OBJECTIVE: To evaluate changes in the position and remodeling of the mandibular rami, condyles and chin with mandibular advancement surgery through the superimposition of 3D Cone-Beam Computed Tomography (CBCT) models. METHODS: This prospective observational study used pre-surgery and post-surgery CBCT scans of 27 subjects presenting skeletal Class II with normal or horizontal growth pattern. An automatic technique of cranial base superimposition was used to assess positional and/or remodeling changes in anatomic regions of interest. Displacements were visually displayed and quantified by 3D color maps. Descriptive statistics consisted of mean values, standard deviations and minimum/maximum displacements. Changes greater than 2 mm were considered clinically relevant, and a categorization was done. Positive and negative displacements showed each region directional tendency. To test if displacements in anatomic regions were associated with each other, Pearson correlation coefficients were used under a 95% significance level. RESULTS: The chin moved anterior-inferiorly 6.81±3.2 mm on average and the inferior portion of the rami moved laterally (left: 2.97±2.71 mm; right: 2.34±2.35 mm). Other anatomic regions showed <2 mm mean displacements, but with evident individual variability. Significant statistical correlations were positive and moderate. The condyles, posterior border and superior portion of the rami showed a bilateral correlation, and the superior and inferior portion of the rami an ipsilateral correlation. CONCLUSION: This 3D method allowed clear visualization and quantification of surgery outcomes, with an anterior-inferior chin displacement and a lateral movement on the inferior portion of the rami, but with considerable individual variability in all the evaluated anatomic regions.
Cone-Beam Computed Tomography; Image processing; Computer-assisted; Surgery, computer-assisted; Computer simulation; Orthodontics; Surgery, oral
