Health problems linked to poor oral hygiene

What the research links to poor oral hygiene

In recent years medical researchers have identified relationships between poor oral hygiene and a number of health conditions.

Among the more significant:

• cardiovascular disease
• diabetes
• respiratory conditions
• dementia
• obesity

The importance of dental hygiene — a window onto your overall health goes through the same three headline associations in more detail, and dental health and general wellbeing takes the broader view.

The honest state of the evidence

The greatest depth of research has been into the relationship between periodontal disease and diabetes.

Other areas require more research to identify causative links.

That distinction is worth stating plainly, and it is often glossed over: an association between two things is not the same as one causing the other. For gum disease and diabetes the evidence is strong and two-directional. For the others, the picture is less settled.

Why associations are easy to over-read. People with untreated gum disease are more likely to smoke, to have poorer access to healthcare, to have lower incomes and to have other untreated conditions. All of those independently raise the risk of heart disease and dementia. Untangling which factor is doing the work is genuinely hard, and studies that adjust carefully tend to find weaker relationships than headlines suggest.

A useful way to hold it:

Only the diabetes row carries strong evidence in both directions. For everything else, take your gums seriously because you want to keep your teeth — that reason is sufficient, and it is certain.

The aspiration pneumonia row, in full, because we previously graded it as strong and that was wrong. The association is not in doubt: poor oral hygiene in dependent older people, particularly in residential aged care, goes with aspiration pneumonia, and the mechanism — oral bacteria inhaled into the lungs — is plausible. What is uncertain is whether improving mouth care prevents it. The current systematic review is Oral care measures for preventing nursing home-acquired pneumonia (Cochrane Database of Systematic Reviews 2022, Issue 11, CD012416), covering six randomised trials in 6,244 nursing home residents in Japan, the United States and France. On whether residents get pneumonia at all, five trials in 5,018 residents gave "insufficient evidence of a difference" between professional oral care and ordinary self-administered care — low-certainty evidence, downgraded two levels for risk of bias and imprecision. On dying of pneumonia, two trials in 454 residents found professional oral care may reduce pneumonia-associated mortality at 24 months, risk ratio 0.43 (95% CI 0.25 to 0.76), about 71 deaths per 1,000 instead of 165 — also low certainty, and one of those two trials lost 38 per cent of participants to follow-up on that outcome. All six trials were at high risk of bias, none was Australian, and no trial has ever compared oral care with no oral care. The review's own conclusion: "the effect of professional oral care on preventing NHAP remains largely unclear". Daily mouth care for a dependent older person is still absolutely worth doing — for pain, infection, tooth loss and the ability to eat — but it should not be sold as pneumonia prevention.

On the pregnancy row, the Australian Dental Association's survey of 25,000 Australian adults found that 75% of women did not have a dental check-up before conception, which it describes as important because "poor oral health in pregnant mothers is associated with poorer pregnancy outcomes like low birthweight babies". Note the word associated — that is the ADA's own framing, and it is the right one. See oral health care while pregnant and is it safe to visit the dentist during pregnancy?; on the diet row, how does your diet affect your teeth? and how does sugar affect your dental health?

What gum disease actually is

An infection of the gums. What is gum disease? and periodontal (gum) disease

It occurs when bacteria are left on the teeth for too long, resulting in inflammation of the gums. The bacteria are organised into plaque, a biofilm — which is why only mechanical disruption removes it, and why rinses, oils and mouthwashes act on what brushing and interdental cleaning leave behind rather than replacing them. The truth and myths about mouthwashes and can oil pulling make my mouth healthier and my teeth whiter?

That inflammation then spreads to the bone supporting the teeth, and causes that bone to dissolve.

If left untreated, teeth become loose and fall out. The replacements — implants, bridges, dentures — are all more involved and more expensive than the prevention would have been. What are the replacement options for missing teeth?

The bone loss is the part that cannot be reversed. Inflamed gums recover; dissolved bone does not grow back. Diabetes Australia says the same thing about periodontitis in its own material: it is a chronic disease requiring life-long care and professional treatment, and the recession of gum and bone it causes is irreversible.

And the defining problem: it does not hurt. Decay announces itself; gum disease does not. By the time a tooth is loose, the supporting bone has already gone. Diabetes Australia puts the warning in almost the same words — these diseases are often painless, and pain tends to arrive only with advanced disease or a sudden flare-up, by which point it may be too late for treatment to save the tooth.

