Effects of low-level laser photobiomodulation on the masticatory function and mandibular movements in adults with temporomandibular disorder: a systematic review with meta-analysis.

Only one of the ten trials measured masticatory function, so the review could not draw any conclusion about laser's effect on chewing or oral-motor performance, which is the outcome most relevant to speech-language therapy. Five of the ten trials had a high risk of bias, and the main gaps were in how participants were randomised, whether allocation was hidden, and whether participants knew which treatment they were receiving. The laser dose varied by a factor of 70 across the included trials (1.5 to 105 J/cm²), making it impossible to tell whether a particular dose is effective or whether the effect depends on the dose. Only six of the ten trials provided enough data to enter the meta-analysis, and the remaining four could not be included in the quantitative synthesis. The included trials were heterogeneous in sample size (15 to 82), number of sessions, frequency, wavelength, and outcome measures, which the authors note makes the results difficult to compare.

Do not read the 2.78 mm improvement in mouth opening as proof that laser works for TMD. The evidence is rated very low certainty, five of the ten trials had a high risk of bias, and the outcome most relevant to speech therapy (masticatory function) had no reliable evidence at all. The one trial that did measure mastication found the benefit came from combining laser with oral myotherapy exercises, not from laser by itself.