Multivariate Analyses of Factors Influencing Masticatory Muscle Activity after the Use of Occlusal Splints

Abstract

Purpose: To elucidate the factors influencing the masticatory muscle activities at maximum voluntary clenching (MVC) after successive use of occlusal splints, we examined the relationships between the changes in the amplitudes of the electromyography (EMG) and possible selected factors by multiple regression analyses.Methods: The subjects were 25 patients with temporomandibular disorders (TMD) who underwent splint therapy. EMG activities from the bilateral masseter and anterior temporal muscles during MVC were recorded while the patients were not wearing the splint. The first measurement was performed on the day when the splint therapy was started and the second measurement was performed an average of 37.8±10.5 days after the start of the splint therapy. Stepwise multiple regression analysis was used to determine the factors related to changes in the integral values on the EMG.Results: Pain on mouth opening, height of the occlusal splint and duration of use of the occlusal splint were selected as important correlation factors. The following correlations were found: 1) The EMG activities of the masticatory muscles at MVC decreased with increase in the height of the occlusal splint and duration of use of the occlusal splint, and 2) the EMG activities of the masticatory muscles at MVC increased with resolution of the pain on mouth opening.Conclusion: 1) It was shown that increase in the height of the bite raising and duration of use of the splint were factors decreasing the EMG activities of the masseter and anterior temporal muscles at MVC in the intercuspal position, while resolution of the pain on mouth opening was a factor increasing the EMG activities of the masticatory muscles. 2) It was suggested that bite raising with the successive use of occlusal splints could have the effect of reducing the load to the temporomandibular joints and the workload of the jaw-closing muscles when the splints are removed.