CT Scanning

Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society

Evaluation of mandibular cortical bone in a healthy paediatric population

Σκοπός: Ο πρωταρχικός στόχος της μελέτης ήταν η συστηματική καταγραφή και αξιολόγηση ποιοτικά και ποσοτικά του συμπαγούς οστού της κάτω γνάθου σε υγιή παιδιά και εφήβους ηλικίας 6-18 ετών. Οι δευτερεύοντες στόχοι ήταν η αξιολόγηση της κατανομής της οστικής πυκνότητας και της ποιότητας του συμπαγούς οστού σε διάφορες ομάδες φύλου και ηλικίας. Επίσης η διερεύνηση της πιθανότητας η οστική πυκνότητα να επηρεάζεται από παράγοντες που γενικά μεταβάλλουν την σύγκλειση και έμμεσα τις μασητικές δυνάμεις, όπως η παρουσία εκτεταμένων τερηδονικών βλαβών, ελλειπόντων δοντιών, εκτεταμένων αποκαταστάσεων σύνθετης ρητίνης και ανοξείδωτων προκατασκευασμένων στεφανών. Απώτερος στόχος της μελέτης ήταν η δημιουργία πινάκων αναφοράς του πάχους του συμπαγούς οστού σε υγιή ελληνικό πληθυσμό παιδιών και εφήβων. Υλικό & Μέθοδος: Πρόκειται για διπλή τυφλή αναδρομική μελέτη κοορτής που αξιολόγησε το συμπαγές οστό μέσω 660 οδοντιατρικών πανοραμικών ακτινογραφιών που ελήφθησαν στην Οδοντιατρική Σχολή Αθηνών στο πλαίσιο των οδοντιατρικών αναγκών των ασθενών. Αναζητήθηκαν τα οδοντιατρικά αρχεία όλων των ασθενών ηλικίας 6-18 ετών του Τμήματος Παιδοδοντιατρικής και του Τμήματος Ορθοδοντικής (Οδοντιατρική Σχολή, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών) που υποβλήθηκαν σε θεραπεία μεταξύ των ετών 2012 έως 2021, για τους οποίους υπήρχε διαθέσιμη οδοντιατρική πανοραμική ακτινογραφία. Η περίοδος που επιλέχθηκε εξασφάλισε ότι όλες οι ακτινογραφίες είναι συγκρίσιμες, καθώς έχουν πραγματοποιηθεί με το ίδιο ακτινογραφικό μηχάνημα και η πιθανή μεγέθυνση είναι η ίδια. Τα κριτήρια επιλογής ήταν ακτινογραφίες που ανήκουν σε άτομα ηλικίας 6-18 ετών, ελληνικής καταγωγής. Θα έπρεπε να υπάρχει διαθέσιμο πλήρες ιατρικό και οδοντιατρικό ιστορικό και οι πανοραμικές ακτινογραφίες να έχουν καλή ποιότητα. Τα κριτήρια αποκλεισμού ήταν ακτινογραφίες που ανήκουν σε άτομα ηλικίας > 18 ετών, σε άτομα με νοσήματα ή καταστάσεις που τα ίδια ή η θεραπεία τους επηρεάζει το οστό π.χ. διατροφικές διαταραχές, πρωορότητα, πρώιμη ήβη, μυοσκελετικές διαταραχές κ.α. Επίσης άτομα που υποβάλλονται ή έχουν υποβληθεί σε ορθοδοντική θεραπεία και ακτινογραφίες που να είναι κακής ποιότητας. Οι πανοραμικές ακτινογραφίες χωρίστηκαν σε ισόποσες ομάδες ανάλογα με την ηλικία και το φύλο. Το συμπαγές οστό της κάτω γνάθου αξιολογήθηκε ποσοτικά και ποιοτικά, χρησιμοποιώντας δυο ανθρωπομετρικούς δείκτες. Η ποσοτική αξιολόγηση έγινε χρησιμοποιώντας τον δείκτη Mandibular Cortical Width (MCW), ο οποίος αξιολογεί το πάχος του συμπαγούς πετάλου της κάτω γνάθου άπω του γενειακού τρήματος. Εφαρμόστηκε η μέθοδος των Paulsson-Björnsson και συν.(2015). Συγκεκριμένα, σε κάθε ημιμόριο σχεδιάστηκε η εφαπτομένη στο χείλος της κάτω γνάθου και στη συνέχεια σχεδιάστηκαν 4 κάθετες γραμμές που περνούν από τα ακόλουθα 4 σημεία: 1. Μια γραμμή που περνά εμπρός από το πρόσθιο χείλος του κλάδου της κάτω γνάθου και τέμνει την περιοχή μπροστά από τη γωνία της κάτω γνάθου (Antegonion). 2. Από την εγγύς επιφάνεια στο ύψος της αδαμαντινοοδοντινικής ένωσης του πρώτου μόνιμου γομφίου. 3. Από τα υψηλότερα σημεία του φύματος του δευτέρου προγομφίου. 4. Από τα υψηλότερα σημεία του φύματος του πρώτου προγομφίου. Αντίστοιχα η ποιοτική ανάλυση έγινε χρησιμοποιώντας τον δείκτη Mandibular Cortical Index (MCI),σύμφωνα με τη μελέτη των Klemetti και συν. (1994), ο οποίος αξιολογεί τη μορφολογία του ορίου του συμπαγούς πετάλου με το σπογγώδες στην περιοχή άπω του γενειακού τρήματος. Ο δείκτης αυτός έχει 3 στάδια ανάλογα με τη βαρύτητα (C1, C2, C3). Όσον αφορά τη ποσοτική αξιολόγηση, το πάχος του συμπαγούς οστού μετρήθηκε με το λογισμικό Image J (Image J 1.50c4 για Windows XP). Καθώς το λογισμικό μετρά το μήκος σε pixel (1024x1024 εικονοστοιχεία- 8-bit- 1 MB), όλες οι μετρήσεις μετατράπηκαν σε mm χρησιμοποιώντας έναν υπολογισμένο συντελεστή. Οι διαστάσεις των