顎機能異常者の睡眠時と食事時における咬筋活動の比較検討

bruxism

北海道歯学会

北海道歯学雑誌

In this study, we aimed to clarify the relationship between masseter muscle activities during periods of eating meal and during periods of sleep. We analyzed this in regard to amplitude and the duration of electromyographic (EMG) bursts in the daily life of patients with parafunction in masticatory muscles. 　The subjects consisted of twenty-five outpatients who had a bruxism diagnosis at Hokkaido University hospital. Masseter muscle activities during the night and day was measured by using an ultraminiature wearable electromyogram system. EMG bursts more than three times the baseline amplitude, 0.08-second duration and 0.08-second interval (3-BL) during meal time were selected. EMG bursts during sleep were selected with the same condition as meal time. EMG bursts more than two times the baseline amplitude and 0.25-second duration were also selected during sleep (2-BL). Further, EMG bursts more than 20% of the amplitude of maximum voluntary contraction in meal time (3-BL) and sleep (2-BL) were selected (20%MVC). Phasic bursts (duration: 0.25-2sec) and tonic bursts (duration: more than 2sec) were also selected from EMG bursts during sleep. The average of %MVC values and duration were calculated for each patient. 　The burst amplitude (%MVC values) at meal time were larger than those in sleep periods in every condition (p<0.01). Moreover, significant positive correlations were found between %MVC values during meal time and during periods of sleep in every condition (p<0.05). Burst durations during sleep were longer than those during meal time in every condition (p<0.01). As for burst durations between meal time and periods of sleep, positive correlations were shown in regard to phasic bursts (2-BL), all bursts (20%MVC) and phasic bursts (20%MVC). 　These findings suggested that masseter muscles of patients with bruxism exert weaker but longer activity during periods of sleep than during meal time. This study shows that a correlation coefficient was not high, while at %MVC values and burst durations a significant positive correlation was found between meal time and sleep periods in some conditions. This was due to leaving aside the possibility that factors including difference of gender and age affecting correlation coefficient were present. This is also considering those fundamental problems that samples were small.