The Impact of Postbiotic Mouthwash on Oral Lichen Planus: A Double-blind, Randomized, Placebo-controlled Trial

Background: Oral lichen planus (OLP) is a chronic, immune-mediated inflammatory disorder. Current treatments, primarily corticosteroids, pose risks of adverse effects and frequent relapses. Emerging evidence highlights the role of oral microbiota dysbiosis in OLP pathogenesis, suggesting that restoring microbial balance may offer therapeutic benefits. This study aimed to evaluate the clinical efficacy of a postbiotic mouthwash in patients with symptomatic OLP. Methods: In this double-blind, randomized controlled trial, 40 patients with ulcerative OLP were assigned to either a postbiotic intervention group or a control group receiving standard treatment. The intervention group received a mouthwash containing 5% postbiotic derived from Lactobacillus plantarum in addition to the standard combination mouthwash. Outcomes, including pain reduction, lesion size, and adverse events, were assessed at baseline, 1-, 2-, and 4-weeks post-treatment. Statistical analyses were performed using SPSS v22, with a p value < 0.05 considered as statistically significant. Results: Both groups demonstrated a significant reduction in pain scores and lesion sizes over time (p < 0.05). The intervention group showed greater reductions in lesion size and pain intensity compared to the control group throughout the treatment period, however, the differences between the groups were not statistically significant (p > 0.05). No adverse event related to the postbiotic mouthwash was recorded. Conclusion: Although statistical significance was not achieved, postbiotic mouthwash showed promising clinical improvements in managing OLP symptoms without adverse effects. Future larger-scale studies with longer follow-up periods are warranted to validate these findings and explore the mechanistic pathways involved.