pixel στο φυσικό κόσμο, βασίστηκαν στο μέγεθος των pixel χρησιμοποιώντας ένα γνωστό δείγμα. Για κάθε ακτινογραφία, η μέση τιμή από τις δύο μετρήσεις για κάθε σημείο και η συνολική μέση τιμή από όλα τα σημεία υπολογίστηκε και καταγράφηκε σε ειδικά σχεδιασμένο φύλλο καταγραφής. Η αξιολόγηση και η ανάλυση όλων των ακτινογραφιών πραγματοποιήθηκε με τυχαία σειρά από δύο βαθμονομημένους παρατηρητές. Οι αξιολογητές ενήργησαν τυφλά όσον αφορά τα δημογραφικά χαρακτηριστικά του ασθενούς, δεδομένου ότι όλες οι ακτινογραφίες αναμείχθηκαν αρχικά από έναν τρίτο ερευνητή που δεν συμμετείχε στη διαδικασία αξιολόγησης. Ο τρίτος ερευνητής, ο οποίος ήταν επίσης βαθμονομημένος, συμμετείχε στην προετοιμασία των ακτινογραφιών για την ποσοτική ανάλυση, δηλαδή στη χάραξη των γραμμών που απαιτούνταν για την ανάλυση και στην περικοπή των ακτινογραφιών έτσι ώστε να είναι ορατή μόνο η κάτω γνάθος για να διευκολυνθεί η ανάλυση. Τυχόν διαφορές μεταξύ των αξιολογητών επιλύονταν με συζήτηση και, εάν δεν επιτυγχανόταν συμφωνία, ζητούνταν η γνώμη ενός τρίτου αξιολογητή που δεν είχε προηγουμένως εμπλακεί στις ανωτέρω διαδικασίες. 100 ακτινογραφίες επανεξετάστηκαν μετά από ένα μήνα από τους ίδιους εξεταστές για να ελεγχθεί η αξιοπιστία µμεταξύ των παρατηρητών. Αποτελέσματα: Η μέση ηλικία των ασθενών ήταν 11,7 έτη (SD: 3,37 έτη). Όσον αφορά τον τύπο της οδοντοφυΐας, το 30,6% των ασθενών ήταν στην πρώιμη μικτή οδοντοφυΐα, το 23,3% στην όψιμη μικτή και το 46,1% στην μόνιμη οδοντοφυΐα. Όσον αφορά την ποιοτική αξιολόγηση, παρατηρήθηκε στατιστικά σημαντική συσχέτιση μεταξύ της μορφολογίας του οστού και του φύλου, με τα κορίτσια να εμφανίζουν συχνότερα ομοιογενές οστό (C1) σε σύγκριση με τα αγόρια που εμφανίζουν συχνότερα C2. Επίσης στατιστικά σημαντική συσχέτιση βρέθηκε και με τις ηλικιακές ομάδες. Συγκεκριμένα, το συμπαγές οστό γίνεται λιγότερο ομοιογενές με την πάροδο της ηλικίας, ιδιαίτερα από την ηλικία των 8-11 και 14+ ετών. Επιπρόσθετα, η μελέτη μας έδειξε στατιστικά σημαντικές διαφορές όσον αφορά τη συσχέτιση μεταξύ της μορφολογίας του συμπαγούς οστού και του τύπου της οδοντοφυΐας, δηλαδή διαπιστώσαμε ότι στη μικτή οδοντοφυΐα επικρατεί η κατηγορία C1 και στη μόνιμη οδοντοφυΐα μειώνεται και αυξάνεται η C2. Όσον αφορά την ποσοτική αξιολόγηση αντίστοιχα υπάρχει στατιστικά σημαντική αύξηση του πάχους του συμπαγούς οστού με την πάροδο της ηλικίας, ιδιαίτερα από την ηλικία των 8-9 και έπειτα. Αυτό το ηλικιακό σκαλοπάτι φαίνεται να σχετίζεται με την έναρξη της εφηβείας και τις ορμονικές αλλαγές. Δεν βρέθηκε συσχέτιση μεταξύ της μορφολογίας του συμπαγούς οστού σύμφωνα με τον δείκτη MCI ή του πάχους του οστού και της παρουσίας τερηδονικών βλαβών, ελλειπόντων δοντιών, αποκαταστάσεων σύνθετης ρητίνης και προκατασκευασμένων ανοξείδωτων στεφάνων. Επιπλέον, δημιουργήσαμε πίνακες αναφοράς της μορφολογίας και του πάχους του συμπαγούς οστού σε υγιή ελληνικό πληθυσμό παιδιών και εφήβων. Συμπεράσματα: Στο πλαίσιο των περιορισμών της παρούσας μελέτης, μπορεί να συναχθεί το συμπέρασμα ότι: - Διαπιστώθηκε στατιστικά σημαντική διαφορά μεταξύ του φύλου και της μορφολογίας του συμπαγούς οστού σύμφωνα με τον δείκτη MCI. Το συμπαγές οστό είναι ομοιόμορφο συχνότερα στα κορίτσια σε σύγκριση με τα αγόρια. - Το στάδιο ανάπτυξης της οδοντοφυΐας συσχετίστηκε στατιστικά σημαντικά με το πάχος του συμπαγούς οστού, δηλαδή το πάχος του συμπαγούς οστού ήταν υψηλότερο στη μόνιμη οδοντοφυΐα σε σύγκριση με την πρώιμη ή την όψιμη μικτή οδοντοφυΐα. - Δεν υπάρχει συσχέτιση μεταξύ του πάχους του συμπαγούς οστού ή της μορφολογίας του οστού και παραγόντων όπως η ύπαρξη εκτεταμένης τερηδόνας, ελλειπόντων δοντιών, αποκαταστάσεων σύνθετης ρητίνης και προκατασκευασμένων ανοξείδωτων στεφανών. - Απαιτούνται ευρύτερες και καλά σχεδιασμένες μελέτες για να υποστηριχθούν οι συσχετίσεις μεταξύ ηλικίας/φύλου και μορφολογίας ή πάχους οστού. - Η ποιότητα των οστών που ανιχνεύεται στις οδοντιατρικές ακτινογραφίες θα μπορούσε να αποτελεί πρωταρχικό σημάδι μιας υποκείμενης συστηματικής