Revisiting the Oral–Gut Axis: Microbial Symbiosis, Dysbiosis, and Bidirectional Links Between Periodontitis and Inflammatory Bowel Disease

Background: Recent scientific evidence indicates that the oral–gut axis represents a critical interface in host–microbiota interactions, carrying profound implications for both periodontal and gastrointestinal diseases. This scoping review aims to evaluate the reciprocal influence between periodontitis and inflammatory bowel disease (IBD). Specifically, the underlying mechanisms of microbial translocation, immune interaction, and metabolite-mediated signaling linking the oral microbiota to gut microbial ecology are critically evaluated. Methods: Studies were selected from the PubMed, Web of Science, and Scopus databases up to May 2026. Eligible criteria included in vivo studies written in English and conducted within the last 10 years, whereas human studies involving participants under 18 years of age were excluded. The included studies analyze the effects of oral and gut dysbiosis on the opposing district. Through the database search, 2094 records were identified, and 34 articles were selected based on the eligibility criteria. Results: The included studies demonstrate the interconnection between the oral and gut microbiota. The included studies reveal that predominant oral taxa, specifically Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans, alter intestinal microbial composition. In particular, P. gingivalis colonizes the gut, exacerbating both oral and intestinal inflammation by stimulating pro-inflammatory cytokine expression via Th17 cell activation. Finally, salivary microbial composition appears to be associated with the presence and status of IBD. Conclusions: Understanding these interconnected microbial ecosystems provides valuable insights that may support the future development of integrated diagnostic and therapeutic strategies for patients suffering from periodontitis and IBD. Further large-scale studies with longer follow-up periods are required to standardize potential salivary markers and multidisciplinary therapeutic protocols for the management of periodontitis and IBD.