Association between nocturnal gastroesophageal reflux and bruxism

Objectives: Nocturnal gastroesophageal reflux (GER) has been reported to be closely associated with sleep arousal such as micro-arousal and swallowing for esophageal lubrication, i.e., acid clearance, supine position, obstructive sleep apnea, smoking, drinking of coffee and alcohol, and psychological stress. Interestingly, nocturnal bruxism, that causes abnormal tooth wear, fracture, hypersensitivity, masticatory muscle discomfort, pain and/or temporomandibular disorders, has also been reported to have several features in common with GER. Therefore, we examined the association between nocturnal GER and bruxism. Methods: Portable pH monitoring, electromyography (EMG), and audio-video recordings were conducted during the night in a subject's home. A controlled descriptive study and double-blind placebo-controlled clinical study were performed by using a proton pump inhibitor (PPI), i.e., a gastric acid-inhibiting drug, which increased the gastric and esophageal pH. Results: The bruxism patients showed a significantly higher frequency of nocturnal bruxism episodes and a higher frequency and percentage of time of GER episodes with pH<4.0 and 5.0 than the normal subjects. In the bruxism patients, 100% of the GER episodes with pH<3.0 and 4.0 included both a bruxism episode and an EMG burst with a duration of around 0.5 to 1.0 second, probably representing saliva swallowing. The majority of GER episodes with a pH of 4.0-5.0 also included both a bruxism episode and an EMG burst, again probably due to saliva swallowing in the bruxism patients and normal subjects. The remaining minority of GER episodes with a pH of 4.0-5.0 contained only an EMG burst (saliva swallowing). The frequency of bruxism episodes after the PPI medication was significantly lower than that after the placebo medication in the bruxism patients and normal subjects. Conclusion: Nocturnal bruxism may be secondary to nocturnal GER, occurring via sleep arousal, and often together with swallowing.