Effectiveness of orthodontic-surgical treatment of skeletal malocclusions : Electromyographic assessment

Aim: This study investigates retrospectively if the initial electromyography (EMG) status of patients who underwent orthognathic surgery correlates with the extent of post-surgical EMG functional recovery. Materials and Methods. Clinical records concerning 20 patients who underwent Le Fort I and/or sagittal osteotomy of the mandibular ramus to correct skeletal or dental class II or III malocclusions were retrieved and pre-surgical and post-surgical EMG data analysed and compared. Additionally, post-surgical EMG recovery was compared with that of a set of healthy, not surgically treated class I patients, with no sign of disorders affecting the temporomandibular joint (TMJ). Finally, the effect of six independent variables (age, sex, time from surgery, extent of segment re-positioning, malocclusion class, upper jaw repositioning) on functional recovery was investigated by means of correlation analysis. Results. A significant increase of the average EMG activity after orthognathic corrective surgery was observed (p=.01) . The post-surgical increase of EMG values showed a negative correlation trend with those collected before surgery (r=-.38, clenching on teeth; r=-.33, clenching on cotton rolls). None of the independent variables had any effect on the post-surgical outcome. Conclusions. Orthognathic surgery improves the masticatory function of patients who present class II or III malocclusions. This improvement can be objectively assessed with EMG measurements. Patients who benefit more from orthognathic surgery seem to be those displaying the lowest pre-surgical EMG activity.