Postoperative stability after sagittal split ramus osteotomies for a mandibular setback with monocortical plate fixation or bicortical screw fixation

Purpose: This comparative study was performed to analyze mandibular stability after bilateral sagittal split ramus osteotomies for a mandibular setback with a monocortical plate fixation or bicortical screw fixation. Patients and Methods: A total of 60 patients with a skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in the present study. Among the patients, 30 were osteosynthesized monocortically with a titanium plate, while the other 30 were osteosynthesized bicortically with positioning screws. This retrospective study used cephalometric radiographs taken preoperatively (TO), and at I week (T1), 3 months (T2), and 1 year (T3) postoperatively. The linear and angular changes of the cephalometric landmarks of the chin region were measured at each time period, and the changes of each cephalometric landmark were determined for 4 different time intervals: TO to T1 (Delta T1), T1 to T2 (Delta T2), T2 to T3 (Delta T3), and TO to T3 (Delta T4). Postoperative changes in mandibular shape were analyzed using a paired t test to determine the stability of fixation methods. Results: The surgical changes (Delta T1) Could be characterized as posterior movements of the mandibular body and posterosuperior movements of the chin landmark. The results of the cephalometirc analysis at 3 and 12 months postsurgery (Delta T2 and Delta T3) could be characterized as anterosuperior movements of the mandible. In both treatment groups, surgical changes were relatively well maintained. Likewise, analysis of the horizontal and vertical movements of the chin landmarks indicated a similar tendency in both groups. There were no statistically significant differences between the measurements of postoperative changes at each time period after surgery. Conclusions: The findings of our study suggest that there were no significant differences in postoperative changes in mandibular shape in both the monocortical and bicortical fixation groups after sagittal split ramus osteotomy. We concluded that monocortical osteosynthesis using a miniplate could be used to obtain stable postoperative changes after mandibular setback. (c) 2008 American Association of Oral and Maxillofacial Surgeons.