EfficacyofLow-LevelLaserTherapyintheTreatmentofTemporomandibularMyofascialPain:ASystematicReviewandMeta-Analysis

Myofascial pain syndrome is a common cause of facial and jaw pain, affecting the muscles used for chewing and other jaw movements. When this pain occurs in the temporomandibular region — the area around the jaw joint — it is classified as temporomandibular myofascial pain. This condition can severely limit mouth opening and make everyday activities like eating and talking uncomfortable. While many treatments exist, including medications, physical therapy, and injections, patients and clinicians often seek non-invasive options with fewer side effects.

Low-level laser therapy (LLLT) has emerged as one such option. Unlike surgical lasers that cut tissue, LLLT uses low-power light to potentially stimulate healing and reduce pain without generating heat. However, studies on LLLT for temporomandibular myofascial pain have produced mixed results, with some showing benefit and others finding no difference compared to placebo. This uncertainty motivated researchers to systematically gather and analyze all available high-quality evidence to determine whether LLLT truly helps patients with this condition.

The researchers conducted a systematic review and meta-analysis following established scientific guidelines (PRISMA). They searched three major medical databases — PubMed, Web of Science, and Cochrane Library — for randomized, placebo-controlled clinical trials published through February 2017. Three independent reviewers screened the results and assessed study quality. To be included, studies had to compare LLLT against an inactive or sham laser in adults diagnosed with temporomandibular myofascial pain using standardized criteria.

The researchers excluded studies comparing LLLT to other active treatments, as well as case reports, reviews, animal studies, and studies in adolescents.

From 167 initial references, they identified 8 eligible studies involving 255 total participants. The number of participants in individual studies ranged from 16 to 60. Most studies included both men and women, with women predominating. Five studies used the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) to diagnose myofascial pain, while others used alternative diagnostic approaches.

The laser devices varied considerably across studies in terms of wavelength, energy density, power, and treatment schedule.

Three reviewers independently assessed each study for risk of bias using Cochrane methodology. Four studies were rated at unclear risk of bias, and four at high risk. No study achieved an overall low risk of bias rating. Common problems included unclear methods of randomization, lack of allocation concealment details, and insufficient description of blinding procedures.

The meta-analysis revealed that LLLT significantly reduced pain intensity compared to placebo laser. At the end of treatment, patients receiving LLLT experienced an average reduction of 2.2 units more than placebo on a 0-to-10 visual analog scale (P = .005). This benefit persisted at 3 to 4 weeks after treatment, with the LLLT group showing an average of 2.4 units greater improvement than placebo (P = .022). When expressed as standardized difference in means, the effect size was –1.241 at end of treatment (P = .001) and –1.405 at 3 to 4 weeks follow-up (P = .022).

According to standard interpretation, these represent large effect sizes.

For mouth opening, the results were more nuanced. Two studies reported interincisal opening data. Immediately after treatment, the increase in mouth opening with LLLT was not significantly different from placebo (P = .079). However, at 1 month after treatment, LLLT showed a significant benefit, with a standardized difference in means of 0.686 (P = .012).

The quality of evidence was rated as moderate for pain reduction using the GRADE system, but low for interincisal opening due to the small number of studies, small sample sizes, and methodological concerns. The researchers noted substantial statistical heterogeneity among studies for pain outcomes, indicating variability in treatment effects across different studies that could not be fully explained.

Sensitivity analyses supported the robustness of findings. Excluding one study that used different diagnostic criteria did not change the significant benefit of LLLT for pain reduction. Similarly, using alternative data from a study that reported multiple laser doses yielded consistent results.

This systematic review provides moderate-quality evidence that low-level laser therapy may effectively reduce pain in adults with temporomandibular myofascial pain, with effects that appear to last at least several weeks after treatment. The average pain reduction of 2.2 to 2.4 points on a 10-point scale exceeds the minimum clinically significant difference of approximately 1.2 points, suggesting patients would likely notice meaningful improvement.

For patients, this means LLLT represents a potentially viable non-invasive treatment option, particularly for those who prefer to avoid medications or more invasive procedures. The therapy appears safe, with no serious adverse effects reported in the included studies.

For clinicians, these findings support considering LLLT as part of a comprehensive management approach for temporomandibular myofascial pain. However, the researchers appropriately caution that the evidence is not definitive. The high heterogeneity across studies, small number of available trials, and methodological limitations — including unclear or high risk of bias in all included studies — mean that results should be interpreted with caution.

The review also highlights important areas for improvement in future research. Standardization of diagnostic criteria (such as using the newer DC/TMD protocol), better blinding methods, and more consistent laser parameters would strengthen the evidence base. The authors specifically recommend that future studies verify whether patients can distinguish active laser from placebo, as proper blinding is essential for valid results.

Overall, while LLLT shows promise for temporomandibular myofascial pain, clinicians and patients should recognize that more well-designed, larger studies are needed before this treatment can be recommended with high confidence. The current evidence suggests benefit but does not establish LLLT as definitively superior to other established treatments.