market, both with separate elements for anterior, posterior and bitewing radiographs as well as multipurpose sets • Usually a positioning device for paralleling technique and bitewings consists of three elements: ring, metallic rod and bite piece with image detector holder • In some sets colour coding is applied, e.g. blue for anterior periapicals, yellow for posterior periapicals, red for bitewings • Positioners for anterior teeth periapicals are symmetrical, so the same assembly can be used for radiography of upper and lower incisors and canines • Positioners for posterior teeth periapicals are asymmetrical. Same assembly can be applied for right maxilla and left mandible, then the opposite for both left maxilla and right mandible • Image detector holders for PSP plates and film packets are similar and contain a groove for fixing edge of image receptor, while positioners for direct digital (“solid state”) detectors are fitted with mobile grips that allow adjusting to a certain image receptor (taking into account different sizes of image detectors) • After exposure all elements of positioning device must be sprayed with disinfectant, while those which were in contact with oral cavity environment sterilised

adjust the vertical angulation basing on assessment of bisector. This of course requires skills and experience. • Horizontal angulation of central X-ray beam is aimed at right angle to tangent to dental arch in the area of radiographed tooth—i.e. orthoradially (Fig. 3.8); unless there are indications for oblique projection.

3.1

Taking a Periapical by Means of Paralleling Technique

3.1.1 Introductory Steps • • • •

Read prescription, if available. Make sure that the radiograph is justified. Make sure that patient or his/her guardian obtained information on radiation risk. Make sure if the patient or his/her guardian signed an informed consent to radiograph, whenever mandatory according to local legislation.

3.1  Taking a Periapical by Means of Paralleling Technique

a

b

c

d

19

Fig. 3.6  Position of image receptor in relations to radiographed teeth. (a) Maxillary anterior. (b) Maxillary posterior. (c) Mandibular anterior. (d) Mandibular posterior Fig. 3.7  The rule of isometry (by Cieszyński). Central X-ray beam is aimed at right angle to theoretical bisector between long axis of tooth and long axis of image detector

Tooth axis

Bisector

Central X-ray beam

Image receptor

20

3  Intraoral Radiography in Dentistry

Table 3.2  Vertical angulation of central X-ray beam in bisected angle technique

Fig. 3.8  Diagram of direction of central X-ray beam in relations to tangent to dental arch— orthoradial or oblique projection

Group of teeth Maxilla Incisors Canines Premolars Molars Mandible Incisors Canines Premolars Molars

Vertical angulation +45° +50° +40° +30° −25° −20° −15° −5°

orthoradial mesial oblique

mesial oblique

distal oblique

distal oblique

• Ask patient in reproductive age if she is not pregnant; although pregnancy is not an absolute contraindication to radiography, if it is possible to delay examination, X-rays should be preferably taken after birth. • Open or create patient file in dedicated software; depending on software at this step it may be necessary to mark tooth that is to be radiographed. • Choose appropriate image receptor. Put a single-use protective sleeve on direct digital image receptor. Pack PSP plate in a single-use protective sleeve. Prepare a fresh film packet, if analogue radiography is still used.

3.1.2 Patient Preparation • Ask patient to remove metallic objects that can cause artefacts from the ­radiographed area. • In case of periapicals such objects are removable dentures, removable orthodontic appliances, piercings, glasses. • For paralleling technique periapicals patient may be sitting or reclining in dental chair. • Whenever mandatory according to local regulations, thyroid shield or thyroid collar must be used, especially in children. If patient’s guardian remains by patient’s side during exposure, he/she must wear protective lead apron, whenever mandatory according to local regulations.

3.1  Taking a Periapical by Means of Paralleling Technique

21

3.1.3 Assembling of Positioning Device 3.1.3.1 Anterior Periapicals of Maxilla and Mandible • Prepare parts of a symmetric positioning device (often marked with blue colour) (Fig. 3.9). • Assemble the positioner in such a way that part supporting image receptor is visible in the middle of the positioning ring. • Protect image receptor from contamination by applying a single-use plastic or rubber protective sleeve. • Place image detector along the dedicated part of positioner, in case of PSP plate or film packet, put them firmly in groove of bite piece to avoid shifting of image detector during positioning; in case of direct digital sensor use adjustable grips to fix the receptor. • Make sure that image receptor is firmly placed in the groove of bite piece or in the grip and would not fall out or be displaced during positioning in oral cavity. • Long axis of image receptor must be vertical. • If image detector is fitted with a “dot” for orientation, it must be positioned with “dot in the slot”—this way in the resultant radiograph the dot will fall around images of crowns and this way will not interfere with interpretation of images of periapical tissues. Fig. 3.9  Control panel of an intraoral X-ray tube. Choice of exposure parameters

22

3  Intraoral Radiography in Dentistry

3.1.3.2 Posterior Periapicals of Maxilla and Mandible • Prepare parts of an asymmetric positioning device (often marked with yellow colour) (Fig. 3.10). • Assemble the positioner in such a way that part supporting image receptor is visible in the middle of the positioning ring. • Remember that assembly of positioning device for right and left maxilla is different, and the same applies to the right and left mandible. But if you rotate the positioner assembled for right maxilla by 180°, it will be suitable for radiography of left mandible (Fig. 3.11a). a

c

b

d

Fig. 3.10  Correctly assembled positioning device—image receptor falls in the centre of ring. (a, b) For radiographs of anterior teeth. (c, d) For radiographs of posterior teeth in the first quadrant

a

b

Fig. 3.11  Difference in assembly of positioner for radiography in third quadrant (a), and fourth quadrant (b) is visible in space provided for soft tissues of cheek

3.1  Taking a Periapical by Means of Paralleling Technique

23

• Vice versa, the assembly for left maxilla is identical as that for right mandible, when rotated by 180° (Fig. 3.11b). • A hint on how to remember this rule is to correlate quadrants of dental arches— odd (quadrants I and III) and even (quadrants II and IV) as compatible when assembly of positioning device is concerned. • Another hint is that one has to imagine that patient’s cheek must fit within space provided by shape of positioning device, otherwise buccal tissues will be stuck against metallic rod of positioner causing even more discomfort to the patient than normally. • Place image detector along the dedicated part, in case of PSP plate or film packet, put them firmly in groove of bite piece to avoid shifting of image detector during positioning; in case of direct digital sensor, use adjustable grips to fix the receptor. • Make sure that image receptor is firmly placed in the groove of bite piece or in the grip and would not fall out or be displaced during positioning in oral cavity. • Long axis of image receptor must be horizontal. • If image detector is fitted with a “dot” for orientation, it must be positioned with “dot in the slot”—this way in the resultant radiograph the dot will fall around images of crowns and this way will not interfere with interpretation of images of periapical tissues.

3.1.4 Positioning • Ask the patient to open the mouth. • Delicately introduce positioning device with image receptor inside oral cavity, then place it in such a way that it is on palatal or lingual side of examined tooth. Distance between image receptor and radiographed tooth varies and depends on anatomical conditions. Usually only in case of lower molars it is possible to place image detector in vicinity of examined tooth. In case of upper teeth the distance between tooth and image receptor may be considerable. • Avoid placing positioning device on top of tongue, on sublingual caruncle (very sensitive) and too close to examined tooth (sensitive gingiva, problems with rotation of bite piece after closing the mouth). • Radiographed tooth shall be positioned facing the middle part of image receptor. • Ask the patient to close the mouth. • Once mouth is closed, patient bites on bite block and this causes change in position of image receptor resulting in positioning of plane of image detector parallel to long axis of examined tooth. • In case it is difficult for patient to bite on bite piece and/or there are missing teeth, a cotton roll can be applied. It must be placed under bite piece opposite to examined tooth. If cotton roll is put directly between radiographed tooth and bite piece, crown will be moved away from bite piece and at the same time margin of image detector displaced away from area of cone of X-ray tube. This way image will be cropped in periapical area. • Check if once patient closed the mouth and bite piece rotated, the image detector is still correctly positioned within positioner—not rotated.

24

3  Intraoral Radiography in Dentistry

a

b

c

d

e

f

Fig. 3.12 (a–f) Positioning for paralleling technique radiograph of anterior maxillary teeth

• Check if image receptor plane is placed parallel to tangent to dental arch in the area of radiographed tooth, i.e. orthoradially. If an oblique periapical radiograph is requested, tube must be aimed from mesial or distal side of examined tooth. Positioning for the following periapical radiographs taken by means of paralleling technique is presented in the subsequent figures: anterior maxilla (Fig. 3.12), posterior maxilla (Fig. 3.13), anterior mandible (Fig. 3.14) and posterior mandible (Fig. 3.15).

3.1.5 Instructions for Patient • Directly before exposure, instruct the patient not to move or displace positioning device.

3.1  Taking a Periapical by Means of Paralleling Technique

a

b

c

d

e

f

25

Fig. 3.13 (a–f) Positioning for paralleling technique radiograph of posterior maxillary teeth. Taking a radiograph in left maxilla requires change in assembly of positioning device from the first quadrant setting

3.1.6 Exposure • Depending on local regulations, which may vary in different countries—leave X-ray room or protect yourself from radiation by means of a lead screen or step away 2 m from source of X-rays. • Press exposure button and hold it for duration of the exposure, which is very short in intraoral radiography. However remember that production of X-rays begins with a slight delay after pressing the exposure button. Generation of X-rays is signalled by sound and light control (e.g. yellow light on exposure button). If you just press the button and let it go, X-rays will not be produced and error sign will appear. • Maintain visual control of the patient via lead window or video camera. • Stop the exposure once you notice that patient moved (e.g. sneezed or coughed). Retake may be needed.

26

3  Intraoral Radiography in Dentistry

a

b

c

d

e

f

Fig. 3.14 (a–f) Positioning for paralleling technique radiograph of anterior mandibular teeth

3.1.7 After Exposure • Remove thyroid shield or thyroid collar. • Delicately remove image receptor from oral cavity. • Direct digital radiograph: remove and discard single-use sleeve from detector, place detector in dedicated grip if available. • Indirect digital radiograph: perform read-out in laser scanner (Fig. 3.16). • Save image in database. • Film radiography: perform film processing. • Wipe positioner, spray with disinfectant and later prepare for sterilisation. • Be ready for the next exposure.

3.2  Taking a Periapical by Means of Bisected Angle Technique

a

b

c

d

e

f

27

Fig. 3.15 (a–f) Positioning for paralleling technique radiograph of posterior mandibular teeth. Taking a radiograph in left mandible requires change in assembly of positioning device from the third quadrant setting

3.2

 aking a Periapical by Means of Bisected T Angle Technique

3.2.1 Introductory Steps Are the same as in paralleling technique (see above), but positioning is different.

3.2.2 Patient Positioning in Bisected Angle Technique • Ask patient to sit in a chair, best if it is a dedicated chair for dental radiography with an adjustable head support (Fig. 3.16).

28

3  Intraoral Radiography in Dentistry

Fig. 3.16  Read-out of PSP plate in laser scanner

• Put patient’s head symmetrically with midline perpendicular to ground. • Align Camper’s plane correctly. This is the line running from tragus of the ear to external canthus of the mouth. For maxillary periapicals it must be horizontal (Fig. 3.17a, b). For mandibular periapicals occlusal plane of mandible must be horizontal (Fig.  3.17c, d). Correct position of patient’s head is essential as in bisected angle technique as vertical angulation of X-ray tube is set in relationship to horizontal plane. • Ask the patient to open the mouth (Fig. 3.18a). • Delicately introduce the image receptor into oral cavity, at first horizontally and centrally, then rotate it and place in such a way that it is located as close as possible to the examined tooth (Fig. 3.18b, c). • Remember that image detector must be facing X-ray tube with the active side. In case of film packet, the correct tube side is usually white and the reverse side of the packet can bear an inscription such as “Opposite side toward tube” or in three languages, e.g. English/French/German—“Back Dos Rückseite”. This way the dot will be facing X-ray tube with convex side. In film packets orientation dot is used to differentiate quadrants in the resultant radiograph. During positioning, the dot should be located in the area of crowns, then it will be easy to differentiate upper from lower teeth. If this rule is not followed, maxillary and mandibular teeth must be differentiated on the basis on radiological anatomy only. Convex side of dot on film packet shall face X-ray tube so that the dot serves to differentiate right from left side of the jaw. When radiograph is placed on lightbox and convex side of dot faces the observer, tooth sequence aids in determination which quadrant it is. • Some PSP plates also have a mark in the form of dot but not convex. • Active surface of a direct digital image receptor is usually clearly marked and back side contains wiring. • Long axis of image receptor must be vertical for radiographs of anterior teeth and horizontal for radiographs of posterior teeth (Fig. 3.3).

3.2  Taking a Periapical by Means of Bisected Angle Technique

a

b

c

d

29

Fig. 3.17  Patient position for bisected angle technique periapical. Patient is seated in a dedicated chair with adjustable headrest. (a, b) Head position for maxillary periapicals. (c, d) Head position for mandibular periapicals

• Image detector must be placed in the oral cavity in such a way that the radiographed tooth is in the middle of the surface of image detector. • Put the image receptor in so that 2–3 mm of active surface projects outside incisive margins or cusps of crowns which guarantees imaging of the whole crown in the resultant radiograph (Fig. 3.18c). • Once image detector is placed in the oral cavity, patient cooperation is needed in supporting the sensor with thumb of contralateral hand for upper teeth or index finger for lower teeth. • In case of uncooperative patients (small children, senile patients, mentally disabled patients), it may be acceptable that patient’s parent or legal guardian or staff member supports image detector when adequate radiation protection is applied. Check local legal provisions if this is allowed. • Image receptor should be supported by operator until it is cross-checked that patient holds it correctly. This is the step which is crucial as patient may intentionally or unintentionally move image detector in order to avoid gagging reflex or even sensation of pain.

30

a

3  Intraoral Radiography in Dentistry

b

c

Fig. 3.18 (a–c) Subsequent stages of introduction of image detector inside oral cavity

• Aim cone of X-ray tube according to the following steps: entry point, vertical and horizontal angulation. • Entry point of central X-ray beam: in maxilla it is aimed at a line connecting ear tragus with ala of the nose, while in mandible at inferior margin of mandible. The following lines are applied for groups of teeth: incisors—midsagittal plane, canines—line passing through internal canthus of the eye, premolars—line passing through pupil, molars—line passing through external canthus of the eye, third molar—1 cm distal to the line for molars (Fig. 3.19). • Aim central X-ray beam at correct vertical angle derived from dedicated tables (Table 3.2), modified according to individual anatomic conditions. Use a graduated arc of X-ray tube to set angulation. Remember that angle values from tables are only guidelines, e.g. in case of lower molars despite guidelines giving value of −5 degrees, image receptor may be ideally parallel to the axes of teeth, thus no vertical angulation on X-ray cone is necessary (0 angle). • At the same time aim central X-ray beam at right angle to tangent to dental arch (orthoradial projection) (Fig. 3.8). • If oblique projection is requested—mesial or distal oblique—tube must be rotated in horizontal plane either anteriorly or posteriorly (Fig. 3.8). Positioning by means of bisected angle technique is presented in the subsequent figures for upper incisors (Fig.  3.20), upper canine (Fig.  3.21), upper premolars (Fig.  3.22), upper molars (Fig.  3.23), lower incisors (Fig.  3.24), lower canines (Fig. 3.25), lower premolars (Fig. 3.26) and lower molars (Fig. 3.27).

3.2  Taking a Periapical by Means of Bisected Angle Technique Fig. 3.19  Lines used for aiming central X-ray beam

a

b

c

Fig. 3.20 (a–c) Positioning for bisected angle technique periapical of upper incisors

31

32

a

3  Intraoral Radiography in Dentistry

b

c

Fig. 3.21 (a–c) Positioning for bisected angle technique periapical of upper canines

a

b

c

Fig. 3.22 (a–c) Positioning for bisected angle technique periapical of upper premolars

3.2  Taking a Periapical by Means of Bisected Angle Technique

a

b

c

Fig. 3.23 (a–c) Positioning for bisected angle technique periapical of upper molars

a

b

c

Fig. 3.24 (a–c) Positioning for bisected angle technique periapical of lower incisors

33

34

3  Intraoral Radiography in Dentistry

a

b

c

Fig. 3.25 (a–c) Positioning for bisected angle technique periapical of lower canines

a

b

Fig. 3.26 (a, b) Positioning for bisected angle technique periapical of lower premolars

3.2.3 During and After Exposure Follow the same steps as for paralleling technique.

3.3

Taking a Bitewing Radiograph

Apart from positioning, other actions are the same as for periapical radiographs. Positioning for bitewing radiograph (Fig. 3.28): • Choose image detector which can be: • Digital sensor in a special positioning device for bitewing radiographs that holds the detector at the same time at level of crowns of upper and lower teeth,

3.3  Taking a Bitewing Radiograph

a

35

b

c

Fig. 3.27 (a–c) Positioning for bisected angle technique periapical of lower molars

• Size 1 film packet (54 × 27 mm) with a special tab (“wing”) for the patient to bite on, • Traditional size 2 film packet with added band with a wing or adhesive bite piece. • Place image receptor at the level of radiographed teeth (mostly premolars and molars) at their lingual side. • Ask patient to close the mouth. This way patient will bite on the bitewing and this allows to maintain correct position of image detector at the level of crowns of upper and lower teeth at the same time. • Digital radiographs: at this step make sure that digital receptor is still correctly positioned in device. • Analogue radiographs: delicately pull tab of film packet so that it adheres to teeth. • If radiograph is not taken using positioning device, then patient’s head must be symmetrical with midsagittal plane perpendicular to the ground and Camper’s line must be parallel to the horizontal plane. • Positioning device guides aiming of the X-ray tube. • If radiograph is not taken using positioning device, then main X-ray beam must fall orthoradially at approximal spaces of teeth at about minus 5–10 degrees in relationship to occlusal plane.

36

3  Intraoral Radiography in Dentistry

a

b

c

d

e

f

Fig. 3.28 (a–f) Positioning for bitewing radiograph

3.4

Taking an Occlusal Radiograph

Apart from positioning, other actions are the same as for periapical radiographs. Positioning for different occlusal projections is discussed in Table 3.3 and in figures—standard maxillary occlusal (Fig. 3.29), oblique maxillary occlusal (Fig. 3.30), standard mandibular occlusal (Fig. 3.31), oblique maxillary occlusal (Fig. 3.32) and axial mandibular occlusal (Fig. 3.33). Axial maxillary occlusals are rarely taken as radiosensitive lens of the eye falls within the central X-ray beam during taking of this radiograph, so direct exposure to ionising radiation is not advocated.

3.4  Taking an Occlusal Radiograph

37

Table 3.3  Positioning for occlusal radiographs

Position of image detector Image detector is placed inside oral cavity and on occlusal surface of lower teeth. Active side of image detector must be facing Axial upwards (in case of film maxillary packets white side must be facing X-ray tube). In adults image receptor is positioned with long axis across midsagittal plane, while in children along midline in antero-posterior direction. Then patient is asked to cautiously close the mouth Standard Patient sitting with Image detector is placed in oral cavity on the mandibular head supported radiographed side, on top against headrest and occlusal plane of occlusal surface of lower teeth. Active side of is horizontal, image detector must be parallel to the facing upwards (in case of ground film packets white side must be facing X-ray tube). Then patient is asked to cautiously close the mouth Oblique Patient sitting with Image detector is placed in oral cavity on the mandibular head supported radiographed side, on top against headrest. Once patient closes of occlusal surface of lower teeth. Active side of the mouth on the image detector must be image detector, patient’s head must facing upwards (in case of film packets white side be turned to the side opposite from must be facing X-ray tube). Then patient is radiographed and asked to cautiously close chin lifted the mouth Standard maxillary Oblique maxillary

Patient position Patient sitting with head supported against headrest and occlusal plane is horizontal, parallel to the ground

Entry point of central X-ray beam Root of the nose

Angulation of central X-ray beam 65–70°

65–70° Inferiorly on cheek on radiographed side 90° Inferiorly in midsagittal plane, towards skull vertex, so more or less along root canals of upper incisors

Chin in midline

45°

X-ray tube is aimed upwards and anteriorly, towards image detector, from below and back of mandibular angle as well as at right angle to tangent to lingual surface of mandible

(continued)

38

3  Intraoral Radiography in Dentistry

Table 3.3 (continued) Entry point of central X-ray Patient position Position of image detector beam Image detector is placed in In midline under Axial Patient sitting. patient’s chin mandibular Once patient closes oral cavity on the radiographed side, on top the mouth on the of occlusal surface of image detector, lower teeth. Active side of patient leans image detector must be forward and then facing upwards (in case of has to tilt head backwards as much film packets white side must be facing X-ray as possible and tube). Then patient is support against asked to cautiously close headrest the mouth

a

b

Fig. 3.29 (a, b) Positioning for standard maxillary occlusal radiograph Fig. 3.30  Positioning for oblique maxillary occlusal radiograph

Angulation of central X-ray beam At right angle to image detector

3.4  Taking an Occlusal Radiograph

a

39

b

Fig. 3.31 (a, b) Positioning for standard mandibular occlusal radiograph

a

b

c

Fig. 3.32 (a–c) Positioning for oblique mandibular occlusal radiograph Fig. 3.33  Positioning for oblique mandibular axial radiograph

40

3.5

3  Intraoral Radiography in Dentistry

Limitations of Taking Intraoral Radiographs

• There is no age limit (upper or lower) for taking an intraoral radiograph, but the real limitation is patient’s ability to cooperate which is decreased or even non-­ existent in small children, but it can also be compromised in elderly patients with dementia or neurological disorders. • Usually the main limitation of taking periapicals in small children is lack of justified indications. • Radiographs taken without positioning devices require maintaining of sitting position, thus are impossible in unconscious patients and those who cannot sit in upright position. • In rare cases of taking periapical radiographs in unconscious patients, paralleling technique is recommended as image detector is supported by positioning device and not by another person, so there are no radiation protection concerns. • Taking a periapical radiograph by means of bisected angle technique is more difficult, and also required assistance from another person such as family member or other staff member (depending on local legal provisions). • Anatomical and pathological conditions in oral cavity (malocclusion, missing teeth, periodontal bone disease with mobile teeth, status after trauma, also with coexisting tooth mobility, etc.) influence positioning which sometimes can be compromised and despite meticulous care good quality radiography is not possible. • In patients with lockjaw, it is not possible to place image receptor inside oral cavity, so panoramic radiography should be considered as an alternative to intraoral radiography. • Many patients suffer from gagging reflex especially when positioning device for paralleling technique is used, then alternatively bisected angle technique can be applied or even panoramic radiography. • In order to diminish gagging reflex patient is asked to breathe calmly via nose, operator can also try to distract patient with some other minor activity by asking to perform a small task not directly related to X-ray procedure. • Some patients feel strong discomfort or even pain related to intraoral image receptor, even without positioning device, and refuse to have an intraoral radiograph taken. Then topical spray anaesthesia application may be a solution.

