Faculty Bibliography

OBJECTIVE: Patients experiencing temporomandibular disorders (TMD) show greater sensitivity to painful stimuli than age- and gender-matched control subjects. This enhanced pain sensitivity may result, at least in part, from an alteration in pain regulatory systems that are influenced by resting arterial blood pressure. In this study, we examined the relationship between resting systolic blood pressure and pain perception in 64 female TMD and 23 age-matched pain-free female subjects. METHOD: Resting arterial blood pressure and measures of thermal and ischemic pain threshold and tolerance were determined for each participant. Subjective ratings of thermal pain evoked by suprathreshold noxious thermal stimuli (45-49 degrees C) using a magnitude matching procedure were also obtained for both groups. RESULTS: TMD patients had lower thermal and ischemic pain thresholds and tolerances than pain-free subjects (ps < .05). Both groups provided equivalent intensity ratings to suprathreshold noxious thermal stimuli. A median split of each group based on resting systolic blood pressure revealed an influence of blood pressure on both thermal and ischemic pain perception for the Pain-Free group. The Pain-Free high resting blood pressure subgroup had higher thermal pain tolerances, higher ischemic pain thresholds, and provided lower magnitude estimates of the intensity of graded heat pulses compared with the Pain-Free low blood pressure subgroup. A trend toward a significant effect of blood pressure level on ischemic pain tolerance was also observed for the Pain-Free group. In contrast to the Pain-Free group, blood pressure level did not influence ischemic or thermal pain perception for TMD patients. Similar to the lack of effect of resting blood pressure on experimental pain perception in TMD patients, resting blood pressure was not related to measures of clinical orofacial pain in TMD patients. CONCLUSIONS: These findings confirm our previous findings that TMD patients are more sensitive to noxious stimuli and suggest that painful TMD may result, at least in part, from an impairment in central pain regulatory systems that are influenced by resting arterial blood pressure.

Recent evidence suggests that a past history of physical and/or sexual abuse is more frequently reported among chronic pain populations; however, the prevalence of reported abuse has not been examined in patients with chronic orofacial pain caused by temporomandibular disorders (TMD). This study compares reported physical/sexual abuse among female TMD subjects recruited from the general population with that of age-matched female control subjects. The association of reported abuse with clinical pain, experimental pain responses, and psychologic variables was examined in the TMD group. Results indicated that a slightly but not statistically greater percentage of TMD subjects (44.8%) reported a history of sexual or physical abuse compared to control subjects (33.3%). Reported abuse among TMD subjects was not related to clinical pain or psychologic variables. Regarding experimental pain responses, TMD subjects reporting a history of abuse exhibited longer ischemic pain tolerances compared to those not reporting abuse; however, the groups did not differ on other experimental pain measures. Results indicate that the reported prevalence of physical/sexual abuse is similar among TMD subjects compared to other chronic pain populations; however, the relationship of abuse to clinical and psychosocial variables remains unclear.

OBJECTIVE: We have previously reported that patients with temporomandibular disorders (TMD) exhibit enhanced sensitivity to experimentally evoked pain (1); however, the clinical relevance of this increased pain sensitivity remains unclear. The purpose of this study was to investigate the relationship of experimental pain sensitivity to clinical and psychosocial variables among patients with TMD. DESIGN: Thirty-six TMD patients were studied, half of whom were pain sensitive (PS) and the other half pain tolerant (PT), based on their ability to tolerate an ischemic pain task. Responses to painful thermal and nonpainful visual stimuli as well as clinical/diagnostic symptoms and psychosocial variables were compared for the two groups (i.e., PS vs. PT). RESULTS: Results indicated that, compared with PT patients, the PS group exhibited greater sensitivity to thermal pain and rated innocuous visual stimuli as more intense. PS patients also reported greater clinical pain, but in general the groups did not differ on diagnostic and psychosocial measures. CONCLUSIONS: The results suggest that ischemic pain tolerance is a clinically relevant marker of pain sensitivity in TMD patients. These findings are consistent with the hypothesis that impairments in CNS inhibitory pathways may contribute to the pain associated with TMD.

Experimental pain can elevate vibrotactile threshold, a phenomenon attributed in the literature to the operation of a 'touch gate.' It is not known, however, whether clinical pain produces similar effects. To explore this possibility, we measured vibrotactile threshold in patients with temporomandibular disorders (TMD) whose pain had a prominent myalgic component. Two-interval forced-choice tracking was used to determine threshold for a 25-Hz vibratory stimulus presented on the cheek. Threshold was found to be significantly elevated in the TMD group, compared to an age- and gender-matched control group of pain-free individuals. Within the TMD group, those with a supra-median level of muscle tenderness (corrected for background levels of spontaneous pain) had significantly higher threshold than those with lower levels of palpation pain. These findings are consistent with the idea of a touch gate, and suggest the usefulness of further research in this area with clinical pain populations. The effects of an adapting stimulus (25 Hz, 20 dB SL) were also studied, and found to produce parallel elevations in vibrotactile threshold in the TMD and pain-free groups. This result indicates that at least some adaptation occurs at a higher (subsequent) level of somatosensory information processing than does the touch gating implied by the unadapted thresholds.

Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandibular joint. We determined whether patients with painful TMD are more sensitive to noxious stimuli than age-matched control subjects. Fifty-two TMD patients (16 with muscle pain and 36 with combined muscle and joint pain) and 23 age-matched and gender-matched volunteers participated. Forearm thermal pain threshold and tolerance values were determined. A submaximal effort tourniquet procedure was used to evoke ischemic muscle pain. Relative to control subjects, TMD patients had significantly lower thermal pain threshold, ischemic pain threshold, and ischemic pain tolerance values; and thermal pain tolerance values also tended to be lower. Pain sensitivity did not differ between the two groups of TMD patients. Furthermore, the submaximal effort tourniquet procedure, which is capable of altering acute orofacial pain (Sigurdsson and Maixner, 1994) did not produce a consistent reduction in orofacial pain associated with TMD. We concluded that TMD patients are more sensitive to noxious stimuli than pain-free controls. These findings provide additional evidence that TMD is a psychophysiological disorder of the central nervous system which modulates emotional, physiological and neuroendocrine responses to emotional and physical stressors.

A major reason for referral to an endodontic practice is management of pain. Most cases are diagnosed as being of pulpal or periapical origin. However, some turn out quite differently than their initial appearance. This case report presents a patient referred to the endodontic clinic because of symptoms mimicking an irreversible pulpitis. On examination no obvious cause of the symptoms could be found. The patient was treated conservatively after which a herpes zoster viral infection was diagnosed. This case stresses the importance of a thorough investigation of all signs and symptoms and the delay of definitive treatment until a diagnosis is made.