Systematic Review: The Role of Lactobacillus rhamnosus in Periodontal Disease

Background: Periodontal diseases are chronic inflammatory conditions driven by dysbiosis of the oral microbiome, affecting a significant proportion of the global population. Lactobacillus rhamnosus (formerly Lactobacillus rhamnosus), a well-characterized probiotic species, has garnered increasing attention for its potential role in modulating oral health. However, its specific involvement in periodontal disease whether protective through probiotic mechanisms or potentially pathogenic in certain contexts remains incompletely understood. This systematic review aims to synthesize current evidence on the role of L. rhamnosus in periodontal disease, examining both its therapeutic potential as an adjunctive probiotic and its possible associations with periodontal pathology. Methods: A systematic literature search was conducted following PRISMA guidelines across PubMed, Web of Science, Scopus, and Embase databases for studies published up to January ۲۰۲۶. Search terms included "Lactobacillus rhamnosus," "Lactobacillus rhamnosus," "periodontal disease," "periodontitis," "gingivitis," "probiotic," and "oral microbiome." Both interventional studies (randomized controlled trials) and observational studies investigating the relationship between L. rhamnosus and periodontal outcomes were included. Data extraction focused on clinical periodontal parameters (probing depth, clinical attachment level, bleeding on probing, gingival index), microbiological outcomes, and safety considerations. Results: The search yielded one high-quality systematic review specifically examining L. rhamnosus and L. plantarum in caries and periodontal diseases, which included ۱۵ RCTs with ۸۷% rated as good quality on the Jadad Scale. Multiple studies demonstrated that L. rhamnosus strains (including GG, L۸۰۲۰, and SP۱) can improve clinical periodontal outcomes when used as adjuncts to non-surgical periodontal therapy. A randomized trial by Morales et al. showed that L. rhamnosus SP۱ supplementation resulted in significantly greater probing depth reduction compared to placebo following scaling and root planing. In vitro evidence confirms that L. rhamnosus strains can inhibit Porphyromonas gingivalis growth and biofilm formation, reduce pathogen adhesion to gingival epithelial cells, and modulate inflammatory responses by decreasing pro-inflammatory cytokines (TNF-α, IL-۱ẞ, IL-۶). However, clinical trial results show heterogeneity, with some studies reporting no significant improvements in plaque indices or bleeding scores. Weaker evidence exists for consistent microbiological benefits, suggesting strain-specific and context-dependent effects. Notably, the reviewed literature focuses exclusively on the therapeutic/probiotic role of L. rhamnosus, with no identified studies reporting pathogenic associations between L. rhamnosus and periodontal disease initiation or progression. Conclusion: Current evidence supports a predominantly beneficial role for specific L rhamnosus strains as adjunctive agents in periodontal management, with demonstrated capacity to improve clinical outcomes and inhibit periodontal pathogens in vitro. However, significant heterogeneity across studies, strain-specific effects, and limited long-term data preclude definitive clinical recommendations. The absence of evidence linking L. rhamnosus to periodontal pathogenesis suggests it functions primarily as a beneficial commensal in the periodontal ecosystem. Future research should prioritize large-scale, standardized RCTs with extended follow-up periods, investigate strain-specific mechanisms of action, and explore optimal delivery vehicles and dosing regimens for clinical application.

Keywords:

Lacticase ibacillus rhamnosus , Probiotics , Periodontal disease , Periodontitis , Gingivitis , Oral microbiome