Changes in the gonial angle following bilateral sagittal split osteotomy and extra oral vertical ramus osteotomy for mandibular excess

Background : Since ages human race have been genuinely concerned about their facial appearance. Mandibular prognathism (MP) or skeletal Class III malocclusion is one of the most severe maxillofacial deformities resulting in aesthetic concerns and also affect the normal functional abilities of an individual and disturbing psychological problem. One of the characteristic features of mandibular prognathism is obtuse gonial angle. In ensuring an esthetic harmonious facial profile, gonial angle plays an important role. Surgical treatment of the mandibular prognathism either Bilateral Sagittal Split Osteotomy(BSSO) or Extra Oral Vertical Ramus Osteotomy(EVRO) will improve this gonial angle. Aim : The aim of this study is to evaluate the change in the Gonial angle following Bilateral Sagittal Split Osteotomy versus Extra Oral Vertical Ramus Osteotomy for Mandibular excess. Methods : In this prospective study Eight patients with mandibular prognathism were included . That 8 patients (5 male and 3 female) were divided into two groups . In group I, 4 patients with mandibular prognathism were treated by BSSO with rigid fixation and MMF for 4 weeks. In group II, 4 patients with mandibular prognathism were treated by EVRO without rigid fixation and MMF for 6 weeks. Gonial angle is measured for all 8 patients in group I and group II , both pre operatively and post operatively using lateral cephalogram. Results : In present study the decrease in gonial angle was observed following mandibular setback surgery by BSSO and EVRO.The average decrease in gonial angle in the first group(BSSO) was 4.7 degree and in second group(EVRO) was 7 degree . Conclusion : By this study we conclude that in patients with increased gonial angle it is better to use EVRO technique as decrease in gonial angle was more that results in better esthetic face , better occlusion, less incidence of inferior alveolar nerve injury and inconspicuous scar. The mandibular setback by BSSRO also give a better esthetic and occlusion, but it may results in increased incidence of neurosensory disturbence and unfavourable split.Thus surgical technique for mandibular prognathism whether BSSRO or EVRO is always depend on surgeons preference and other individual factors