Anatomic Landmarks on CBCT in Orthodontics: Utility, Accuracy, and Reliability

Abstract

INTRODUCTION: CBCT is an increasingly utilized imaging modality in orthodontics, however the increased diagnostic data from it is not being fully utilized. The goal of this study was to develop a comprehensive list of accurate, reliable anatomic landmarks which could be used in the development of a three-dimensional measurement analysis.METHODS: A list 58 landmarks on the dentition, maxilla, mandible, and cranial base was developed and each landmark defined based on a literature review and discussions with orthodontists, radiologists and anatomists. CBCTs were taken of 31 dried human skulls before and after fiducial markers were placed. Images were superimposed to equilibrate orientation and coordinate axes. Two examiners (1 orthodontic resident and 1 dental student) located the landmarks on CBCT images based on the landmarks’ definitions. Coordinates for landmarks were recorded in each plane (x, y, z). Accuracy was calculated via ICC and Mean Difference, and reliability was determined via Dahlberg’s error. These values were calculated for Examiner 1 (E1) vs True Landmark, Examiner 2 (E2) vs True Landmark, and E1 vs E2. RESULTS: All landmarks had an excellent Intraclass correlation coefficient (ICC) of ≥ 0.97. A value of >0.5mm was considered the threshold for a significant Mean Difference (Mean Diff.) and Dahlberg’s Error (D. Error). All landmarks had excellent accuracy (Mean Diff. ≤0.5mm) and reliability (D. Error ≤0.5mm) except for: maxillary canine cusp tips, mandibular molar mesial root apices, maxillary alveolar crest, anterior palate, greater palatine foramina, zygomaticomaxillary sutures, superior and posterior condyle, mandibular alveolar crest, anterior gonial angle, and gonion. All of these landmarks were within 1.4mm of the True Landmark. CONCLUSION: There are many landmarks with excellent accuracy and reliability on the dentition, maxilla, mandible, and cranial base that can be used in the development of a three-dimensional CBCT measurement analysis for orthodontic diagnosis. A final comprehensive list was compiled.