'My gums bleed when I brush' is a symptom, not a normal event. Healthy gums do not bleed. Most people assume they are brushing too hard — usually the opposite is true, and the area bleeds because it has not been cleaned. Brushing harder is its own problem, and a different one: over brushing: what can it do to my teeth? and how much pressure should I apply when brushing my teeth?

Warning signs: bleeding gums, gums that have receded or teeth that look longer, persistent bad breath, loose teeth, teeth that have drifted, or new gaps appearing — the same list Diabetes Australia publishes, which also names sensitive teeth and food becoming stuck in newly opened spaces. Bleeding gums, what causes bad breath and how can I fix it? and why do teeth shift?

How it reaches the rest of the body

Bacteria accumulating on the teeth can travel via the bloodstream to other areas of the body, including the heart and the brain.

The immune system responds by producing immune cells and inflammation at that site — which in turn affects the whole body.

Bacteria can also enter the airways, affecting the respiratory tract.

A sense of scale helps here. In advanced periodontitis the ulcerated surface area inside the pockets around the teeth is substantial — a continuous, inflamed interface between a bacterial population and the bloodstream, present every day for years. That is the plausible mechanism, and it is why the associations exist even where causation is unproven.

The clearest single case of mouth bacteria causing trouble elsewhere is an untreated infection rather than gum disease: can a dental abscess affect your general health? and what is a tooth abscess? Should I have it treated?

The one to act on: diabetes

It runs in both directions. Poorly controlled diabetes worsens gum disease, and gum disease makes glycaemic control harder. Diabetes and oral health and diabetes and dental health: the two-way street that most people don't know about

The numbers give a sense of the size of it. Preshaw and colleagues, reviewing the relationship, put the risk of periodontitis at approximately threefold in people with diabetes compared with people without. In the US NHANES III survey, adults with an HbA1c above 9% had a significantly higher prevalence of severe periodontitis — OR 2.90, 95% CI 1.40–6.03 — after adjustment for age, ethnicity, education, sex and smoking. Glycaemic control is what drives that: Diabetes Australia states that with optimum blood glucose management, the risk of developing periodontitis is the same as for a person without diabetes.

The return leg is real but modest, and worth stating accurately rather than enthusiastically. The Preshaw review reports HbA1c reductions of approximately 0.4% following periodontal treatment. Diabetes Australia is more cautious still: the improvement in blood glucose it describes is mild, and the documented effect lasted about three months, with longer-term studies ongoing.

So:

• If you have diabetes, tell your dental team, and say how well controlled it is.
• If you have gum disease that is not responding as expected, it is worth asking your GP about diabetes screening. Dentists do sometimes find undiagnosed diabetes this way.
• Treating the gum disease is part of managing the diabetes, not a separate concern — but treat it primarily to keep your teeth. When do you need deeper cleaning?

Looking after your oral hygiene

Your hygienist removes the plaque and calculus that act as a reservoir of bacteria. That is the part you cannot do at home — hardened calculus does not come off with a toothbrush. Dental cleans and hygienists, what does a dental hygienist do? and your Smile Solutions dental hygienist visit: what to expect

With regular hygiene treatment, plus brushing twice daily and flossing once daily, gum disease can be prevented or at least controlled — and the risk of the other conditions lessened. Twice daily for two minutes is the standard; more is not better. What is the ideal daily routine for oral hygiene?, how often should I brush my teeth? and is flossing really that important?

Some refinements:

• Where the spaces between teeth admit them, interdental brushes have better evidence than floss — and the right size is specific to you. Ask to be shown. Diabetes Australia gives the same advice in the same terms: ask your dentist whether interdental brushes suit you, alongside or instead of floss. Note the limit either way: floss reaches about 3mm below the gum margin, and a pocket of 5mm or more is periodontitis, which needs professional treatment rather than better technique.
• Spit, don't rinse after brushing, and wait about an hour after anything acidic before you brush. The benefits of fluoride and brushing your teeth: before or after breakfast?
• A soft brush at 45 degrees into the gum line, small movements, not scrubbing. Which toothbrushes do dentists recommend? and how to care for your toothbrush
• Ask for your pocket-depth numbers. They are the objective record of whether treatment is working.

