Abstract / Summary
Temporomandibular disorders (TMD) are common, often heterogeneous musculoskeletal conditions involving the temporomandibular joint, the masticatory muscles, and associated structures, and they are a leading cause of nondental orofacial pain. Low-level laser therapy (LLLT), also known as photobiomodulation (PBM), has attracted growing interest as a conservative, noninvasive option because of its analgesic and anti-inflammatory effects. This narrative review focuses on the practical technical parameters of LLLT, including wavelength, fluence, output power, emission mode, application sites, session number and frequency, and irradiation time per point, and on its clinical effects on the principal symptoms of TMD. A narrative search of PubMed, Scopus, Google Scholar, and ScienceDirect was conducted, prioritizing systematic reviews, meta-analyses, randomized controlled trials, and clinically relevant studies reporting technical parameters and outcomes. Because the marked heterogeneity of diagnostic criteria is a principal source of variability in this literature, the review also emphasizes the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and the distinction between myogenic, arthrogenic, and mixed subtypes, whose optimal parameters are likely to differ. Current evidence suggests that LLLT may reduce pain intensity, improve maximum mouth opening, and decrease muscular tender points and joint sounds in selected patients; however, the magnitude of these effects varies considerably across studies, reflecting substantial heterogeneity in diagnostic criteria, dosimetric protocols, and outcome measures, and these findings should not be interpreted as a uniformly predictable clinical response. Near-infrared wavelengths of approximately 810 to 1100 nm are supported, although the optimal subrange differs between reviews (810 to 940 nm vs. 910 to 1100 nm); reported protocols commonly use energy densities of 3 to 12 J/cm² and three to 12 sessions applied one to three times per week, with highly variable irradiation times per point, mainly targeting the temporomandibular joint region and the masseter and temporalis muscles. In the limited number of active-comparator trials, generally short-term, LLLT appeared comparable or superior to occlusal splints, nonsteroidal anti-inflammatory drugs (NSAIDs), and transcutaneous electrical nerve stimulation (TENS), and it was well-tolerated, with only rare and transient adverse effects. However, considerable heterogeneity persists regarding diagnostic criteria, dosimetry reporting, device characteristics, treatment duration, and follow-up, and this variability, rather than a consistent dose-effect relationship, is a central finding of the present review. LLLT may therefore be a useful adjunctive treatment for TMD within multidisciplinary conservative management, but standardized, fully reported dosimetric protocols and high-quality randomized trials are needed to determine optimal parameters by TMD subtype, chronicity, and patient characteristics.