長時間連続の律動性咀嚼筋筋活動を認めた覚醒時ブラキシズムの一例

awake bruxism

北海道歯学会

北海道歯学雑誌

Purpose: Rhythmic masticatory muscle activity (RMMA), a series of phasic bursts 　with short duration , is anelectromyographic (EMG) characteristic of grinding-type sleep bruxism (SB). There have been no reports of long-lasting RMMA regarding awake bruxism (AB), like SB. In this article, we present an AB case with a long-lasting RMMA. Case: This paper reports a case of a woman in her 60s with previously treated temporomandibular disorder (TMD) on the left side (anterior displacement of the temporomandibular joint [TMJ] disc without reduction) who visited our clinic for her relocation and underwent full mouth reconstruction. At a routine follow-up 7 years after the first visit, the anterior maxillary teeth were increasingly mobile, and the fiber post-core of the right maxillary canine tooth, an abutment of a fixed bridge, was found fractured. Subsequently, a maxillary fixed bridge and upper and lower partial dentures were remade. She was instructed to wear the dentures to maintain the occlusal support of the molars during sleep, besides during the daytime. However, even after following the instruction, the mobility of the anterior maxillary teeth persisted. Since SB was suspected 9 years after her first visit, we planned the night-time use of an oral appliance with a denture-type structure in the missing tooth area. A masseteric EMG was recorded to diagnose the SB presence precisely before applying the oral appliance. Since the possibility of AB was also considered, EMG during daytime wakefulness before going to bed and getting up was also measured besides during sleep. Results: The number of episodes, i.e., groups of EMG waveforms during sleep, was 3.7/h, which was small and within the normal range. Conversely, the number of episodes during wakeful ness was 54.1/h, which was exceptionally high, and most of the waveforms were typical RMMA. Conclusion: Based on the clinical experience of this patient, some patients can show a significantly large amount of masticatory muscle activity during the daytime even though masticatory muscle activity is within the normal range during sleep. In addition, it was indicated that long-lasting RMMA can occur in AB during the day.