Jaw muscle activity patterns in women with chronic TMD myalgia during standardized clenching and chewing tasks

Objective: To examine jaw muscle activity of women with chronic temporomandibular myalgia (mTMD). It was hypothesized that mTMD patients had a different masticatory muscle activity, increased work during isometric clenching, and a reduced chewing frequency as compared to TMD-free subjects. Methods: The electromyographic (EMG) activity of temporalis anterior (TA) and masseter (MM) of 27 women with mTMD and 18 TMD-free women was recorded during clenching tasks and while chewing. EMG indices comparing the activity of paired jaw muscles were computed. Results: Women with TMD myalgia had greater muscular work than controls (p = 0.025). The activity of TA and MM were similar between right and left sides in both groups. mTMD patients had a greater activity of MM than TA (p = 0.028). No between-groups differences were found in chewing rate. Conclusion: Women with mTMD showed an abnormal recruitment of the jaw-closing muscles during functional tasks, which may predispose to further tissue injury.