PURPOSE: The purpose of this study was to investigate mandibular stability after lengthening the mandible by means of distraction. MATERIALS AND METHODS: Fifty patients (mean age, 14.7 years; range, 11.2 to 37.3 years) with Angle Class II mandibular hypoplasia were treated by bilateral distraction osteogenesis to lengthen the mandible. Patients were divided into a high-angle group, with a high mandibular angle (sella/nasion-mandibular plane [SN-MP] >38 degrees), and a normal-to-low mandibular angle group (SN-MP <or=38 degrees). Clinical measurements and standardized cephalometric radiographs were taken just before operation; postdistraction at time of removal of the distraction devices, and 6 months and 1 year postoperatively. Analysis was performed by means of angle measurements: sella/nasion-maxilla point A (SNA), sella/nasion-mandibular point B (SNB), and SN-MP. RESULTS: Eight of 14 high-angle patients showed a degree of relapse (57%), and only 3 of 36 patients showed relapse in the low/normal-angle group (8.3%). CONCLUSION: It can be concluded that high-angle patients are still at risk of relapsing and that distraction osteogenesis cannot prevent relapse in cases with a high mandibular plane angle. For low-angle patients, however, distraction is a safe and predictable procedure.
PURPOSE: The purpose of this study was to investigate mandibular stability after lengthening the mandible by means of distraction. MATERIALS AND METHODS: Fifty patients (mean age, 14.7 years; range, 11.2 to 37.3 years) with Angle Class II mandibular hypoplasia were treated by bilateral distraction osteogenesis to lengthen the mandible. Patients were divided into a high-angle group, with a high mandibular angle (sella/nasion-mandibular plane [SN-MP] >38 degrees), and a normal-to-low mandibular angle group (SN-MP <or=38 degrees). Clinical measurements and standardized cephalometric radiographs were taken just before operation; postdistraction at time of removal of the distraction devices, and 6 months and 1 year postoperatively. Analysis was performed by means of angle measurements: sella/nasion-maxilla point A (SNA), sella/nasion-mandibular point B (SNB), and SN-MP. RESULTS: Eight of 14 high-angle patients showed a degree of relapse (57%), and only 3 of 36 patients showed relapse in the low/normal-angle group (8.3%). CONCLUSION: It can be concluded that high-angle patients are still at risk of relapsing and that distraction osteogenesis cannot prevent relapse in cases with a high mandibular plane angle. For low-angle patients, however, distraction is a safe and predictable procedure.