Isn't it strange that dentistry and medicine have remained largely separate? The mouth is often treated as an isolated part, especially in the UK, where dental care is not free at the point of use like medical services. Historically, dentistry emerged as a trade in the Middle Ages, with barber surgeons handling extractions and jewellers crafting dentures. Today, the two fields still have separate training, professional bodies, and NHS structures. However, this division is being challenged as evidence mounts linking oral health to systemic conditions.
The Mouth as a Gateway
"People forget that the mouth is an open portal, a gateway into the bloodstream and your lungs, and inside your body," says Steve Kerrigan, professor of precision therapeutics at RCSI University of Medicine and Health Sciences in Dublin. Our mouths host about 700 species of bacteria. Gum disease is extremely common: around half of UK adults have some form, caused by plaque buildup. Gingivitis is the milder, reversible version, while periodontitis involves irreversible detachment of teeth from gums and is the main cause of adult tooth loss.
"Gum disease is now classed as a chronic inflammatory condition in its own right," says Kerrigan, "up there with asthma, COPD, Crohn's disease and ulcerative colitis." Some studies show that up to 90% of people with cardiovascular disease also have gum disease. Research into this relationship is the most advanced, showing causation rather than mere association.
Cardiovascular Connections
Oral infections can cause bloodstream infections, which is why patients with replacement heart valves receive prophylactic antibiotics before dental procedures. Oral bacteria can also leach into the bloodstream through rotten teeth or bleeding gums, damaging the cardiovascular system. Atherosclerosis involves cholesterol, fat, and calcium building up on artery walls. "The majority of bacteria in atherosclerotic plaque is from the mouth," says Kerrigan. Scientists are investigating whether oral bacteria cause atherosclerosis or adhere to existing plaque. Either way, they increase inflammation and health risks.
Oral bacteria can also increase the risk of blood clots and strokes. "Once these bacteria breach the barriers in the mouth, they get into the bloodstream, and they can bind to the blood clotting cells, called platelets," explains Kerrigan. This causes platelets to stick together, forming clots that can block blood vessels in the brain, leading to a mini-stroke or full-blown stroke. If the clot gets stuck in heart vessels, it can cause a heart attack. Clots on heart valves lead to infective endocarditis, potentially causing heart failure.
Diabetes and Oral Health
Diabetes has a well-established link with oral health. A 2025 study found that root canal treatment significantly lowered blood sugar levels, cholesterol, and fatty acids, suggesting that removing infected pulp can help protect against type 2 diabetes. The connection is bidirectional: gum disease increases diabetes risk due to systemic inflammation, while poorly controlled diabetes makes gum disease worse. "People with gum disease or periodontitis and diabetes have a three times higher mortality risk than those without gum disease," says Kerrigan.
Dementia and Cognitive Decline
Correlations between oral health and dementia are under investigation, though no causal link has been proved, says Jing Kang, senior lecturer at King's College London. A 2016 study found that gum disease was associated with a six-fold increase in cognitive decline over six months. The study also linked gum disease to a pro-inflammatory state, which can increase vulnerability to major illnesses. Kang notes that it's hard to pinpoint a precise mechanism: "It is possible that behaviours, such as our choice of food or choice of lifestyle, could also impact on our oral health." Poor education in childhood may lead to worsening oral health over time, with resulting inflammation affecting cognitive function later in life.
Arthritis and Other Conditions
According to Kang's research, brushing twice a day and flossing may even help with aching knees. "People who had arthritic knees were more likely to have had gum disease, and vice versa. People suffering from more gum disease were diagnosed with arthritis, or they saw deterioration much quicker than those who had healthy teeth."
Practical Steps for Better Oral Health
Kang advises against panic: "Don't worry too much if when brushing your teeth there's blood, that you're going to get dementia the next day. It is just a message to deliver to the public to keep our teeth and gums healthy."
The government's 2021 oral health survey found that a quarter of adults with natural teeth had damaged teeth. Accessing NHS dental care is increasingly difficult, leading to self-treatment. Kerrigan notes that even professional tooth removal can alter the mouth's microbiome, which is critical for digestion.
To minimise risks, Kerrigan recommends brushing at least twice daily, ideally with an electric toothbrush with rotating heads. Flossing and cleaning between teeth are also important. Diet plays a key role: "When you snack, it's going to be on sugary foods. The more sugar you put into your mouth, the more you're feeding the bacteria."
Ultimately, oral health is one aspect of an overall healthy lifestyle. "The person who runs several times a week probably has perfect oral hygiene as well. If you look after one part of your body, you tend to look after all parts," says Kerrigan.
