Purpose This study aimed to measure masseter muscle activity throughout the day in outpatients suspected of having awake bruxism (AB) and/or sleep bruxism (SB) and examine the relationship between AB and SB by comparing muscle activity during daytime wakefulness and nighttime sleep.Methods Fifty outpatients with suspected SB and/or AB participated in this study. A single-channel wearable electromyogram (EMG) device was used for EMG recording. The selected EMG bursts were divided into bursts during sleep (S-bursts) and bursts during awake state (A-bursts). The number of bursts per hour, average burst duration, and ratio of burst peak value to maximum voluntary contraction were calculated for both the S- and A-bursts. These values of the S- and A-bursts were then compared, and the correlations between them were analyzed. Additionally, the ratios of phasic and tonic bursts in the S- and A-bursts were compared.Results The number of bursts per hour was significantly higher for A-bursts than for S-bursts. No significant correlation was found between the numbers of S- and A-bursts. The ratio of phasic bursts was large and that of tonic bursts was small in both the S- and A-bursts. A comparison of the S- and A-bursts showed that the S-bursts had a significantly lower ratio of phasic bursts and higher ratio of tonic bursts than the A-bursts.Conclusions The number of masseteric EMG bursts during wakefulness did not show any association with that during sleep. It became clear that sustained muscle activity was not dominant in AB.
Keywords: Awake bruxism; Electromyogram; Masseter muscle activity; Single-channel EMG; Sleep bruxism.