How dental health may impact brain health; experts describe how poor oral hygiene is linked to higher risk of developing dementia

Dentist Dr Raymond Lee at Pacific Dental and Orthodontic Care in Hong Kong stresses that good oral care isn’t just about supporting teeth and gum health.

“It influences our overall physical well-being,” he says. How? The mouth is connected to important systems – respiratory, digestive and cardiovascular – and contains numerous bacteria and microorganisms, some of which can harm our health.

Our body’s defence system usually keeps these in check. But, if we don’t brush and floss regularly, if we ignore oral health, a build-up of plaque and tartar on our teeth creates a breeding ground for bad bacteria which can lead to gum disease, Lee says.

There are two types: gingivitis, which affects only the soft gum and is reversible, and periodontitis (symptoms include bad breath, loosening teeth and painful chewing), which is “an advanced form of gum disease that can’t be reversed – the damage to the bone and gum tissue is permanent leading to tooth loss”.

Part of what explains the close link between oral health and whole body health lies in the body’s immune system, he explains, which responds to damage or disease by inflammation.

“Inflammation can help the body heal – but if it persists, it can become chronic and lead to more severe problems. Periodontal disease, diabetes, heart disease, respiratory infections and dementia are all diseases associated with an inflammatory response.”

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What happens, explains West, is that the build-up of disease-causing bacteria (pathogens) within infected gums – even if the patient is unaware of this infection – may overwhelm and travel through blood vessels infecting and triggering inflammation in the bloodstream and other body tissues, including in the brain, which is situated very close to the teeth and gums and “has direct routes to them”, West says.

According to one study, losing a tooth is linked to an extra year of brain ageing, while severe gum disease is linked to 1.3 years of brain ageing.

Although the precise relationship between poor dental health and loss of brain volume is unclear, says Lee, research in Finland shows that people with poor dental hygiene are 21 per cent more likely to develop Alzheimer’s disease.

Other studies have identified a bacteria called Porphyromonas gingivalis which is involved in periodontal disease. This and the enzyme it produces (gingipains) present as strong risk factors for Alzheimer’s disease. Both can cross the blood-brain barrier, says Lee, “and both were found in the brain tissue of people suffering from Alzheimer’s”.

Researchers at the School of Dentistry at the University of Central Lancashire in the UK found that when the gingipains enzyme interacts with nerve cells in the brain, “it releases a protein that causes the cell to self-destruct, leading to cell death.

“Once the nerve cell dies, the protein may attach itself to healthy neighbouring nerve cells, repeating the process and causing further damage to the brain as the disease spreads.”

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Alzheimer’s is linked to a build-up of amyloid-beta protein in the brain. Lee says researchers have identified that amyloid-beta protein is abundant around the surfaces of infected teeth and diseased gums.

“The suggestion is these proteins may filter into the bloodstream and make their way to the brain, leading to a higher risk of cognitive decline.”

West and Lee agree that it would not be accurate to suggest that everyone with poor oral health will get Alzheimer’s disease.

“We do know,” says Lee, “that if you have severe periodontitis, the chance of getting Alzheimer’s disease is higher.”

At the same time, West says, “diminished cognitive ability may also result in even poorer dental hygiene and health”.

I recall how teeth brushing became increasingly difficult as my mother’s cognition frayed – she couldn’t remember how to brush her teeth or why she needed to.

The current study at the University of Bristol attempts to understand whether regular dental assistance of individuals with both Alzheimer’s and gum disease may cause mitigation in decline of cognitive function, or even an improvement in the condition, West says.

My mother’s tooth loss might have been a marker of her generation – one which grew up without the understanding of, and access to, the better oral healthcare and electric toothbrushes we have now. But it could also have been compromised by years of antidepressant medication.

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Other drugs, ageing and health problems can all cause this problem. Having adequate saliva is important as it plays a crucial role in balancing mouth acids and clearing food debris and bacteria away, says Lee.

In Hong Kong, a considerable number of elderly people suffer from dental decay and periodontal disease, Lee says. A 2011 oral health survey found “almost half of the non-institutionalised older adults aged (from) 65 to 74 had untreated dental cavities, and nearly 90 per cent had bleeding gums and signs of periodontal disease”.

So – how to look after your teeth, now and into old age? West and Lee are adamant: Brush and floss – or use a small interdental brush after brushing – consistently.

“Follow a regular routine in which you brush your teeth twice a day and floss every day,” says Lee.

West says to use a fluoride toothpaste – and stresses that brushing before bed is especially important.

If you have crooked or uneven teeth, consult an orthodontist to see if you are suitable for braces. Straight teeth are easier to clean and floss, which is crucial for maintaining good oral hygiene, Lee says.

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There is no age limit for orthodontic treatment, but it is better to get it done earlier.

Visit your dentist for regular check-ups and a good cleaning. Reduce the amount of sugar and sugary foods that you eat. Drink enough to counteract the effects of a dry mouth, and if you take medication that gives you a dry mouth, talk to your dentist about an artificial saliva spray.

And remember that he or she will gain excellent insight into your overall health just by looking into your mouth.