Masticatory muscle activity as a function of parafunctional, active and passive oral behavioural patterns

Oral behavioural patterns have received limited empirical support for their causal role in the development of head and facial pain. The present study was designed to assess electromyographic (EMG) variations in six muscle groups (i.e., bilateral masseter, temporalis and orbicularis oris) as a function of various oral behavioural patterns. A second purpose was to determine whether mandibular movement patterns and specific oral behaviours could be predicted by EMG patterns. Eleven non-pain subjects followed each of twenty oral behavioural patterns while EMG was recorded. Electromyographic change scores were computed for each behaviour relative to baseline measures. Initial analyses were performed using factorial repeated measures ANOVAS. Using post hoc analyses as general guides, specific EMG criteria were developed for classifying mandibular movements. For most subjects, EMG patterns accurately classified teeth clenching, protrusive/retrusive movements, right movements, left movements and lip movement patterns. Wide individual variations were found among muscle groups for identical behaviours. The association between particular oral behaviours and EMG patterns may explain 'sinus' headaches and certain types of facial pain.