Stress-induced muscular activity in mandibular dysfunction: effects of biofeedback training.

Surface electromyographic (EMG) recordings from the left and right masseteric areas during physical and psychological induced stress were obtained from 20 patients with mandibular dysfunction and 20 healthy controls. Integrated electromyographic activity was not significantly different for the two sides but was higher for patients than for controls during both stress and relaxation. Anxiety level, as measured with the Taylor Manifest Anxiety Scale, was higher for patients. Biofeedback treatment for the patients resulted in significantly reduced signs and symptoms of mandibular dysfunction. When the test procedures were repeated, the controls had not changed in their electromyographic responses during stress, whereas the patients showed a significant decrease in this respect. The results obtained are discussed in terms of a systems-oriented etiological concept.