Comparative efficacy of low-level diode laser therapy with different wavelengths in burning mouth syndrome: a randomized, single-blind trial.

Burning mouth syndrome (BMS) is a chronic condition with no effective treatment currently available. Low-level laser therapy (LLLT) shows promise for neuropathic pain management, but evidence comparing its efficacy across different wavelengths in BMS patients remains limited. This study aimed to assess the clinical efficacy of LLLT with three distinct wavelengths in BMS patients, and to determine the optimal therapeutic wavelength. This study was a single-blind randomized controlled trial, with blinding applied only to the participants. 201 participants were scheduled for enrollment, divided into three groups with 67 individuals each. Finally, 63 participants with BMS were enrolled from April 2019 to December 2022, with 53 completing the study. Randomization was performed using SPSS software to generate random numbers. Participants were sequentially assigned based on their enrollment order to the 660 nm group (n = 10, 50 mW, 1.5 J/cm², 30 s/point), 810 nm group (n = 26, 500 mW, 3 J/cm², 6 s/point), or 975 nm group (n = 17, 30 mW, 10 J/cm², 33 s/point). Each participant underwent LLLT once a week for 4 sessions. Outcomes, including pain intensity, numbness, and altered taste, were assessed using the visual analogue scale (VAS). Efficacy was assessed by comparing VAS scores at baseline and after the last treatment, using the Kruskal-Wallis test for comparisons among the three groups and the Mann-Whitney U-test for pairwise analysis. Effect sizes were reported using Cohen's d. Statistically significant pain relief was observed in all groups (median reduction of 40%). The improvement of numbness in the 810 nm and 975 nm groups (median reduction of 40%) was also significant (p < 0.05). However, no significant differences in efficacy were noted among the three groups (p > 0.05). These results suggested that LLLT with three different wavelengths effectively reduced pain and that the 810 nm and 975 nm wavelengths also significantly alleviated numbness in BMS patients. However, further investigation is warranted to elucidate any potential differences in efficacy among the three groups. Clinical trial registration: ChiCTR1900021674 (March 5, 2019).