Suggested Reading Bahrami G, Hagstrøm C, Wenzel A.  Bitewing examination with four digital receptors. Dentomaxillofac Radiol. 2003;32(5):317–21. Dixon DA, Hildebolt CF.  An overview of radiographic film holders. Dentomaxillofac Radiol. 2005;34(2):67–73. Farman AG.  Standards for intraoral radiographic imaging. Dentomaxillofac Radiol. 2000;29(5):257–9. Gonçalves A, Wiezel VG, Gonçalves M, Hebling J, Sannomiya EK. Patient comfort in periapical examination using digital receptors. Dentomaxillofac Radiol. 2009;38(7):484–8.

Suggested Reading

41

Langlais RP. Exercises in oral radiology and interpretation. 5th ed. St Louis: Saunders; 2016. Larheim TA, Westesson P-LA, editors. Maxillofacial imaging. 2nd ed. Berlin: Springer; 2018. Mamoun JS.  Assembly and clinical use of the XCP dental X-ray film holder and orientation devices in dentistry. Dent Assist. 2011;80(1):8, 10, 12–4 passim. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. Wenzel A, Møystad A. Experience of Norwegian general dental practitioners with solid state and storage phosphor detectors. Dentomaxillofac Radiol. 2001;30(4):203–8. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014. Zhang W, Huynh C, Jadhav A, Pinales J, Arvizu L, Tsai J, Flores N. Comparison of efficiency and image quality of photostimulable phosphor plate and charge-coupled device receptors in dental radiography. J Dent Educ. 2019;83(10):1205–12.

4

Panoramic Radiography in Dentistry

Features of panoramic radiography: • Allows one-time imaging of teeth, mandibular bone, parts of maxilla including a large portion of maxillary sinus, hard palate as well as both TMJs. • Always must be justified and referral is based on indications and radiation risk assessment, and cannot be taken as a “routine” radiograph. • Is a tomographic radiograph which means that only the so-called focal trough (focal plane) is clearly visible while structures outside the focal trough are invisible or blurred (Fig. 4.1). • Requires synchronised movement of X-ray tube and image detector in opposite directions. • Tomographic movement is carried out in horizontal plane along a curve adjusted to shape of dental arches owing to application of a robotic C-arm in panoramic machine (Fig. 4.2). • Complex projection geometry with rotational movement results in different types of shadows obtained in the panoramic radiograph—single shadows of structures located within the focal trough, double real shadows of single structures located near midline, but outside focal trough and ghost shadows of double structures closer to edges of panoramic radiograph, also located outside the focal trough. • Advances in panoramic radiography are based on reduction of exposure time, reduction of exposure dose, increase of image sharpness as well as registration of several parallel thinner layers within the focal trough instead of one thick slice. Automatic image postprocessing can be applied to select the best-quality segments within these layers and compile them to one high-quality radiograph (Fig. 4.3). Alternatively operator can scroll through layers choosing more buccal or more palatal images, and assess, for example, roots of upper molars separately. Taking of a panoramic radiograph is fairly easy when the rules of positioning are obeyed. If subsequent steps in taking a panoramic are carefully followed, in © Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_4

43

44

4  Panoramic Radiography in Dentistry

Fig. 4.1  Diagram of focal trough

Fig. 4.2  Diagram of rotational tomographic movement of X-ray tube and image sensor in opposite directions

Image receptor X-ray tube

Fig. 4.3  Diagram of creation of a high-quality panoramic radiographs from the most clear segments of registered layers (courtesy of Mr. Bartosz Sywula)

4.1  Steps in Taking a Panoramic Radiograph

45

majority of patients it is possible to obtain a good diagnostic-quality radiograph. Every retake of a radiograph is an additional, unjustified patient exposure to ionising radiation. Despite advances in panoramic technology including image registration and positioning devices, still in some patients it is not possible to obtain a good-­ quality radiograph due to uncooperativeness or anatomical/pathological considerations.

4.1

Steps in Taking a Panoramic Radiograph

4.1.1 Introductory Steps • • • •

Read the prescription. Make sure that the radiograph is justified. Make sure that patient or his/her guardian obtained information on radiation risk. Make sure if the patient or his/her guardian signed an informed consent to radiograph, whenever mandatory according to local legislation. • Ask patient in reproductive age if she is not pregnant; although pregnancy is not an absolute contraindication to radiography, if it is possible to delay examination, X-rays should be preferably taken after birth. • Open or create patient file in dedicated software; depending on software at this step exposure settings and dental arch shape are chosen (Fig.  4.4). Inputting patient’s date of birth and gender results in default settings which can be individually adjusted. If possible, choose a section of panoramic radiograph to be taken instead of the whole radiograph.

Fig. 4.4  Screenshot of software with choice of exposure parameters and shape of dental arches

46

4  Panoramic Radiography in Dentistry

4.1.2 Patient Preparation • Ask patient to remove metallic objects that can cause artefacts from the radiographed area. • The objects include: removable prosthesis, removable orthodontic appliances, earrings, piercing (including tongue), glasses, necklaces, chain necklaces, hair pins, hearing aids. • Whenever mandatory according to local legal provisions, lead apron without thyroid collar must be used. As X-ray tube rotates around patient’s back, the lead apron should be worn with longer side on patient’s back or a two-sided (front and back) one should be used. If patient’s guardian remains by patient’s side during exposure, he/she must wear protective lead apron, whenever mandatory according to local regulations.

4.1.3 Patient Positioning • Depending on patient’s dentition choose a bite piece (Fig. 4.5) and if patient’s anterior (and more) teeth are missing, teeth are mobile (e.g. periodontal bone disease) or patient is traumatised, chin support for edentulous people (Fig. 4.6). • Cover the bite piece with a single use sleeve or use a sterile bite piece. Spray chin support with disinfectant solution. • Initially adjust the level of C-arm with positioning device to patient’s height. • Ask the patient to enter inside the C-arm. In many machines it is possible to choose such a position of C-arm which is more convenient for patient to enter a

Fig. 4.5 (a, b) Bite piece for dentate patients

b

4.1  Steps in Taking a Panoramic Radiograph

a

47

b

Fig. 4.6 (a, b) Chin support for edentulous patients Fig. 4.7 Handles

inside without risk of hitting elements of the device. If the device is fitted with a dedicated seat, ask patient to sit down. If the device is designed to accommodate patients standing up, and patient is too tall or too short, modify the technique. If a patient is too tall, ask him to sit down on a stool without back rest. If a child is too small, use a step stool. In machines without dedicated seat you can examine patients in wheelchair, unless wheels collide with base of the machine (in free standing machines). Finally adjust the C-arm to the level of patient’s head. • Ask the patient to grab the handles (Fig. 4.7). It may be necessary to ask a standing up patient to take half a step forward as if he/she gets an impression to be falling backwards (Fig. 4.8). This move results in straightening of cervical spine.

48

4  Panoramic Radiography in Dentistry

Fig. 4.8  Adopting straight position

• Ask the patient to put chin on chin support or on a special chin support for edentulous individuals. The level of chin support must be chosen in such a way that patient’s neck is straight. • Ask a dentate patient to bite on bite piece and put incisive edges of upper and lower anterior teeth in groove on the bite piece. • Use laser lights to guide positioning (Fig. 4.9). • The first laser light is used to position head symmetrically. It should fall between upper central incisors. Remember that soft tissues of face may be asymmetrical and midline of dental arch may not correlate with midline of patient’s facial tissues. Positioning of the first laser light may be challenging in patients with dental anomalies concerning anterior teeth and in those with missing anterior teeth (Fig. 4.10). • The second laser light is used to highlight the Frankfort plane i.e. line running from tragus of the ear to infraorbital rim. Correct position of this line ensures horizontal alignment of occlusal plane which in the resultant radiograph will be flat or resemble a wide, flat letter U (Fig. 4.11).

4.1  Steps in Taking a Panoramic Radiograph Fig. 4.9  Use of laser lights for positioning

Fig. 4.10 Symmetrical positioning of head using the first laser light

49

50

4  Panoramic Radiography in Dentistry

Fig. 4.11  Adjustment of Frankfort plane using the second laser light

• Some panoramic devices are fitted with cameras aiding in positioning. Then the Frankfort plane is highlighted with colour in camera image, and e.g. red when incorrect and green when acceptable. • Not every panoramic machine is equipped with the third laser line. The course of this line aids in choice of correct focal trough. This line should run between upper lateral incisor and upper maxillary canine, while in edentulous patients it should fall on the angle of the mouth (Fig. 4.12). This line should be checked in image of lateral camera or when operator is standing at patient’s side. • Cross-check if patient position is correct. • At this step temporal supports must be closed (either by pressing a button or automatically after pressing “Ready” button on control panel).

4.1.4 Instruct the Patient • Fulfilling of correct instructions by the patient directly before exposure is crucial for obtaining a high-quality radiograph. • Directly before exposure ask the patient to: –– Swallow—in order to prevent swallowing during exposure which may result in motion artefacts. –– Close the mouth—to remove air from between open lips and prevent from radiolucent shadow cast on images of crowns of incisors. –– Put the tongue against the hard palate—to push air from the oral cavity in order to prevent from appearance of radiolucent shadow in form of a flat crescent overlapping periapical areas of maxillary teeth thus making diagnosis of periapical lesions more difficult. –– Breath normally during the exposure—some patients cannot hold breath for a longer while. –– Not move for the duration of the exposure—to avoid motion artefacts.

4.1  Steps in Taking a Panoramic Radiograph

51

Fig. 4.12  Selection of focal trough using the third laser light

4.1.5 X-ray Exposure • Press ready button on control panel. • According to local legal provisions leave X-ray room or protect yourself behind a wall or lead screen, or step away from the controlled area around the source of radiation. • Press exposure button and hold it for the duration of the exposure. Remember that production of X-ray starts with a little delay in relation to the moment of pressing the button. If you just press and release immediately, exposure will not take place. Generation of X-rays is usually marked by means of visual and/or audio signals e.g. yellow light on the exposure button as well as on the machine itself. • Survey the patient during the exposure via a lead window or a screen of a video camera.

52

4  Panoramic Radiography in Dentistry

• If during the exposure you notice abnormal patient activity (sneezing, coughing, other movement), immediately release the exposure button to discontinue X-ray generation as most probably the radiograph will have to be retaken. In some machines image preview is visible live on screen during exposure and it allows verification whether patient movement caused motion artefacts in the resultant radiographic image. In some panoramic machines patient movement compensation is applied, but only in limited range (up to 1.5 cm) and is not useful in case of sharp, severe movements.

4.1.6 After Exposure • • • •

Release the patient. Remove protective lead apron, whenever applicable. Save the ready radiograph in database. Prepare the panoramic machine for the next exposure (remove single-use protective sleeve from bite piece, use disinfectant spray for multiple use parts that are in contact with patient’s body). Limitations and difficulties in panoramic radiography:

• Errors and artefacts may occur at every stage of taking a panoramic radiograph (see: Chap. 7). • Panoramic radiography cannot be taken in neonates, unconscious patients and individuals who cannot maintain erect position of cervical spine even when sitting. • Lack of cooperation in a child. Although sometimes age limitations for panoramic radiography are set by legal provisions (e.g. 5 years), in many countries there is no strict age limit. The possibility of taking a panoramic X-ray depends on ability to follow the instructions of staff and then to maintain motionless position during the exposure. Sometimes it is possible to obtain a good panoramic even in a 3-year-old child, while anxiety may hamper taking the exposure even in much older and not mentally impaired children. The main reason for limitation of panoramic radiography in the youngest patients is lack of justified indications at this age. • Involuntary movements (tics, jerks, myoclonic seizures, tremors) may result in inferior-quality radiographs or giving up the exposure altogether. It is advocated to examine patients with diseases such as Parkinson’s disease in panoramic machines allowing compensation for smaller movements. • Taking a panoramic in a mentally disabled patient or a senile one with dementia can be very challenging, too, and sometimes impossible. The reasons are again impossibility to stand or sit still during the exposure producing movements larger than potentially compensated by a modern panoramic machine. Also incomprehension of instructions of staff (due to dementia, illness, hearing impairment) may result in inferior-quality radiographs or giving up the exposure altogether.

4.1  Steps in Taking a Panoramic Radiograph

53

• In patients with advanced Class II or Class III malocclusion it may be impossible to place upper and lower incisors in groove on bite piece. The resultant radiograph will clearly show either upper or lower jaw depending on whether maxillary or mandibular teeth were positioned within the focal trough. Systems allowing one-time registration of multiple thinner layers within the focal plane make it easier to examine such demanding patients. • Large facial skeleton asymmetry makes positioning of right and left side of the face within the focal trough challenging. The resultant radiograph will present one side more clearly than the other. • Advanced periodontal bone disease with tooth mobility affects patient ability to bite the groove on the bite piece as during closing the mouth mobile teeth tend to tilt. In such case using a chin support for edentulous patients and separating upper and lower incisors with a cotton roll may be considered. • Some patients following trauma presenting with swelling, lockjaw and/or injuries of lips or tongue may require use of chin support for edentulous patients, too, supplemented with a cotton roll. Even when meticulous care is paid to steps in taking a panoramic radiograph, some drawbacks of the technique may affect the final image: • Image magnification. Theoretically magnification coefficient is constant for a given machine and provided by manufacturer in technical records. In practice magnification is unequal even within the same panoramic radiograph, especially when positioning errors were committed or patient presents with facial skeleton asymmetry. Image distortion is more advanced in horizontal plane than in vertical one. Therefore, although panoramic image is not recommended for performing linear measurements, if necessary, the ones in vertical plane are more reliable than the ones registered in horizontal plane. • Tomographic character of the image. The focal trough measures around 20 mm in lateral portions and around 10 mm in anterior area. It is the main concept of the radiograph to clearly demonstrate just the structures within the focal plane and eliminate images of the ones outside the trough. However this means that only a portion of maxilla is visible in the panoramic radiograph, thus it is not reliable enough to diagnose midfacial fractures and diseases of maxillary sinuses. Also some pathological lesions, foreign bodies, etc., located outside the focal plane may not be visible, partly or totally, in the radiograph, therefore leading to underdiagnosis. TMJ condyle axis may not be aligned with the focal trough which affects image of the condylar head in panoramic radiograph—one of common artefacts in panoramic radiography is the so-called pseudocyst of condyle which mimics a cyst but is only radiographic image of concavity in condylar process. • Anatomy of panoramic radiograph is complicated due to double and ghost shadows of normal anatomical structures.

54

4  Panoramic Radiography in Dentistry

4.1.7 T  aking a Tomographic Radiograph of Temporomandibular Joints (TMJs) • Many panoramic machines offer possibility to record a tomographic image of temporomandibular joints in closed and open mouth position. • Patient and machine preparation are identical as for panoramic radiograph. • TMJ imaging mode should be selected on screen or control panel. • If the patient had an axial skull radiograph taken earlier, it can be used to measure angulation of long axis of condylar heads in relation to coronal plane. The values should be then input in control panel or software. If angulation value is not known, a default value will be applied (e.g. 17°). • Dedicated positioner is used providing stable support for nose, but at the same time allows opening the mouth (Fig. 4.13).

4.1.8 E  xample of Positioning for a Tomographic Radiograph of Temporomandibular Joints in Panoramic Machine • One radiograph is taken with mouth closed, the other part of exposure with mouth open. The sequence of radiographs can be opposite in different machines. • In the first stage mouth is closed and teeth in intercuspation (Fig. 4.14). • The head must be positioned symmetrically in sagittal plane (the first laser light). • Frankfort plane is tilted 5° caudally (the second laser light). • Using a ruler measure distance between the third laser light and condylar head, and input this value in control panel or screen. a

b

Fig. 4.13 (a, b) Nasal support for TMJ tomographic imaging

4.1  Steps in Taking a Panoramic Radiograph

55

Fig. 4.14 TMJ tomographic imaging, closed mouth position

• Cross-check head position, close temporal supports and proceed with the first part of the exposure. • Once exposure is over, ask the patient to open the mouth wide, but without other changes in head position (Fig. 4.15). • The set distance must be decreased by 10 mm as condylar heads move out of articular fossae in open mouth position therefore are located anteriorly to the previous position. • Again cross-check head position and proceed with the second part of the exposure. Limitations of tomographic images of TMJs • Similar to those affecting panoramic radiography (lack of cooperation, movements, inability to maintain stable and straight neck position, inability to maintain standing up or sitting position). • Lockjaw. • The result depends on anatomy of TMJ as parasagittal slices are not always at right angle to long axis of condylar head especially when angulation of the axes is not known (no axial radiograph prior to TMJ tomography). • In the era of CBCT TMJ tomographic images become obsolete.

56

4  Panoramic Radiography in Dentistry

Fig. 4.15 TMJ tomographic imaging, open mouth position

Suggested Reading Farman AG, editor. Panoramic radiology. Seminars on maxillofacial imaging and interpretation. Berlin: Springer; 2007. Kim YK, Park JY, Kim SG, Kim JS, Kim JD. Magnification rate of digital panoramic radiographs and its effectiveness for pre-operative assessment of dental implants. Dentomaxillofac Radiol. 2011;40(2):76–83. Langlais RP. Excercises in oral radiology and interpretation. 5th ed. St Louis: Saunders; 2016. Larheim TA, Westesson P-LA. Maxillofacial imaging. 2nd ed. Berlin: Springer; 2018. Laster WS, Ludlow JB, Bailey LJ, Hershey HG. Accuracy of measurements of mandibular anatomy and prediction of asymmetry in panoramic radiographic images. Dentomaxillofac Radiol. 2005;34(6):343–9. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. principles and interpretation. St Louis: Mosby; 2014.

5

Cephalometric Radiograph in Dentistry/Oral Health

Features of the cephalometric radiograph: • It is radiograph of skull taken with patient’s head fixed in a cephalostat which is a device used to standardise positioning and provide immobilisation of patient’s head in the desired position. • X-ray tube must be located at some distance from image receptor (over 150 cm, up to 400 cm) in order to achieve elimination of divergence of X-ray beam and this way to limit image magnification (Fig. 5.1). • Usually a cephalostat (also called craniostat) is an additional part of panoramic machine or a CBCT scanner, but seldom it can also be a stand-alone device (Fig. 5.2). • Cephalostat allows for repeatability of radiograph, which guarantees possibility of comparison of radiographs taken in the same patient in different time slots. • Cephalostat contains ear rods which are inserted into external auditory meati as well as nasal support in which a radiopaque scale is embedded in the form of millimetre ruler or, for example, markers every 1 cm (Fig. 5.3). Ear rods also comprise radiopaque elements and their shadows are used as indicators whether patient was symmetrically positioned for a true lateral cephalometric radiograph. • Visibility of soft tissue profile is a prerequisite of a lateral cephalometric image. In analogue machines an aluminium wedge placed on top of cassette was used to filter and attenuate X-ray beam in order to avoid the so-called burning out of image soft tissues due to too large exposure settings. In digital machines it is the dedicated image processing software that is automatically applied to demonstrate soft tissue profile (Fig. 5.3). • The main indication for cephalometric radiographs is cephalometric tracing— analysis of relationships between teeth and bone based on cephalometric landmarks and analysed using many systems.

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_5

57

58

5  Cephalometric Radiograph in Dentistry/Oral Health

Fig. 5.1  Diagram of radiographic technique of obtaining a lateral cephalometric radiograph

Cephalostat Image receptor

X-ray tube X-ray beam

Fig. 5.2  Patient in a cephalostat which is a part of panoramic machine with “one shot” image detector

Although the term cephalometric radiograph is generally associated with the lateral radiograph (also called true cephalometric lateral radiograph), other cephalometric projections are available and can be acquired within the environment of dental practice. These additional projections include postero-anterior (PA) projection and submento-vertex (SMV), also called axial skull view.

5.1

Steps in Taking a Cephalometric Radiograph

5.1.1 Introductory Steps • • • •

Read the prescription. Make sure that the radiograph is justified. Make sure that patient or his/her guardian obtained information on radiation risk. Make sure if the patient or his/her guardian signed an informed consent to radiograph, whenever mandatory according to local legislation.

5.1  Steps in Taking a Cephalometric Radiograph

59

Fig. 5.3 Cephalometric lateral radiograph demonstrating soft tissue profile apart from skeletal tissues as well as radiopaque shadows of markers in ear rods and nasal support

• Ask patient in reproductive age if she is not pregnant; although pregnancy is not an absolute contraindication to radiography, if it is possible to delay examination, X-rays should be preferably taken after birth. • Open or create patient file in dedicated software. Inputting patient’s date of birth and gender results in default exposure settings which can be individually adjusted. At this step, it may be appropriate to choose size of lateral radiograph, whether limited to maxillofacial skeleton only or the whole skull shall be visible (Fig. 5.4). • Put single-use protective sleeves on ear rods.

5.1.2 Patient Preparation • Ask patient to remove metallic objects that can cause artefacts from the radiographed area. • The objects include removable prosthesis, removable orthodontic appliances, earrings, piercing (including tongue) and glasses. • Whenever mandatory according to local legal provisions, lead apron with a thyroid collar must be used. If patient’s guardian remains by patient’s side during exposure, he/she must wear protective lead apron, whenever mandatory according to local regulations.

