Comparative study of inferior alveolar disturbance restoration after sagittal split osteotomy by means of bicortical versus monocortical osteosynthesis.

The comparative study of neurosensory disturbance of the inferior alveolar nerve after bilateral sagittal split osteotomies was carried out. The 112 patients who underwent bilateral sagittal split osteotomies were divided into two groups: one group consisted of 62 patients (124 osteotomy sites) who received bicortical osteosynthesis using the lag screw principle (bicortical fixation group), and the other group consisted of 52 patients (104 osteotomy sites) who underwent monocortical osteosynthesis using miniplates (monocortical fixation group). The incidence of neurosensory disturbance of the inferior alveolar nerve as well as its recovery course was compared by patients' interview and Semmes-Weinstein pressure esthesiometer. Mean follow-up period was 12 months (minimum 3 months, maximum 36 months). The incidences of sensory disturbance of both groups were not significantly different at 2 weeks postoperatively. During the period 6 to 12 months postoperatively, the number of patients having light touch sensory disturbance was significantly less in the monocortical fixation group than in the bicortical fixation group. Moreover, the number of patients complaining of numbness during 6 to 18 months postoperatively was significantly less in the monocortical fixation group. These findings suggested that the monocortical osteosynthesis had less damage on the inferior alveolar nerve, leading to the better restoration of neurosensory disturbance in patients in whom the nerve damage was moderate.