Association between Sleep Bruxism and Transient Relaxation of the Lower Esophageal Sphincter

Objective: Transient lower esophageal sphincter relaxation (TLESR) is known to be an important cause of gastroesophageal reflux. Recently, we reported an association between sleep bruxism and gastroesophageal reflux. The purpose of this study was to examine the relationship between sleep bruxism and TLESR. Methods: Seven adult volunteers were studied. We measured the masticatory muscle activity (EMG), orofacial movements, and pressure of the lower esophageal sphincter and esophagus during sleep. Using the EMG and audiovisual data, we scored bruxism episodes according to the research criteria of Lavigne et al. TLESR episodes according to conventional objective manometric criteria. Saliva swallowing was scored by the primary peristalsis. The relationship between sleep bruxism and TLESR episodes was statistically analyzed. Results: There was a significant correlation between the frequency of sleep bruxism and that of TLESR episodes. The duration from TLESR to sleep bruxism was significantly shorter than that from sleep bruxism to the next TLESR. Also, the duration from sleep bruxism to saliva swallowing was significantly shorter than that from swallowing to sleep bruxism. Sleep bruxism and saliva swallowing were frequently observed after relaxation of the lower esophageal sphincter. Conclusion: The results suggest that the occurrence of sleep bruxism is closely associated with transient relaxation of the lower esophageal sphincter.