Researchers Discover Why Gum Disease Causes Heart Disease

December 31, 2020

Think skipping your nightly dental care routine is no big deal? The results of a recent study linking gum health to inflammatory diseases like heart disease may convince you to never skip oral hygiene again.

Medical science has now firmly established a link between periodontal (gum) disease and inflammation-linked conditions such as cancer, heart disease, and diabetes. But the mechanism linking these conditions has remained a medical mystery—until now.

Researchers at the University of Toronto’s Faculty of Dentistry have identified what they believe is the correlation between these conditions—blood cells called neutrophils. The new findings present the first evidence pointing to the body’s own immune system response.

The controlled clinical experiment, conducted in collaboration with top dentists from Sinai Health Systems and Princess Margaret Cancer Centre in Toronto, indicates that neutrophil immune cell activity is the “missing link” connecting periodontal disease with other inflammatory diseases. Their findings were published in the October 2020 Journal of Dental Research.

Excessive Immune Response

Neutrophils are a type of white blood cell that is activated to respond to areas of acute inflammation. When neutrophils, which play a critical role in immune system response, were activated to fight infections from active cases of gum disease, researchers observed a hyperactive, systemic response that they believe makes the body susceptible to damage from secondary inflammatory conditions.

The study’s senior author, professor Michael Glogauer, put it this way: “It’s almost as if these white blood cells are in second gear when they should be in first.”

Produced initially in vivo models, the findings were confirmed through a controlled clinical experiment involving mice with induced periodontal disease (PD). A human gingivitis study was conducted in tandem, with volunteers being instructed to cease all oral hygiene practices for three weeks to induce gingivitis, followed by a two-week recovery period.

Blood and tissue samples were taken from the mice; blood and saliva samples were also collected from human gingivitis study volunteers. Multiplex cytokine analysis was performed on immune system cells for both human and mouse subjects to indicate the presence of neutrophils.

Periodontal Disease and Pre-Existing Conditions

After analyzing immune system cells harvested from the oral cavities of both healthy and PD-infected tissues, researchers observed that the numbers of neutrophils in diseased tissues were greatly increased over the neutrophils present in healthy tissues. They further found that PD in mice mimics human PD when it comes to the number of neutrophils recruited to sites of oral bacterial infection.

This aggressive neutrophil response to PD primes the immune system to attack, and much like what is seen in autoimmune diseases, the target of the attack is the body’s own tissues and organs. If secondary infection sites are present in the body, as is often the case with cardiac and diabetic patients, the abundance of neutrophils can respond to these areas with excessive force, leading to negative health outcomes for patients.

The study’s lead author, Noah Fine, states: “We believe this is the mechanism by which oral hygiene can impact vulnerability to unrelated secondary health challenges. Neutrophil (immune) priming … can connect these seemingly distinct conditions.”

Healthy Mouth, Healthy Body

Studies like this underscore the importance of oral health as a window into the overall health of the body. Periodontitis is a serious yet common gum infection that can destroy the soft tissues and bone structure supporting teeth. Over time, this damage can result in permanent tooth loss and lead to worsening comorbid conditions. Symptoms of periodontitis include:

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