60

a

5  Cephalometric Radiograph in Dentistry/Oral Health

b

c

Fig. 5.4  Choice of size of radiographed area (field of view). (a) Control panel. (b) Radiograph of phantom limited to maxillofacial area. (c) Radiograph of the whole skull in a phantom

5.1.3 Patient Positioning Patient positioning for a cephalometric view depends on the type of radiographic projection.

5.1.3.1 Patient Positioning for a Lateral Cephalometric View (True Cephalometric Lateral) (Fig. 5.5) • Position the cephalostat so that ear rods are placed in the same line between X-ray tube and image detector, and perpendicular to it. • Initially adjust the level of cephalostat to the level of patient’s head with the ear rods on the level of patient’s external auditory meati. • Ask the patient to enter into the cephalostat. • Position the head so that midsagittal plane is parallel to image sensor and orbitomeatal line (Frankfort plane) is horizontal. • Patient’s left profile is facing image sensor. • X-ray beam is aimed at right angle to plane of image sensor and to patient’s midsagittal plane.

5.1  Steps in Taking a Cephalometric Radiograph

a

61

b

Fig. 5.5 (a, b) Patient positioning for a lateral cephalometric radiograph with a direct digital image sensor (scanography) Fig. 5.6 Patient positioning for a postero-­ anterior cephalometric radiograph

• Cross-check head position and carefully insert ear rods into external auditory meati as deep as possible without causing discomfort to the patient, but deep enough to ensure immobilisation of head during exposure. • Adjust the level of nasal support and slide it towards the nasal bridge. • Ask the patient to clench the teeth so that they are in maximum intercuspation.

5.1.3.2 Patient Positioning for a Postero-Anterior (PA) Cephalometric View (Fig. 5.6) • Rotate cephalostat by 90° in comparison with the position for the lateral cephalometric view. • Initially adjust the level of cephalostat to the level of patient’s head with the ear rods on the level of patient’s external auditory meati. • Ask the patient to enter into the cephalostat.

62

5  Cephalometric Radiograph in Dentistry/Oral Health

• Position the head so that sagittal plane is perpendicular to image sensor and orbitomeatal line (Frankfort plane) is horizontal. • Patient is facing the image sensor and occiput is directed towards the X-ray tube. This way X-ray beam passes from patient’s back (posterior) to the front (anterior). • X-ray beam is aimed at right angle to plane of image sensor and parallel to patient’s midsagittal plane. No soft tissue filtering is used in this type of projection as soft tissue profile is not visible in the resultant radiograph. • Cross-check head position and carefully insert ear rods into external auditory meati as deep as possible without causing discomfort to the patient, but deep enough to ensure immobilisation of head during exposure. • Nasal support is not always used for PA views as its shadow is projected on radiographic image of skull. • Ask the patient to clench the teeth so that they are in maximum intercuspation.

5.1.3.3 Patient Positioning for an Axial Cephalometric View: Submento-Vertex (SMV) (Fig. 5.7) • Rotate cephalostat by 90 degrees in comparison with the position for the lateral cephalometric view. Raise the nasal support as it is not useful in this projection. • Initially adjust the level of cephalostat to the level of patient’s head with the ear rods on the level of patient’s external auditory meati. • Ask the patient to enter into the cephalostat. • Position the head so that patient is facing the X-ray tube and occiput is directed towards image sensor. • Then ask the patient to tilt the head backwards as much as he/she can. This way patient’s chin will be facing X-ray tube, and vertex of the skull will be directed towards image sensor. Patient’s midsagittal plane is vertical and perpendicular to plane of image sensor. • Orbitomeatal line is vertical and parallel to plane of image detector. Fig. 5.7 Patient positioning for a submento-vertex cephalometric radiograph

5.1  Steps in Taking a Cephalometric Radiograph

63

• No soft tissue filtering is used in this type of projection as soft tissue profile is not visible in the resultant radiograph. • Central X-ray beam is aimed in the middle of distance between external auditory meati and anterior nasal spine and at the same time between chin and laryngeal prominence; another way of determining of entry point of central X-ray beam is at oral floor in the middle of the line joining the first lower molars. • Central X-ray beam is perpendicular to image sensor plane and at the same time parallel to patient’s midsagittal plane. • Cross-check head position and carefully insert ear rods into external auditory meati as deep as possible without causing discomfort to the patient, but deep enough to ensure immobilisation of head during exposure.

5.1.4 Instruct the Patient • Directly before the exposure ask the patient to swallow, breath normally and not move during the exposure. Standing or sitting still aids in avoiding motion artefacts.

5.1.5 X-ray Exposure • Press ready button on control panel. • According to local legal provisions, leave X-ray room or protect yourself behind a wall or lead screen, or step away from the controlled area around the source of radiation. • Press exposure button and hold it for the duration of the exposure. Remember that production of X-ray starts with a little delay in relation to the moment of pressing the button. If you just press and release immediately, exposure will not take place. Generation of X-rays is usually marked by means of visual and/or audio signals, e.g. yellow light on the exposure button as well as on the machine itself. • Survey the patient during the exposure via a lead window or a screen of a videocamera. • If during the exposure you notice abnormal patient activity (sneezing, coughing, other movement), immediately release the exposure button to discontinue X-ray generation as most probably the radiograph will have to be retaken. In some machines image preview is visible live on screen during exposure and it allows verification whether patient movement caused motion artefacts in the resultant radiographic image.

5.1.6 After Exposure • Release the patient.

64

5  Cephalometric Radiograph in Dentistry/Oral Health

• Remove protective lead apron, whenever applicable. • Save the ready radiograph in database. • Prepare the X-ray machine for the next exposure (remove single-use protective sleeve from ear rods, use disinfectant spray for multiple use parts that are in contact with patient’s body). Limitations and Difficulties in Cephalometric Radiography: • Limitation of cephalometric radiography is lack of indications, just like in case of all other radiological examinations. • Usually there are no age limits below which a cephalometric radiograph can be taken (local legal provisions may vary), but again it is patient cooperation and lack of justification which are the major limitations in performing this X-ray examination. • In X-ray machines with “one-shot” technology the whole cephalometric image is registered in a single “1-second” exposure. In X-ray devices with a scanning mode direct digital image receptor moves along patient’s head registering X-ray attenuation. The movement lasts for several seconds, so probability of motion artefacts increases. • Tilting the head backwards may be challenging for patients with osteoarthritis of cervical spine. The radiograph is not advocated in patients following recent trauma to cervical spine. • It is crucial to instruct the patient to maintain teeth in maximum intercuspation as the position of teeth is later extremely important in cephalometric tracing. • Asymmetry in the lateral cephalometric radiograph may be due to either real asymmetry of patient’s skeleton or incorrect head position during radiography. If it is patient’s asymmetry which is the reason, the images of radiopaque markers in the ear rods will be aligned so overlap or look like “aim target” (see Chap. 7).

Suggested Reading Jacobson A, Jacobson RL.  Radiographic cephalometry. From basics to 3-D imaging. Hanover Park: Quintessence Books; 2006. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014.

6

Dental Cone-Beam Computed Tomography (CBCT)

Cone-beam computed tomography (CBCT), also called digital volumetric tomography (DVT), is a method of cross-sectional imaging of teeth and tooth-bearing structures using X-radiation. It was first elaborated in 1990s for use in dentistry, but nowadays it is also applied in other fields of medical imaging, therefore the adjective Dental is added to describe this technique. Features of CBCT are listed below: • During exposure X-ray tube rotates around patient’s head emitting beam in the form of a cone—hence the name cone-beam computed tomography—or in form of a pyramid (Fig. 6.1). • Full (i.e. 360°) or partial (over 180°) rotation of the X-ray tube is single which differentiates CBCT from medical MDCT in which multiple helical rotations of X-ray tube or two tubes synchronised with introduction of patient into the gantry on a mobile examination table are required to produce the image. • X-ray beam emission can be continuous or pulsed. • During the image acquisition few hundreds of individual two-dimensional images differing in angulation are registered and saved as the so-called raw data.

Fig. 6.1 Image acquisition in CBCT

Image receptor X-ray tube

FoV

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_6

65

66

6  Dental Cone-Beam Computed Tomography (CBCT)

• Image reconstruction is then performed by dedicated software basing on the raw data. • The rotation is performed around an axis which is in the centre of the region of interest (ROI), which corresponds to the imaged volume. • The other name of CBCT—Volumetric Tomography—is derived from imaging of a certain volume within patient’s tissues, unlike in MDCT, where patient is scanned from a certain level to another level, and all tissues within the range are included in the examination. • In general, the imaged volume can be divided into small, medium or large, basing on coverage—from several teeth in vicinity via full upper and lower dental arches to large volumes presenting whole maxillofacial skeleton and even skull (Fig. 6.2). Smaller volumes with overlapping areas can be virtually “stitched” to produce a larger image range (Fig. 6.3). Stitching requires at least two separate exposures and sometimes cannot be performed if overlapping areas cannot be matched (e.g. due to patient movement between the exposures). • Shapes of volumes substantially depend on type of image detector used. Systems fitted with image intensifiers tend to have spherical field of view (Fig. 6.2f), but they become obsolete due to image distortion as well as small difference between the lowest and highest signal detected (dynamic range). Majority of CBCT units available nowadays register cylindrical volumes by means of flat panel detectors, direct and indirect. Few CBCTs are characterised by a jaw-shaped field of view in the form of a wide, three-dimensional horseshoe. Stitched volumes are polycyclic (Fig. 6.3). a

b

c

d

e

f

Fig. 6.2  Different sizes and shapes of FoV. (a) Cylindrical 5 × 5 cm. (b) Cylindrical 8 × 8 cm. (c) Cylindrical 8  ×  8  cm focused on TMJ.  D. Cylindrical 10  ×  5  cm for upper or lower jaw. (e) Cylindrical 10 × 10 cm. (f) Spherical 15 cm in diameter

6  Dental Cone-Beam Computed Tomography (CBCT)

a

67

b

Fig. 6.3  Stitching. (a) Diagram. (b) Stitched volume

Fig. 6.4  Relationship between voxel size and image resolution

• A CBCT volume consist of voxels, which are three-dimensional elements, volume elements just like pixels, picture elements, in two-dimensional radiographs (Fig.  6.4). In CBCT voxels are isotropic which means that all their sides are equal. This feature also differentiates CBCT from MDCT, where height of voxel depends on slice thickness and voxels are anisotropic. • Voxel size to a great extent determines spatial resolution of CBCT, i.e. ability to discriminate between two structures. The resolution is also affected by X-ray tube focal spot size, projection geometry, patient-related factors such as patient motion, and last but not least, reconstruction algorithm. Image quality of a CBCT with larger voxel size but more powerful reconstruction algorithms may be better than that of an exam with a smaller voxel size (Fig. 6.5). • CBCT machines offer a choice of resolutions from very high, e.g. 0.05 mm (crucial in evaluation of root canals), to lower (in the range of 0.3–0.6 mm) applied in large FoV to demonstrate big structures like maxillary sinuses where numerous thin slices are not important for diagnosis. Image resolution also depends on

68

a

6  Dental Cone-Beam Computed Tomography (CBCT)

b

Fig. 6.5  Images acquired with different volume size and reconstruction algorithms. (a) Voxel size 76 μm. (b) Voxel size 90 μm

•

• •

•

• •

the purpose of the examination—e.g. only implant planning vs. evaluation of dental pathologies and/or necessity to export data to external software. Once a volume is reconstructed, numerous slices in different planes are available for viewing—axial, coronal, sagittal, tangential, cross-sectional as well as oblique and drawn along a line or a free hand curve (Fig. 6.6). Software options are used to perform, e.g. implant planning (Fig. 6.7). Exposure doses from CBCT vary depending on protocols used—from ultralow dose via standard dose to high doses in bigger FoVs, and also in smaller FoVs with very high resolution dedicated to endodontics (see Chap. 10). CBCT is not free from drawbacks. They include image noise due to scatter and artefacts such as motion artefacts in uncooperative patients, beam hardening and streak artefacts from metallic objects, ring artefacts resulting from faults in image detector calibration (see Chap. 7). Currently it is still not possible to reliably apply Hounsfield units (HU) in CBCT like they are used in MDCT for differentiation of soft tissues. Therefore evaluation of soft tissues in CBCT remains subjective and not based on objective measurement of HU. Nowadays there is a large variety of cone-beam CT machines available in the market and new releases appear frequently. Further developments in the field are expected in the near future. Majority of CBCT scanners resemble panoramic machines, and many of them are capable of both taking panoramic radiographs and CBCT scans. Few machines look like MDCT with gantry and patient reclining in an examination table or chair. Usually CBCT is performed in patients sitting or standing, but

6  Dental Cone-Beam Computed Tomography (CBCT)

69

a

b

Fig. 6.6  Examples of image viewing software in CBCT. (a) Small FoV, basic planes—axial highlighted in yellow, coronal in purple and sagittal in green. (b) Small FoV, slices adjusted to dental imaging, tangential highlighted in red, oblique cross-sectional in blue, axial in yellow. (c) Medium FoV, basic planes—axial highlighted in yellow, coronal in purple and sagittal in green. (d) Medium FoV focused on TMJs. Inclined basic planes adjusted to orientation of long and short axis of condylar head

70

6  Dental Cone-Beam Computed Tomography (CBCT)

c

d

Fig. 6.6 (continued)

6  Dental Cone-Beam Computed Tomography (CBCT)

71

a

b

Fig. 6.7 (a, b) Implant planning software in CBCT

even machines designed for a patient examined in standing position are more and more often fitted with a removable or foldable stool whenever examination in sitting position is preferred. • CBCT requires thorough knowledge of anatomy and pathology as well as skills to operate software and abilities to distinguish abnormalities in cross-sectional images. If correctly performed and evaluated, becomes an invaluable aid in numerous clinical cases in dental practice, also in conjunction with other methods like implant planning in external software, CAD/CAM solutions, intraoral scanners and facial photographs (see Chap. 1).

72

6  Dental Cone-Beam Computed Tomography (CBCT)

6.1

 teps in Taking a Cone-Beam Computed S Tomography Scan

6.1.1 Introductory Steps • • • • • • • •

Read the prescription. Make sure that the CBCT is justified. Make sure that patient or his/her guardian obtained information on radiation risk. Make sure if the patient or his/her guardian signed an informed consent to CBCT, whenever mandatory according to local provisions. Ask patient in reproductive age if she is not pregnant; although pregnancy is not an absolute contraindication to radiography, if it is possible to delay examination, X-rays should be preferably taken after birth. Open or create patient file in dedicated software. Choose volume size and image resolution if such option is available. Whenever possible, depending on indications for CBCT, use the smallest field of view with the lowest resolution suitable for the main aim of the scan. Optimise exposure. Default exposure settings will be set according to the above-mentioned choice, but individual adjustment may be possible.

6.1.2 Patient Preparation • Ask patient to remove metallic objects that can cause artefacts from the radiographed area. • The objects include removable prosthesis, removable orthodontic appliances, earrings, piercing (including tongue), glasses, necklaces, chain necklaces, hair pins and hearing aids. • Whenever mandatory according to local legal provisions, lead apron must be used. If patient’s guardian remains by patient’s side during exposure, he/she must wear protective lead apron, whenever mandatory according to local regulations. Use of thyroid shielding for CBCT is now advocated in adults up to 50 years of age, and especially in children, regardless of the position of FOV.

6.1.3 Patient Positioning Depends on type of CBCT unit and its design—whether for examinations in sitting, standing or lying supine position—as well as devices applied for immobilisation of head (for dentate patients, edentulous individuals, for cephalometric scans— Fig. 6.8). Below there are described examples of positioning in a large and small FoV machines with patient standing up.

6.1  Steps in Taking a Cone-Beam Computed Tomography Scan

a

73

b

c

Fig. 6.8  Positioning devices in a large FoV CBCT. (a) For dentate patients. (b) For edentulous patients. (c) For cephalometric scans

6.1.4 Large FoV CBCT • Cover the bite piece with a single-use sleeve or use a sterile bite piece. Spray chin support with disinfectant solution. • Ask the patient to enter the machine. • Ask the patient to grab the handles. • Ask the patient to insert incisive edges of upper and lower anterior teeth in groove on bite piece (Fig. 6.9a) or place chin on a chin support for edentulous patients (Fig. 6.9b). For examination of TMJs with mouth closed, use of silicon index is recommended so that the patient maintains stable position of teeth and condyles in glenoid fossae, as indicated by referring dentist. • Use laser light to position face symmetrically. • Place Frankfort plane horizontally so that occlusal plane is horizontal. • Cross-check if the maxillofacial skeleton is encompassed by the Field of View as large FoVs may considerably vary in sizes.

6.1.5 Small FoV CBCT • Positioning depends to a great extent on the design of devices used for supporting patient’s head. Ask the patient to bite in the groove on bite piece (Fig. 6.10a) or to place chin on chin rest for edentulous individuals (Fig. 6.10b).

74

a

6  Dental Cone-Beam Computed Tomography (CBCT)

b

Fig. 6.9  Patient positioning in large FoV CBCT. (a) Bite piece for dentate patients. (b) Chin support for edentulous patients and TMJ scans

• Choose adequate FoV—it may be done by placement of cross in the middle of the planned ROI, by choice of location of FoV on a diagram or adjust freely on control panel (Fig. 6.11). • In case of small FoVs, additional laser lights as an aid in correct placement of limits of the ROI (Fig. 6.12). • Low-dose scout image can be acquired before the actual exposure to cross-check if FoV was correctly set which and corrections of patient positioning can be done at this stage.

6.1.6 Instruct the Patient • Fulfilling of correct instructions by the patient directly before exposure is crucial for obtaining a high-quality radiograph. • In anxious patients, especially children, it may be recommended to demonstrate in test mode (no X-rays produced) how the C-arm will be moving during exposure and explain that the machine will be rotating and emitting sounds during examination. • Directly before exposure ask the patient to swallow in order to prevent motion artefacts from swallowing during exposure, which is crucial in machines with less advanced motion artefacts correction algorithms. • Ask the patient not to move and breath normally for the duration of the exposure.

6.1  Steps in Taking a Cone-Beam Computed Tomography Scan

a

75

b

Fig. 6.10  Patient positioning for small FoV CBCT. (a) Bite piece for dentate patients. (b) Chin support for edentulous patients

a

b

Fig. 6.11 (a, b) Choice of small FoV

6.1.7 X-ray Exposure • Press ready button on control panel. • According to local legal provisions leave X-ray room or protect yourself behind a wall or lead screen, or step away from the controlled area around the source of radiation. • Press exposure button and hold it for the duration of the exposure. Remember that production of X-ray starts with a little delay in relation to the moment of

76

6  Dental Cone-Beam Computed Tomography (CBCT)

a

b

Fig. 6.12  Use of laser lights for adequate placement of ROI in a small FoV CBCT. (a) Bite piece for dentate patients. (b) Chin support for edentulous patients

pressing the button. If you just press and release immediately, exposure will not take place. Generation of X-rays is usually marked by means of visual and/or audio signals, e.g. yellow light on the exposure button as well as on the machine itself. • Survey the patient during the exposure via a lead window or a screen of a video camera. • If during the exposure you notice abnormal patient activity (sneezing, coughing, other movement), immediately release the exposure button to discontinue X-ray generation as most probably the scan will have to be retaken. In some machines patient movement compensation is applied, but only in limited range and is not useful in case of sharp, severe movements.

6.1.8 After Exposure • • • •

Release the patient. Remove protective lead apron, whenever applicable. Save the CBCT volume in database. Get ready for the next exposure.

Suggested Reading Abramovitch K, Rice DD. Basic principles of cone beam computed tomography. Dent Clin N Am. 2014;58(3):463–84. Bruellmann D, Schulze RK. Spatial resolution in CBCT machines for dental/maxillofacial applications—what do we know today? Dentomaxillofac Radiol. 2015;44:20140204. Carter L, Farman AG, Geist J, Scarfe WC, Angelopoulos C, Nair MK, Hildebolt CF, Tyndall D, Shrout M, American Academy of Oral and Maxillofacial Radiology. American Academy of Oral and Maxillofacial Radiology executive opinion statement on performing and interpreting

Suggested Reading

77

diagnostic cone beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2008;106(4):561–2. European Commission. Radiation Protection 172. Evidence based guidelines on cone beam CT for dental and maxillofacial radiology. Office for Official Publications of the European Communities, Luxembourg. 2012. https://ec.europa.eu/energy/sites/ener/files/documents/172. pdf. Accessed 28 Jan 2020. Feragalli B, Rampado O, Abate C, Macrì M, Festa F, Stromei F, Caputi S, Guglielmi G. Cone beam computed tomography for dental and maxillofacial imaging: technique improvement and low-­ dose protocols. Radiol Med. 2017;122(8):581–8. Horner K, O’Malley L, Taylor K, Glenny AM.  Guidelines for clinical use of CBCT: a review. Dentomaxillofac Radiol. 2015;44:20140225. Larheim TA, Westesson P-LA, editors. Maxillofacial imaging. 2nd ed. Berlin: Springer; 2018. Miles DA, Danforth RA. Cone beam computed tomography: from capture to reporting. Dent Clin North Am. 2014;58(3):ix–x. Nemtoi A, Czink C, Haba D, Gahleitner A.  Cone beam CT: a current overview of devices. Dentomaxillofac Radiol. 2013;42:20120443. Pauwels R, Araki K, Siewerdsen JH, Thongvigitmanee SS.  Technical aspects of dental CBCT: state of the art. Dentomaxillofac Radiol. 2015a;44:20140224. Pauwels R, Jacobs R, Bogaerts R, Bosmans H, Panmekiate S. Reduction of scatter-induced image noise in cone beam computed tomography: effect of field of view size and position. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016;121:188–95. Scarfe WC, Angelopoulos C, editors. Maxillofacial cone beam computed tomography. Berlin: Springer; 2018. Schulze R, Heil U, Gross D, Bruellmann DD, Dranischnikow E, Schwanecke U, Schoemer E. Artefacts in CBCT: a review. Dentomaxillofac Radiol. 2011;40:265–73. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014.

7

Technical Errors and Artefacts in Dental Radiography

Reasons of appearance of technical errors and artefacts in dentomaxillofacial radiology: • Very complex anatomy of maxillofacial region; • Variety of radiographic projections and methods used for imaging of maxillofacial area; • Differences in knowledge, skills and abilities between dentists, radiologists, radiographers and other members of dental staff (if legally entitled to taking dental radiographs); • Unlawful taking of dental radiographs by persons who are not qualified and entitled for that task. The means of limitation of occurrence of technical errors and artefacts: • Reduction of number of technically unacceptable radiographs which require retakes; • Careful taking of X-rays and CBCT examinations according to radiographic rules; • Meticulous patient preparation for radiographic examinations, when applicable; • Digitalisation of dental radiography lab if still analogue techniques are used; • Knowledge on reasons of appearance of technical errors and artefacts in radiographs; • Periodic check-ups of technical status of radiographic equipment according to provisions of quality control; • Periodic analysis of radiographs which required retaking, identification of sources of errors and introduction of remedial actions such as additional staff training or fixing of faulty radiographic devices.

