Effects of Occlusal Splint on Salivary Flow Rate, Acid Reflux, and Sleep Bruxism

Objective: Various occlusal splints have been extensively used to control sleep bruxism, but their mechanisms of action remain controversial. Recently, we reported that sleep bruxism may be closely associated with saliva swallowing and acid reflux. The purpose of this study was to investigate the effects of an occlual splint on salivary flow rate, acid reflux, and sleep bruxism. Methods: The subjects were 7 bruxism patients and 7 age- and sex- matched normal subjects. Firstly, we measured the salivary flow rate with or without the splint. These subjects were classified into two groups again according to changes in salivary flow after splint application. Secondly, we measured the masticatory muscle activity (EMG) and pH in the lower esophagus during sleep with or without the occlusal splint. The order of measurements made with and without the splint was randomly determined. Using EMG and audiovisual data, we scored bruxism episodes according to the research criteria of Lavigne et al. Acid reflux episodes were automatically scored. The mean difference between groups was statistically analyzed. Results: Bruxism patients showed a significantly longer duration of acid reflux episodes, and higher frequency and longer duration of bruxism episodes during sleep than the normal subjects. In the group with a higher rate of increase in salivary flow after the splint application, the duration of acid reflux and bruxism episodes per hour of sleep after splint application were significantly shorter than without the splint application. Conclusion: The results suggest that the increase in salivary flow rate caused by splint application may be an important treatment mechanism for sleep bruxism in relation to acid reflux.