διαταραχής και, ως εκ τούτου, οι οδοντίατροι θα μπορούσαν να διαδραματίσουν κρίσιμο ρόλο στην έγκαιρη ανίχνευση και την παραπομπή των ασθενών για περαιτέρω έλεγχο.Introduction The skeletal system plays a pivotal role in children's growth, development, and overall health. Bones provide structural support, protect vital organs, facilitate movement, and serve as a reservoir for minerals essential for numerous physiological processes. Understanding the intricacies of bone health in a healthy paediatric population is of utmost importance, as it lays the foundation for lifelong musculoskeletal well-being. Bone mineral density, is one of the most important factors to measure bone quality, as it is a reliable and non-invasive method. There are various available techniques that have been used to assess and/or quantify bone density. Radiographic imaging, such as dual-energy X-ray absorptiometry (DXA), remains the gold standard for evaluating bone mineral density. Another frequently used technique is panoramic radiography. Many valid indicators have been developed and used to analyze bone quality and quantity in panoramic radiographs, two of which are the Mandibular cortical index (MCI) and Mandibular Cortical Width Index (MCW). These two indices were created during the past several decades to evaluate the mandibular bone mass's quality and quantity and detect resorption in panoramic radiography. Aim The primary aim of the study is to systematically record and evaluate qualitatively and quantitatively the cortical bone of healthy children aged 6-18 years. Secondary objectives are: 1. To evaluate the distribution of bone density in different gender and age groups. 2. To evaluate cortical bone quality in different gender and age groups. 3. To investigate the possibility that bone density is affected by factors that generally alter occlusion and indirectly masticatory forces such as the presence of extensive carious lesions, missing teeth, extensive resin composite restorations, and Stainless-Steel Crowns. The ultimate goal of the study is to create reference tables of the thickness of the cortical bone in a healthy Greek population of children and adolescents. Material and Methods It was a double-blinded retrospective cohort study evaluating mandibular cortical bone of healthy children and adolescents through dental panoramic radiographs taken in the context of the patient’s dental needs. The dental records of all patients from the Department of Paediatric Dentistry and the Department of Orthodontics (Dental School, National and Kapodistrian University of Athens) treated between 2012 and 2021 were searched for patients, aged 6-18 years of age, with a dental panoramic radiograph available. The period selected ensured that all radiographs are comparable as they have been performed with the same radiographic machine and the possible magnification is the same. Panoramic radiographs of 660 children aged 6-18 were divided into different groups according to age and gender. The inclusion criteria were panoramic radiographs of good quality of patients with updated medical and dental records. Exclusion criteria were panoramic radiographs of poor quality of patients with diseases/ conditions/ treatments affecting the bone e.g. eating disorders, prematurity, early puberty, musculoskeletal disorders, etc. and of patients undergoing/ undergone orthodontic treatment. Quantitative assessment was performed by measuring the cortical bone width bilaterally using the Mandibular cortical width (MCW) Index (according to Paulsson-Björnsson et al. 2015) and qualitative assessment using mandibular cortical index (MCI) (according to Klemetti et al 1994). MCI is a qualitative index that evaluates the morphology of the threshold of the cortical bone with the trabecular bone distally to the mental foramen at both sides of the mandible. It is categorized according to a three-point scale C1, C2, C3. MCW is a quantitative index that evaluates