Effect of Female Hormones on Mastication and Pain

Objectives: The aim of this study was to evaluate whether female hormonal fluctuation that occur during the menstrual cycle would change maximum occlusal force, masticatory performance and pain sensitivity of women with TMD. Methods: Fifty complete dentate subjects (mean age=27 years) were selected and divided into two groups: (1) with TMD and using oral contraceptives (OC) (control, n=25), and (2) with TMD and not using OC (experimental, n= 25).  TMD was diagnosed by applying the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Maximum occlusal force was measured bilaterally in the molar region using a force transducer, and masticatory performance was evaluated using the artificial material comminution and sieving method. Pain sensitivity was verified by visual analogic scale before any masticatory evaluation.  All variables were measured in four phases of one complete menstrual cycle, identified by ovulation testing.  Similar to experimental, women from control group were evaluated four times. Data were submitted to ANOVA with repeated measures by adopting generalized linear mixed model (GLMM) calculated by the procedure GLIMMIX SAS statistical program. Multiple comparisons were made using the Student t test (P≤ .05). Results: Comparisons among menstrual
 phases showed no differences in maximum occlusal force (P = .81) and masticatory performance (P = .73) for experimental group, however women of this group showed lower pain in ovulatory phase (P=.03).  Similar results were noted for women using OCs. Comparisons between groups revealed that women with TMD and not using OC (experimental group) showed higher maximum occlusal force (P = .007) and no differences were observed for masticatory performance (P = .20) and pain (P= .42).  Conclusion: hormonal fluctuation influenced pain sensitivity in women with TMD, however mastication was not affected.