Acupuncture in the Treatment of Pain in Temporomandibular Disorders: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Objectives: The aim of this study is to perform a qualitative and quantitative analysis of the scientific literature regarding the use of acupuncture in the treatment of pain associated with temporomandibular disorders (TMDs). Methods: By using electronic databases, the goal was to search and evaluate all the randomized controlled trials (RCTs) in which acupuncture was used in the management of pain attributed to these clinical entities. For the meta-analysis, an adequate description of the results' statistical data was required along with a comparison of the treatment with a control group using a placebo or sham. Two independent reviewers evaluated the quality of the studies using the Jadad scale. Results: A total of 8 RCTs were selected, and the quality of only 4 was considered acceptable. These 4 studies showed positive results such as reducing pain, improving masticatory function, and increasing maximum interincisal opening. By combining the studies (n=96) and analyzing the results, it was concluded that acupuncture is more effective than placebo in reducing pain intensity in TMD (standardized mean difference 0.83; 95% confidence interval, 0.41-1.25; P=0.00012). Discussion: The results of this meta-analysis suggest that acupuncture is a reasonable adjunctive treatment for producing a shortterm analgesic effect in patients with painful TMD symptoms. Although the results described are positive, the relevance of these results was limited by the fact that substantial bias was present. These findings must be confirmed by future RCTs that improve the methodologic deficiencies of the studies evaluated in this metaanalysis. Key Words: acupuncture, temporomandibular disorders, orofacial pain, randomized controlled trial, meta-analysis, review (Clin J Pain 2010;26:541-550) T emporomandibular disorders (TMDs) refer to various conditions affecting the temporomandibular joint, masticatory muscles, and contiguous tissues components. 1 Different types of painful TMDs are encountered: myogenous or muscle-generated pain; arthrogenous or joint generated pain; or both. 1-4 According to Stohler, 5 between 90% and 95% of TMD patients have facial pain of muscular origin without identifiable structural causes. Among the painful TMD of muscular origin, the most frequent is myofascial pain (MP). 6 At present, the therapeutic management of TMD is approached using a medical multidisciplinary model, and the treatment options range from conservative, noninvasive therapeutic measures to more aggressive treatment interventions. However, in most of the mild and moderate cases of TMD, a significant clinical improvement can be obtained with conservative therapeutic modalities. Acupuncture is an increasingly used treatment modality for the therapeutic management of pain symptoms. A meta-analysis performed by Ter Riet et al 9 showed that the majority of the studies documented positive results. However, the main conclusion obtained from that meta-analysis was that the methodologic quality of the studies analyzed required more evidence. For this reason, the investigators concluded that the effects of acupuncture for chronic pain are doubtful. In terms of TMD and acupuncture treatment, the results obtained were similar to those obtained in an earlier systematic review published in 1999. It is important to emphasize that in the last 10 years, additional studies have been published using acupuncture to treat TMD. This meta-analysis will review the publications of the last 10 years to include the improved evidence that has accumulated over that time. The aim of this study is to perform an analysis that evaluates the quality of the studies and the effectiveness of acupuncture treatment in relieving painful TMD symptomatology