Accuracy and Reproducibility of CBCT Assessment of Mandibular Changes Before and After Treatment for Class III Growing Patients -An Easy and Quick Way for Evaluation

Introduction: The objective of this study was to evaluate accuracy and reproducibility for 3-dimensional(3D)assessment of mandibular changes after treatment for growing patients with Class III malocclusion. Methods: : Cone-beam computed tomography (CBCT) scans were performed before and after orthodontic treatment. The scans before treatment were obtained under the condition that the patient’s mandibular plane were parallel to floor. Three observers independently constructed 180 3D virtual surface models from CBCT scans of 30 patients in InvivoDental software 5.1.3, reoriented 3D models before treatment to natural head posture. Mandibular voxel-based registration was done using an area encompassing from the internal part of the symphysis to the distal aspect of the first molars at the level of basal bone as a reference. Three observers independently identified 10 landmarks three times in the 3D models of before and after treatment, recorded three-dimensional coordinates of landmarks. The accuracy and reproducibility of the method were analyzed. Results: : The ICCs was > 0.90 for 25 (92.6%) of the intraobserver assessments. The precision of the measurement method was < 0.3 mm in 24 (88.9%) cases. The interobserver reproducibility errors were < 0.3 mm in 21 of the 27 cases. Conclusions: : Overall, the accuracy and reproducibility of 3D-dimensional assessment of mandibular changes for growing patients were excellent.