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_7

79

80

7  Technical Errors and Artefacts in Dental Radiography

From the practical point of view, errors and artefacts in dentomaxillofacial radiography will be further discussed in the following groups: 1 . Positioning errors in intraoral techniques. 2. Positioning errors in panoramic radiography. 3. Positioning errors in cephalometric radiography. 4. Errors resulting from incorrect settings of radiographic parameters. 5. Errors resulting from incorrect handling of X-ray films in analogue radiography. 6. Errors resulting from incorrect chemical processing of X-ray films in analogue radiography. 7. Errors resulting from incorrect read-out of digital radiographs. 8. Errors and artefacts in cone-beam computed tomography. Some of the above-mentioned errors do not arise in contemporary dentomaxillofacial radiology when only digital equipment is used. However patients still possess old analogue radiographs and when they present them for comparison, it is essential that dentist or radiographer to know the faults of these radiographs that could have an impact on interpretation of radiographic image.

7.1

Positioning Errors in Intraoral Techniques

Positioning errors in paralleling technique (Figs. 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, and 7.9) a

b

Fig. 7.1  Incorrect mounting of positioning device. (a) Incorrect assembly of positioning device for anterior teeth radiography. (b) Shadow of positioning device is visible on the resultant radiograph. Moreover, cone-cut artefact is observed

7.1  Positioning Errors in Intraoral Techniques

a

81

b

c

Fig. 7.2 (a) Plane of image detector is not parallel to axis of upper anterior teeth as the bite block is placed too deep in oral cavity. As a result, after closing the mouth image detector cannot be positioned in parallel position to axis of examined teeth. Moreover, tube cone is incorrectly aimed. (b) Elongation of image of teeth, image detector placed not deep enough, finally image detector reversed in relationship to X-ray tube. (c) Foreshortening of image of teeth Figure Effect Radiograph Means of elimination Type of error Make sure the positioner Incorrect mounting of Fig. Lack of possibility of Fig. 7.1b is correctly mounted, positioning device 7.1a placing the positioner according to manual of into the oral cavity. manufacturer of In case it is possible positioning device, as to place the devices might slightly positioning device differ in design inside the oral cavity, incorrect mounting will result in incorrect spatial relationship between image detector and ring of the positioner Fig. 7.2b, c Check if once patient had Elongation or Non-parallel position Fig. bitten the bite block of 7.2a foreshortening of of plane of image the positioner and closed image of teeth detector in the mouth, surface of relationship to axis of image detector is still the examined tooth parallel to long axis of the examined tooth

82

7  Technical Errors and Artefacts in Dental Radiography

Figure Effect Type of error Fig. Cropped image of, Incorrect position of 7.3a for example, root long axis of image apices detector in relationship to positioning device and examined teeth

Radiograph Means of elimination Fig. 7.3b Long axis of image detector should be positioned vertically for anterior teeth and horizontally for posterior teeth. Shape of positioning device aids in correct choice of position of long axis of image detector. Sometimes the rule is modified if in case of lower anterior teeth image detector cannot be placed deep in the mouth due to shallow or sensitive oral floor Fig. 7.4c Check if once patient had Fig. Cropped image, Image detector bitten on the bite block 7.4a, b elongation of displaced within and closed the mouth, foreshortening of positioning device image detector was not image of teeth, when once patient had bitten displaced or bent image detector on the bite block and (especially analogue closed the mouth. film packet) is Alternatively, if heavily bent, flexible image detector obtained (PSP plate, film) is radiographic image is bent against hard very distorted palate or oral floor Fig. 7.5b Check if once patient had Fig. Overlapping of Incorrect horizontal bitten on the bite block 7.5a images of angulation of and closed the mouth, approximal surfaces positioner in image detector was not of teeth relationship to displaced in the examined tooth positioner Avoid placement of positioner on surface of tongue, instead put it between tongue and dental arch Fig. 7.5b Careful aiming of cone Fig. Overlapping of Incorrect horizontal of X-ray tube at ring of images of angulation of cone of 7.6 positioning device so that approximal surfaces X-ray tube in it covers the whole ring of teeth relationship to ring of and surface of cone is positioner, unless parallel to surface of ring oblique (mesial or distal) projection is requested Fig. 7.7b Careful aiming of cone Fig. Foreshortening or Incorrect vertical of X-ray tube at ring of elongation of image angulation of cone of 7.7a positioning devices so of teeth X-ray tube in that it covers the whole relationship to ring of ring and surface of cone positioner is parallel to surface of ring

7.1  Positioning Errors in Intraoral Techniques

83

Figure Effect Radiograph Means of elimination Careful aiming of cone Fig. Surface of cone does – of X-ray tube at ring of 7.8 not correlate with positioning devices so ring of positioner that it covers the whole resulting in cropping ring and surface of cone of image and the is parallel to surface of so-called cone-cut ring artefact This artefact is relatively rare in paralleling technique as ring of positioning device is designed to aid in avoiding the error Fig. 7.9b Careful placement of Fig. In indirect digital Image detector image detector in 7.9a radiography a reversed in positioner with active radiograph will be positioner—With side facing X-ray tube obtained, but it may active surface facing and not away from it be too pale. In away from X-ray tube The error is rare in digital indirect radiography radiography and almost PSP plates with non-­existent in direct metallic circle, digital radiography as shadow of the circle reverse side of a will be visible in the solid-state detector is resultant radiograph usually fitted with a wire It is impossible to and this also indicates obtain a radiograph correct positioning with a direct digital In analogue radiography (solid) sensor placed film packet contains a in the reversed convex dot which has to manner in positioner be placed facing X-ray tube. This serves as a guideline in correct positioning In some indirect digital radiography systems PSP plates contain metallic circles in the reverse side. This can be a hint in positioning Some PSP plates contain a flat dot or mark similar to that in film radiography. This serves as a guideline in positioning Type of error Incorrect, non-central position of cone of X-ray tube in relation to ring of positioner

84

a

7  Technical Errors and Artefacts in Dental Radiography

b

c

Fig. 7.3  Incorrectly placed image detector. (a, b) Positioning device for anterior teeth applied in radiography of posterior teeth, thus with long axis of image detector vertical instead of horizontal. (c) Radiograph of lower anterior teeth taken with image detector positioned with long axis horizontal, just like for radiographs of posterior teeth

7.1  Positioning Errors in Intraoral Techniques

a

85

b

c

Fig. 7.4  Displacement of image detector. (a) Image detector displaced in positioning device once mouth closed. PSP plate is stuck against hard palate. (b) Rotated direct digital image detector. (c) Image cropped due to displacement of image detector—in upper part of radiograph radiolucent air space is visible, while periapical areas of teeth no. 45–47 are outside the coverage of the radiograph

a

b

Fig. 7.5  Incorrect position of image detector in horizontal plane. (a) Positioning device rotated in horizontal plane as it was placed on top of tongue instead of between tongue and examined teeth. (b) Overlapping of approximal surfaces of teeth due to non-parallel position of image detector in relation to examined teeth

86

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.6 Incorrect horizontal angulation of cone of X-ray tube in relationship to ring of positioning device when there are no indications for an oblique intraoral projection

a

b

Fig. 7.7  Incorrect vertical angulation of cone of X-ray tube in relationship to ring of positioning device. (a) Photograph. (b) Foreshortening of radiographic image of examined teeth

a

b

Fig. 7.8 (a, b) Incorrect, non-central position of cone of X-ray tube in relation to ring of positioner leads to appearance of “cone-cut” artefact

7.1  Positioning Errors in Intraoral Techniques

a

87

b

Fig. 7.9  Image detector reversed in positioning device. (a) Photograph demonstrating PSP plate facing X-ray tube with non-active side. (b) Shadow of metallic ring from the reverse side is visible in the obtained radiograph

Positioning errors in bisected angle technique (Figs. 7.10, 7.11, 7.12, 7.13, and 7.14) Type of error Incorrect vertical angulation of X-ray tube

Figure Fig. 7.10a, b, d

Incorrect horizontal angulation of X-ray tube, unless oblique (mesial or distal) projection is requested Incorrect positioning of image detector in oral cavity in relationship to examined tooth

Fig. 7.11a

Fig. 7.12a

Fig. Image receptor is 7.13a not placed centrally in the area covered by cone of X-ray tube

Effect Radiograph Means of elimination Fig. 7.10c, Positioning of cone of Elongation of image X-ray tube at right angle of teeth when angle is e to bisector—Theoretical too small. line bisected angle Foreshortening of between image detector image of teeth when plane and long axis of angle is too big examined tooth Fig. 7.11b Position cone of X-ray Overlapping of tube at right angle images of approximal (orthoradial position) in surfaces of teeth relationship to tangent to dental arch at examined tooth Examined tooth is not Fig. 7.12b–d located centrally within the range of image detector. Image receptor is placed too shallow or too deep in oral cavity, or rotated in relationship to examined teeth Cropping of a part of Fig. 7.13b image, the so-called cone-cut artefact

Place image detector in such a way that the examined tooth is in the middle of the plane of receptor and 2–3 mm of image detector project above incisal edge or cusps of examined tooth Make sure that the whole area of image detector is covered by cone of X-ray tube, especially in case of rectangular collimation

88 Type of error Bending of image detector, for example, against hard palate. Indirect digital radiography PSP plate or film packet—More prone to flexing than PSP Image detector reversed in positioner—With active surface facing away from X-ray tube

7  Technical Errors and Artefacts in Dental Radiography Figure Effect Radiograph Means of elimination Fig. 7.14 Place image detector in See Elongation and such a way that it is not Fig. 7.5a distortion of image of bent, for example, against teeth. In case of hard palate. Use a smaller severe bending of a film packet if regular size film packet sometimes film is bent against a line appears that can shallow hard palate mimic fracture line in Direct digital (solid state) the resultant analogue image sensor is not radiograph flexible See Careful placement of See In indirect digital Fig. 7.9b image detector with Fig. 7.9a radiography a active side facing X-ray radiograph will be tube and not away from it obtained, but it may The error is rare in digital be too pale. In indirect radiography and almost radiography PSP non-existent in direct plates with metallic digital radiography as circle, shadow of the reverse side of a circle will be visible solid-state detector is in the resultant usually fitted with a wire radiograph and this also indicates It is impossible to correct positioning. obtain a radiograph In analogue radiography with a direct digital film packet contains a (solid) sensor placed convex dot which has to in the reversed be placed facing X-ray manner tube. This serves as a guideline in correct positioning In some indirect digital radiography systems PSP plates contain metallic circles in the reverse side. This can be a hint in positioning Some PSP plates contain a flat dot or mark similar to that in film radiography. This serves as a guideline in positioning

7.1  Positioning Errors in Intraoral Techniques

a

89

b

Central X-ray beam

Tooth axis Bisector

below 90º

Image receptor

Tooth axis

c

d

Central X-ray beam

Bisector above 90º

Image receptor

e

Fig. 7.10  Incorrect vertical angulation of X-ray tube in bisected angle technique. (a, b, c) Excessive angulation results in foreshortening of images of teeth. (d, e) Insufficient angulation produces elongated images of teeth

90

a

7  Technical Errors and Artefacts in Dental Radiography

b

Fig. 7.11  Incorrect horizontal angulation of X-ray tube in bisected angle technique. (a) Tube aimed obliquely to tangent to dental arch instead of orthoradial, when there are no indications for an oblique projection. (b) Overlapping of images of approximal surfaces in the resultant radiograph

a

c

b

d

Fig. 7.12  Incorrect position of image detector in oral cavity in relationship to examined tooth in bisected angle technique. (a) Too shallow in maxilla. (b) Not parallel to long axis of examined teeth. (c) Too shallow in mandible—periapical area outside field of view of the resultant radiograph. (d) Too deep in mandible—images of dental crowns cropped, but inferior mandibular margin is visible instead. Moreover cone-cut artefact is present

7.1  Positioning Errors in Intraoral Techniques

a

91

b

Fig. 7.13 (a, b) Image detector not placed centrally in the area of cone of X-ray tube

Fig. 7.14 Excessive flexing of film packet led to distortion of image of teeth as well as appearance of crescent in the area of the most severe bending

92

7  Technical Errors and Artefacts in Dental Radiography

Positioning errors in bite-wing radiography (Fig. 7.15, 7.16, 7.17,7.18, and 7.19) Fig. 7.15  Image detector not parallel to examined tooth—occlusal plane running obliquely across bite-wing radiograph

Fig. 7.16 Incorrect vertical angulation of X-ray beam for bite-wing radiograph

Fig. 7.17 Incorrect horizontal angulation of X-ray beam for bite-wing radiograph

7.1  Positioning Errors in Intraoral Techniques

a

93

b

Fig. 7.18  Image detector not placed centrally in area of cone of X-ray tube in bite-wing radiography. (a) Photograph. (b) Resulting “cone-cut” artefact

a

b

Fig. 7.19  Image detector reversed in positioning device in bite-wing radiography. (a) Photograph demonstrating PSP plate facing X-ray tube with non-active side. (b) Shadow of metallic ring from the reverse side is visible in the obtained radiograph

Figure Effect Type of error – Elongation of Image receptor foreshortening of tooth placed in a images, overlapping of non-parallel way approximal surfaces of in relationship to teeth, oblique course of examined teeth occlusal plane on resultant radiograph Elongation of image of Incorrect vertical Fig. 7.16 teeth when angle is too angulation of small. Foreshortening of X-ray tube image of teeth when angle is too big Fig. Overlapping of images of Incorrect 7.17 approximal surfaces of horizontal teeth angulation of X-ray tube

Radiograph Means of elimination Fig. 7.15 Place image detector in parallel position to tangent to curve of dental arch in the examined area

–

Place cone of X-ray tube correctly in relationship to both image receptor and radiographed teeth

–

Position cone of X-ray tube at right angle (orthoradial position) in relationship to tangent to dental arch at examined tooth

94 Type of error Image receptor is not placed centrally in the area covered by cone of X-ray tube Image detector reversed in positioner—With active surface facing away from X-ray tube

7  Technical Errors and Artefacts in Dental Radiography Figure Effect Fig. Cropping of a part of 7.18a image, the so-called cone-cut artefact

Fig. 7.19a

Radiograph Means of elimination Fig. 7.18b Make sure that the whole area of image detector is covered by cone of X-ray tube, especially in case of rectangular collimation

Fig. 7.19b In indirect digital radiography a radiograph will be obtained, but it may be too pale. In indirect radiography PSP plates with metallic circle, shadow of the circle will be visible in the resultant radiograph It is impossible to obtain a radiograph with a direct digital (solid) sensor placed in the reversed manner.

Careful placement of image detector with active side facing X-ray tube and not away from it The error is rare in digital radiography and almost non-existent in direct digital radiography as reverse side of a solid-state detector is usually fitted with a wire and this also indicates correct positioning In analogue radiography film packet contains a convex dot which has to be placed facing X-ray tube. This serves as a guideline in correct positioning In some indirect digital radiography systems PSP plates contain metallic circles in the reverse side. This can be a hint in positioning Some PSP plates contain a flat dot or mark similar to that in film radiography. This serves as a guideline in positioning

Positioning errors in occlusal radiography (Figs. 7.20 and 7.21)

7.1  Positioning Errors in Intraoral Techniques

95

a

b

Fig. 7.20  Image detector not placed centrally in area of cone of X-ray tube in mandibular occlusal radiography. (a) Photograph. (b) Resulting “cone-cut” artefact

a

b

Fig. 7.21  Incorrect angulation of X-ray beam for occlusal radiography. (a) Photograph of positioning for mandibular occlusal radiograph. (b) More than half of the area of occlusal radiograph is covered by air and mandibular teeth are only slightly visualised

Type of error Image receptor is not placed centrally in the area covered by cone of X-ray tube Incorrect horizontal and/or vertical angulation of X-ray tube

Figure Effect Radiograph Means of elimination Fig. 7.20b Make sure that the whole area of Fig. Cropping of a image detector is covered by cone of 7.20a part of image, the X-ray tube so-called cone-cut artefact

Fig. 7.21a

Elongation or foreshortening of image

Fig. 7.21b

Place cone of X-ray tube correctly in relationship to both image receptor and radiographed teeth and/or jaws

96

7  Technical Errors and Artefacts in Dental Radiography

Radiograph Means of elimination Type of error Figure Effect Careful placement of image detector – In indirect digital – Image with active side facing X-ray tube and radiography a detector not away from it radiograph will reversed— The error is rare in digital radiography be obtained, but it With active and almost non-existent in direct may be too pale. surface digital radiography as reverse side of a In indirect facing away solid-state detector is usually fitted radiography PSP from X-ray with a wire and this also indicates plates with tube correct positioning. metallic circle, In analogue radiography film packet shadow of the contains a convex dot which has to be circle will be placed facing X-ray tube. This serves visible in the as a guideline in correct positioning. resultant In some indirect digital radiography radiograph systems PSP plates contain metallic It is impossible to circles in the reverse side. This can be obtain a a hint in positioning radiograph with a Some PSP plates contain a flat dot or direct digital mark similar to that in film (solid) sensor radiography. This serves as a guideline placed in the in positioning reversed manner.

Errors in intraoral radiography due to lack of patient cooperation (Figs.  7.22, 7.23, and 7.24) Fig. 7.22 Periapical radiograph taken in a child who moved during exposure—blurred image of teeth. Moreover “cone-cut” artefact is visible

7.1  Positioning Errors in Intraoral Techniques

97

Fig. 7.23 Periapical radiograph taken in a child who displaced digital image detector in oral cavity during exposure. Axis of image detector is not parallel to axis of examined tooth no. 13, moreover double outlines of teeth point out to motion artefacts

a

b

c

Fig. 7.24  Incorrect patient preparation for a periapical radiograph. (a) Left removable prosthetic device. (b) Left removable orthodontic device. (c) Piercing in upper lip and ala of the nose. Moreover “cone-cut” artefact is visible

98

7  Technical Errors and Artefacts in Dental Radiography

Type of error Figure Effect – Blurred radiographic image. Patient Possibly cropped image. movement during exposure

Displacement – of image detector by patient after positioning or/and during exposure

Incorrect patient preparation

–

Radiograph Means of elimination Fig. 7.22 Explain the X-ray procedure to patient. Obtain maximum possible patient cooperation Shorten the time between end of positioning and pressing of exposure button Cropped and/or blurred Fig. 7.23 Explain the X-ray radiographic image procedure to patient. Obtain maximum possible patient cooperation Shorten the time between end of positioning and pressing of exposure button to diminish patient discomfort thus avoiding unintended displacement of image detector Fig. 7.24a, Make sure that patient Resultant radiograph removed all removable includes radiopaque shadows b, c radiopaque objects from of objects such as glasses, the radiographed area removable denture, such as glasses, dentures removable orthodontic or orthodontic appliances appliance, piercing

Types of error occurring in analogue intraoral radiography (Figs. 7.25 and 7.26) Fig. 7.25  Film packet placed with reverse side containing lead foil towards X-ray tube. The resultant radiograph is too pale, there is visible pattern from lead foil which looks like “tire tracks”

7.1  Positioning Errors in Intraoral Techniques

99

Fig. 7.26  Double image of teeth due to repeated use of the same PSP plate without laser read-out between the two exposures

Type of error Film packet placed in reversed way towards X-ray tube, i.e. with white/plain side facing away from it and the coloured side (containing lead foil) facing the tube

Figure Effect – The resultant radiograph is too pale and there is visible pattern from lead foil which can look like “tire tracks” or “cob web”

Single-use film packet applied for more than one X-ray exposure

–

Double image in one radiograph

Radiograph Means of elimination Fig. 7.25 Make sure film packet faces the X-ray tube with white/plain side and reverse side (marked, e.g. “Back/dos/Rückseite” or “opposite side toward tube”) away from X-ray tube Discontinue use of analogue radiography in favour of digital radiography Fig. 7.26 Make sure that single-use film packet is applied only once Make sure that exposed film packets are immediately taken to film processor and cannot be mixed with unexposed film packets The error may occur also in case of indirect digital radiography if a PSP plate is reused before being introduced into laser scanner

100

7.2

7  Technical Errors and Artefacts in Dental Radiography

Positioning Errors in Panoramic Radiography

Examples of positioning errors are presented in the Figs. 7.27–7.44. Type of error Incorrect patient preparation— Removable radiopaque objects not removed before exposure Removable prosthetic appliance Removable orthodontic appliance Earrings Piercing Necklace Hearing aid Glasses

Protective lead apron placed too high on patient’s back or thyroid shield mistakenly applied for panoramic radiography

Figure Effect Radiopaque shadows of metallic objects on the resultant radiograph. If metallic object is within the panoramic trough, it will produce only one – shadow Some objects such as Fig. earrings in ear lobes will 7.28a produce two shadows— Real image and blurred, Fig. enlarged “ghost” image 7.29a on contralateral side of Fig. panoramic radiograph 7.30a projected above the level Fig. of the real shadow. It is 7.31a due to projection – geometry and rotational Fig. movement of X-ray tube 7.33a during panoramic radiography around patient’s head Fig. Triangular shadow in 7.34a inferior part of panoramic radiograph, often close to midline called “shark fin artefact”. Sometimes shadows are double or more pronounced if lead apron was placed very high on patient’s back

Radiograph Means of elimination Instruct patient that removal of all removable radiopaque objects from radiographed area is essential for success of Fig. 7.27 the procedure. In case patient does not agree to Fig. 7.28b, remove some objects c (e.g. jewellery), he/she must be informed on Fig. 7.29b, negative effect of c metallic objects on Fig. 7.30b, resultant radiograph and c, d its inferior quality, Fig. 7.31b appropriate information on patient disagreement Fig. 7.32 should be noted in Fig. 7.33b patient records

Fig. 7.34b–d

Whenever use of protective lead apron is indicated by local legal provisions, in panoramic radiography apply only apron without thyroid shield Do not place protective lead apron too high on patient’s back Explain to anxious patients that thyroid shield cannot be used in panoramic radiography as its shadow will cover major part of the resultant radiograph

