Cephalometric Changes Associated with Clockwise and Counterclockwise Mandibular Rotation in Adult Orthodontic Patients, with an Assessment of Reuleaux Center-of-Rotation Estimation

The mandibular center of rotation (CoR) influences orthodontic treatment outcomes, yet most previous studies focused on counterclockwise (CCW) rotation in homogeneous populations. This study evaluated cephalometric changes associated with clockwise (CW) and CCW mandibular rotation and analyzed mandibular CoR location in a racially diverse adult population. One hundred adults who completed comprehensive orthodontic treatment (CCW, n = 33; CW, n = 67) were retrospectively analyzed. Pretreatment and posttreatment cephalograms generated from cone-beam computed tomography (CBCT) datasets were assessed for sagittal and vertical skeletal changes. Mandibular CoR was determined using the Reuleaux method after anterior cranial base superimposition. CCW rotation was associated with decreased mandibular plane angle and anterior facial height, whereas CW rotation was associated with corresponding increases. Pogonion moved posteroinferiorly in the CW group. In the CCW group, its anterior movement was not statistically significant, although the change in pogonion position differed significantly between groups. The median CoR was found to be 35.2 mm anterior and 37.8 mm inferior to condylion, but individual estimates spanned more than 2000 mm and did not stabilize when the analysis was restricted to larger rotations. The median rotation was 1.6°. CW and CCW mandibular rotations were associated with opposite changes in facial height and chin position. At rotations of this magnitude, CoR locations found by the Reuleaux method are highly uncertain and should not be interpreted as characteristic positions of the mandibular center of rotation.