Changes in pressure-pain thresholds of the jaw muscles during a natural stressful condition in a group of symptom-free subjects

Aims: To investigate the effects of a natural emotional stressor on pressure-pain thresholds (PPTs) of the masticator) muscles of sympton-free subjects. Methods: Sixteen healthy dental students were selected before they undertook an academic examination. Sixteen gender-matched students who were not exposed to an examination served as controls. The 2 groups of students were monitored in parallel on 5 separate days over a month period: 2 days before the examination (T1), on the tiny of the examination (T2), 2 days after (T3), 1 month after (T4), and again after another 2 days (T5). On the day of the examination (T2), the control students were only required to complete a brief, non-demanding questionnaire. On each day, the following parameters were assessed: PPTs of the masseter, the anterior temporalis, and the Achilles tendon; state anxiety; and present stress measured on a visual analog scale [VAS]). Furthermore, in the students undergoing the examination, venous blood samples for assessment of beta -endorphin levels were obtained at T2 and T5. Results: In the stressed students, the PPTs of the masticatory muscles and the Achilles tendon were significantly lower analysis of variance [ANOVA], P less than or equal to 0.02) on the day of the examination (T2) and on the days nearest the exam (T1, T3), and state anxiety and present stress were significantly higher (ANOVA, P less than or equal to 0.003). No significant change suns found in beta -endorphin plasma levels (P > 0.05). In the control group, PPTs, state anxiety: and present stress did not change significantly, (ANOVA, P > 0.05). Conclusion: The results support a relationship between psychologic stress and pressure pain sensitivity of the masticatory muscles.