Reliability and Reproducibility of CBCT Assessment of craniomaxillary Changes Before and After Treatment for Class III Growing Patients – An convenient and intuitively Way for Evaluation

Objectives To evaluate reliability and reproducibility of 3-dimensional (3D) assessment of maxillary protraction treatment using voxel-based superimposition of cone-beam computed tomography (CBCT) models of the anterior cranial base in growing patients with skeletal class III malocclusion. Methods CBCT scans were performed before and after maxillary protraction treatment for Class III malocclusion. Three observers independently constructed 162(27*2*3) 3D virtual models from CBCT scans, which had been reoriented 3D models before treatment to natural head posture, of 27 patients in software. The anterior cranial base was used to register the 3D models pre- and port- treatment. Three observers independently identified 9 landmarks(Including those in the contralateral side)and recorded in three-dimensional coordinates in the 3D models. Each observers performed this three times on the pre- and post-treatment model. The mean value of the 3 sets of coordinates at different times was taken as the coordinates for each landmark. The intraobserver reliability and inter-observer reproducibility of the method for craniomaxillary changes were analyzed. Results The ICCs was > 0.90 for 25 (92.6%) out of the total 27 intraobserver assessments. The precision of the measurement method was within 0.3 mm in 21 (77.8%) cases. The interobserver reproducibility errors were < 0.3 mm in 21 of the 27 cases (77.8%). Conclusions The reliability and reproducibility of the method for assessment of maxillary protraction treatment in growing patients with skeletal Class Ⅲ malocclusion were judged to be excellent.