Probiotics in Periodontal Diseases: Mechanisms, Evidence Mapping, Limitations, and Future Directions

Periodontal disease represents a spectrum of inflammatory disorders that impact the teeth's supporting tissues. It is initiated by the buildup of microbial plaque and sustained by dysbiosis, an imbalance in the oral microbiome that causes tissue damage and disturbs host-microbe homeostasis. These diseases can range from reversible inflammation of the gingiva (gingivitis) to irreversible destruction of the periodontal apparatus (periodontitis). While scaling and root planing, with or without antimicrobials, can effectively reduce bacterial burden, mechanical debridement by itself may not restore microbial symbiosis and may allow disease-associated microbial populations to persist. Incomplete pathogen clearance from deep pockets, residual calculus, or inaccessible root surfaces frequently results in bacterial regrowth and disease progression. Probiotics have emerged as a possible alternative or supplement in periodontal therapy. Their possible benefits include microbial balance restoration in the oral cavity, as well as anti-inflammatory, immunomodulatory, and bone-preserving actions. Nonetheless, the strain-specific effects, dosage regimen, safety profile especially in certain patients and the absence of large-scale, long‑term randomized controlled trials to definitively establish their efficacy remain as concerns. This review discusses the mechanisms through which probiotics may influence periodontal diseases, systematically maps preclinical and clinical evidence, and highlights current limitations and future directions for their application in periodontal therapy.