Changes in mandibular angle and intergonial width after bilateral sagittal split ramus osteotomy or bimaxillary surgery with/without counterclockwise rotation.

Abstract

The aim of this retrospective study was to evaluate the morphological changes in the mandibular angle area after orthognathic surgery with or without mandibular counterclockwise rotation in Class II deformity patients, and to investigate the associated factors. Computed tomography scans obtained preoperatively (T0), within 1 month postoperatively (T1), and 6 months postoperatively (T2) were collected from 58 patients who underwent either bilateral sagittal split ramus osteotomy (group I), bimaxillary surgery with mandibular counterclockwise rotation (group II), or bimaxillary surgery without mandibular counterclockwise rotation (group III). The intergonial width increased after surgery, by 2.78 ± 2.02 mm in group I, 2.86 ± 2.81 mm in group II, and 2.53 ± 2.42 mm in group III (all P < 0.001). The mandibular angle (MA) increased in group I (ΔMA 4.76 ± 2.79°; P < 0.001) and group III (ΔMA 3.50 ± 2.58°; P < 0.001); however no significant increase was observed in group II. The increase in intergonial width was positively correlated with the lateral displacement of the proximal segment. Counterclockwise rotation of the proximal segment resulted in an increase in MA, while counterclockwise rotation resulted in a reduction in this increasing trend. The results indicate that reducing the displacement and rotation of the proximal segments is key to minimizing changes in the mandibular angle area.