Psychosocial Scores and Jaw Muscle Activity in Women

Aims: To test whether women with temporomandibular disorder (TMD)-related pain showed higher psychosocial scores and higher awake- and sleep-time jaw muscle activities (characterized by duty factors) compared to pain-free controls and whether psychosocial scores and the jaw muscle duty factors were associated. Methods: Subjects gave informed consent to participate. The Diagnostic Criteria for TMD (DC/TMD) were used for diagnosis of TMD pain, and 31 and 36 women were included in the TMD-related pain and control groups, respectively. DC/TMD Axis II instruments were used to determine psychosocial scores. Subjects self-recorded masseter and anterior temporalis electromyography (EMG) over 3 days and 3 nights. The duty factor (time of muscle activity/total recording time [%]) was quantified using subject-specific EMG/bite-force calibration via data recorded in the laboratory. Group differences (α = .05) were assessed for psychosocial scores and duty factors using chisquare and two-sample t tests. Linear regression assessed whether psychosocial scores were associated with duty factors. Results: Average duty factors were ≤ 2.4% for awake and sleep times in both muscles, and between-group comparisons showed no significant differences. For physical symptom scores, there were significantly fewer TMD-related pain subjects in the normal category and significantly more in the moderate-severe category (all P .01) compared to controls. Subjects with elevated compared to normal psychosocial scores showed significantly higher jaw muscle duty factors by ≥ 1.5-fold. Conclusion: A significantly larger proportion of TMD-related pain subjects compared to control subjects had moderate-severe physical symptom scores. Awake- and sleep-time jaw muscle duty factors were not different between groups and were generally low among all subjects. Additionally, higher than normal psychosocial scores were associated with significantly more low-magnitude jaw muscle activity. Keywords: bruxism, EMG, jaw muscle, pain, psychosocial factors, TMD