An investigation of the mechanism of muscle contracture in TMD patients using analysis of muscular energy metabolism

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The purpose of this study was to investigate the mechanism of the masseter muscle contracture which caused resistance to stretch of jaw.1.In clinical examinations, most of the TMD patients with contracture had little muscular pain during rest, jaw closing, and biting. During maximal jaw opening, they felt hard resisting power of their masseter muscles, but did not feel strong pain. The pain during maximal jaw opening was mostly slight and dull. These characteristics were different from characteristics of TMD patients with typical muscular pain.2.In EMG examinations, abnormal pattern of EMG activity was not found apparently during rest jaw closing and biting. However, the EMG during jaw opening showed hyperactivity of masseter muscles. These two results suggest that the mechanism of masseter muscle contracture will be different from that of muscular pain. In other words, it is likely that the masseter muscle contracture is not necessarily due to the hyperactivity of masseter muscles during rest, jaw closing and biting.3.In analysis of muscular energy metabolism (31P-magnetic resonance spectroscopy) , phosphocreatine (PC_r) /beta-ATP values of the patients with contracture was lower than normal controls. This result suggested that the PC_r would be consumed and the masseter muscles would be on a low level of latent energy. Therefore the improvement of peripherad blood flow using physical treatment such as massage of muscles will be necessary for the patients with contracture.