Reliability and reproducibility of CBCT assessment of craniomaxillary changes before and after treatment for Class III growing patients - a cautious or critical approach.

BACKGROUND: 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 post- treatment. Three observers independently identified 9 landmarks(Including those in the contralateral side)and recorded in three-dimensional coordinates in the 3D models. each observer 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 reliability for intraobserver assessments, with ICC > 0.90 for 25 (92.6%) of intraobserver assessments. 24 of 27 (88.9%) cases showed that the accuracy of the measurement method were below 0.3 mm. 21 of the 27 cases showed that the inter-bserver reproducibility errors were below 0.3 mm; only 6 cases (22.2%) showed error ≥ 0.3 mm. CONCLUSIONS: The reliability andreproducibility of the method for assessment of maxillary protraction treatment in growing patients with skeletal Class Ⅲmalocclusion were judged to be excellent.