This randomized, double-blind, placebo-controlled study sought to determine the efficacy of a topical capsaicin cream in the treatment of localized pain in the temporomandibular joint (TMJ) region.
Capsaicin is a topical analgesic that has been used to treat such conditions as osteoarthritis, rheumatoid arthritis, atypical odontalgia, neck pain, and various other neuralgic disorders.
In this study 30 patients with histories of unilateral TMJ pain were randomly split into an experimental group (17 patients) and a placebo group (13 patients). The experimental (Cap) patients were treated with an active 0.025% capsaicin cream while the placebo (Pla) patients were treated with a non-active cream. All patients were subjected to a complete craniomandibular examination. Medical and dental histories were also examined.
Information gathered weekly via questionnaire regarding pain behaviors and side-effects of the cream application was analyzed in relation to the following variables:
- Intensity of "present pain" (PresP) during the examination on a visual analog scale (VAS).
- Most severe, or "maximal pain" (MaxP) experienced during the previous week on VAS.
- Disruption of daily activities (DA) and social interactions due to pain.
- Reduction in pain experienced during the previous week. This variable was measured on a scale from 0 to 10 (0 representing no relief and 10 representing absolute relief) referred to as the "pain relief scale" (PRS)
- Severity of burning or irritation caused by the cream application on a scale from 0 to 4.
When completed each week, the answered questionnaire was sealed in an envelope by the patient to preserve the integrity of the double blind experiment. Each patient was examined by the same clinician, whose hand pressure had been calibrated in several tests on scales and tested for "intraexaminer reliability." The following variables were evaluated:
- Sensitivity to applied hand pressure on the painful joint side and on the non-painful side of the superficial masticatory muscles.
- Sensitivity to applied hand pressure on the painful and on the non-painful sides of the lateral pole of the joint.
- Degree to which the patient was able to open her mouth, measured in millimeters.
The results of this experiment showed little difference between the effects of the capsaicin cream and the placebo cream. The researchers explain their findings in this manner:
"In the present study, the patients were actively engaged in topical application of cream on the painful area 4 times daily. Their personal involvement in the treatment process, in addition to physician attention, interest and concern in a healing setting, patient expectations, etc., could have played a role in pain modulation and sensation that resulted in pain reduction. In other words, the lack of differences between the 2 treatment groups (Cap versus Pla) can be attributed to the placebo effect."
Other possible explanations for the similar results of the two groups include positive effects of massage during the cream application process itself as well as the possibility that the unique characteristics of TMJ anatomy rendered the capsaicin cream ineffective.
Winocur E, Gavish A, Eli I, Gazit E. Topical application of capsaicin fro the treatment of localized pain in the temporomadibular joint area. The Journal of Orofacial Pain 2000;14:31-36.