Effect of Controlling Daytime Clenching on Bruxism and Sleep Apnea

Objectives: Daytime clenching, one of awake bruxism (AB), has a negative impact on tooth and temporomandibular joint. Although the importance of reduction in daytime clenching has already elucidated, an effective method to reduce daytime clenching is not fully established. In addition, the relationship between sleep apnea-hypopnea and not only SB but AB is unclear. The objectives of this study were to evaluate (1) the effectiveness of instruction method to control daytime clenching on the occurrence of AB and (2) the effect of control of daytime clenching on the occurrence of sleep bruxism (SB) and/or sleep apnea-hypopnea.
Methods: Eleven adults (five patients with obstructive sleep apnea and six healthy individuals) were participated in this study. Surface electromyograms (sEMG) of masseter muscle were recorded with an ambulatory sEMG recorder while participants were awake and asleep. Apnea-hypopnea index (AHI) was recorded with a portable apnomonitor. Experiments were performed at baseline (T0) and 1 week after an instruction to control their daytime clenching by using a device (T1). sEMG activity with amplitudes that exceeded more than 5% of maximal voluntary clenching was classified as phasic, tonic or mixed episodes for analysis. Outcome variables were awake and sleep bruxism episodes, and AHI. Wilcoxon signed-rank test was applied to the data. Significance level was set at 5%.
Results: There was a significant decrease in AB episodes and AHI at T1 compared with at T0 (phasic: p=0.047, tonic: p=0.038, mixed: p=0.047, AHI: p=0.021). On the other hand, there was no significant difference in SB episodes between at T1 and T0.
Conclusions: These results suggested that (1) our instruction method to control daytime clenching might be useful for the reduction in AB events and (2) the reduction in of daytime clenching might contribute to reduction in the occurrence of AB episodes as well as sleep apnea-hypopnea.