The silent period in the masseter muscle of patients with TMJ dysfunction.

The silent period (SP) following a jaw jerk elicited during sustained contraction in the masseter muscles has been studied in two groups of subjects, one with and one without, acute and distinct symptoms of TMJ dysfunction. The subjects with acute TMJ dysfunction symptoms showed significantly shorter latency and longer duration of the silent period and the period of their depressed activity (DA) was also significantly longer than in the group without TMJ dysfunction. The duration of the SP of both muscles was symmetrical in about 60% of subjects in each group. This study validates that the duration of the silent period may be a useful diagnostic tool of clinical interest.