Stability and effect on the soft tissue profile of mandibular setback with sagittal split osteotomy and rigid...

The stability and the effect on the soft tissue profile of mandibular setback with sagittal split osteotomy and rigid internal fixation was studied prospectively in 29 consecutive patients, 17 to 55 years old, who had mesial occlusion. Profile cephalometric radiographs were taken immediately before and short after surgery as well as 14 months postsurgically. The mean setback of the mandible 1 to 8 days after surgery was 6.0 mm. On average, there was also a small decrease in the anterior facial height. The setback relapsed an average of 1.1 to 1.3 mm, so that at the follow-up the mean net effect was 80%. In eight patients, however, the mandible had retruded slightly further. During the follow-up period there was a further small decrease in the anterior facial height. The net effects on the labial fold and the soft tissue chin were closely correlated with those on their underlying hard structures. On average, the labial fold and the chin followed the hard structures to 106% and 107%, respectively. The mean net effect for the lower lip was only 88% of the setback of the mandibular incisor. The soft tissue facial height followed the decrease in the skeletal facial height to 60%. The setback procedure also affected the upper lip, which, on average, retruded and lengthened 1.0 to 2.0 mm.