Masticatory muscles pressure-pain threshold and electrical activity across menstrual cycle

The differential prevalence of temporomandibular disorders in man and women has long puzzled researchers. Female endogenous reproductive hormones and also the use of exogenous estrogen have been reported to influence pain perception. Objective: The aim of this study was analyses the electrical activity and pressure-pain threshold (PPT) of anterior temporalis and masseter muscles across menstrual cycle of oral contraceptive (OC) users and non users. Methods: Twenty eight women of reproductive age were selected. Thirteen were OC users, and 15 were non users. They answered a questionnaire and were submitted to electromyographyc exams and algometry of the muscles during three consecutive menstrual cycles. The EMG activity was recorded at 1) the mandibular rest position; 2) During unilateral chewing of the three dry grape on their side of preference and non preference. The EMG activity and PPTs means of the three menstrual cycles were considered to results analysis. The different phases or weeks of each group were compared. Results: The results showed that was no statistical differences in the electrical activity during rest position and neither in the pressure pain threshold (PPT) of both muscles. During chewing, working side temporalis activity was statistically more elevated in oral contraceptive users than in non users verified by ANOVA and Tukey's test with 5% of significance. However, electrical activity of masseter did not demonstrate difference when correspondent weeks were compared between groups. Conclusions: Electrical activities during rest and PPTs of temporalis and masseter muscles could not be affected by menstrual cycle or by OCs uses. Electrical activities of temporalis during chewing were statistically increased in OCs users in all phases of menstrual cycle. However, masseter activity at each correspondent week did not demonstrate difference.