Reliability of a portable electromyographic unit to measure bruxism

This study evaluated the effect of different rates of increase of occlusal force and of removal and replacement of the electromyographic electrodes on the amount of occlusal force needed to trigger a modified electromyographic measuring unit. Seven subjects placed the electrodes on the masseter area on one side, and bit ipsilaterally on a bite force transducer. The electromyographic recorder was adjusted to be triggered only when the subject clenched. Occlusal force was recorded simultaneously with triggering of the electromyographic recorder. The subjects performed two series of five repetitions of clenching at each of four different rates of increase of force, by visual feedback from a second oscilloscope until the electromyographic recorder was triggered, and an occlusal force measurement was made from the first oscilloscope. Repeated measures of ANOVA analysis revealed no statistically significant differences among the different rates of increase in occlusal force or between the two recording series. Interaction between the two factors also was not significant. The intraclass correlation coefficient was large and statistically significant, indicating that this device was reliable for this method.