Skeletal stability after bilateral sagittal split osteotomy or distraction osteogenesis of the mandible: a randomized clinical trial

A randomized clinical trial was carried out to evaluate postoperative stability after mandibular advancements in non-syndromal class II patients with a bilateral sagittal split osteotomy (BSSO) or distraction osteogenesis (DO). In total 32 patients could be included in the BSSO group and 34 patients in the DO group. The BSSO was converted to a unilateral procedure for one patient, and two patients in the BSSO group were lost during follow-up. A total 63 patients could be evaluated, 29 in the BSSO group and 34 in the DO group. Advancement was comparable in the two groups (mean 7.2 mm). The mean follow-up period was 23.8 months (range 11-50 months). Lateral cephalograms were hand-traced. Horizontal relapse was measured in Y-B (mm) and SNB (degrees). For DO this was -0.324 mm and -0.250 degrees, and for BSSO this was -0.448 mm and -0.259 degrees, respectively (both not significant; NS). Vertical relapse measured in X-B was -0.074 mm for DO and -0.034 mm for BSSO (NS). The magnitude of advancement, a high mandibular plane angle, age and gender were not identified as independent risk factors for relapse. In conclusion, a BSSO and DO gave both similar stable results in advancements of the mandible up to 10 mm.