Morphologic study of mandibular outer cortex osteotomy

Background: The purpose of this study was to the morphologic changes of the mandible after outer cortex osteotomy. Methods: Ten patients had undergone mandibular outer cortex osteotomy. By using the true-up and dissection techniques based on three-dimensional spiral computed tomography, variables of effect and bone regeneration were evaluated 6 months postoperatively. Results: Concavity could be seen in the area from which the mandibular outer cortex had been removed 6 months postoperatively, especially at the external oblique line region. The average cup depth was 3.64 +/- 1.67 mm postoperatively. Diminution of bone volume was 1.7 +/- 0.5 percent for the entire mandible and 55 +/- 9 percent for the local area 6 months postoperatively. Bone regeneration could be seen in the area from which the mandibular outer cortex had been removed. Compared with immediately postoperatively, the ratio of neoformative bone was 84.6 +/- 7.3 percent 6 months postoperatively. The main region of bone regeneration was the mandibular angle. Conclusions: Mandibular outer cortex osteotomy is an effective technique for reducing the width of the lower face. Masseter muscular movement should be restricted postoperatively to prevent hyperostosis at the angle area.