INFLUENCE OF VARIATION IN JAW POSTURE ON STERNOCLEIDOMASTOID AND TRAPEZIUS ELECTROMYOGRAPHIC ACTIVITY

This study was conducted in order to determine the influence of variat ion in the occlusal contacts on electromyographic (EMG) cervical activ ity in 20 patients with myogenic cranio-cervical-mandibular dysfunctio n, EMG recordings during maximal voluntary clenching were performed by placing surface electrodes on the left sternocleidomastoid and upper trapezius muscles in the following conditions: intercuspal position; e dge to edge left laterotrusive contacts (ipsilateral); edge to edge ri ght laterotrusive. contacts (contralateral); edge to edge protrusive c ontacts; and retrusive occlusal contacts. A significant higher EMG act ivity was recorded in both muscles during maximal voluntary clenching in retrusive occlusal contact position, whereas no significant differe nces in EMG activity were observed between intercuspal position, ipsil ateral, contralateral and protrusive contact positions. The EMG patter n observed suggests that a more frequent intensity and duration of too th clenching in retrusive occlusal contact position could result in mo re clinical symptomatology in these cervical muscles in patients with myogenic cranio-cervical-mandibular dysfunction.