The Oral–Systemic Axis: Mechanistic Pathways Linking Oral Dysbiosis to Cardiovascular, Metabolic, and Neuroinflammatory Disease

Abstract

Background. The oral cavity harbours the second most diverse microbial community of the human body, and its disruption—oral dysbiosis—has moved from a strictly dental concern to a recognised contributor to systemic disease. Yet the field remains fragmented across cardiology, metabolism, and neurology, with mechanistic threads rarely woven together.

Objective. This review synthesises current mechanistic evidence linking oral dysbiosis to cardiovascular, metabolic, and neuroinflammatory disease, with particular attention to the shared inflammatory and oxidative pathways that may explain why a single dysbiotic state produces such heterogeneous distal outcomes.

Key findings. Three non-exclusive routes recur across organ systems: direct haematogenous dissemination of periodontal pathogens and their virulence factors, low-grade systemic inflammation driven by pro-inflammatory cytokines, and translocation along the oral–gut axis that reshapes distant microbial ecology. Porphyromonas gingivalis emerges as a keystone organism whose gingipains, lipopolysaccharide, and outer-membrane vesicles couple local periodontal injury to endothelial dysfunction, insulin resistance, and neurodegenerative pathology. The strength of evidence, however, varies sharply—robust for mechanistic plausibility, weaker for causal inference in humans.

Conclusion. Oral dysbiosis is best understood not as a single causal agent but as an amplifier of inflammatory and oxidative load that interacts with host susceptibility. Translating this understanding into clinical benefit will require intervention trials that treat periodontal status as a modifiable systemic risk factor rather than a localised condition.