Beyond the routine

Other ways to lower your risk:

• avoid smoking
• avoid overconsumption of alcohol — what impact does wine have on my teeth?
• eat a healthy, well-balanced diet — six foods to avoid for healthy teeth
• drink enough water — fluoridated tap water where it is available, which Diabetes Australia calls "the safest and most effective way to reduce tooth decay"
• avoid foods and drinks high in sugar — are sugar free soft drinks better for my teeth than regular soft drinks?

Smoking is the one with the largest single effect on gum disease, and the one where stopping produces the clearest improvement. The Preshaw review names smoking as a major risk factor for periodontitis in its own right, independent of diabetes. The effects of vaping on your oral health and are e-cigarettes bad for my teeth?

And a trap worth knowing: smoking hides the disease. Nicotine constricts blood vessels, so smokers' gums bleed less while the disease progresses faster. Periodontitis in a smoker is routinely more advanced than it looks. Quitline is 13 7848.

Two more risk factors that are not about hygiene at all:

• Genetics. Some people are considerably more susceptible, and a family history of early tooth loss is meaningful.
• Dry mouth from medication. Hundreds of common drugs reduce saliva, which accelerates both decay and gum problems. Bring your medication list to appointments; do not stop anything on your own. My mouth is always dry: why is this and does it affect my teeth? and my mouth always feels dry! What can I do?

Where to draw the line on claims

Because this subject attracts overstatement:

• No dental treatment prevents heart attacks, and nobody can honestly promise it will.
• Treating gum disease will not cure a systemic condition. Even in diabetes, where the evidence is strongest, the measured effect on HbA1c is fractions of a percentage point and short-lived.
• Nor does mouth care in aged care come with a guarantee against pneumonia, however often that is repeated — the trial evidence is low-certainty, as set out above.
• 'Focal infection' claims — that root-filled teeth cause systemic disease and should be extracted to treat it — have been examined repeatedly and are not supported by evidence. Extracting sound root-filled teeth on that basis causes harm. Everything you need to know about root canal treatment, root canal and what is holistic dentistry?

What is true is narrower and still worth a great deal: gum disease is common, largely preventable, painless until late, and the leading cause of adult tooth loss.

Related pages: Bleeding Gums, Dental Cleans and Hygienists, Specialist Periodontists, Bad Breath.

Common questions

Does poor oral hygiene cause mouth cancer?

Not as a primary cause, and it is worth being precise rather than frightening about this — the condition is serious enough not to need exaggeration.

The dominant risk factors are elsewhere. A 2023 review in the Royal Australian College of General Practitioners' journal lists oral cancer as linked with "age >45 years (especially men), tobacco use, alcohol consumption, areca (betel) nut chewing and limited access to dental care". Hygiene itself is not on that list; access to care is. The same review notes an emerging group that fits none of the classic risk factors — non-smoking, non-drinking middle-aged women with tongue cancers.

What makes attendance matter is timing rather than brushing. Oral cancer "has a relatively low five-year survival rate, at around 50%, mostly due to diagnostic delays", and the review's explanation of why delays happen is the uncomfortable part: the people most at risk "tend to have irregular dental attendance". A routine examination is where an early lesion is most likely to be seen, because early ones do not hurt — the review states that "initial lesions of oral cancer are generally painless".

The threshold for having something looked at is specific: any unexplained or non-healing change lasting more than two to three weeks — a persistent ulcer, a red or white patch, a lump, a sore throat, an unexplained loose tooth or a socket that has not healed. See oral cancer: how your dentist can help with early detection.

Is the aspiration pneumonia link strong evidence or not?

The association is solid; the proof that mouth care prevents it is not. This page used to grade that row as strong, and on checking the source we could not stand behind it.

The 2022 Cochrane review, six trials in 6,244 nursing home residents, found "insufficient evidence of a difference" in whether residents developed pneumonia at all — low-certainty evidence. The one positive finding is narrower: from two trials totalling 454 residents, professional oral care may reduce deaths from pneumonia at 24 months, risk ratio 0.43 (95% CI 0.25 to 0.76) — also low certainty, with 38 per cent attrition in one of the two trials. Every included trial was at high risk of bias, none was Australian, and none compared mouth care against no mouth care at all. The review's conclusion is that the effect on preventing pneumonia "remains largely unclear".

