Mandibular positions and jaw-closing muscle activity during sleep.

The aim of this study was to clarify the relationship between the mandibular position with tooth contacts and jaw-closing muscle activity during sleep using electromyography and newly devised equipment for detecting tooth contacts and also to confirm the validity of this system. Five males volunteered for this study and three of them reported their bruxing during sleep. Occurrences of tooth contacts at eccentric mandibular positions in addition to the intercuspal position during sleep were detected using micro photo sensors and sensor targets prepared for the individuals. Electromyographic activities (EMG) from right and left masseter and anterior temporal muscles were also recorded. Results of the polygraphic recordings demonstrated that the mandibular positions during bruxism could be distinguished clearly whether it's in the right or left position, or has no lateral deviation, and further, that bruxing events could be categorized based on mandibular position pattern. The relationship between the mandibular position and muscle activity could be evaluated using this system. The study suggested the validity of the system for measuring nocturnal bruxing events.