the thickness of the cortical bone in both sides of the mandible. In each side a line was drawn along the lower border of the mandible, followed by four perpendicular lines to the tangent at the following points: 1. Antegonion 2. the mesial cementoenamel junction of the first molar perpendicular to the mandibular base 3. the most superior cusp tip of the second premolar perpendicular to the mandibular base 4. the most superior cusp tip of the first premolar perpendicular to the mandibular base The thickness of the cortical bone was measured using the software Image J (Image J 1.50c4 for Windows XP). As the software measures length in pixels (1024x1024 pixels; 8-bit; 1 MB), all measurements were converted into mm using a calculated coefficient factor. The examiners were calibrated prior to the initiation of the study for both qualitative and quantitative evaluation. Results The mean age of the patients was 11.7 years (SD: 3.37 years). Regarding the stage of dentition, for 30.6% of the patients it was early mixed, 23.3% late mixed and 46.1% permanent. A statistically significant correlation was observed between bone morphology and gender, with girls having more frequent even and sharp endosteal margin of the cortex(C1) compared to boys and boys having more frequent endosteal margin which shows semilunar defects(C2). When bone was evaluated on both the right and left side as in total, a statistically significant correlation was observed with age groups. In particular, the endosteal margin of the cortex was even and sharp on both sides frequently in patients aged 8 to 11 years old compared to other ages. On the other hand, the endosteal margin showed semilunar defects (lacunar resorption) and/or seems to form endosteal cortical residues on one or both sides were more frequent in patients 14+ years old. In addition, a statistically significant positive relationship was found between all points assessing bone thickness and age (years), meaning that as age increases, bone thickness also increases. Our study also showed statistical differences in terms of the correlation between cortical bone thickness and type of dentition, namely between mixed dentition and permanent dentition. We found that in mixed dentition C1 predominates and in permanent dentition decreases and increases C2. Νο correlation was found between bone morphology according MCI Index or bone thickness and the presence of carious lesions, missing teeth, resin composite restorations, and stainless-steel crowns. Furthermore, we created reference tables of bone morphology and the thickness of the cortical bone in a healthy Greek population of children and adolescents. Conclusions Within the limitations of this study, it can be concluded that: • A statistically significant difference was found between gender and bone morphology according to MCI Index. The endosteal margin of the cortex is even and sharp more frequent in girls compared to boys and shows seminular defects more frequent in boys than girls. • The developmental stage of dentition was statistically significant correlated with the cortical bone thickness, i.e. cortical bone thickness was significantly higher in permanent dentition compared to early or late mixed dentition. • There is no correlation between cortical bone thickness or bone morphology and factors such as the existence of extensive caries, composites, stainless steel crowns and missing teeth. • More broad and well-designed studies are required to support the correlations between age/gender and bone morphology or thickness. • The results of this study can be an important guide for the clinical dentist, who may check the cortical bone thickness in a panoramic radiograph and refer the patient for further examination. Early detection and adequate treatment of low BMD is essential especially when osteoporosis prevention should occur on time or when orthodontic treatment will occur (bone density affects tooth movement)

