Changes in mandibular width and frontal-lower facial profile after orthognathic surgery using sagittal split ramus osteotomy with removal of internal bone interference in patients with class III skeletal malocclusion

Background The purpose of this study is to analyze changes in mandibular width and frontal view ramus inclination using cone beam CT in patients with skeletal class III malocclusion who underwent BSSRO, with the removal of bone interference between segments. Methods For all 20 subjects, cone-beam CT imaging was performed prior to surgery (T1), immediately post-surgery (T2), and 6 months after surgery (T3). Reorientation was performed using R2GATE software (MegaGen, Seoul, Korea). The gonion and antegonial notch were used as reference points in the sagittal view, and the most lateral point of the condyle head was used as the reference point in the frontal view. All measurements were recorded in the frontal view. Results Inter-gonial width decreased by 2.64 mm at T3-T2 (P < .001) and by 2.58 mm at T3-T1 (P < .05). Inter-antegonial width decreased by 1.75 mm at T3-T2 (P < .05) and by 3.5 mm at T3-T1 (P < .001). In the frontal view, the right ramus inclination based on the gonion increased by 2.07 degrees at T3-T1 (P < .05). The left ramus inclination based on gonion increased by 2.45 degrees at T2-T1 (P < .05) and by 3.94 degrees at T3-T1 (P < .001). The right ramus inclination based on antegonial notch increased by 2.35 degrees at T2-T1 (P < .05) and by 3.04 degrees at T3-T1 (P < .01). The left ramus inclination based on antegonial notch increased by 2.73 degrees at T2-T1 (P < .001) and by 3.18 degrees at T3-T1 (P < .001). Conclusions During bilateral sagittal split osteotomy, removing bone interference between the proximal and distal segments results in a reduction of postoperative mandibular width and an increase in frontal view ramus inclination.