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 pressur e-pain thresholds (PPTs) of the masticator) muscles of sympton-free subject s. Methods: Sixteen healthy dental students were selected before they under took 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 befor e 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 Achi lles tendon; state anxiety; and present stress measured on a visual analog scale [VAS]). Furthermore, in the students undergoing the examination, veno us blood samples for assessment of beta -endorphin levels were obtained at T2 and T5. Results: In the stressed students, the PPTs of the masticatory m uscles and the Achilles tendon were significantly lower analysis of varianc e [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 s tress 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 chang e significantly, (ANOVA, P > 0.05). Conclusion: The results support a relat ionship between psychologic stress and pressure pain sensitivity of the mas ticatory muscles.