MASSETER MUSCLE HYPERACTIVITY AND MYOFASCIAL PAIN DYSFUNCTION SYNDROME - A RELATIONSHIP UNDER STRESS

Myofascial pain dysfunction syndrome (MPD) of the temporomandibular jo int (TMJ) is a psychophysiological disorder that develops because of h yperactive muscles of mastication. Ten women meeting criteria for MPD and 12 symptom-free women participated in the study. The rationale for this study was to observe cardiovascular and masseter muscle changes during four contiguous experimental periods: baseline/adaptation, reac tion time, recovery, and relaxation. MPD patients showed less masseter muscle activity and higher heart rates at baseline than controls. Con trols had significantly higher masseter EMG activity during reaction t ime. Both groups showed significant elevation in masseter muscle activ ity and heart rate over the 14-min reaction period. MPD patients' reco very from stress was equivalent to controls' for both heart rate and m asseter muscle activity. MPD patients exhibited significantly slower r eaction times than controls. The results suggest that masseter muscle hyperactivity may not account for the development and maintenance of M PD.