7.2  Positioning Errors in Panoramic Radiography Figure Effect – In older panoramic machines ghost shadow of cervical spine appears in midline. In more contemporary machines ghost shadow of cervical spine is reduced or completely eliminated owing to automatic compensation of exposure parameters Size of field of view may Incorrect choice of Fig. 7.36a be too small or too big in shape and size of relationship to patient’s dental arches (field anatomy of view) on control Some parts of resultant panel radiographic image may be distorted and/or fall outside the focal trough, e.g. TMJs In case of too large field of view in a smaller patient panoramic radiograph will cover too many structures including orbits and cervical spine Resultant image will be Asymmetric patient Fig. 7.37a enlarged on one side and position in diminished on the other panoramic unit side of the radiograph

Type of error Patient is slumped, neck is not straight

Frankfort plane is not horizontal— Chin tilted down Frankfort plane is not horizontal— Chin tilted up

Fig. 7.38a, b Fig. 7.39a, b

Occlusal plane in the resultant radiograph is V-shaped Occlusal plane in the resultant radiograph resembles a flattened letter W or is even reversed

101 Radiograph Means of elimination Fig. 7.35 Position patient with neck straight. Use contemporary panoramic machines with automatic compensation of exposure parameters

Fig. 7.36b

Fig. 7.37b, c

Fig. 7.38c, d Fig. 7.39c, d

Carefully choose shape (U, V, square, intermediate) and size of dental arches corresponding to patient’s anatomy In some panoramic machines size of field of view will be automatically adjusted to patient’s date of birth, but this must be cross-checked as patient’s size may not correspond to chronological age Place the first laser light between upper central incisors. Remember that midline of dental arch may not correspond with midline of facial tissues Adjust head position so that the second laser line runs from tragus of the ear to infraorbital rim. This way occlusal plane will be horizontal and on the resultant radiographic image flat or slightly raised. Newer panoramic machines are fitted with cameras demonstrating patient’s image on screen and Frankfort plane is highlighted with colour—Green when correctly placed and red when incorrect

102

7  Technical Errors and Artefacts in Dental Radiography

Figure Effect Type of error Images of anterior teeth Incisors positioned Fig. too far to the front 7.40a are too narrow. Images of dental arches are too in relationship to narrow, and both sides of groove in bite piece panoramic radiograph present cervical spine Images of anterior teeth Incisors positioned Fig. too far to the back 7.41a too wide and blurred. Sometimes images of in relationship to TMJs may be cropped groove in bite piece from the resultant radiograph. Ghost shadows of contralateral mandibular ramus and body can be visible

Radiograph Means of elimination Fig. 7.40b, Make sure that patient’s c incisive edges of upper and lower teeth fall in the groove on the bite piece. In case of edentulous patients use Fig. suitable chin support for 7.41b,c edentulous patients. In case of patients with multiple missing teeth, mobile teeth (periodontal bone disease, post trauma cases) using chin support instead of bite piece may be advocated In modern panoramic machines postprocessing algorithms (automatic or operator-dependent) aid in obtaining clear image despite some incorrect tooth positioning in relation to groove in bite piece Remember that despite considerable advances in panoramic radiography still it is not possible to obtain a good-quality image in case of patients with severe class II or class III malocclusion as well in patients with asymmetries of maxillofacial skeleton

7.2  Positioning Errors in Panoramic Radiography Figure Effect Type of error – Motion artefacts visible Inadequate as blurred areas in the immobilisation of resultant image. Severity patient head during of artefact depends on exposure, e.g. duration of movement as temporal supports well as direction of not closed during movement (horizontal or exposure or lack of vertical or both) patient cooperation

103 Radiograph Means of elimination Fig. 7.42a, Explain necessity of b standing or sitting still for the duration of the exposure. Obtain maximum possible patient cooperation taking into account patient’s age (small children, senile individuals) and mental condition (disabled patients, dementia). Instruct patient to swallow at the end of positioning to avoid swallowing movement during exposure. Maintain visual control of patient during exposure and in case of motion (e.g. sneezing, coughing and fainting) immediately release exposure button to stop exposure. Shorter exposure times reduce chance of patient movement. Periodically check whether temporal supports are fully operational. In some panoramic machines algorithms compensating patient movement up to 1.5 cm are available making it possible to examine patients with involuntary movements, e.g. with Parkinson’s disease

104

7  Technical Errors and Artefacts in Dental Radiography

Figure Effect Type of error Motion artefact C-arm may briefly – stop during rotation when X-ray tube or less probably image detector encounters an obstacle, e.g. lead apron or patient’s shoulder

– Unintentional release of exposure button before its end

Fig. 7.27 Incorrect preparation for panoramic radiograph—left removable prosthetic device

Radiograph Means of elimination Fig. 7.43 Ask patient to remove excessive outer clothing so that shoulders are less bulky. Whenever use of protective lead apron is required according to local legal provisions, position the apron in such a way that it does not collide with X-ray tube movement. Ask a more bulky patient to grab handles of panoramic machine with arms crossed in order to lower the shoulders Only a part of radiograph Fig. 7.44 Hold the button during is obtained the whole exposure until end of exposure signal is heard or visible (light on machine, light on exposure switch, etc.) Remember that production of X-rays is slightly delayed after pressing the exposure button, while releasing it stops exposure immediately

7.2  Positioning Errors in Panoramic Radiography

a

105

b

c

Fig. 7.28  Incorrect preparation for panoramic radiograph—left removable orthodontic appliance. (a) Photograph of phantom. (b) Radiograph of phantom. (c) Example of panoramic radiograph

a

b

c

Fig. 7.29  Incorrect preparation for panoramic radiograph—left earrings. (a) Photograph of phantom. (b) Radiograph of phantom demonstrates double shadows of earrings—real on one side of radiograph and ghost on contralateral side, moreover blurred, enlarged and projected above the level of real shadow. (c) Example of panoramic radiograph

106

7  Technical Errors and Artefacts in Dental Radiography

a

b

c

d

Fig. 7.30  Incorrect preparation for panoramic radiograph—left piercing. (a) Radiograph of phantom demonstrates a distorted shadow of round piercing in oral floor. (b) Piercing in upper lip. (c) Multiple piercings in right auricule. (d) Piercing in ala of the nose

a

b

Fig. 7.31  Incorrect preparation for panoramic radiograph—left necklace. (a) Photograph of phantom. (b) Example of panoramic radiograph with necklace. Ghost shadow of necklace is visible in the midline as it is produced by part of necklace on patient’s back. Real shadow of necklace is not visible as it falls below the field of view of panoramic radiograph in front of patient’s neck Fig. 7.32 Metallic elements of a hearing aid are visible on the left side of the panoramic radiograph

7.2  Positioning Errors in Panoramic Radiography

a

107

b

Fig. 7.33  Incorrect preparation for panoramic radiograph when glasses were not removed. (a) Photograph of phantom. (b) Radiograph of phantom with visible metallic elements of glass frames

a

b

c d

Fig. 7.34  Protective lead apron placed too high on patient’s back or thyroid lead collar used for panoramic radiography. (a) Photograph of phantom. (b) Radiograph of phantom—major part of radiograph is covered by shadow of lead collar. (c) Example of panoramic radiograph with “shark’s fin” artefacts. (d) Two “shark’s fin” artefacts as well as radiopacity along lower border of panoramic radiograph due to lead apron placed far too high on patient’s back

108

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.35  Blurred ghost shadow of cervical spine running vertically across panoramic radiograph around midline

Fig. 7.36  Choice of size and shape of dental arches. (a) Control panel. (b) Panoramic radiograph in child aged 3—field of view too large in relationship to anatomy of small patient—on both sides of the radiograph shadows of cervical spine are visible, including spinous processes. Orbits and skull base fall within the panoramic trough, as well. Moreover “shark’s fin” artefact is visible

a

b

7.2  Positioning Errors in Panoramic Radiography

a

109

b

c

Fig. 7.37  Asymmetric patient positioning in panoramic machine. (a) Photograph of phantom. (b) Radiograph of phantom. (c) Example of panoramic radiograph

a

b

c

d

Fig. 7.38  Incorrect patient positioning in panoramic machine—chin tilted too much down. Occlusal plane is V-shaped in the resultant radiograph. (a, b) Photograph of phantom. (c) Radiograph of phantom. (d) Example of panoramic radiograph

110

a

7  Technical Errors and Artefacts in Dental Radiography

b

c

d

Fig. 7.39  Incorrect patient positioning in panoramic machine—chin tilted too much up. Occlusal plane resembles flattened W in the resultant radiograph. (a, b) Photograph of phantom. (c) Radiograph of phantom. (d) Example of panoramic radiograph

a

b

c

Fig. 7.40  Incorrect patient positioning in panoramic machine—incisive edges too far to the front in relation to groove in bite piece. Images of anterior teeth too narrow and blurred in the resultant radiograph, cervical spine is excessively visible in lateral parts of radiograph. (a) Photograph of phantom. (b) Radiograph of phantom. (c) Example of panoramic radiograph

7.2  Positioning Errors in Panoramic Radiography

a

111

b

c

Fig. 7.41  Incorrect patient positioning in panoramic machine—incisive edges too far to the back in relation to groove in bite piece. Images of anterior teeth widened and blurred in the resultant radiograph; images of condylar heads are cropped. (a) Photograph of phantom. (b) Radiograph of phantom. (c) Example of panoramic radiograph

a

b

Fig. 7.42  Motion artefacts. (a) Patient rotated head horizontally. (b) Patient was moving head up and down during almost the whole duration of exposure

Fig. 7.43  Local motion artefact due to hitting of X-ray tube against patient’s shoulder

112

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.44 Unintentional termination of panoramic radiograph exposure due to releasing of exposure button—only a part of radiograph was obtained

7.3

 ositioning Errors in Lateral P Cephalometric Radiography

• Asymmetric positioning of patient’s head in cephalostat may be due to insufficiently deep placement of ear rods into external auditory meati (Fig. 7.45a). Ear rods contain radiopaque markers, usually a dot in one ear rod and a circle in the contralateral one. If on resultant lateral cephalometric radiograph dot is in the middle of the circle, it means that patient was symmetrically positioned and any asymmetry in maxillofacial skeleton image is due to patient’s anatomy and not error in radiographic procedure (Fig. 7.45b). During orthodontic and/or orthognathic surgery, changes in anatomic relationships affect maxillofacial skeleton, while external auditory meati are constant, thus symmetric placement of ear rods in them guarantees comparable radiographs obtained in follow-up. In order to eliminate this error, always place ear rods as deep as possible in external auditory meati without hurting patient. Remember that in patients with maxillofacial developmental anomalies atresia of external auditory meatus may coexist, and it will not be possible to put ear rods inside the meatus. • Incorrect angulation of orbitomeatal line (Fig. 7.46). Position patient’s head with Frankfort plane horizontal. • Teeth not occluded in the lateral cephalometric radiograph due to unclear or missing instructions to patient or lack of patient cooperation (Fig. 7.47). In order to avoid retakes ask patient to put teeth in maximum possible intercuspation. Remember that in some types of malocclusion full intercuspation may be compromised.

7.3  Positioning Errors in Lateral Cephalometric Radiography

a

113

b

Fig. 7.45  Lateral cephalometric radiograph. (a) Incorrect location of radiopaque markers in ear rods—dot is not in the middle of circle which testifies to asymmetry of head position during exposure. Moreover blurred image of teeth points out to motion artefact. (b) Correctly taken radiograph—shadow of dot marker falls in the middle of radiopaque circle. In this case image asymmetry between right and left side of the jaw is due to actual anatomical asymmetry of the patient and not due to incorrect positioning Fig. 7.46  Frankfort plane tilted too much up

114

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.47  Upper and lower teeth not occluded in lateral cephalometric radiograph

• Motion artefacts may occur especially in case of scanography cephalometric acquisition connected with longer exposure times (several seconds) in comparison with “one-shot” registration techniques (1-s exposure) (fig. 7.45a). • In analogue radiography missing aluminium filter will result in overexposure in an area of facial soft tissues and produce “burn-out” effects. Lack of soft tissues profile on lateral cephalometric radiograph will compromise cephalometric tracing.

7.4

 rrors Resulting from Incorrect Settings E of Radiographic Parameters

• These errors are less frequent in contemporary dentomaxillofacial radiography due to automatisation of exposure. In intraoral radiography choosing of tooth icon or number will result in default settings for a given group of teeth. In panoramic radiography inputting date of birth and gender will result in automatic setting of exposure parameters. However, discrepancies between patient’s size and chronological age and/or gender occur, so sometimes individual settings are

7.5  Errors Resulting from Incorrect Handling of X-ray Films in Analogue Radiography

a

115

b

Fig. 7.48  Incorrect exposure settings. (a) Radiograph too dark. (b) Radiograph too pale—even post-processing in digital radiography did not allow for a satisfactory diagnostic image quality

• •

•

•

recommended basing on experience of operator. In extraoral radiography, Automatic Exposition Control (AEC) consisting of a system of ionising chambers is used, which stops exposition once set ionisation level in chambers is achieved during production of X-rays. These errors can be due to faulty equipment thus periodical check-ups of X-ray machines is mandatory, even if not imposed by local laws and regulations. Too high tube voltage (pkV) or current (mA) as well as prolonged exposure time will result in overexposure and increased blackening of radiograph (Fig. 7.48a). Too low tube voltage, current or insufficient exposure time will result in underexposure and radiographic images which are too pale (Fig. 7.48b). Digital radiography image detectors are characterised by higher dynamics than conventional analogue films, and image postprocessing (contrast and/or brightness correction) may increase diagnostic quality of a radiograph which in analogue version would have been of unacceptable diagnostic quality. The means of avoiding over- or underexposure is correct choice of exposure settings based on manual, automatic exposition control and professional experience.

7.5

 rrors Resulting from Incorrect Handling of X-ray Films E in Analogue Radiography

• These errors affect only analogue radiography, thus switching to digital radiography will eliminate them (Figs. 7.49 and 7.50).

116

a

7  Technical Errors and Artefacts in Dental Radiography

b

Fig. 7.49  Film exposed to external light source. (a) Leaking intraoral film packet. (b) Light entering faulty cassette caused fogging of panoramic radiograph

a

b

c

Fig. 7.50  Mechanical damage to emulsion of radiographic film. (a) Bent mark. (b) Fingerprint. (c) Traces of inscription on film packet Effect Type of error Fogging of the whole film Inadequate light in or its part darkroom, faulty film package or leaking cassette for extraoral projections allowing light to act on film emulsion

Radiograph Means of elimination Fig. 7.49a, Apply only adequate b darkroom light safe for radiographic films Eliminate sources of leakage of light such as aperture around doors of darkroom Open cassette with radiographic film only in darkroom conditions, and film packet only in darkroom conditions or within film processor (automatic or semi-automatic)

7.6  Errors Resulting from Incorrect Chemical Processing of X-ray Films in Analogue… Type of error Mechanical damage to film emulsion—Film packet excessively bent, film emulsion scratched with fingernail or a sharp object, fingerprint, signing of film packet with a ball-pen, film packet bitten by patient Electrostatic discharge

7.6

Effect Visible area of mechanical damage with no radiographic image, e.g. line where film packet was bent, crescent corresponding to fingernail, fingerprint pattern, traces of inscription Branching radiolucencies resembling trees or thunders visible in resultant radiograph

117

Radiograph Means of elimination Fig. Carefully handle 7.50a–c radiographic films, avoiding damage to film emulsion

–

Carefully handle radiographic films. Avoid rubbing of films in order to diminish chance of collection of electrostatic charges in film surface

 rrors Resulting from Incorrect Chemical Processing E of X-ray Films in Analogue Radiography

• Also these errors affect only analogue radiography thus switching to digital radiography will eliminate them (Figs. 7.51, 7.52, 7.53, 7.54, and 7.55). a

b

Fig. 7.51  Incorrect chemical processing of analogue films—radiograph too dark. (a) Periapical radiograph. (b) Panoramic radiograph

a

b

Fig. 7.52  Incorrect chemical processing of analogue films—radiograph too pale. (a) Periapical radiograph. (b) Panoramic radiograph

118 Fig. 7.53  Dark stain in radiograph due to spraying of emulsion with developer solution before chemical processing

Fig. 7.54  Multiple bright stains on right (patient’s) side of panoramic radiograph are due to spraying of emulsion with fixer solution before chemical processing

Fig. 7.55 Mechanical damage to surface of panoramic radiograph during automatic film processing due to contact of film emulsion with contaminated rollers of processor

7  Technical Errors and Artefacts in Dental Radiography

7.7  Errors Resulting from Incorrect Read-out of Digital Radiographs Effect Type of error Depleted chemicals Film underdeveloped—Too in film processor pale Too low temperature of chemicals in film processor Too short time of film processing

Too high concentration of developer solution

Film overdeveloped—Too dark

Radiograph Means of elimination Fig. 7.51a, Change chemicals in film b processor on regular basis Maintain constant, adequate temperature of chemicals in film processor

Fig. 7.52a, b

Too high temperature of chemicals in film processor Too long time of film processing

Film emulsion sprayed with developer solution before chemical processing Film emulsion sprayed with fixer solution before chemical processing Mechanical damage to film emulsion in automatic film processor

7.7

119

Correctly adjust time of chemical processing in case of manual process. Use automatic or semi-automatic film processors instead of manual film processing Maintain adequate concentration of chemicals according to manufacturer’s guidelines Maintain constant, adequate temperature of chemicals in film processor Correctly adjust time of chemical processing in case of manual process. Use automatic or semi-automatic film processors instead of manual film processing Avoid contact between chemicals and film emulsion before film processing

Dark spots in radiograph

Fig. 7.53

Bright spots in radiograph

Fig. 7.54

Avoid contact between chemicals and film emulsion before film processing

Radiograph bent and/or scratched across due to movement of film along contaminated rollers of automatic film processor

Fig. 7.55

Regular maintenance of film processor with cleaning of rollers

 rrors Resulting from Incorrect Read-out E of Digital Radiographs

• Digital radiography is not free from technical errors and artefacts. • Despite developments in positioning aids, positioning errors can occur also in digital radiography. • Solid-state direct digital image receptor is rigid and thicker than PSP, so positioning of a solid-state detector is more demanding in intraoral radiography, especially when projecting wire is quite bulky. This also produces more frequent

120

7  Technical Errors and Artefacts in Dental Radiography

gagging reflex leading to displacement of image receptor in patient’s oral cavity, sometimes even before or during exposure. • Storage phosphor layer covering a PSP plate is sensitive to mechanical damage (scratching, bending, biting, mishandling). In areas of mechanical damage of PSP plate image is no longer registered and an unexposed area is visible on all radiographs taken with the same plate (Fig. 7.56). a

b

c

Fig. 7.56  Mechanical damage to a PSP plate. On two different radiographs (a, b) obtained using the same PSP plate, same shape of artefacts is visible. (c) Indirect digital panoramic radiograph also contains multiple streak mechanical artefacts

7.8  Errors and Artefacts in Cone-Beam Computed Tomography

a

121

b

Fig. 7.57  Incorrect read-out of a PSP plate due to faulty insertion into a dedicated laser scanner. (a) Periapical radiograph. (b) Panoramic radiograph

a

b

Fig. 7.58  Faulty read-out of a PSP plate. (a) Periapical radiograph. (b) Panoramic radiograph

• Errors in digital image read-out occur, e.g. lack of read-out of latent image, incorrect read-out when a PSP plate is obliquely introduced to a dedicated scanner (Fig.  7.57), uneven read-out due to a faulty scanner (Fig.  7.58), image-­ stitching artefacts in CCD-based cephalograms.

7.8

 rrors and Artefacts in Cone-Beam E Computed Tomography

• Motion artefacts—due to lack of patient cooperation, involuntary patient movements or when X-ray tube or image detector collide with patient’s bulky shoulders or back (Fig. 7.59). • Despite many artefact reduction algorithms, still not all CBCT examinations are completely free from artefacts produced by dense objects such as dental fillings, fixed prosthetic appliances, fixed orthodontic appliances, dental implants, orthodontic mini implants, miniplates used in maxillofacial surgery and radiopaque markers in implant stents.

122

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.59  Motion artefacts in CBCT in child

• Examples of artefacts in CBCT include the following: –– Streak artefacts spreading from the dense object to the borders of field of view (Fig. 7.60), but even if present, are less pronounced than those produced in medical computed tomography (CT). –– “Cupping” artefacts due to non-linear X-ray beam hardening (Fig. 7.61). • Laser print-outs can be damaged due to, for example, high temperatures and light (Fig. 7.62).

7.8  Errors and Artefacts in Cone-Beam Computed Tomography

123

a

b

c

Fig. 7.60  Streak artefacts in CBCT due to orthodontic braces, including one on exposed crown of buccally impacted lower canine. (a) Cross-sectional slice. (b) Axial slice. (c) Three-dimensional reconstruction

124

7  Technical Errors and Artefacts in Dental Radiography

Fig. 7.61  Beam hardening artefacts in CBCT due to inlays in teeth no. 24 and 25 compromise diagnostics of a suspected root fracture

Fig. 7.62  Laser print-out of CBCT images damaged due to high temperature and light—print-out left out in a car parked in full sunshine

Suggested Reading Brocklebank LM.  The quality of the X-ray image: fault analysis. Dent Update. 1998;25(5):188–90. 192-4 Çalışkan A, Sumer AP.  Definition, classification and retrospective analysis of photostimulable phosphor image artefacts and errors in intraoral dental radiography. Dentomaxillofac Radiol. 2017;46(3):20160188. Deniz Y, Kaya S. Determination and classification of intraoral phosphor storage plate artifacts and errors. Imaging Sci Dent. 2019;49(3):219–28. Dhillon M, Raju SM, Verma S, Tomar D, Mohan RS, Lakhanpal M, Krishnamoorthy B. Positioning errors and quality assessment in panoramic radiography. Imaging Sci Dent. 2012;42(4):207–12.

