Effect of acupuncture for temporomandibular disorders: a randomized clinical trial

This randomized controlled clinical trial investigated the efficacy of acupuncture in the treatment of temporomandibular disorder (TMD), a condition that affects 11-33% of the population and represents the leading cause of facial pain and the second leading cause of musculoskeletal conditions. The study was conducted at a traditional Chinese medicine hospital in Beijing, between April 2019 and July 2022, following rigorous methodological standards including adequate randomization, blinding of participants and assessors, and intention-to-treat analysis. Sixty participants with pain-related TMD, diagnosed by DC/TMD criteria, were randomized to receive real or sham acupuncture. The real acupuncture group received treatment at specific points (LI-4 and GB-34 bilaterally, SI-19, ST-6, and ST-7 on the affected side) with stainless steel needles penetrating the skin and de qi elicitation.

The control group received sham acupuncture using the Park device with blunt needles that did not penetrate the skin, maintaining the appearance of real treatment. Both groups received three weekly sessions for four weeks, totaling 12 sessions. The primary outcome was the change in mean weekly pain intensity from baseline to week 4, measured by visual analog scale in pain diaries completed by patients. The results demonstrated significant superiority of real acupuncture over sham.

The difference in pain reduction was -1.49 points (95% CI: -2.32 to -0.65; P<0.001) at week 4, remaining significant at week 8 (-1.33 points; P=0.001). Clinically, 86.7% of patients in the acupuncture group achieved at least 30% pain reduction compared to 43.3% in the sham group, while 53.3% versus 20.0% achieved at least 50% reduction. In addition to pain improvement, real acupuncture produced significant improvements in mandibular function, including pain-free mouth opening, maximum assisted and unassisted opening, and protrusive and lateral movements. Participants also experienced significant reductions in graded chronic pain scales, jaw functional limitations, depression, anxiety, stress, and sleep quality.

Interestingly, no significant differences between groups were observed in pressure pain thresholds or surface electromyography, suggesting that the mechanisms of action may be more central than peripheral. Safety was excellent, with only two mild adverse events in the acupuncture group (subcutaneous hematoma and post-needling pain) and none in the sham group. Blinding was effective, as evidenced by the Bang index and balanced distribution of participants' perceptions of which treatment they received. The clinical implications are substantial, considering that conservative treatment options for TMD are limited and often have questionable efficacy or adverse effects.

Acupuncture demonstrated effect sizes comparable to pharmacological treatments such as propranolol (-1.8) and botulinum toxin (-1.16), but with a superior safety profile. The study has limitations including being single-center, a relatively small sample, the impossibility of blinding acupuncturists, and a cultural context favorable to acupuncture in China. However, the methodological strengths, including use of validated diagnostic criteria, diary-derived outcomes to avoid recall bias, excellent participant retention, and exploration of long-term effects, lend high credibility to the findings.