Computational design and engineering of polymeric orthodontic aligners

Transparent and removable aligners represent an effective solution to correct various orthodontic malocclusions through minimally invasive procedures. An aligner-based treatment requires patients to sequentially wear dentition-mating shells obtained by thermoforming polymeric disks on reference dental models. An aligner is shaped introducing a geometrical mismatch with respect to the actual tooth positions to induce a loading system, which moves the target teeth toward the correct positions. The common practice is based on selecting the aligner features (material, thickness, and auxiliary elements) by only considering clinician's subjective assessments. In this article, a computational design and engineering methodology has been developed to reconstruct anatomical tissues, to model parametric aligner shapes, to simulate orthodontic movements, and to enhance the aligner design. The proposed approach integrates computer-aided technologies, from tomographic imaging to optical scanning, from parametric modeling to finite element analyses, within a 3-dimensional digital framework. The anatomical modeling provides anatomies, including teeth (roots and crowns), jaw bones, and periodontal ligaments, which are the references for the down streaming parametric aligner shaping. The biomechanical interactions between anatomical models and aligner geometries are virtually reproduced using a finite element analysis software. The methodology allows numerical simulations of patient-specific conditions and the comparative analyses of different aligner configurations. In this article, the digital framework has been used to study the influence of various auxiliary elements on the loading system delivered to a maxillary and a mandibular central incisor during an orthodontic tipping movement. Numerical simulations have shown a high dependency of the orthodontic tooth movement on the auxiliary element configuration, which should then be accurately selected to maximize the aligner's effectiveness

Investigating the ultrastructure of enamel white spot lesions (WSL) using Optical Coherence Tomography at different length scales

