Changes in pressure-pain thresholds of the jaw muscles during a natural stressful condition in a group of symptom-free subjects.
OBJECTIVE
To investigate the effects of a natural emotional stressor on pressure-pain thresholds (PPTs) of the masticatory muscles of symptom-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 1-month period: 2 days before the examination (T1), on the day 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 < or = 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 < or = 0.003). No significant change was 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).


CONCLUSIONS
The results support a relationship between psychologic stress and pressure-pain sensitivity of the masticatory muscles.
Michelotti
A
A
School of Dentistry, Department of Orthodontics, University of Naples Federico II, Via Pansini, 5, I-80131 Naples, Italy. michelot@unina.it
Farella
M
M
Tedesco
A
A
Cimino
R
R
Martina
R
R
D000125:Achilles Tendon / Q000503:physiopathology; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000523:psychology*; D018709:Statistics, Nonparametric; D013315:Stress, Psychological / Q000097:blood / Q000503:physiopathology*; D013732:Test Anxiety Scale; D001615:beta-Endorphin / Q000097:blood
D001615:beta-Endorphin