Effects of Photobiomodulation on Burning Mouth Syndrome: A Systematic Review and Meta-Analysis

The objective of this research is to evaluate the effectiveness and safety of photobiomodulation or low-level laser therapy on burning mouth syndrome compared to placebo, no-laser, clonazepam and alpha-lipoic acid.

A systematic review of randomised clinical trials was performed. The databases consulted were MEDLINE, CENTRAL, LILACS, EMBASE and clinical trial registries ClincalTrial.org and WHO-ICTRP, to retrieve citations published until April 4, 2023. In addition, we consulted the grey literature for unpublished studies. There were no restrictions on language, publication status and publication date. Outcomes included pain relief, change in oral health quality of life, adverse effects and change in the quality of life concerning anxiety and depression. Two independent authors performed the study selection, and the risk of bias was assessed using the Cochrane collaboration tool. The random effect was calculated with a 95% confidence interval to calculate the relative risk. We performed heterogeneity by I² and subgroup analysis. For all calculations, we used Review Manager 5.4.1 software.

In total, 528 references were located, and 13 studies were included, with 503 participants. Seven studies were evaluated qualitatively, and six were grouped for data meta-analysis according to the type of laser used, red or infrared. The following comparisons were evaluated: laser versus placebo, laser versus clonazepam and laser versus alpha-lipoic acid. Less pain was reported with the use of a laser, with low quality of evidence, in the comparisons: red laser versus placebo with a weighted mean difference (WMD) of -1.18; 95% CI [-2.16 to -0.19]; I² = 61%; N = 58; 2 RCTs; infrared laser versus placebo with WMD = -1.34; 95% CI [-1.86 to -0.82]; I² = 14%; N = 87; 3 RCTs; laser versus clonazepam with mean difference (MD) of -1.66; 95% CI [-3.17 to -0.15]; I² = 0%; N = 33; 1 RCT. Oral health quality of life was better with the use of the laser, with very low quality of evidence, in the comparisons: red laser versus placebo with WMD = -1.08; 95% CI [-1.49 to -0.66]; I² = 0%; N = 105; 2 RCTs; infrared laser versus placebo with WMD = -0.46; 95% CI [-1.70 to 0.78]; I² = 86%; N = 85; 3 RCTs; laser versus clonazepam with MD = -19.65; 95% CI [-45.97 to 6.67]; N = 33; 1 RCT. For anxiety and depression, there was no significant difference between the groups, with very low quality of evidence, in the comparisons: infrared laser versus placebo, for anxiety with MD = 0.11; 95% CI [-2.64 to 2.86]; N = 28; 1 RCT; and for depression with MD = -0.66; 95% CI [-3.56 to 3.44]; N = 28; 1 RCT. Likewise, the comparison of laser versus clonazepam for anxiety and depression with MD = 1.05; 95% CI [-2.83 to 4.93]; N = 33; 1 RCT.

Pain was less common, and quality of life was better when using a low-level laser than placebo and clonazepam. The certainty of the evidence obtained was low and very low, respectively, meaning that the true effect may differ substantially from the effect estimate. Further well-conducted RCTs are needed to increase the degree of certainty of the evidence obtained.