White spot lesion (WSL) is the clinical presentation of early caries, which is a demineralisation that occurs at subsurface level, with a well-mineralised surface layer enclosing the lesion. Early diagnosis and treatment of WSL is crucial to prevent further destruction of tooth structure. The aim of this research is to investigate the potential of optical coherence tomography (OCT) to be used as an adjunct diagnostic clinical tool to evaluate the severity of such lesions. This research also compared the OCT outputs with traditional histology, X-ray Microtomography (XMT), Synchrotron X-ray Diffraction (SXRD) and Scanning Electron microscope (SEM). All specimens were collected from patients undergoing dental treatment at Eastman Dental Hospital with informed consent following ethical approvall. Initially, Artificial WSLs were induced on sound enamel surfaces using a buffered methylcellulose gel system at pH 4.6 for 7 and 14 days. Type-matched native WSL and healthy control teeth were selected based on ICDAS for comparison. Imaging of samples was obtained using OCT of whole teeth and by polarised microscopy, SXRD, XMT and SEM of polished 250 μm thick sections. Polarised microscope, XMT and SEM confirmed the findings of the OCT results. Images showed that the more back scattered signals recorded, the deeper the destruction throughout enamel thickness. SXRD results showed changes in enamel texture, which was interpreted from measuring crystallite orientations and lattice parameter. SXRD result showed some correlation with OCT images, however more investigation is required to confirm the findings. In conclusion, the variations observed in the back-scattered light in OCT experiment were because of mineral density variation within enamel structure, as well as the changes in prismatic structure and may be related to crystallite texture and orientation. OCT has shown to be a reliable non-destructive technique, that can investigate the internal structure, by measuring the back-scattered light from materials such as enamel and dentine. In healthy samples, OCT B-scans showed a homogenous pattern of scattering intensity throughout enamel structure, indicating healthy structure, while in both natural and induced white spot lesions, a non homogenous scattering intensity was observed, indicating changes in enamel structure

Periodontal Disease

This book aims to provide readers with the latest updates and an informative overview of the most successful diagnostic aids for periodontal diseases. This book is divided into three sections. Section 1 discusses the periodontal disease pathogenesis and how the disease develops and the contributing factors in disease development. Section 2 includes three chapters that focus mainly on the most common and recent biomarkers that aid in diagnosis of periodontal diseases. Section 3 includes one chapter and discusses a non-surgical treatment modality that could provide definite improvement in the mild to moderate conditions in periodontal diseases

Perception of Bone Mineral Loss on Cone-Beam Computed Tomography (CBCT) & Digital Periapical (PA) Film: An Ex-Vivo Comparison

Using micro computed tomography (micro-CT) as a reference standard, the purpose of this investigation was to evaluate the influences of bone mineral loss and radiographic contrast in digital periapical (PA) film and cone-beam computed tomography (CBCT). Seven dog and human mandibles were sectioned, followed by modification via cortical bone drilling to create 248 lesions and/or trabecular bone acid demineralization to create 96 coronal slice pairs. Pretreatment and post-treatment radiographs (PA, CBCT, and/or micro-CT) were taken for lesion rating/perception in addition to two-dimensional (area) and three-dimensional (volumetric) measurements of 50 drilling lesions and 20 coronal slice pairs. 4-7% bone mineral loss is needed for radiographic perception of cortical bone drilling lesions (rating ≥3), and at least 17.34% bone mineral loss is needed for trabecular bone acid demineralization perception. Radiographic contrast indices were difficult to ascertain and may be related to regional differences and lesion anatomical location. This study suggests that even though %BML is a major factor in radiographic lesion perception, additional factors of regional and anatomical contrast influence lesion rating. With a limited sample size, further testing is needed to investigate cortical bone lesion perception differences between dog and human mandibles, to quantify radiographic contrast, and to identify more precise trabecular bone demineralization thresholds

An evaluation of computer-based radiographic methods in estimating dental caries and periodontal diseases

