MECHANISM OF TRANSIENT MENTAL NERVE PARESTHESIA IN SAGITTAL SPLIT MANDIBULAR RAMUS OSTEOTOMY

We investigated the mechanism involved in paraesthesia associated with sagittal split mandibular ramus osteotomy by three-dimensional comput ed tomography (3-D CT). Ten female patients underwent this procedure b etween 1988 and 1991. The inferior alveolar neuro-vascular bundles rem ained intact during the sagittal osteotomy in all cases. We examined t he changes in the shape of the foramen mandibulae over a period of 6 m onths during which the transient mental nerve paraesthesia was recover ed, and studied the distance from the foramen mandibulae to the spina mentalis (F-S distance) as measured on 3-D film. The postoperative 3-D CT scan showed bone resorption in front of the foramen mandibulae, an d the F-S distance was shortened by an average of 2.94 mm. These findi ngs suggest that possible causes of the paraesthesia is due to compres sion of the nerve trunk resulting from posterior movement of the mandi bular ramus.