The year 2025 may be remembered as the moment oral health moved beyond the mouth — and into the centre of systemic disease prevention.
As Dr. Thomas Van Dyke noted at SmileCon in October, dentistry and medicine have historically evolved on parallel tracks. But in 2025, a growing body of research brought those worlds closer than ever.
During a panel discussion on oral–systemic integration, Van Dyke addressed the long-standing divide between dental and medical care and suggested perceptions are beginning to shift.
“Our profession, for the most part, considers ourselves physicians of the mouth,” he said. “And specialists who deal with inflammatory diseases are starting to recognize the connections to oral health.”
Still, researchers caution that many of these links are not yet fully understood. In an upcoming Brush Up podcast, Dr. Paul J. Allison, a professor in McGill University’s Faculty of Dental Medicine and Oral Health Sciences, said most research linking oral health and systemic disease is associative rather than causal, but added that periodontal disease may still serve as an early indicator of broader health issues tied to chronic inflammation.
Against the backdrop of broader improvements in oral hygiene behaviors, new data from the Canadian Health Measures Survey (CHMS) suggest Canadians are retaining more of their natural teeth than they were 15 years ago—but indicators of gum disease have worsened sharply. In the podcast, Allison, who led the national research team that secured funding and developed the proposal for the CHMS oral health cycle, discusses the findings and offers his insights. Stay tuned.
So, here are some of the key studies that helped situate oral health beyond the mouth in 2025:
Flossing and stroke risk
The year began with a U.S. study linking a simple oral hygiene habit to cardiovascular outcomes. Researchers reported that people who flossed at least weekly had a 22 per cent lower risk of ischemic stroke, a 44 per cent lower risk of cardioembolic stroke, and a 12 per cent lower risk of atrial fibrillation.
“Oral health behaviours are linked to inflammation and artery hardening,” said Dr. Souvik Sen, chair of neurology at the University of South Carolina School of Medicine. “Flossing may reduce stroke risk by lowering oral infections and inflammation.”
Presented at the American Stroke Association’s International Stroke Conference in February, the preliminary findings drew on data from more than 6,200 adults in the long-running Atherosclerosis Risk in Communities (ARIC) cohort, followed for roughly 25 years. About 65 per cent of participants reported flossing at least once a week.
Dementia enters the oral-systemic conversation
In February, researchers from New York University urged The Lancet to formally recognize oral health as a modifiable dementia risk factor, arguing that poor oral health may carry nearly three times the dementia risk associated with diabetes or hypertension.
“We believe that oral health is a significant risk factor for cognitive decline and the onset of dementia,” said Bei Wu, dean’s professor in global health and vice-dean for research at NYU’s Rory Meyers College of Nursing.
In a related study, Wu’s team found that older adults with gum disease who received periodontal treatment experienced slower cognitive decline and a 38 per cent lower risk of developing dementia than those who did not receive treatment.
Gum disease and gastric cancer risk
By July, evidence linking oral inflammation to cancer risk also emerged. A large-scale study published in BMC Medicine found that gum disease may raise the risk of developing gastric cancer by up to 25 per cent.
Led by researchers at Southeast University’s School of Public Health in China, the study analyzed dental and health records from 5.8 million adults in Sweden, using sibling-controlled comparisons to strengthen causal inference.
“Promoting dental health in the general population could have significant public health implications,” the authors wrote.
Tooth loss and mortality in older adults
In October, another study underscored the stakes of untreated oral disease in aging populations. Research published in BMC Geriatrics found that the rate of tooth loss, rather than tooth count alone, was associated with all-cause mortality in older adults.
Using data from the Chinese Longitudinal Healthy Longevity Survey, researchers reported that faster tooth loss predicted a significantly higher risk of death — regardless of how many teeth participants had at baseline.
A microbial link to Parkinson’s disease
Perhaps the most striking biological evidence arrived in September. Researchers identified a direct microbial pathway linking a variant of Streptococcus mutans — a bacterium best known for causing tooth decay — to Parkinson’s disease.
The study, published in Nature Communications, analyzed stool samples from nearly 500 patients with Parkinson’s disease and 234 healthy controls. Researchers found that S. mutans produced a metabolite capable of damaging dopamine-producing neurons, a hallmark of Parkinson’s.
Root canals and metabolic health
By November, researchers from King’s College London added to the oral–systemic narrative. Patients with chronic root canal infections who received successful endodontic treatment showed improved blood sugar control, healthier lipid profiles and reduced systemic inflammation over two years.
“Long-standing root canal infections can allow bacteria to enter the bloodstream and trigger inflammation,” said lead author Dr. Sadia Niazi. “It is vital that dental professionals recognize the wider impact.”