PORTABLE EMG RECORDING/ANALYSING SYSTEM OF NOCTURNAL BRUXISM

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We developed the portable electromyographic (EMG) recording/analyzing system, which consists of a portable EMG unit and a cassette data recorder, and a software for data acquisition and analysis. This system allows long-time noctumal EMG recordings of the subject by his or herself in the natural envirorment for us to investigate bruxism. With this system we can analyze the bruxism activity of the subject in detail, i.e., the number of bruxism event, duration, the activity of jaw muscles. Nocturnal EMG recordings of the masseter muscle from 18 bruxers and 2l normal subjects were described to establish the criteria for detection of bruxism events. From the data, we defined the bruxing event if the activity of the masseter muscle exceeded a 10% of his or her maximum voluntary contraction, and objectively described bruxers from EMG duration and activity. A clinical examination disclosed that bruxers showed significant tenderness of the superficial masseter and anterior temporalis muscles. We also described the reliability and reproducibility of the system as the accuracy, precision and consistency of mesuremens by valuating day to day variation from 4 bruxers and 5 normal subjects.Finally we studied the effect of occlusal splints on the masseter muscle activity during sleep. The subjects were instructed to ware stabilization type occlusal splints during sleep at night for 7 days and the data was obtained from 10 bruxers and 10 normal subjects every night between 7 days before and 7 days after the beginning of splint trials, i.e., 14 conservative nights. Although occlusal splint did not significantly reduce masseter muscle activity in bruxers in total, 3 bruxers showed a reduction of EMG duration and 4 bruxers showed reduced EMG duration and activity compared to the baseline.