Postural and maximal activity in elevators of mandible before and after treatment of functional disorders.

In a longitudinal study we compared clinical data on pain and tenderness and electromyographic recordings of postural and maximal activity from 37 patients before and after treatment of functional disorders of the masticatory system. Forty-three dental students served as controls. Treatment was followed by a concomitant decrease of pain, tenderness and postural activity. Muscle strength in terms of the activity during maximal bite in the intercuspal position was not altered by treatment, but activation of the right and left anterior temporal muscles became more uniform. The relative postural loading of the elevators was assessed as their activity in percent of full effort. Following treatment, loading in patients decreased significantly and became more symmetrical in the anterior temporal muscles. Loading also tended to decrease in the posterior temporal and masseter muscles. However, it still significantly exceeded postural activity in percent of full effort in the controls. Since treatment involved correction of the occlusion we conclude that the intermaxillary conditions of tooth contact during function play a role in the etiology of functional disorders and that the reduction of the relative postural loading of the elevators of the patients due to this treatment contributed to their relief. The relatively high percentage of full effort displayed as postural activity by the patients even after treatment may explain fluctuation of symptoms and signs of functional disorders of the masticatory system. It also emphasizes the need for improved methods of treatment to reduce the probability of recurrence.