[The influence of muscle fatigue on masseteric silent period].

Muscle fatigue due to clenching, grinding is suggested to be in relation to the pain in TMJ dysfunction patients. A number of investigators report that in normal persons experimental muscle fatigue provoked the similar symptoms seen in TMJ dysfunction patients. These reports suggest that muscle fatigue plays a great role in the onset of TMJ dysfunction. The purpose of this study was to investigate the effects of muscle fatigue on the silent period of normal subjects. The results were summarized as follows: 1. The silent period during tooth tapping was either absent or incomplete after muscle fatigue. This tendency is seen in patients with TMJ dysfunction. 2. In one subject, double silent periods occurred. After muscle fatigue, the subject may be to have a lower pain threshold. 3. The silent period following jaw-jerk showed significantly shorter latency and longer duration after muscle fatigue. The longer duration may be observed that double silent merged together. 4. In the present study, the silent period is suggested to be useful in the diagnosis and prognosis of TMJ dysfunction.