Suggested Reading

125

Ekströmer K, Hjalmarsson L.  Positioning errors in panoramic images in general dentistry in Sormland County, Swedan. Swed Dent J. 2014;38(1):31–8. Farman AG, editor. Panoramic radiology. Seminars on maxillofacial imaging and interpretation. Berlin: Springer; 2007. Jacobson A, Jacobson RL.  Radiographic cephalometry. From basics to 3-D imaging. Hanover Park: Quintessence Books; 2006. Langlais RP. Exercises in oral radiology and interpretation. 5th ed. St Louis: Saunders; 2016. Mauriello SM, Tang Q, Johnson KB, Hadgraft HH, Platin E. A comparison of technique errors using two radiographic intra-oral receptor-holding devices. J Dent Hyg. 2015;89(6):384–9. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. Pfeiffer P, Bewersdorf S, Schmage P. The effect of changes in head position on enlargement of structures during panoramic radiography. Int J Oral Maxillofac Implants. 2012;27(1):55–63. Riecke B, Friedrich RE, Schulze D, Loos C, Blessmann M, Heiland M, Wikner J. Impact of malpositioning on panoramic radiography in implant dentistry. Clin Oral Investig. 2015;19(4):781–90. Rondon RH, Pereira YC, Do Nascimento GC. Common positioning errors in panoramic radiography: a review. Imaging Sci. Dent. 2014;44(1):1–6. Rushton VE, Horner K, Worthington HV. The quality of panoramic radiographs in a sample of general dental practices. Br Dent J. 1999;186(12):630–3. Scarfe WC, Angelopoulos C, editors. Maxillofacial cone beam computed tomography. Berlin: Springer; 2018. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014. Yeo DK, Freer TJ, Brockhurst PJ.  Distortions in panoramic radiographs. Aust Orthod J. 2002;18(2):92–8. Zhang W, Huynh CP, Abramovitch K, Leon IL, Arvizu L.  Comparison of technique errors of intraoral radiographs taken on film versus photostimulable phosphor (PSP) plates. Tex Dent J. 2012;129(6):589–96.

8

Normal Anatomical Landmarks in Dental X-rays and CBCT

In this chapter radiological anatomy of intraoral and extraoral radiographs will be presented in the subsequent figures. Intraoral radiographs are supplemented by diagrams, while in panoramic radiographs landmarks are highlighted with colour on one side only. Teeth are marked with numbers according to the FDI dental notation (Figs. 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 8.10, 8.11, 8.12, 8.13, 8.14, 8.15, 8.16, 8.17, 8.18, 8.19, 8.20, and 8.21). Normal anatomy in panoramic radiographs: • Includes shadows of bone shadows (Figs. 8.22, 8.23, 8.24, 8.25, and 8.26), soft tissue (Fig. 8.27) and air spaces (Fig. 8.28);

Fig. 8.1  Tooth and alveolar bone anatomy. Blue—enamel. Yellow—cervix. Between blue and yellow—cemento-enamel junction. Red—pulp chamber and root canal. Light green—periodontal ligament space surrounded by lamina dura of alveolar socket. Dark green—cortex of alveolar ridge in interdental septum. White checkered pattern—trabecular bone of interdental septum. Grey are between pulp, enamel and periodontal ligament space—dentine © Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_8

127

128

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

Fig. 8.2  Maxillary upper incisors periapical in a child with primary dentition and germs of permanent teeth. Teeth marked with numbers— permanent teeth in green, primary teeth in red

• Depending on relationship towards the focal trough, some of these structures produce single shadow (Figs.  8.22, 8.23 and 8.24), some produce double real shadows (Fig. 8.25) and finally some of them give two shadows of which one is real on the side where the structure is actually located and the second shadow, called “ghost” shadow—this is a blurred, magnified shadow cast above the original real shadow (Fig. 8.26) due to projection geometry in panoramic unit—X-ray beam is directed at about 8° upwards in relation to the horizontal plane, • All the above-mentioned shadows overlap making panoramic radiographic anatomy complicated, • Shadows of soft tissues are better visible in edentulous patients than in dentate ones in whom they overlap dense shadows of teeth and even denser ones of possible dental restorations;

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

129

Fig. 8.3  Maxillary upper incisors periapical in a child with mixed dentition. Teeth marked with numbers—permanent teeth in green, primary teeth in red. Note wide open apices of erupted permanent teeth with incomplete root development

• Ghost shadows are more readily visible in case of faulty patient positioning, e.g. when patient’s head was placed too far forward resulting in pronounced shadows of contralateral mandibular angle and ramus as well as blurred shadow of cervical spine around midline of the radiograph; • Asymmetric patient positioning in panoramic unit results in differences in shadows of anatomical structures cast on both sides of the radiograph which in case of insufficient knowledge on normal radiographic anatomy results in mistakes in interpretation such as suspicion of osteolytic lesions in areas where pharyngeal air shadow overlaps mandibular bone (see Fig. 7.37).

130

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

b

Fig. 8.4 (a, b) Maxillary incisors periapical in a dentate patient. Parallel blue lines—intermaxillary suture, median palatal suture. Green ellipse—incisive foramen. Orange V-shaped line—anterior nasal spine. Yellow—floor of nasal cavity. Pink—soft tissues of the nose. White—alveolar ridge

a

b

Fig. 8.5 (a, b) Maxillary alveolar periapical near midline in an edentulous patient. Shadows of anatomical structures are better visible than in a dentate patient due to lack of dense shadows of teeth. Pink—soft tissues of the nose. Blue—air in right anterior nostril. White—shadow of gingiva (partly marked). Orange—alveolar ridge. Black—interface between mucosa of nasal floor and inferior nasal meatus and air in inferior nasal meatus. Red—anterior nasal spine. Yellow—floor of nasal cavity. Dark green—nasal septum—bony part. Light purple ellipse—Columella. Purple— inferior nasal concha

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

131

b

Fig. 8.6 (a, b) Periapical of left maxillary lateral incisor. Pink—shadow of soft tissues of the nose. Yellow—floor of the nasal cavity

a

b

Fig. 8.7 (a, b) Periapical of right maxillary lateral incisor. White ellipse—lateral fossa, incisive fossa. Red—anterior nasal spine. Yellow—floor of nasal cavity. Dark green—nasal septum. Light green ellipse—nasal openings of nasopalatine ducts. Black—interface between mucosa of nasal floor and inferior nasal meatus and air in inferior nasal meatus. Light blue—anterior recess of right maxillary sinus. Dark blue—septum in maxillary sinus

132

a

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

b

Fig. 8.8 (a, b) Maxillary right canine periapical. Pink—nasolabial fold. Yellow—floor of nasal cavity. Blue—border of maxillary sinus

a

b

Fig. 8.9 (a, b) Periapical of root of endodontically treated maxillary right canine. Shadows of anatomical structures are better visible than in a dentate patient due to lack of dense shadows of teeth. Red—Ala of the nose. Orange—alveolar ridge (partly marked). Pink—nasolabial fold. White—gingival margin. Yellow—floor of nasal cavity. Blue—border of maxillary sinus

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

133

b

Fig. 8.10 (a, b) Maxillary right premolars and molars periapical. White—floor of maxillary sinus, and above—air shadow in antrum. Dark blue—septum in maxillary sinus. Blue—floor of alveolar recess of maxillary sinus. Between blue and white lines—air in alveolar recess of maxillary sinus. Red—zygomatic process of maxilla. Pink circle—maxillary tuberosity. Yellow—soft tissues of gingiva (partly marked). Orange—margin of interdental septum

a

b

Fig. 8.11 (a, b) Maxillary left molars periapical. Pink ellipse—maxillary tuberosity. Green— coronoid process. Purple—zygoma. Red—zygomatic process of maxilla

a

b

Fig. 8.12 (a, b) Maxillary posterior left alveolar periapical in an edentulous patient. Shadows of anatomical structures are better visible than in a dentate patient due to lack of dense shadows of teeth. White—gingiva. Orange—alveolar ridge. Blue—floor of alveolar recess of maxillary sinus in edentulous area in alveolar process. Dark blue—bony septum in maxillary sinus. Pink—mucosa of maxillary sinus. Red—zygomatic process of maxilla. Purple—zygoma. Green—coronoid process

134

a

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

b

Fig. 8.13 (a, b) Maxillary right third molar periapical. Green—coronoid process. Red—hamulus of medial pterygoid plate of sphenoid bone. Yellow—medial pterygoid plate of sphenoid bone. Purple—zygoma

a

b

Fig. 8.14 (a, b) Mandibular incisors periapical. Red—lower lip shadow. Pink—lingual foramen. Purple—superimposed walls of the lingual canal

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

135

b

Fig. 8.15 (a, b) Mandibular left canine periapical. Dark blue—inferior mandibular cortex

a

b

Fig. 8.16 (a, b) Mandibular right premolars and molars periapical. Orange—mental foramen. Yellow—inferior alveolar nerve canal

136

a

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

b

Fig. 8.17 (a, b) Mandibular left molars periapical. Green—internal oblique line (mylohyoid line). Yellow—inferior alveolar nerve canal. Dark blue—inferior mandibular cortex

a

b

Fig. 8.18 (a, b) Mandibular right molars periapical. Light blue—external oblique line. Dark blue—inferior alveolar nerve canal. Purple ellipse—submandibular fossa

a

b

Fig. 8.19  Bitewing radiographs. (a) Right side. (b) Left side

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

137

b

Fig. 8.20 (a, b) Maxillary occlusal radiograph. Paired structures are marked on one side only. Dark blue—midline palatal suture. Dark green—nasal septum. Light green ellipse—large incisive foramen. Yellow—floor of the nasal cavity. Light blue—wall of maxillary sinus. White ellipse—air in nasal cavity. Purple ellipse—inferior nasal concha. Pink ellipse—nasolacrimal duct. Area between yellow and dark green lines represents superimposed nasal cavity floor and hard palate

a

b

Fig. 8.21 (a, b) Mandibular occlusal radiograph. Red—lower lip shadow. Yellow—mental ridge. Dark blue—inferior mandibular cortex. Light blue—genial tubercles. White ellipse—radiolucent oral floor. Pink—tongue

138

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

Fig. 8.22  Mandibular bone in panoramic radiographs. Paired structures are highlighted with colour only on one side of the diagram. Blue—coronoid process. Purple—sigmoidal notch. Pink— condylar process. Orange—inferior margin of mandible. Dark blue—lingual foramen. Light green—inferior alveolar nerve canal, mandibular canal. Dark green—incisive canal of mandible. Brown—mental foramen. Red—external oblique line

Fig. 8.23  Midfacial structures. Paired structures are highlighted with colour only on one side of the diagram. Red—panoramic innominate line—is not a real anatomical landmark, but consists of shadows of lateral orbital margin in upper portion and zygomatic process of maxilla in the lower part. Green—maxillary sinus. Orange—nasal cavity. Yellow—inferior nasal concha. Dark blue— inferior margin of orbit. Blue—infraorbital canal. Black—incisive foramen. White—hamulus of medial pterygoid plate of sphenoid bone. Purple—zygomaticotemporal suture. Brown—zygomatic arch

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

139

Fig. 8.24  Temporal bone and temporomandibular joints. Paired structures are highlighted with colour only on one side of the diagram. Red—mastoid process of temporal bone. Green—styloid process of temporal bone. Dark blue—external auditory meatus. Dark pink—glenoid fossa of temporomandibular joint. Purple—articular eminence of temporomandibular joint. Light pink—condylar head

Fig. 8.25  Single anatomical structures that produce double real shadows. Red—epiglottis. Green—hyoid bone. Dark blue—cervical spine. Orange—uvula, soft palate. Yellow—hard palate

140

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

Fig. 8.26  Anatomical structures that produce two shadows—real and ghost. Red—on the right side of panoramic radiograph ghost shadow of left side of hyoid bone is visible. Green—on the left side of panoramic radiograph ghost shadow of right mandibular bony is cast over mandible and pharyngeal air tissues. Yellow—real shadow of right side of hard palate. Orange—ghost shadow of left side of hard palate

Fig. 8.27  Air spaces visible in panoramic radiograph. On the right (patient’s) side of panoramic radiograph: Red—epiglottis. Green—posterior pharyngeal wall. Dark blue—uvula. On the left (patient’s) side of panoramic radiograph: Red—hypopharynx. Green—oropharynx. Dark blue—nasopharynx

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

141

Fig. 8.28  Soft tissue shadows. Paired structures are highlighted with colour only on one side of the diagram. Red—nasolabial fold. Green—upper surface of tongue. Yellow—nose. Dark blue— ear lobe. Purple—air between patient’s lips

Fig. 8.29  Temporomandibular joints anatomy in closed and open mouth position

142

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

b

c

d

e

f

Fig. 8.30 (a–h) Radiological anatomy of CBCT axial slices

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

g

h

Fig. 8.30 (continued)

a

c

b

d

Fig. 8.31 (a–h) Radiological anatomy of CBCT coronal slices

143

144

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

e

g

Fig. 8.31 (continued)

f

h

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

a

c

b

d

e

Fig. 8.32 (a–e) Radiological anatomy of CBCT sagittal slices

145

146

8  Normal Anatomical Landmarks in Dental X-rays and CBCT

Suggested Reading Farman AG, editor. Panoramic radiology. Seminars on maxillofacial imaging and interpretation. Berlin: Springer; 2007. Langlais RP. Exercises in oral radiology and interpretation. 5th ed. St Louis: Saunders; 2016. Larheim TA, Westesson P-LA, editors. Maxillofacial imaging. 2nd ed. Berlin: Springer; 2018. Miles DA, Van Dis ML, Williamson GF, Jensen CW. Radiographic imaging for the dental team. St Louis: Elsevier; 2009. Orhan K, Rozylo-Kalinowska I, editors. Imaging of the temporomandibular joint. Berlin: Springer; 2019. Pasler FA, Visser H. Pocket atlas of dental radiology. Stuttgart: Thieme; 2007. Scarfe WC, Angelopoulos C, editors. Maxillofacial cone beam computed tomography. Berlin: Springer; 2018. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014.

9

Analysis of Dental Radiographs and CBCT Studies

During reading of radiographs one must always take into consideration that they are only a two-dimensional shadow of three-dimensional structures. Owing to that a single radiograph is not enough to fully describe shape and localisation of a pathological lesion as it contains only partial information on examined objects. In medical radiology when a lesion is detected in one radiograph, as a rule the second radiograph is taken preferably at right angle to the first radiographic projection. However in dentomaxillofacial radiography this goal is not always feasible due to complicated anatomy of examined structures. Moreover it is impossible to place an image receptor between teeth, only on their buccal, lingual or occlusal surfaces. In practice imaging diagnostics is often limited to a periapical or bitewing radiograph, or a panoramic radiograph. If there are indications for further radiographs, the following should be considered: • Oblique periapical (mesial or distal) in order to separate images of two root canals which otherwise are overlapped in the basic orthoradial projection (Fig. 9.1). • Two periapicals at different angulation for paralaxis rule (Fig. 9.2). • Panoramic radiograph and maxillary or mandibular occlusal to visualise impacted teeth, cysts, dental trauma, etc. (Fig. 9.3). • Panoramic radiograph and true lateral cephalometric radiograph in orthodontic diagnosis (Fig. 9.4). According to the guidelines of many national and international associations there are defined indications for implementation of CBCT in diagnostic algorithms in different dental specialties (Fig. 9.5). Discussing all dental pathologies falls beyond the scope of this concise textbook, therefore examples of most common anomalies and lesions are presented. Dental pathologies are much more straightforward for dental professionals to diagnose as they encounter them in daily lives and possess in-depth knowledge on these lesions. The main problem is that many lesions remain undetected in radiographs and CBCT © Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_9

147

148

9  Analysis of Dental Radiographs and CBCT Studies

Fig. 9.1 Oblique periapical (mesial or distal) in order to separate images of two root canals which otherwise are overlapped in the basic orthoradial projection

scans as systematic reading and reporting are not always performed. Patient prognosis depends on early detection of such pathologies and quick implementation of adequate treatment. If lesions are missed, their growth continues and treatment becomes more complicated. Some of these pathologies are contraindication for implant placement. Therefore it is crucial to possess abilities to be able to pick up pathological conditions in X-rays and CBCT volumes. Systematic approach to reading and reporting of a diagnostic imaging examination is crucial. In general the following radiographic signs and symptoms are distinguished: 1. Processes in which bone destruction is more intense than new bone formation (osteopenia). This group includes osteoporosis, osteomalacia and osteolysis. 2. Processes in which bone formation dominates over bone destruction, called osteosclerosis. 3. Periosteal new bone formation. 4. Calcifications and ossifications. 5. Effects of treatment and iatrogenic lesions.

9  Analysis of Dental Radiographs and CBCT Studies

a

149

b

Fig. 9.2 (a, b) Two periapicals at different angulation for paralaxis rule in an impacted upper canine

a

b

Fig. 9.3  Panoramic radiograph and maxillary occlusal to visualise lesions in two projections differing in X-ray beam angulation. (a) Panoramic radiograph demonstrating radiolucency between central maxillary incisors. (b) Maxillary occlusal radiograph allows determination that the radiolucency corresponds to incisive foramen

Osteoporosis is a generalised or local bone loss. The process affects bone in qualitative and quantitative way, both mineralised and not mineralised bone tissues are involved. The radiographic image of osteoporosis consists of decrease in number of bony trabecula resulting in increased radiolucency of bone, enlargement of bone marrow spaces, thinning of outer cortex and resorption of inner aspect of outer cortex (Fig.  9.6). Generalised osteoporosis is diagnosed in post-menopausal females, aged individuals of both genders, as well as in some endocrine diseases, malnutrition and connective tissue diseases. Possibilities of diagnosis of post-­ menopausal osteoporosis have been discussed for many years, and so far the conclusion is that panoramic radiographs can be used as an aid in selection of patients in

150

9  Analysis of Dental Radiographs and CBCT Studies

a

b

Fig. 9.4 (a, b) Panoramic radiograph and true lateral cephalometric radiograph in orthodontic diagnosis

Fig. 9.5  Cone-beam CT in diagnostic algorithm of a complicated case of impaction of maxillary left canine

9  Analysis of Dental Radiographs and CBCT Studies

151

Fig. 9.6 Panoramic radiograph taken in a female aged 90 years demonstrates radiographic features of osteoporosis

a

b

Fig. 9.7  Example of an osteolytic lesion—incisive canal cyst. (a) Periapical radiograph. (b) CBCT

risk group of osteopenia so that they can be referred for bone mineral density estimation. In dentistry local bone loss is more common as one of the first radiological signs of such pathologies as osteomyelitis, tuberculosis or periodontal bone disease. Osteomalacia is disorder of bone structure due to abnormal or delayed mineralisation of osteoid bone as a result of vitamin D deficiency due to malnutrition as well as several metabolic defects. In children it is manifested as rickets (rachitis) with most prominent signs and symptoms related to lower limbs and ribs. In oral cavity it mostly presents with enamel abnormalities. In adults bone is osteoporotic, trabecular pattern is coarse, demineralisation occurs as blurred, “fuzzy” areas. Long bones are affected by the so-called Looser-Milkman zones which are radiolucencies running across the bone as a form of insufficiency fracture due to stress. Joint symptoms similar to ankylosing spondylitis are rare. Osteolysis is one of the most common radiological signs that are found in dentomaxillofacial radiology. It is related to destruction of both cancellous and cortical bone. Examples of lesions involving osteolysis include periapical lesions, cysts, some tumours and inflammation of bone tissue. Radiographic appearance of osteolysis is a radiolucency with or without sclerotic rim (Fig. 9.7).

152

a

9  Analysis of Dental Radiographs and CBCT Studies

b

Fig. 9.8  Example of an osteosclerotic lesion—dense bone island. (a) Cropped panoramic radiograph. (b) CBCT

Osteosclerosis is the opposite of osteolysis, so production of new bone is more intense than bone destruction while in normal bone the rates of bone destruction and production are comparable leading to dynamic balance. Radiographic sign of osteosclerosis is increase in bone density with loss of differentiation between cancellous and cortical bone. While quality of diagnostic images has considerably improved over the last years, small areas of osteosclerosis are more readily picked up by dentists. Many of these cases are the so-called dense bone islands which are a form of anatomical variant in the form of localised, but not encapsulated areas of sclerotic bone dispersed within the limits of cancellous bone (Fig.  9.8). These lesions are more prevalent in mandible, but can be observed in maxilla, too. If present under mandibular nerve canal, usually do not cause diagnostic difficulties, but if above the canal and cast over periapical areas, must be differentiated from sclerosing osteitis. Another differential is fibrous dysplasia characterised by ground glass or orange peel appearances, less commonly “finger print” arrangement of bony trabecula (see: Fig. 9.11d, e). Whether osteopenic or osteosclerotic, lesions can be well-defined, with or without a radiopaque rim, or ill-defined. A well-defined lesion is the one which has a distinctive border (Figs. 9.7 and 9.9). It can be surrounded by a corticated (thin) or sclerotic (thick) margin composed of reactive bone. A lesion may be well-defined, but not possess the rim, and such areas are called “punched out” as they are compared to holes in paper made by means of a paper punch (Fig. 9.10) for example in plasmacytoma. In odontogenic lesions such as cementoblastoma and odontoma, radiolucent rim is visible between calcified tumour masses and corticated margin.

