The review, published by an international group of researchers, argues that the mouth and liver are more connected than we thought.
Gum disease, especially in its more advanced form known as periodontitis, is a chronic inflammatory condition caused by bacterial infections in the tissues that support the teeth. It is one of the most common diseases worldwide, and its severity tends to increase with age, smoking, alcohol use, and poor access to dental care. For patients already struggling with liver disease—many of whom share these same risk factors—oral health can often be neglected.
A hidden link
The review has laid out multiple ways that periodontitis may aggravate liver disease. The first is via the ‘oral-gut-liver axis’, a term researchers use to describe the complex interplay between oral bacteria, the gut microbiome, and liver function. Pathogenic bacteria from the mouth can be swallowed or enter the bloodstream during everyday activities like chewing and brushing. Once in the gut, these microbes may alter the composition of the intestinal microbiome, leading to dysbiosis and increased gut permeability—also known as a ‘leaky gut’. This can allow bacterial products such as endotoxins to reach the liver, triggering inflammation and fibrogenesis.
Animal models have offered further support for this theory. Studies have shown that oral administration of specific periodontal pathogens, such as Porphyromonas gingivalis, can exacerbate liver steatosis and inflammation in mice with pre-existing metabolic disease. These microbes, or their byproducts, have even been found in liver tissue, suggesting that translocation from the mouth to the liver is biologically plausible.
The immune system also plays a central role in this interaction. Chronic periodontal inflammation leads to the release of pro-inflammatory cytokines like TNF-alpha and IL-6, which have long been implicated in the progression of liver disease. Additionally, the review highlighted the involvement of Th17 cells—a type of immune cell activated by oral pathogens that may migrate to the liver and worsen metabolic dysfunction. Together, these pathways form a vicious cycle: liver disease impairs oral health, while oral inflammation accelerates liver damage.
The clinical data, while still developing, supports this association. Patients with cirrhosis consistently show worse oral health than the general population, with higher rates of gingival overgrowth, attachment loss, and bone loss. The prevalence of periodontitis among patients awaiting liver transplantation can be as high as 72 per cent. Studies have also found links between severe periodontal disease and increased mortality in cirrhosis patients.
For those with MASLD, the most common form of chronic liver disease, the evidence is also compelling. Population-level studies have found that people with advanced periodontitis are significantly more likely to have MASLD, even after adjusting for shared risk factors like obesity and diabetes. And in a small trial, periodontal treatment led to a short-term improvement in liver enzyme levels.
However, the authors have cautioned that the research is still at an early stage. Much of the clinical data comes from observational studies, which cannot definitively prove cause and effect. There is also the challenge of disentangling shared lifestyle and socioeconomic factors that affect both oral and liver health.
The review has called for multidisciplinary collaboration. Gastroenterologists and hepatologists, who typically manage liver disease, may not think to ask about oral health or refer patients for dental care. However, the researchers said the data suggests they should. Similarly, dental professionals may not be aware of how their work could influence liver outcomes. According to the researchers, closer cooperation between these specialties could lead to earlier detection and better care.