Pain Threshold Responses to Two Different Modes of Sensory Stimulation in Patients with Orofacial Muscular Pain: Psychologic Considerations

This study focuses on the influence of trait anxiety and mood variables on changes in tooth pain threshold following two similar methods of somatic afferent stimulation, one familiar (manual acupuncture) and one unfamiliar (low-frequency transcutaneous electrical nerve stimulation [low-TENS]). Twenty-one acupuncture responders, treated for long-lasting orofacial muscular pain but naive to low-TENS, were selected for the study. In an experimental session, acupuncture and low-TENS were randomly given during two periods separated by a rest interval. Tooth pain thresholds (PT) were measured before and after stimulation with a computerized electrical pulp tester. Trait anxiety and depression were assessed with psychometric forms before the experimental session in all patients, whereas momentary mood was assessed in 10 randomly selected patients with visual analogue scales during and after the two types of stimulation. Following acupuncture, the group average PT increased significantly, whereas no significant change was observed following low-TENS. Higher scores on trait anxiety correlated significantly with a low PT increase following low-TENS, and higher ratings of stress correlated significantly with a low PT increase following acupuncture. This indicates that the magnitude of analgesia induced by these methods may be modified by psychologic factors like anxiety and stress.