9  Analysis of Dental Radiographs and CBCT Studies

a

b

153

d

c

e

f

Fig. 9.9  Well-defined lesion with a cortical rim. (a) diagram. (b) Periapical radiograph of a radicular cyst. (c) CBCT of a radicular cyst. (d) Cropped panoramic radiograph showing complex odontoma. (e, f) Complex odontoma in tangential and cross-sectional slices

154

a

9  Analysis of Dental Radiographs and CBCT Studies

b

Fig. 9.10  Punched-out lesion. (a) Diagram. (b) Plasmacytoma—multiple well-defined radiolucencies without sclerotic or cortical borders spread throughout the mandible in panoramic image

An ill-defined lesion is described when it is not possible to make a distinction between healthy and diseased bone (Fig. 9.11). It is due to infiltration of bone (permeative bone destruction with remnants of normal bone intercalated with pathological infiltrations) by neoplasm (Fig. 9.11b, c) or inflammatory process or changes such as fibrous dysplasia and sclerosing osteitis (gradual change from normal bone to pathological one). Shape of a lesion can be irregular or regular—round, oval or scalloped (with multiple arcuate outlines). As far as internal structure is concerned, it can be unilocular (with one compartment) (Fig.  9.9a–c) or multilocular (containing many compartments divided by septa) (Fig. 9.12). Some typical appearances in radiographs and CBCT scans are gathered in Table 9.1. Periosteal new bone formation is reaction of periosteal bone to a pathological process such as neoplasm (mostly sarcoma), inflammation (most commonly osteomyelitis) and trauma (reparation processes). Periosteum is thickened and may also be perforated and displaced away from bone surface by masses of tumour. There are several types of periosteal new bone formation: onion peel, Codman’s triangle and sun ray. They are more readily identified in long bones, but mandible can also be affected and then the appearances can be diagnosed on axial occlusal, on inferior border of mandibular body in panoramic as well as in CBCT scans in different locations. The first type is diagnosed when there are layers of thickened periosteum parallel to surface of bone causing enlargement of bone outlines, and is most commonly observed in osteomyelitis (Fig.  9.13). However, it may accompany such tumours as Ewing’s sarcoma. In some cases of healing of post-traumatic injuries onion skin periosteal new bone formation may be even more pronounced and festoon-­like thickening of periosteum is observed. Codman’s triangle and sunray appearance are associated with sarcomas (Fig. 9.14a, b). The name triangle or angle comes from triangular shape of periosteal bone separated from surface of bone and perforated by tumour masses. Multiple thin spicules projecting from bone surface resemble rays of sun, hence the name. Nevertheless, as sarcomas are rare tumours and it is squamous cell carcinoma which is most frequent cancer of maxillofacial

9  Analysis of Dental Radiographs and CBCT Studies

155

b

a

c

d

e

f

g

Fig. 9.11  Ill-defined lesion. (a) Diagram. (b) Squamous cell carcinoma of left mandibular ramus visible in panoramic radiograph. (c) Squamous cell carcinoma of anterior maxilla in a young male—CBCT. (d, e) Moth-eaten areas of bone destruction in osteomyelitis in tangential (d) and cross-sectional (e) views. (f, g) Fibrous dysplasia—cropped panoramic view (f) and axial slice (g)

156

a

9  Analysis of Dental Radiographs and CBCT Studies

b

c

Fig. 9.12  Example of a multilocular lesion—ameloblastoma. (a) Diagram. (b) Panoramic radiograph. (c) CBCT

area, vast majority of malignancies in this region develop without periosteal new bone formations as cancer does not induce it (Figs. 9.11a, b and 9.14c). It is mandatory to analyse the effect of the lesion on structures in vicinity—teeth and anatomical landmarks. Teeth may be displaced (in case of slowly growing pathological areas) (Fig. 9.15a) or resorbed (Fig. 9.15b). As far as lamina dura is concerned, it may be resorbed or intact, the latter being mostly a piece of evidence against odontogenic origin of a lesion. Periodontal ligament space may be normal, widened with intact lamina dura (e.g. in early acute periapical inflammations or during orthodontic treatment) (Fig.  9.16a) and widened with loss of lamina dura (inflammatory processes, tumours, etc.) (Fig. 9.17). Anatomic landmarks such as inferior alveolar nerve canal and floor of maxillary sinus can be displaced (Fig. 9.9c) or invaded with loss of cortical borders (Fig. 9.11b).

9  Analysis of Dental Radiographs and CBCT Studies

157

Table 9.1  Characteristic radiographic appearances Appearance Beaten metal Cauliflower-­ like Champagne bubbles Codman’s triangle Copper beaten skull Cotton wool Finger print Golf ball Ground glass Hair on end Honeycomb Moth eaten Onion-skin Orange peel Pepper pot skull Punched out Salt and pepper sign Soap bubbles Step ladder Sunburst, sunray Tennis racket

Radiographic image Lesion or disease Crouzon syndrome Indentations in inner cortex of skull due to impressions from brain gyri in increased intracranial pressure Dense, calcified masses branching like a cauliflower Calcifications in lymph nodes Multiple small chambers with septa Ameloblastoma Triangular shape of periosteal bone separated from surface of bone and perforated by tumour masses Indentations in inner cortex of skull due to impressions from brain gyri in increased intracranial pressure Patches of sclerotic bone chaotically scattered within previously osteoporotic bone Spiral alignment of bony trabecula, resembling finger print Round, dense radiopacity attached to dental root apex Thickening and shortening of bony trabecula lead to appearance of dense radiopaque bone, “milky” in appearance Expansion of diploic space of skull vault with thickening of bony trabecula which are located at right angle to skull surface Multilocular appearance with short, straight septa Irregular areas of osteolysis combined with remnants of normal bone

Sarcoma Crouzon syndrome Paget’s disease Fibrous dysplasia Cementoblastoma Fibrous dysplasia Sickle cell anaemia Thalassemia

Odontogenic myxoma Osteomyelitis Osteonecrosis Some tumours Layers of thickened periosteum parallel to surface of Osteomyelitis bone causing enlargement of bone outlines Osteonecrosis Ewing’s sarcoma Fine pattern of dense, short bony trabecula Fibrous dysplasia Fine pattern of multiple well-defined radiolucencies Hyperparathyroidism in skull due to resorption of bony trabecula Well-limited radiolucency, without sclerotic rim Plasmacytoma Fine pattern of multiple well-defined radiolucencies Hyperparathyroidism in skull due to resorption of bony trabecula Large chambers with thick septa Ameloblastoma, keratocyst Scarce, horizontally aligned trabecula between Sickle cell anaemia dental roots with increased bone marrow spaces Multiple thin spicules projecting from bone surface Sarcoma Multilocular with straight septa

Odontogenic myxoma

Location of a lesion may be a hint in diagnosis. Ameloblastoma is found four times more frequently in mandible than in maxilla, and if in the upper jaw, then almost solely in posterior maxilla (Fig. 9.12). In the lower jaw ramus and posterior body are usually affected. Keratocyst (previously also classified as keratocystic odontogenic tumour) is more prevalent around mandibular angle (Fig.  9.18).

158

9  Analysis of Dental Radiographs and CBCT Studies

a

b

c

Fig. 9.13  Onion-skin periosteal new bone formation in osteomyelitis of left mandibular angle. (a) Diagram. (b) Panoramic radiograph. (c) CBCT

9  Analysis of Dental Radiographs and CBCT Studies

159

a

b

c

Fig. 9.14  Diagrams of periosteal new bone formation. (a) Codman’s triangle. (b) Sunray appearance. (c) Bone destruction without periosteal reaction

Cementoblastoma, being the only tumour arising from radical cementum, is found at an apex of tooth (Fig. 9.19). Within the head and neck area osteoma occurs preferentially in paranasal sinuses, especially frontal ones. Central giant cell granuloma is named “central” as it tends to develop anteriorly to the first molars. Widening of mandibular nerve canal should raise suspicion of development of a process arising from contents of the canal, i.e. neurovascular bundle. The tumours found in this location include neuroma, neurofibroma and schwannoma. Lesions arising below inferior alveolar nerve canal are very likely of non-odontogenic origin, while these located above the canal most commonly are odontogenic. Location in the area of mandibular angle, below inferior mandibular nerve canal, is typical for Stafne bone defect (cavity), but anterior variants of this anomaly can be detected, too (Fig. 9.20). Size of detected lesion not necessarily is a hint in differential diagnosis as many pathologies may be incidental findings and patients unaware of onset of their development. What is important is lack of changes in dimensions which means no progression in case of, for example, Stafne bone cavity (Fig.  9.20) or a dense bone island (Fig. 9.8).

160

9  Analysis of Dental Radiographs and CBCT Studies

a

b

Fig. 9.15  Effects of pathological lesions on teeth. (a) Panoramic radiograph presents left mandibular third molar displaced up the left mandibular ramus by a large follicular cyst. (b) Resorption of roots of the left mandibular first molars induced by an odontogenic keratocyst

Whether a lesion is single or multiple also is important in differential diagnosis. Apart from, for example, periapical inflammatory pathologies, many lesions in maxillary and mandibular bones are single. Examples of multiple lesions include plasmacytoma (previously named multiple myeloma) (Fig. 9.10), periapical cemental dysplasia (Fig.  9.21) and metastases. However it must be underlined that all above-mentioned pathologies can present as single lesions, too, and not necessarily are multiple. Patient’s age is helpful in making differential diagnosis. Ameloblastoma tends to occur in middle-aged individuals, while tumours of earlier decades of life include adenomatoid odontogenic tumour (second decade), keratocyst (10–30 years of age), odontogenic myxoma (10–40  years old). Cherubism affects young children and usually spontaneously regresses around seventh year of life. Typical age of

9  Analysis of Dental Radiographs and CBCT Studies

161

Fig. 9.16  Panoramic radiograph demonstrates generalised widening of periodontal ligament spaces without loss of lamina dura during orthodontic treatment with fixed appliances

a

b

Fig. 9.17  Widening of periodontal ligament space with loss of lamina dura and osteolysis in a periapical abscess. (a) Periapical radiograph. (b) CBCT cross-sectional images

162

9  Analysis of Dental Radiographs and CBCT Studies

Fig. 9.18  Odontogenic keratocyst in right mandible visible in panoramic radiograph

detection of osteoma is 40–50 years. Oral cancer used to be a disease of older individuals, over 50 years of age, but nowadays it is diagnosed also in young adults, mostly males, in association with human papillomavirus infection.

9.1

Calcifications and Other Radiopacities

Radiopacities in radiographs and other imaging studies of maxillofacial include the following: • • • • • • • • • • •

Calcifications and ossifications in neoplasms (as above). Salivary stones (sialoliths) (Fig. 9.22). Phleboliths—venous stones (Fig. 9.23). Dystrophic calcifications, e.g. in palatine tonsils (Fig. 9.24). Calcifications in lymph nodes (Fig. 9.25). Calcified stylohyoid ligament and elongation of styloid process (including symptomatic Eagle’s syndrome) (Fig. 9.26). Metastatic calcifications around joints, in patients with disorders of calcium and phosphate metabolism (e.g. undergoing dialysis). Calcified atherosclerotic plaques. Calcifications in skull cavity. Foreign bodies. Salivary stones (sialoliths) (Fig. 9.22): The following radiographs can be used to demonstrate salivary stones: –– Axial mandibular occlusal for stones in submandibular ducts. –– Panoramic radiograph—stones overlap body and/or mandibular ramus. –– Other: oblique lateral, modified PA, intraoral radiograph of buccal soft tissues.

9.1  Calcifications and Other Radiopacities

163

a

b

Fig. 9.19  Cementoblastoma of left mandibular second molar. (a) Panoramic view. (b) CBCT tangential and cross-sectional images

Fig. 9.20  Stafne bone cavity located below inferior alveolar nerve canal in posterior mandible

164

9  Analysis of Dental Radiographs and CBCT Studies

a

b

c

Fig. 9.21  Example of multiple lesions—periapical cemental dysplasia. (a) Panoramic radiograph. (b) CBCT tangential images. (c) CBCT cross-sectional images of anterior mandibular teeth

9.1  Calcifications and Other Radiopacities

165

a

b

Fig. 9.22  Sialolithiasis. (a) Stone in duct of right submandibular gland in mandibular occlusal radiograph. (b) Calculus in left submandibular gland in CBCT verified by ultrasound (lower right corner)

• Only radiopaque stones are visible in radiographs, and these comprise 70–90% of all sialoliths; up to 60% of parotid stones are perceivable in X-rays and up to 80% of submandibular calcifications. • Nowadays use of sialography is limited to diagnosis of duct strictures as well as in interventions such as stone removal and balloon dilatation of stenotic ducts. • CBCT is not a method of choice in diagnosis of sialoliths, but when visible, it must be reported. • Ultrasound is recommended in diagnosis of salivary stones and related inflammations. Phleboliths (Fig. 9.23):

166

9  Analysis of Dental Radiographs and CBCT Studies

Fig. 9.23  Ring-like calcifications in soft tissues of cheek in CBCT correspond to phleboliths

• Single or multiple radiopacities. • Roundish, sometimes ring-like with a radiolucency inside which is due to layered structure. • Their presence is worth noting as may be the only sign of cavernous haemangioma. Dystrophic calcifications in palatine tonsils (Fig. 9.24): • Are frequent incidental findings. • Radiopacities, single or multiple. • On panoramic radiographs their shadows are cast on ramus or mandibular angle, and also on soft tissues below mandibular angle and posterior to mandibular ramus. • Are overdiagnosed as salivary stones. • In panoramics sometimes they produce double shadows—real and ghost on contralateral side. • In CBCT true localisation of these calcifications is evident. Calcifications in lymph nodes (Fig. 9.25): • Arise in course of inflammations including granulomatous diseases such as tuberculosis, sarcoidosis, cat scratch disease or fungal infection. • Well-limited, lobulated radiopacities of variable intensity. Calcified atherosclerotic plaques: • Visible in panoramic radiographs as radiopacities at the level of C3-C4 vertebra, at 45° inferior and posterior to mandibular angle.

9.1  Calcifications and Other Radiopacities

a

b

Fig. 9.24  Dystrophic calcifications in palatine tonsils. (a) Panoramic radiograph. (b) CBCT

167

168

9  Analysis of Dental Radiographs and CBCT Studies

Fig. 9.25  Cauliflower-like radiopacity below left mandibular angle corresponds to calcifications in a group IB lymph node

a

b

Fig. 9.26  Bilateral elongation of styloid processes of temporal bones with calcification of stylohyoid ligaments produced symptoms of Eagle’s syndrome. (a) CBCT axial view presents cross sections of elongated processes. (b) CBCT three-dimensional reconstruction demonstrates the course of calcified structures

Calcifications in skull cavity: • Visible in lateral cephalometric radiographs and large FoV CBCTs. • Physiological—pineal gland, falx cerebri, vascular plexi of lateral ventricles. • Pathological—wall of aneurysm, old abscess, calcified parasites, rarely in brain tumours. • Premature and intensive calcifications in falx cerebri can occur in basal cell nevus syndrome (Gorlin-Goltz).

9.1  Calcifications and Other Radiopacities

169

Radiographic appearances of iatrogenic lesions and effects of treatment are presented in Fig. 9.27. When reporting a radiograph or a CBCT scan, the following remarks should be considered: –– Check whether the radiographic examination was correctly taken and there are no technical issues that decrease quality of obtained image, influence or even hamper image reading, and if this examination should not be retaken. –– Exclude possible shadows of anatomical structures, especially bearing in mind that in an asymmetrically taken panoramic radiograph, radiolucent shadows of air spaces will be asymmetrical, too, thus influencing appearance of bone tissue due to uneven distribution of air shadows between right and left side. a

b

Fig. 9.27  Examples of effects of treatment including iatrogenic errors. (a) Overextension of root canal filling material (gutta percha point) protruding outside root apex into soft tissues of cheek along anterior wall of maxillary sinus. CBCT cross-sectional image. (b) Overextension of root canal filling material (sealer) visible in axial CBCT scan on buccal side of anterolateral wall of right maxillary sinus. (c) Overextension of root canal filling material (sealer) in floor of left maxillary sinus and cortical bone of maxillary sinus floor. (d) Overextension of root canal filling material (sealer) into inferior alveolar nerve canal. Panoramic view (d) and (e) CBCT tangential and cross-sectional images demonstrate location of dense foreign body in the canal highlighted with purple. (f) In a cropped panoramic radiograph shadow of root of upper left second molar is visible in left maxillary sinus following an attempt on extraction. (g) Status post resection of left mandibular body and ramus without reconstruction—panoramic radiograph. (h) Status post resection of mandibular body with reconstruction by means of bone grafts fixed with plate. (i) Status post fixation and healing of fracture of left mandible. Panoramic radiograph. (j) Multiple fixation devices after orthognathic surgery are visible in a panoramic radiograph. (k) Status post resection of tumour. Multiple dense foreign bodies in soft tissues correspond to surgical staples. (l) Status post bone grafting and implant placement in left maxilla. (m) Patient during orthodontic treatment with fixed devices including a palatal appliance. (n) Retainer after completed orthodontic treatment is visible as a radiopaque line across crowns of lower anterior teeth. (o) Dense foreign bodies in soft tissues of cheek correspond to gold threads used in face lifting. (p) Patient following cervical spine stabilisation surgery presents with double real shadow of stabiliser in panoramic radiograph

170

c

d

Fig. 9.27 (continued)

9  Analysis of Dental Radiographs and CBCT Studies

9.1  Calcifications and Other Radiopacities

e

f

Fig. 9.27 (continued)

171

172

g

h

i

Fig. 9.27 (continued)

9  Analysis of Dental Radiographs and CBCT Studies

9.1  Calcifications and Other Radiopacities

j

k

l

Fig. 9.27 (continued)

173

174

m

n

Fig. 9.27 (continued)

9  Analysis of Dental Radiographs and CBCT Studies

9.1  Calcifications and Other Radiopacities

175

o

p

Fig. 9.27 (continued)

–– Try to assign the detected lesion into one of these groups: developmental anomalies, inflammatory processes, trauma, cysts, tumours, other lesions, as this will help in narrowing down differential diagnosis. –– Describe effects of treatment if already performed. –– Describe the radiographic findings in detail, and whenever possible write the diagnosis and if not possible to determine one, provide differential diagnosis and suggestion of further imaging studies to be applied.

176

9  Analysis of Dental Radiographs and CBCT Studies

Suggested Reading Carter L, Farman AG, Geist J, Scarfe WC, Angelopoulos C, Nair MK, Hildebolt CF, Tyndall D, Shrout M, American Academy of Oral and Maxillofacial Radiology. American Academy of Oral and Maxillofacial Radiology executive opinion statement on performing and interpreting diagnostic cone beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2008;106(4):561–2. Cremonesi I, Nucci C, D'Alessandro G, Alkhamis N, Marchionni S, Piana G. X-linked hypophosphatemic rickets: enamel abnormalities and oral clinical findings. Scanning. 2014;36(4):456–61. European Society of Radiology (ESR). Good practice for radiological reporting. Guidelines form the European Society of Radiology. Insights Imaging. 2011;2:93–6. Gjørup H, Beck-Nielsen SS, Haubek D. Craniofacial and dental characteristics of patients with vitamin-D-dependent rickets type 1A compared to controls and patients with X-linked hypophosphatemia. Clin Oral Investig. 2018;22(2):745–55. Horner K, Barry S, Dave M, Dixon C, Littlewood A, Pang CL, Sengupta A, Srinivasan V. Diagnostic efficacy of cone beam computed tomography in paediatric dentistry: a systematic review. Eur Arch Paediatr Dent. 2019; https://doi.org/10.1007/s40368-019-00504-x. Jacobs R, Salmon B, Codari M, Hassan B, Bornstein MM. Cone beam computed tomography in implant dentistry: recommendations for clinical use. BMC Oral Health. 2018;18(1):88. Meyer KA, Bancroft LW, Dietrich TJ, Kransdorf MJ, Peterson JJ.  Imaging characteristics of benign, malignant and infectious jaw lesions: a pictorial review. AJR Am J Roentgenol. 2011;197:23–32. Miles DA, Danforth RA. Cone beam computed tomography: from capture to reporting. Dent Clin N Am. 2014;58(3):ix–x. More CB, Das S, Gupta S, Bhavsar K. Mandibular adenomatoid odontogenic tumor: radiographic and pathologic correlation. J Nat Sci Biol Med. 2013;4(2):457–62. Mupparapu M, Creanga AG, Singer SR. Interpretation of cone beam computed tomography volumetric data: how to report findings. Quintessence Int. 2017;48(9):733–41. Patel S, Durack C, Abella F, Shemesh H, Roig M, Lemberg K. Cone beam computed tomography in endodontics—a review. Int Endod J. 2015;48(1):3–15. Scarfe WC, Li Z, Aboelmaaty W, Scott SA, Farman AG. Maxillofacial cone beam computed tomography: essence, elements and steps to interpretation. Aust Dent J. 2012;57(Suppl 1):46–60. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014.

Safety Precautions for Dental Patient and Dental Staff Using X-Rays

10

X-radiation (called also X-rays) is a kind of electromagnetic radiation that arises in an accelerator called X-ray tube (Fig. 10.1). An X-ray tube consists of cathode with filament made of tungsten, anode with focal spot (target) made usually of tungsten embedded in a copper block to dissipated heat. The whole appliance is encased in a glass envelope to ensure presence of vacuum conditions inside the X-ray tube. Fig. 10.1  X-ray tube. (a) Photograph. (b) Diagram

a

b

Glass envelope

Anode (+)

Cathode (-)

Copper block

Target

© Springer Nature Switzerland AG 2020 I. Rozylo-Kalinowska, Imaging Techniques in Dental Radiology, https://doi.org/10.1007/978-3-030-41372-9_10

Filament in cathode

177

178

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

Moreover, the device is shielded by a lead case with only one slot for emission of X-rays. The lead case is filled with oil also for the purpose of dissipation of heat generated during production of X-radiation. When electric current is applied to the X-ray tube, the filament of the cathode is heated and following the increase in temperature emission of electrons begins. This phenomenon is called thermal emission. Due to difference in potentials between the electrodes, electrons are accelerated between the cathode and the anode in vacuum conditions. Therefore the X-ray tube can be considered to be an accelerator. When accelerated electrons hit the surface of anode target, they are suddenly stopped as they encounter atoms of tungsten in which 74 electrons located on 6 shells rotate around the nucleus. Depending on the course of the incoming electron in relation to tungsten atom, X-rays or heat are produced, and it should be underlined that heat-producing interactions prevail (99%). It is more probable that an incoming electron encounters tungsten electrons located on outer shells than that it is able pass deeper inside the atom. When the incoming electron is deflected by one of electrons on outer shell of tungsten, its loss of energy is emitted as heat. When the incoming electron hits one of outer shell electrons of tungsten, it also loses energy which is inverted to heat, while the atom without one electron becomes an ion. Hence another name of X-rays, i.e. ionising radiation. If the incoming electron passes close to the tungsten nucleus, it is slowed down with excess of energy released as emission of X-rays. This is called braking radiation or, from German, Bremsstrahlung. It is also called continuous spectrum as the beam consists of photons of different energies from low (which prevail in the spectrum) to the least numerous high-energy photons. The highest photon energy in the beam is limited by peak X-ray tube voltage. When the incoming electron collides with one of electrons on inner shells, the latter electron will be ejected—either outside the atomic shells (which again will cause ionisation) or to one of outer shells, and this phenomenon is called excitation. When electrons from outer shells cascade to fill the gap in one of the inner shells (lower energy level), excess energy is released in the form of X-rays, too. This part of X-ray spectrum is called characteristic spectrum as it depends on the material of the anode focal spot. The energies are specific for atom shells from which electrons are emitted. The final X-ray beam is composed of both continuous and characteristic spectra. X-rays interact with matter and out of four interactions only two have significance in dentomaxillofacial radiography and radiobiology, i.e. Compton effect and photoelectric effect. Compton effect is related to scatter and absorption of X-ray photons, and results in ionisation of tissues. In photoelectric ionisation and effect pure absorption of X-rays occur, and this effect is used in generation of radiographic image in some image receptors. Properties of X-radiation: • X-ray beam consists of photons of electromagnetic radiation. • Absorption and scattering of X-radiation during passage through examined object leads to attenuation of the radiation depending on thickness, density and internal structure of the object.

