Oral–Gut Microbial Translocation Axis in Periodontitis: A Critical Review of Mechanisms and Systemic Implications (2015–2025)

Abstract

Periodontitis is a dysbiosis-driven chronic inflammatory disease affecting the tooth-supporting structures that extends its pathological influence well beyond the oral cavity. Over the past decade, the oral–gut microbial translocation axis has emerged as a biologically compelling framework through which periodontal dysbiosis may shape the composition and functional output of the intestinal microbiota, with downstream consequences for systemic health. This review critically examines the mechanistic basis of oral-to-gut bacterial translocation, addressing the survival of swallowed periodontal pathogens through the gastric environment, their disruption of intestinal colonisation resistance, impairment of epithelial tight junction integrity, and induction of systemic immunological cascades involving Th17 cells, regulatory T cells, and inflammasome activation. A comprehensive literature search was conducted across the following electronic databases: PubMed/MEDLINE, Web of Science, Scopus, Embase, and Google Scholar. The roles of keystone periodontal pathogens—principally Porphyromonas gingivalis, Fusobacterium nucleatum, and Klebsiella spp.—are scrutinised in both animal models and clinical studies. The review further evaluates evidence linking the oral–gut axis to inflammatory bowel disease, colorectal cancer, metabolic-associated steatotic liver disease, and cardiovascular disease. The effect of non-surgical periodontal therapy on gut microbial composition is assessed, alongside emerging microbiome-targeted therapeutic strategies including probiotics, prebiotics, and bacteriophage-based approaches. The synthesis of current evidence reveals a bidirectional and mechanistically intricate communication channel between the oral and intestinal ecosystems, yet causal inference from human data remains constrained by methodological heterogeneity, the preponderance of cross-sectional designs, and residual confounding. Future longitudinal and interventional research employing multi-omics platforms is necessary to translate the mechanistic insights reviewed herein into actionable clinical guidance.