Changes in electromyographic activity following superior repositioning of the maxilla.

Surgical reduction of lower anterior facial height may alter several aspects of jaw muscle function. This study examined the biomechanics, electromyographic activity, and maximal bite forces in three patients manifesting vertical maxillary excess prior to and six months following superior repositioning of the maxilla. Reduction of lower anterior facial height by Le Fort I osteotomy tends to increase mechanical advantage of the jaw adductor muscles. It may also decrease muscle activity during isometric biting. It does not appear to alter the maximal isometric bite force.