Causes and signs of temporomandibular joint pain and dysfunction: an electromyographical investigation.

The spontaneous muscular activity of the masseter and two non-masticatory muscles, and their activity under conditions of noise and flickering light, were recorded in 30 patients with mandibular dysfunction, and in 25 control subjects. The mood of the subjects during the investigation, and the possible presence of emotional disturbances was evaluated by means of questionnaires. The enhanced muscular activity of the masseter muscle differentiated patients from the control group, although it does not constitute a pathognomic sign. Unilaterality of complaints, and dysfunctions of differing intensity were not reflected in differential EMG findings. One-fifth of the patients exhibited neck muscle activity occurring simultaneously with the masseter activity. The effect of the applied stimuli on the muscular activity was not homogeneous, leading to activation in some cases and inhibition in others. Symptoms of anxiety could be observed in seven TMJ patients. Anxious patients showed higher levels of muscular activity and emotional irritability during the experiment than non-anxious patients.