Oral lichen planus (OLP) is a relatively common immunological mucocutaneous disease that causes pain, burning sensations and poor quality of life. The use of low-level light therapy (LLLT) to treat OLP is still debated. This systematic review and meta-analysis aimed to systematically and quantitatively assess the efficacy of LLLT in the treatment of OLP.

The PubMed, Embase, Cumulative Index of Nursing and Allied Health Literature (CINAHL), Cochrane Library, and Web of Science electronic databases were searched up to February 28, 2023, to identify randomized controlled trials (RCTs) examining the use of LLLT in OLP patients reporting pain or other outcomes. The mean difference (MD) or log risk ratio (log RR) with 95% confidence intervals (CIs) were estimated separately for each outcome to determine the effect sizes. Subgroup analysis was used to detect the sources of heterogeneity. Sensitivity analysis was used to test the robustness of the pooled results. Funnel plots, Egger's test, and Begg's test were used to test publication bias. All the statistical analyses were performed using Stata 16.0 software. A graph of risk of bias was drawn using RevMan 5.4.1 software for the assessment of bias.

A total of twelve RCTs were included in this systematic review, 7 of which were also included in the meta-analysis. Among the included studies, 1 had a low risk of bias, whereas 7 had an unclear risk of bias. The meta-analysis results indicated that LLLT significantly improved long-term analgesic efficacy (over 12 weeks posttreatment, measured by the visual analogue scale; MD = -1.20, 95% CI -2.01 to -0.38, P < .001), whereas no significant changes were observed in either the short term (MD = -0.68, 95% CI -1.38 to 0.01, P = .05) or the medium term (MD = -0.89, 95% CI -1.96 to 0.17, P = .10). Furthermore, LLLT improved the clinical severity of lesions (as assessed by the biopsy sign scores or reticular atrophic erosive scores; MD = -1.13, 95% CI -1.62 to -0.63, P < .001) and reduced the recurrence rate (log RR = -1.34, 95% CI -2.30 to -0.37, P = .01). Additionally, there were no statistically significant differences in the clinical response rate (measured by efficacy indices; log RR = -0.12, 95% CI -0.37 to 0.13, P = .35). No adverse events related to LLLT were reported.

LLLT appears to alleviate pain, enhance the clinical outcomes of OLP lesions, and lower the likelihood of relapse in OLP patients. Future research should focus on longer intervention courses, larger sample sizes, and multidisciplinary intervention designs.

This meta-analysis was registered on PROSPERO (CRD42023384852).