Gut Microbiome Dysbiosis and Periodontitis: Emerging Insights into the Oral–Gut Axis

Background: Periodontitis is a chronic inflammatory disease increasingly associated with systemic immune dysregulation and microbial imbalance beyond the oral cavity. Emerging evidence suggests that gut microbiome dysbiosis contributes to periodontal inflammation through the oral–gut microbial axis. Methods: This systematic review was conducted according to PRISMA guidelines using the PECOS framework. A comprehensive literature search was performed across PubMed, Embase, Scopus, Web of Science, Cochrane Library, CINAHL, and Google Scholar databases to identify studies evaluating the association between gut microbiota and periodontitis, including microbiome alterations, inflammatory pathways, and microbiome-modulating interventions. Results: The included studies demonstrated that patients with periodontitis frequently exhibit reduced gut microbial diversity, enrichment of pro-inflammatory taxa, impaired intestinal barrier function, and elevated inflammatory mediators including C-reactive protein, interleukin-6, and tumor necrosis factor-alpha. Several studies identified translocation of periodontal pathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum to the gastrointestinal tract, supporting the existence of an oral–gut axis. Probiotics, prebiotics, synbiotics, and periodontal therapy showed potential benefits in improving periodontal parameters and restoring microbial homeostasis. Conclusions: Current evidence supports a significant relationship between gut microbiome dysbiosis and periodontitis through immune, inflammatory, and metabolic mechanisms. However, heterogeneity among studies and limited longitudinal evidence warrant further standardized clinical and mechanistic investigations to establish causality and optimize microbiome-targeted therapeutic strategies in periodontal disease.