Understanding the Oral-Gut Axis

There is growing awareness of periodontal diseases as indicators of systemic problems, including intestinal disorders. In fact, for clinicians who know what to look for, it can be the first sign of inflammatory bowel disease (IBD) such as Crohn disease or ulcerative colitis.^1,2

Indeed, oral pathogens associated with periodontal diseases are often implicated in gut dysbiosis (an imbalance in gut microbiota) and pathology leading to disorders such as IBD and colorectal cancer. In addition, oral bacteria can initiate host immune responses, leading to colitis and other inflammatory diseases.³

TWO-WAY STREET

In cases of periodontitis, oral bacteria may enter the bloodstream directly to wreak havoc on extraoral organs. But recent studies have found that oral bacteria can also access these organs more directly via the oral-gut axis — through ingestion.

The oral-gut axis — the link between the mouth and the gut — provides oral bacteria easy access to the gastrointestinal tract, potentially exacerbating gastrointestinal conditions. For instance, F. nucleatum, associated with periodontal diseases, has been found in colorectal cancer tissue originating from saliva.

Conversely, recent research also shows that oral health can be impacted by bacteria originating in the gut. Further, studies have revealed the possibility of a round-trip ticket for oral pathogens returning from the gut back to the oral cavity.³

Besides Fusobacterium nucleatum, other oral pathobionts associated with both periodontal disease and gut pathology include Klebsiella aerogenes, Porphyromonas gingivalis, Haemophilus parainfluenzae, and Streptococcus mutans. The last of these, commonly associated with dental caries, has been connected to heart disease, with certain strains linked to colitis.^1,3

ORAL SIGNIFIERS

In addition to periodontitis, up to 50% of patients with IBD report being plagued with oral manifestations of the disease, such as canker sores, gingivitis, caries, and angular cheilitis. Such symptoms are particularly severe in patients with Crohn disease.^1,3

Oral manifestations can occur either simultaneously with intestinal symptoms or before the presentation of IBD. In 60% of these patients, oral lesions may be the primary sign, before any gastrointestinal symptoms are evident. One study identified the oral microbiome in saliva as a predictive biomarker for the presence of Chron disease or absence with more than 70% accuracy.^2,3

Current research shows that both caries and periodontal diseases occur at a higher rate in patients with IBD than those without it. In addition, oral disease tends to be more severe in patients with IBD than in their healthy counterparts.²

DIAGNOSTIC BENEFITS

Medical professionals often overlook orofacial manifestations in nondental settings. In fact, reports indicate that up to 50% of gastroenterologists find it difficult to identify oral lesions compatible with Chron disease compared to experienced dental professionals. Yet, it’s estimated that up to 60% of patients with Chron disease have oral lesions at some point.⁴

Because symptomatic IBD can lag behind the development of oral lesions, cooperation between oral health professionals and gastroenterologists is critical in arriving at an early diagnosis followed by optimal treatment.

REFERENCES

1. Klein S. The surprising relationship between oral health and IBD. Time Magazine. December 2, 2024.
2. Ribaldone DG, Brigo S, Mangia M, Saracco GM, Astegiano M, Pellicano R. Oral manifestations of inflammatory bowel disease and the role of noninvasive surrogate markers of disease activity. Medicines (Basel). 2020;7:33.
3. Yamazaki K, Kamada N. Exploring the oral-gut linkage: Interrelationships between oral and systemic diseases. Mucosal Immunology. 2024;17:147-153.
4. Joshi S, Moore A, Mawdsley J, et. Oral manifestations of inflammatory bowel disease: a guide to examination. Frontline Gastroenterology. 2024;15(4):328-335.