Changes in the gonial angle following bilateral sagittal split osteotomy and vertical ramus osteotomy for mandibular...

The gonial angle plays an important role in ensuring a harmonious facial profile. Changes in this angle after surgery may be an esthetic concern for both the patient and the surgeon. The aim of the present study was to evaluate gonial angle changes after mandibular setback by the bilateral sagittal split osteotomy (BSSO) and vertical ramus osteotomy (VRO) techniques.

Fifty-eight male patients with mandibular prognathism only were treated from 2004 to 2006 (deformities such as discrepancy of jaws, mandibular setback of more than 10 mm, asymmetry, and vertical discrepancy were excluded). Patients were randomly divided into 2 groups. In the first group, mandibular setback was performed using the Obwegeser technique and wire osteosynthesis with 4 weeks' fixation (IMF), and in the second group, mandibular setback via VRO without wire osteosynthesis and 4 weeks' IMF was carried out. Lateral cephalograms were obtained for all the patients before surgery (T(0)) and 1 year after surgery (T(1)). Gonial angle and occlusal plane-SN in T(0) and T(1) were evaluated.

After surgery, the gonial angle had decreased in all patients. Decrease in the gonial angle in the VRO group was greater than the BSSO group. The average decrease in the gonial angle was significantly more (P < 0.05) in the VRO group (7 degrees) than in the BSSO group (2 degrees).

Gonial angle decrease was observed in the present study following mandibular setback by the VRO and BSSO techniques. This decrease in the VRO group was significantly greater.