Bruxism is thought to be divided into sleep bruxism and awake bruxism. However, there are very few reports comparing masticatory muscle activity during sleep and wakefulness in the same outpatient. In this study, we presented a case in which the numbers of bruxism during sleep were low, but bruxism was frequently detected during awake state.

A case was a female patient in her 40s diagnosed with bilateral temporomandibular disorders (intermittent lock). Just after waking up in the morning, intermittent lock in the left temporomandibular joint, masseter muscle pain and tooth pain occurred. Stabilization appliance (splint) was applied during night, and the symptoms after waking up improved. Since fatigue at the masseteric area occurred after waking up in case of not wearing the splint, splint therapy was continued and her condition was periodically observed. In the seventh year after the first visit, though there was no particular change in oral hygiene or usage of the splint, periodontal disease worsened. Therefore, we suspected exacerbation of bruxism and measured masseteric electromyogram during sleep and awake state using a wearable electromyographic device. As a result, during sleep, the average number of EMG waveform episodes was 3.2/h for two nights without the splint, and 3.9/h for the two nights with the splint, both of which were small values. On the other hand, the score was 66.5/h during awake state except mealtime, which was quite high frequency.

Based on the findings of electromyography in the present case, it was indicated that bruxism during sleep and awake state can occur independently.