Reductions in dental diseases have resulted in a need for more accurate diagnostic and monitoring methods. The purpose of this study was to 1) identify the best diagnostic technique, 2) investigate the main factors which limit its validity and reliabilty and 3) devise methods to improve its reliability and 4) investigate ways of automating its use for general dental practice. From the literature review radiography was identified as the best current method with regard to validity, reliability, production of stable objective data and ease of use. However, irradiation geometry variations between serial films and subjective measurement errors were its principle limitations. Although an accurate semi-automatic caries measuring system exists, it is unsuitable for general practice due to lengthy operator interaction. A series of computer-based experiments were devised to evaluate further the digital subtraction radiography technique (DSR); develop a new method using stored regions of interest (ROI) to reduce subjective measurement errors; investigate the feasibility of completely automatic image analysis. In addition, an in vitro caries experiment was designed to demonstrate the effects of irradiation geometry variation on lesion size and caries scores. The results demonstrated that small variations in irradiation geometry can change radiographic scores. Misalignment of subsequent films beneath a video camera can cause significant errors in the DSR technique. The stored ROI method reduced cement-enamel junction to alveolar crest measurement errors to standard deviation 0.15mm. A fully automatic method for recognising teeth and bone crests was demonstrated. It was concluded that 1) radiography is currently the technique of choice, 2) a new significant methodological error for DSR has been demonstrated, 3) the subjective ROI method produced lower intra- and inter-examiner measurement errors compared to similar methods, 4) routine use of automatic methods may be feasible and should be investigated further and 5) standardised irradiation geometry is essential

Diagnostic imaging of the tympanic bulla and temporomandibular joint in the dog, cat and rabbit.

The area of the skull incorporating the tympanic bulla (TB) and temporomandibular joint (TMJ) is significant clinically in the dog, cat, and more recently the rabbit. Diagnostic imaging is important in the assessment of disease of these structures but there is a relative lack of comparative anatomical information relating to the normal that may be used to understand the abnormal features encountered when using currently available diagnostic imaging modalities. A review of conventional radiography demonstrated that views for imaging the canine and feline TB could be extrapolated for use in the rabbit but the same did not apply to the TMJ. Plastinated multiplanar anatomical sections proved useful for the identification of anatomical features on corresponding tomographic images. Ultrasound imaging of this region has not been widely reported but allowed evaluation of the TB in all three species, although the information obtained regarding the TMJ was limited. Directly acquired computed tomography (CT) and Magnetic Resonance (MR) images were of better quality than previous publications due to technological advances in the equipment available. Directly acquired images were still better than reconstructed ones and reduced image acquisition times are likely to make this viable in clincal cases. CT produced optimal imaging of the TB but only allowed assessment of the bony elements of the TMJ. Little information was obtained regarding the normal TB using MR imaging due to the indistinguishable signal voids produced by the bone wall and gas lumen. However, T1 weighted sequences allowed identification of intra-articular TMJ soft tissue structures in the dog and rabbit. While opening the mouth altered the areas of the TMJ examined using each modality, it did not improve visualisation of the intra-articular structures. The introduction of fluid into the middle ear cavity of dog, cat and rabbit cadavers aided identification of the TB and acted as a model of one of the major features of acute otitis media, or inflammation of the middle ear cavity. CT was most accurate at identifying middle ear material in cadavers and clinical cases, while ultrasound produced better results than radiography in cadavers but not clinical cases. These imaging modalities also proved useful in the characterisation of the unexpected anatomical anomalies that were encountered during the study. The results of this study indicate that the optimal imaging technique will vary with the species and area being examined, and that extrapolation between species is not always appropriate. Continual improvements in technology and image quality make studies such as this necessary to allow selection of the most appropriate single or combination of imaging techniques and to obtain the maximum amount of information from the resulting images

‘Recommendations for the development of a framework for radiological imaging studies during implant therapy in SA’

Philosophiae Doctor - PhDRadiographic examination is an essential facet of dental implant therapy, and the success of this therapy depends on a suitable treatment based on adequate clinical and radiographic information. International organisational bodies have published guidelines on the use of radiographic imaging during implant therapy, but since the cone beam computed tomography modality became available, a need for the development of comprehensive imaging guidelines to limit the misuse of this modality became necessary. There is a lack of stringency regarding the recommendations and guidelines on radiographic imaging modalities used during implant therapy. This is due to variations in practice, experience, and socioeconomic factors. The most recent published global guidelines and recommendations and their relevance to dental implant therapy are described in this chapter