Development of a portable electromyographic recording device and an application for the evaluation of the day to day variation of nocturnal masseter mascle activity
1999 Volume 6 Issue 1 Pages 67-77
Details
1999 Volume 6 Issue 1 Pages 67-77
We developed a portable electromyographic (EMG) recording/analyzing system, which consists of a portable EMG recording unit and a cassette data recorder, and a software for data analysis. This system allows longterm nocturnal masticatory muscle self-EMG recordings at home under natural conditions. With this system, bruxism activity in detail, e.g., the number of bruxism events, duration, and activity, can be analyzed using nocturnal masseter muscle EMG recordings. In addition, data containing artifacts can be removed as much as possible by checking the raw EMG data, procedure that improves the quality of the data.
We measured the nocturnal masseter muscle activity in 2 bruxers and 2 normal control subjects for 7 consecutive nights using this system. A bruxism event was defined as the activity of the masseter muscle that exceeded the 10% of the maximum voluntary contraction (MVC) . Then the number of bruxism events, duration and activity were calculated. We also evaluated the day to day variation of the bruxist activity within each subject.
The nocturnal masseter muscle activity that represents the same activity as the bruxism-like voluntary grinding and clenching movement was confirmed in bruxers. The EMG activity for the bruxers was significantly larger than that for the controls (p <0.05, ANOVA) . The 2 bruxers in this study showed many bruxism events, whose EMG activity was between 50 and 70%MVC level, compared with control subjects. The distribution of EMG activity was different among subjects, and varied in the recording period even in the same subject. We also confirmed the day to day variation of the bruxism activity within each subject. The coefficient of variance of the bruxism activity showed 20-30% for each subject.
These results suggested that the newly developed portable EMG recording/analyzing system is useful for the evaluation of nocturnal bruxism.
