The temporal/masseter co-contraction: an electromyographic and clinical evaluation of short-term stabilization splint therapy in myogenous CMD patients.

The short-term effect (3-6 weeks) of the use of a stabilization splint was investigated in a group of 35 myogenous craniomandibular disorder patients. The patients were clinically examined and surface EMG recordings of the temporal and masseter muscles were made during clenching in the intercuspal position (ICP), immediately after the insertion of the splint (SSP), and after at least 3 weeks of splint treatment (SSP 3). With the use of the error variance of the activity index changes in EMG activity were investigated. Three groups of patients were then recognized. One group showed a decrease in temporal muscle activity during splint treatment. Another group did not show any significant change during splint treatment. The third group showed an increase of temporal muscle activity. In general, significant reductions in the amount of static pain were found. In the group with a significant reduction of temporal muscle activity (n = 15) there was a greater decrease in the amount of static pain (P < 0.05) than in the group (n = 4) with a significant increase of temporal muscle activity. The results may indicate that the temporal muscle plays an important role in the perception of static pain in the masticatory system.