Autorotation of the mandible: effect of surgical superior repositioning of the maxilla on mandibular resting posture.

Mandibular autorotation is a generally accepted cephalometric phenomenon that occurs when surgical superior repositioning of the maxilla is planned. This investigation was undertaken to determine whether autorotation of the mandible is a biologic phenomenon as well. Fifteen adults with vertical maxillary excess who underwent a mean surgical superior repositioning of 6.2 mm. were evaluated with cephalometric, kinesiometric, and electromyographic instrumentation immediately before and 3 months following surgery. Five persons selected at random from the original group (who also underwent a mean surgical superior repositioning of 6.2 mm.) were similarly evaluated 24 months following surgical intervention. The results of this study, which were analyzed by the Wilcoxon Matched-Pairs Signed-Rank test, revealed that a significant compensatory autorotation of the mandible occurred by the third month and was still constant 2 years later. We propose, on the basis of this preliminary evidence, that an "occlusal programming feedback mechanism" within the central nervous system mediated the compensatory autorotation of the mandible following surgical superior repositioning of the maxilla.