Periodontitis and NAFLD: A systemic challenge beyond the oral cavity

Periodontitis, a chronic inflammatory pathology mediated by bacterial dysbiosis, no longer limits its deleterious effects solely to dental supporting tissues. While its links with cardiovascular or renal pathologies are documented, the involvement of the oral microbiota in non-alcoholic fatty liver disease (NAFLD) — which now affects 25 to 30% of the world's population — raises major clinical questions. Despite the emergence of the "multiple parallel hits" theory, suggesting that environmental and microbial factors influence hepatic health, the exact nature of this interaction remains debated and often contradictory in the literature.

Review objectives: Deciphering the oral-liver axis

This systematic review aims to synthesize evidence from 16 original studies to elucidate the molecular "crosstalk" between periodontal disease and NAFLD. The objective is to identify the mechanisms of inflammation spread via the oral-liver and oral-gut-liver axes. The authors test the hypothesis that periodontal pathogens and the host inflammatory response act as direct mediators of hepatic progression. Finally, this review evaluates whether non-surgical periodontal intervention can represent a concrete therapeutic perspective for improving liver pathology markers, thus offering a multidisciplinary approach to the management of metabolic patients.

The analysis also focused on the therapeutic impact of non-surgical periodontal treatment (NSPT) as a modulating intervention for hepatic fibrogenic and inflammatory mediators.

A clinical correlation confirmed by large cohorts

The analysis of 16 original studies highlights a close link between the severity of periodontology and the progression of non-alcoholic fatty liver disease (NAFLD). Epidemiological data, based on massive samples, suggest that the presence of deep periodontal pockets constitutes an independent risk factor for chronic liver diseases.

Study	Sample (n)	Periodontal Parameters	Key Results
Helenius Hietala et al.	6 165	Pockets ≥ 4 mm	Modifiable risk factor for chronic liver disease.
Shin	4 061	Periodontal pockets	Independent association with FLI and HSI indices.
Akinkugbe et al.	2 623	CAL ≥ 3 mm ; PD ≥ 4 mm	History of periodontitis correlated with the risk of NAFLD.
Sato et al.	164	> 10 pockets ≥ 4 mm	Significant increase in liver stiffness (VCTE/MRI).

Inflammatory signature and metabolic deregulation

Beyond clinical observation, the review identifies precise molecular mechanisms. Periodontology and its pathogens activate hepatic inflammatory responses via the elevation of systemic pro-inflammatory cytokines: IL-6, IL-17 and TNF-α.

• Metabolic imbalance: Chronic inflammation exacerbates insulin resistance, marked by an increase in HOMA-IR.
• Liver markers: A significant correlation is observed with the elevation of transaminases (ALT and AST).
• Periapical involvement: Bordagaray et al. (n=59) report that even lesions of endodontic origin are associated with an increase in serum transaminases.

Impact of non-surgical periodontal therapy (NSPT)

A major result of this synthesis concerns the therapeutic potential of periodontal debridement. NSPT is not limited to local improvement; it helps mitigate the progression of NAFLD by simultaneously reducing hepatic pro-inflammatory cytokines and fibrogenic mediators. Although the methodological heterogeneity of current studies is noted, the data suggest that periodontal treatment improves liver health parameters.

The oral-liver axis: a driver of hepatic inflammation

The analysis of these 16 original studies confirms that periodontology acts as an aggravating lever for non-alcoholic fatty liver disease (NAFLD). The systemic passage of oral pathogens and their mediators stimulates a hepatic inflammatory response marked by an increase in IL-6, IL-17, and TNF-α. Clinically, this impact results in an exacerbation of insulin resistance (HOMA-IR) and an elevation of hepatic cytolysis markers (ALT, AST). The existence of an "oral-gut-liver axis" suggests that periodontal dysbiosis actively facilitates progression toward more severe stages of hepatic fibrosis.

Methodological limits and nuances

The major weakness identified in this review lies in the heterogeneity of the protocols. Studies often diverge on the very definition of periodontology (pocket depth vs. attachment loss vs. IgG serology against P. gingivalis), which makes the conclusions sometimes contradictory. Nevertheless, the compiled data demonstrate a tangible benefit of non-surgical periodontal treatment (scaling and root planing): by reducing the oral inflammatory load, the practitioner contributes to the attenuation of hepatic fibrogenic mediators, thus offering a significant complementary therapeutic path.

Summary of results

This review of 16 studies demonstrates that periodontology aggravates non-alcoholic fatty liver disease (NAFLD) via the oral-liver and oral-gut-liver axes. Systemic inflammatory activation (TNF-α, IL-6) and increased ALT/AST markers confirm the direct impact of the infection on insulin resistance (HOMA-IR).

In concrete terms, for the practitioner:

• Systemic screening: Integrate the risk of hepatic steatosis into your follow-up of chronic periodontal patients presenting with metabolic syndrome or obesity.
• Therapeutic lever: Position non-surgical periodontal treatment as a concrete intervention to help stabilize liver enzymes and slow the progression of fibrogenic mediators.
• Multidisciplinary communication: Inform hepatologists and general practitioners that oral sanitation improves insulin sensitivity, thereby contributing to the global management of NAFLD by controlling bacterial translocation.

Technical Lexicon of the Study

NAFLD (Non-alcoholic fatty liver disease): Liver disease characterized by an excessive accumulation of fat (steatosis) in the liver in the absence of significant alcohol consumption (less than 20-30 g/day).

Oral-Gut-Liver Axis: Pathophysiological communication pathway through which oral pathogens and their inflammatory mediators reach the liver, either directly via the systemic circulation or indirectly by disrupting the gut microbiota.

HOMA-IR (Homeostatic Model Assessment for Insulin Resistance): A biological index used to assess insulin resistance, calculated from fasting blood glucose and fasting insulin levels; a key marker of metabolic dysfunction associated with NAFLD.

NSPT (Non-surgical periodontal therapy): Non-surgical periodontal treatment mainly including scaling and root planing (SRP) aimed at removing bacterial biofilm and calcified deposits.

ALT / AST (Alanine aminotransferase / Aspartate aminotransferase): Liver enzymes whose elevated serum levels indicate cytolysis (damage to liver cells) often observed during the inflammatory phases of steatohepatitis.

Porphyromonas gingivalis: Major Gram-negative periodontal pathogen, identified in this review as a central player in bacterial translocation and the activation of hepatic inflammatory responses.

"article": "The idea that the oral cavity is a mirror of systemic health is no longer an intuition, but a biological reality supported by precise molecular data. This systematic review, synthesizing 16 original studies, explores the connection between periodontology — a chronic inflammatory disease destroying the tooth's supporting apparatus — and non-alcoholic fatty liver disease (NAFLD). While NAFLD now affects 25 to 30% of the global population, identifying modifiable risk factors such as periodontal health is becoming a major clinical challenge for the dental surgeon and the hepatologist.

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