Causal Mechanisms Linking Periodontitis and Systemic Diseases via the Oral-gut Axis

Abstract

Periodontitis is a chronic inflammatory disease of the periodontal tissues driven by dysbiosis of the oral microbiota and remains a leading cause of tooth loss. Beyond its local effects in the oral cavity, growing evidence indicates that periodontitis contributes to the onset and progression of a wide range of systemic diseases. Traditionally, this association has been explained by the hematogenous spread of oral bacteria, bacterial products, and activated immune cells through a disrupted gingival epithelial barrier, leading to inflammation and metabolic disturbances in distant organs. More recently, attention has focused on the oral–gut axis, particularly the impact of swallowed oral bacteria on the intestinal environment. Clinical studies have detected diverse oral bacterial species in the gut of patients with periodontitis-associated systemic conditions. In experimental disease models, administration of pathogenic oral bacteria induces gut microbial dysbiosis, impairs barrier integrity, promotes inflammation, alters metabolism, and modulates immune responses, thereby exacerbating disease phenotypes. This article reviews the relationship between periodontitis and systemic diseases, with special emphasis on mechanisms involving the oral–gut axis.