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

179

• Intensity of X-radiation follows the inverse square rule which means that the intensity of radiation is four times lower when distance from the source of radiation is doubled. • X-rays cause ionisation of atoms which is one of factors contributing to harmful effects of X-radiation in living organisms. • X-rays cause luminescence which is used in registration of X-ray image in digital image receptors and was applied in intensifying screens of cassettes for extraoral analogue radiography. • X-radiation causes blackening of photographic emulsion which in the past was utilised in analogue intraoral radiography. • X-radiation is undetectable to human senses. • X-rays are characterised by potentially harmful effect on human organism. Potentially harmful effects of ionising radiation on human beings are listed below: • Ionisation and excitation due to X-radiation acting on atoms may lead to effects at cellular level and structural changes. • Some components of cells are more prone to harmful effects of radiation, for example DNA and RNA, and the damage can be divided into direct (less common as direct hit by X-ray photon is less probable) and indirect. • Indirect damage is based on appearance of free radicals following ionisation of molecules, for the greater part water molecules as this compound is the most prevalent in human body. • Free radicals include hydroxyl radical ·OH and a single atom of hydrogen as it has an unpaired electron H·. Free radicals are not stable and undergo further reactions leading to occurrence of molecules such as hydrogen peroxide (H2O2) and free organic radicals. • Indirect effect may but not necessarily must induce permanent cell damage as cells possess mechanisms of reparation and often are able to return to the baseline status. • Permanent damage is the result of many factors such as susceptibility of a given tissue to ionising radiation, patient’s age, gender and efficiency of reparation mechanisms. • Young organisms contain a lot of dividing cells in differentiating and growing tissues, therefore foetuses and small children are more susceptible to potential harmful effect of ionising radiation than older individuals in whom tissue development is finished and cell divisions occur with lower intensity. As far as mature tissues are concerned, they are characterised by much lower rate of cell division like bone tissue and nervous tissue are more resistant to effects of ionising radiation than tissues with quickly dividing cells such as bone marrow or epithelium of gastrointestinal tract (Table 10.1). • The effects of ionising radiation on human organism are divided into somatic deterministic, somatic stochastic and genetic stochastic. • Deterministic effects are all those where a threshold exists below which no effect will occur and above which the effect will always occur and its strength will depend on the dose of radiation. Deterministic effects may be acute or chronic.

180

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

• Acute deterministic effects include radiation-induced damage to dividing cells such as bone marrow, intestinal epithelium, hair follicles. The most widely heard of type of acute deterministic effect is acute radiation syndrome (radiation sickness) that is not observed in dentomaxillofacial radiology. • Chronic deterministic effects include skin reddening and development of cataract. • Stochastic effects are accidental events that may but do not have to occur; there is no safe threshold below which the effect will never occur; stochastic effects may concern both somatic cells and gametes. Examples of stochastic effects are mutations leading to congenital anomalies or development of some neoplasms like leukaemia in 5–7 years after irradiation or development of bone sarcoma in a region that had been treated by radiotherapy due to another tumour tens of years ago or thyroid cancer in children and young adults. • Occurrence of harmful effects of ionising radiation depends on extent of exposure to radiation—whether local, limited like in radiotherapy or extensive, systemic, e.g. victims of nuclear bombing in Hiroshima and Nagasaki in 1945 or nuclear power plant failures, in Chernobyl in 1986 or in Fukushima Daiichi in 2011. Measures of dose used in evaluation of effects of ionising radiation: • Absorbed dose D is the energy of ionising radiation that was passed to matter in an element of volume and divided by mass of this element. Absorbed dose is an average dose for a tissue or organ in Grays (Gy) = J/kg. • Equivalent dose HT is the absorber dose in a tissue or organ T, weighted for type and energy of ionising radiation R.  For X-radiation the weighting factor is 1, therefore the equivalent dose is equal to absorbed dose for this type of radiation. The measure of equivalent dose is Sievert (Sv). • Effective dose E is the sum of weighted equivalent doses from external and internal irradiation of tissues and organs, taking into account tissue weighting factors for X-radiation (Table 10.1). The measure of effective dose is also Sievert (Sv). When taking into consideration harmful effects of ionising radiation, it must be remembered that human organisms are exposed to radiation from various sources, and medical exposure is not necessarily the main source. Exposure to natural sources of radiation varies in different countries and even regions within one country and depends on many factors (Fig. 10.2). The sources of radiation are as follows: • Radioactive gas radon and its isotopes, and exposure to the gas is related to its amount in buildings as well as applied methods of shielding, if any. • Internal sources of radiation in the form of radioactive isotopes—such as iodine 131 taken in by thyroid, potassium 40, carbon 14, strontium 90 that accumulates is an analogue of calcium and is inbuilt in bone tissue. • Cosmic radiation—higher levels at higher altitudes (mountains, aircrafts) as well as at higher latitudes (due to less-efficient geomagnetic shielding).

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

181

Table 10.1  Tissue weighting factors according to the International Commission on Radiological Protection from 1990 to 2007 Tissues and organs Red bone marrow Breast tissue Colon Lungs Stomach Bladder Oesophagus Gonads Liver Thyroid Bone surface Brain Salivary glands Skin Remaining tissues (listed below)

ICRP 1990 0.12 0.05 0.12 0.12 0.12 0.05 0.05 0.20 0.05 0.05 0.01 Within the remaining tissues – 0.01 0.05

ICRP 2007 0.12 0.12 0.12 0.12 0.12 0.04 0.04 0.08 0.04 0.04 0.01 0.01 0.01 0.01 0.12

Remaining tissues according to ICRP 2007 are (in alphabetical order): adrenals, extrathoracic region, gall bladder, heart, kidneys, lymphatic nodes, muscle, oral mucosa, pancreas, prostate in males, small intestine, spleen, thymus, uterus/cervix in females

Average annual exposure dose in Poland 3.74 mSv 0,091

0,001

0,011

1,2 1,3

0,46 0,1

Radon Medical diagnostics

0,28

Gamma radiation Food

0,39

Cosmic radiation Utilities

Fig. 10.2  Average annual exposure to radiation in Poland

Internal sources Other

Toron

182

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

• Radioactive isotopes in ground and minerals—depending on geological structure of Earth’s crust. • The percentage of average annual exposure to radiation derived from natural sources of radiation depends not only on intensity of different sources of radiation but also on amount of medical examinations and therapies based on ionising radiation. In countries where X-ray-based imaging techniques are more readily used, the percentage from natural sources is lower, but altogether the average annual dose may be higher than in other countries. • For example in Poland in 2018 average exposure from medical sources of radiation was estimated at 1.31 mSv, which comprises 34.7% of total average annual exposure. The main components were CT 0.86 mSv as well as radiography and fluoroscopy 0.17 mSv (Fig. 10.2). • Other non-natural sources of radiation are industrial radiography, industrial applications of radioactive isotopes, airport security check systems, as well as nuclear power plant failures and other nuclear incidents. Effective doses encountered in dentomaxillofacial radiology are estimated using studies on phantoms or derived from the Dose-Area Product (DAP) as a measure of entry radiation dose to area of skin surface by using coefficients. There is a wide variation in dose quantities being displayed on panoramic machines and CBCT scanners precluding comparison of doses between different machines and scanning protocols. The effective doses fall in a broad range as there are many factors influencing the dose estimates—patient’s age and gender, type of machine (intraoral, panoramic, cephalometric, CBCT), range of exposure parameters, differences in low-dose protocols between machines, high-resolution CBCT scans, variable FoVs and voxel sizes, etc. Effective doses encountered in dentomaxillofacial radiology estimated using the 2007 guidelines of the International Commission on Radiation Protection (ICRP) are presented in Table 10.2. It should be taken into consideration that the change in tissue weighing factors effectuated by the ICRP in 2007 caused considerable increase in doses from dentomaxillofacial radiographs in comparison with estimates from 1990. Salivary glands and oral mucosa absorb the highest doses of X-rays during common dental radiographic examinations, while thyroid gland with the tissue weighing factor of 0.04 is particularly sensitive to radiation. Table 10.2  Effective doses in dentomaxillofacial radiology

X-ray examination Periapical Bitewing Full mouth series Panoramic radiography Cephalometric radiography Small FoV CBCT Medium FoV CBCT Large FoV CBCT MDCT

Dose in μSv 0.1–2.6 0.3–1.4 15 19–75 1.1–3.4 11–252 5–674 52–368 500–1500

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

183

Radiation protection: • It encompasses all actions aimed at prevention of exposure of humans and contamination of natural environment, and when is not possible to prevent such situations, to minimise their effects to the level as low as achievable taking into account economical, sociological and health issues. • Radiation protection concerns patients, staff working in ionising radiation conditions and general public, so people who may be close to source of radiation (patient’s guardian, people in waiting room, other staff members, passer-by, etc.) • The ALARA rule—As Low As Reasonably Achievable—means that in radiodiagnostics there must be applied limitations and actions that will minimise patient exposure to ionising radiation to a level at which it is still possible to obtain required and justified diagnostic information or effects of treatment. • The ALADA acronym is also used meaning As Low As Diagnostically Acceptable. • Recently the ALADAIP principle has been introduced which is derived from: As Low as Diagnostically Acceptable being indication-oriented and patient-specific. • Every diagnostic examination using ionising radiation must be justified by proving that expected health benefits for the patient or the whole society will be higher than potential harmful effect caused by ionising radiation. These benefits include possibility of making a diagnosis as well as influence on treatment options. • Minimisation of exposure is achieved by means of adequate and carefully performed radiographic techniques, which reduce the number of radiographs requiring retaking, optimisation of exposure, transition from analogue to digital radiography as well as use of shielding. • There are no strict rules stating how many radiographs can be taken on annual basis—the ALADA rule is the guideline and all radiographs that are justified shall be taken. • Dose limits are set for staff and general public, but they do not concern use of ionising radiation for inpatients for diagnostic or medical purposes. • Pregnancy is not an absolute contraindication to procedures based on X-rays, it is a relative contraindication which means that if it is possible to reschedule diagnostic examination employing ionising radiation until period after birth, it should be done. However, if postponing an X-ray will be potentially more harmful to health of female and foetus than taking it especially in life-threatening situations, then diagnostic radiographs and even CBCT or CT scans can be prescribed. Local legal provisions concerning radiation protection considerably vary in different countries. Practitioners must check on regular basis the status of regulations in the field of radiation protection in their countries and states. Current status of radiological protection issues can be found in the publications of the International Atomic Energy Agency (IAEA), the International Commission on Radiological Protection (ICRP) and the European Commission as “Radiation Protection. European Guidelines on Radiation Protection in Dental Radiology. The Safe Use of Radiographs in Dental Practice” no. 136. Evidence-based Guidelines on Radiation

184

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

Protection in Cone-Beam CT for Dental and Maxillofacial Radiology which resulted from the SEDENTEX-CT project are published as document no. 172 of the European Commission and available at www.sedentexct.eu. National agencies for radiation protection like Australian Government Australian Radiation Protection and Nuclear Safety Agency (ARPNSA) provide guidelines, too. Also guidelines of numerous international and national societies on use of cone-beam CT contain issues related to dose limitation and optimisation. These societies include among others American Academy of Oral and Maxillofacial Radiology (AAOMR), European Academy of Dentomaxillofacial Radiology (EADMFR), European Association of Osseointegration (EAO), European Society of Endodontology (ESE) and Swiss Association of Dentomaxillofacial Radiology (SADMFR). In general the means of protection against harmful effects of ionising radiation of dental and radiological staff include the following issues: • Introduction and following of radiation protection rules are the responsibility of the head of unit, department, dental office, institution, etc. • A dedicated staff member with adequate training must be assigned to serve as radiation safety officer. He or she is responsible for introduction of local legal provisions concerning application of ionising radiation in clinical settings and for informing the head of unit about encountered problems in meeting the requirements. • Personal monitoring (thermoluminescent dosemeter, TLD) is applied according to local legal provisions in the form of dose meter (Fig. 10.3). When a staff member is examined as a patient, the dose meter must not be worn. • There is a set dose limit for radiation workers, e.g. 20 mSv a year, which can be exceeded during calendar year if during five consecutive years it does not exceed 100 mSv. It is little probable that such a dose is attained in dental office settings. The dose limit for radiation workers is much higher than for general public which usually equals 1 mSv per year. • Use of shields such as lead barriers, walls of adequate thickness and lead windows. • During exposure the operator must protect himself/herself from radiation, hide behind a lead barrier, step away for the controlled area around the source of radiation (at least 1.5  m) or altogether leave X-ray room, depending on local legal provisions. • Inverse square law is applied. Fig. 10.3 Personal dose meter

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

185

• If a staff member must stay in the X-room during exposure, he/she must stay at least 2  m from the source of radiation and never in the line of the primary X-ray beam. • Personal protection in the form of lead aprons is used only when a staff member must stay in the X-ray room during exposure. Thickness of layer of lead in the apron depends on distance from the source of radiation. • Ionised air from X-ray room must be removed on regular basis by means of mechanical or gravitational ventilation. • Adequate maintenance of X-ray equipment in order to ensure stability and repeatability of X-ray tube settings and to avoid failures including leaking X-ray tube which may be the main source of X-ray exposure to staff in environment of dental office. The means of protection for dental patient include the following: • In the first place application of the ALARA/ALADA/ALADAIP rules as it leads to limitation of dose. • It is the responsibility of dental or medical practitioner to make sure that each X-ray examination is justified and appropriate. • Signing of an informed consent by patient or his/her parent or legal guardian after having been provided with information on estimated radiation risk. • Clearly announced information that females should report to the staff the fact of being pregnant before an examination using X-rays is conducted. • Adequate maintenance of X-ray equipment in order to ensure stability and repeatability of X-ray tube settings and to avoid failures including leaking X-ray tube. • Recording of radiation dose for each patient and keeping the records in a clear way enabling to track the dose in case it is necessary. • Recommendations for the use of protective lead garments are different throughout the world. Use of lead thyroid collar or shield is generally recommended for intraoral radiography (Fig. 10.4a). However, obligation of wearing a lead apron during panoramic radiography is not imposed in many countries (Fig. 10.4b). It has been proved that doses to abdomen and foetus are low and the dose difference between patients wearing a lead apron and not wearing it is statistically insignificant. Thyroid collar should be routinely used during cephalometric radiography if recording images of cervical vertebra are unnecessary for cephalometric tracing or skeletal maturity estimation. A novel cephalographic thyroid protector (CTP) has been designed to shield thyroid but not obscure cervical spine in lateral cephalometric radiography to be used in children aged 7 years and more. Recently evidence exists that is thyroid shielding should be used during CBCT, especially in children, and in adults until 50 years of age, irrespective of the position and size of the FoV. Protective lead apron should be worn by a parent or legal guardian who must remain in the X-ray room during exposure.

186

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

a

b

c

Fig. 10.4  Protective lead garments. (a) Thyroid collar. (b, c). Lead apron without thyroid collar

The means of radiological protection for general public in a dental office: • Mounting X-ray devices in such a way that the main X-ray beam is directed away from the waiting room, common room, other dental units in a multichair room. • Adequate thickness and construction material of walls of X-ray room. • Application of inverse square law. • Adequate maintenance of X-ray equipment in order to ensure stability and repeatability of X-ray tube settings and to avoid failures including leaking X-ray tube. • Warning signs with information on X-ray controlled area and signals that announce the X-ray exposure by means of light and sound.

Suggested Reading Anissi HD, Geibel MA. Intraoral radiology in general dental practices—a comparison of digital and film-based X-ray systems with regard to radiation protection and dose reduction. Rofo. 2014;186(8):762–7. Annual Report: Activities of the President of the National Atomic Energy Agency and assessment of nuclear safety and radiological protection in Poland in 2018 http://paa.gov.pl/strona-401president_s_annual_report.html. Accessed 29 Jan 2020. Crane GD, Abbott PV. Radiation shielding in dentistry: an update. Aust Dent J. 2016;61(3):277–81. European Commission. Radiation protection 172. Evidence based guidelines on cone beam CT for dental and maxillofacial radiology. Office for Official Publications of the European Communities, Luxembourg. 2012. https://ec.europa.eu/energy/sites/ener/files/documents/172. pdf. Accessed: 28 Jan 2020. Feragalli B, Rampado O, Abate C, Macrì M, Festa F, Stromei F, Caputi S, Guglielmi G. Cone beam computed tomography for dental and maxillofacial imaging: technique improvement and low-­ dose protocols. Radiol Med. 2017;122(8):581–8.

Suggested Reading

187

Granlund C, Thilander-Klang A, Ylhan B, Lofthag-Hansen S, Ekestubbe A. Absorbed organ and effective doses from digital intra-oral and panoramic radiography applying the ICRP 103 recommendations for effective dose estimations. Br J Radiol. 2016;89(1066):2015105. Hafezi L, Arianezhad SM, Hosseini Pooya SM.  Evaluation of the radiation dose in the thyroid gland using different protective collars in panoramic radiography. Dentomaxillofac Radiol. 2018;47(6):20170428. Han GS, Cheng JG, Li G, Ma XC. Shielding effect of thyroid collar for digital panoramic radiography. Dentomaxillofac Radiol. 2013;42:20130265. Hedesiu M, Marcu M, Salmon B, Pauwels R, Oenning AC, Almasan O, Roman R, Baciut M, Jacobs R, DIMITRA Research Group. Irradiation provided by dental radiological procedures in a pediatric population. Eur J Radiol. 2018;103:112–7. Hoogeveen RC, Hazenoot B, Sanderink GC, Berkhout WE. The value of thyroid shielding in intraoral radiography. Dentomaxillofac Radiol. 2016;45(5):20150407. Kadesjö N, Lynds R, Nilsson M, Shi XQ.  Radiation dose from X-ray examinations of impacted canines: cone beam CT vs two-dimensional imaging. Dentomaxillofac Radiol. 2018;47(3):20170305. Lee C, Lee SS, Kim JE, Huh KH, Yi WJ, Heo MS, Choi SC.  Comparison of dosimetry methods for panoramic radiography: thermoluminescent dosimeter measurement versus personal computer-based Monte Carlo method calculation. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016;121(3):322–9. Ludlow JB, Timothy R, Walker C, Hunter R, Benavides E, Samuelson DB, Scheske MJ. Effective dose of dental CBCT – a meta analysis of published data and additional data for nine CBCT units. Dentomaxillofac Radiol. 2015;44(1):20140197. Pauwels R, Cockmartin L, Ivanauskaité D, Urbonienė A, Gavala S, Donta C, Tsiklakis K, Jacobs R, Bosmans H, Bogaerts R, Horner K.  SEDENTEXCT Project Consortium. Estimating cancer risk from dental cone-beam CT exposures based on skin dosimetry. Phys Med Biol. 2014;59(14):3877–91. Pauwels R, Horner K, Vassileva J, Rehani MM. Thyroid shielding in cone beam computed tomography: recommendations toward appropriate use. Dentomaxillofac Radiol. 2019;48:20190014. Qiang W, Qiang F, Lin L. Estimation of effective dose of dental X-ray devices. Radiat Prot Dosim. 2019;183(4):417–21. Rottke D, Gohlke L, Schrödel R, Hassfeld S, Schulze D.  Operator safety during the acquisition of intraoral images with a handheld and portable X-ray device. Dentomaxillofac Radiol. 2018;47(3):20160410. Rottke D, Grossekettler L, Sawada K, Poxleitner P, Schulze D. Influence of lead apron shielding on absorbed doses from panoramic radiography. Dentomaxillofac Radiol. 2013;42(10):20130302. Schulze R.K.W., Cremers C., Karle H., de Las Heras gala HSkin entrance dose with and without lead apron in digital panoramic radiography for selected sensitive body regions. Clin Oral Invest 2017; 21(4):1327–1333. Shin HS, Nam KC, Park H, Choi HU, Kim HY, Park CS. Effective doses from panoramic radiography and CBCT (cone beam CT) using dose area product (DAP) in dentistry. Dentomaxillofac Radiol. 2014;43(5):20130439. Suomalainen A, Kiljunen T, Kaser Y, Peltola J, Kortesniemi M. Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography scanners. Dentomaxillofac Radiol. 2019;38:367–78. Whaites E, Drage N.  Essentials of dental radiography and radiology. Edinburgh: Churchill Livingstone; 2013. White SC, Pharoah MJ. Oral radiology. Principles and interpretation. St Louis: Mosby; 2014. White SC, Scarfe WC, Schulze RK, Lurie AG, Douglass JM, Farman AG, Law CS, Levin MD, Sauer RA, Valachovic RW, Zeller GG, Goske MJ. The image gently in dentistry campaign: promotion of responsible use of maxillofacial radiology in dentistry for children. Oral Surg Oral Med Oral Pathol Oral Radiol. 2014;118:257–61.

188

10  Safety Precautions for Dental Patient and Dental Staff Using X-Rays

Wrzesień M, Olszewski J. Absorbed doses for patients undergoing panoramic radiography, cephalometric radiography and CBCT. Int J Occup Med Environ Health. 2017;30(5):705–13. Yalda FA, Holroyd J, Islam M, Theodorakou C, Horner K.  Current practice in the use of cone beam computed tomography: a survey of UK dental practices. Br Dent J. 2019;226(2):115–24. Yeung AWK, Jacobs R, Bornstein MM.  Novel low-dose protocols using cone beam computed tomography in dental medicine: a review focusing on indications, limitations, and future possibilities. Clin Oral Invest. 2019;23:2573–81.