Masseteric silent periods electrically evoked in normal subjects and patients with temporomandibular joint dysfunction.

The mean latency and duration of electromyographic silent periods were compared in normal subjects and patients with symptoms of temporomandibular joint (TMJ) dysfunction. The silent periods were evoked in the masseter muscle by electrical stimulation of the mental nerve area and recorded at 100% and 50% of maximum masseter EMG activity. Two silent periods were typically observed. The mean latency of the early silent period as well as the mean duration of both the early and late silent periods were shorter at 100% than at 50% of the maximal voluntary activity. In comparing the two groups, the mean latencies were shorter and the mean durations were longer for both silent periods in the TMJ group compared with the normal group. The prolonged silent periods in the TMJ group do not appear to be caused by a difference in stimulus intensity or level of voluntary activity in the masseter muscle. These results permit the speculation that the mechanism of the prolonged silent period in the TMJ patients might be central rather than peripheral.