So the practical position is unchanged and the wording is not: assist someone who cannot clean their own mouth, because a neglected mouth causes pain, infection, tooth loss and an inability to eat, and those consequences are certain. Expect a possible benefit for pneumonia; do not rely on one.

I have smoked for decades. Is the damage already done?

No — and this is one of the few places in dentistry where the evidence is unambiguously encouraging.

The Australian Dental Association's consumer position is that "quitting smoking can improve your oral health significantly even after smoking for a long time". That is stated without qualification about how long you have smoked.

It is worth knowing what smoking is doing in the meantime, because the mechanisms are separate and each one is reversible to a different degree. The ADA lists that smoking can stain teeth, cause bad breath, affect taste, cause sores in the mouth to heal slowly, change "the type and amount of saliva your body makes", and raise the risk of both severe gum disease and oral cancer — concluding flatly that "smokers are more likely to lose their teeth than non-smokers". On saliva it makes a point that is easy to miss: teeth are less protected "if you have a lack of saliva or saliva that is thick and frothy instead of thin and runny".

One timing note if you are having a tooth out: the ADA advises not smoking "for as long as possible after getting a tooth removed to decrease your risk of developing a dry socket". Quitline is 13 7848.

Does drinking tap water still help me as an adult, or is that only for children?

It helps adults too, by a smaller margin. The National Health and Medical Research Council's assessment is that water fluoridation reduces tooth decay by 26 to 44% in children and adolescents, and by about 27% in adults. Australian research it cites also suggests that access to fluoridated water from an early age is associated with less decay later in adult life.

That is a population-level effect rather than a promise about one mouth, and it does not replace anything else on this page. But it is a reason to make tap water the default drink rather than bottled or sweetened alternatives — and unlike almost everything else in this article, it costs nothing and requires no appointment.

How often should I actually be having a hygiene appointment?

There is no single correct interval, and any page that gives you one is guessing about you.

Diabetes Australia's wording is the honest version: see a dentist regularly for a check of teeth and gums, and "the dentist will advise you how often to return for check-ups and treatment. This may be more often if you have any of the above complications". The interval is a clinical judgement based on your risk — your pocket depths, your bleeding scores, whether you smoke, whether you have diabetes, how dry your mouth is, and what has changed since last time.

Which makes it a fair thing to ask about directly: why this interval for me, and what would have to change for it to become longer or shorter? A recall period that has never been reviewed is a scheduling habit rather than a decision.

I have not been to a dentist in years. What happens at the first appointment?

Mostly looking and measuring, rather than treatment. The RACGP review describes an oral cancer examination as a "comprehensive oral cavity examination with readily available equipment, including gloves, a mouth mirror" and a tongue depressor — that is the level of technology involved in the part that matters most. Gum assessment adds a graduated probe to measure pocket depths around each tooth, and usually radiographs, because bone levels and decay between teeth cannot be seen by looking.

On cost, the thing to know before you go is that dental fees in Australia are not set by any schedule. The Australian Dental Association's Dental Fees Survey 2022 found "considerable variation in the fees charged within and between states" across the 122 items it surveys, and a consumer submission to the 2017 Senate inquiry into private health insurance complained that patients "can go to multiple dentists and receive conflicting diagnoses and widely varying quotes". So ask for the plan in writing, itemised, and ask what is urgent versus what can be staged over time. Published fees for this practice are in the price guide.

The part nobody says out loud: a long gap is common and it is not what a dental team finds remarkable. The RACGP's own observation is that irregular attendance clusters among the people most at risk — which is an argument for going, not for waiting until the mouth is in better shape first.

Related reading

• 3 oral hygiene tips you need to know
• How good oral hygiene can increase your lifespan
• Dental hygienist vs dentist
• Why would I need to see a dental specialist? and specialist care
• How often should I go to the dentist?
• Price guide

Practical details

Written by Belinda Smithwick, Dental Hygienist at Smile Solutions. Registration DEN0002159598, verifiable free on the AHPRA public register at ahpra.gov.au. The clinical team is listed by name.

We have registered specialist periodontists on site for cases beyond routine hygiene treatment — registered specialists.

Smile Solutions, Level 1, 220 Collins Street, Manchester Unity Building, Melbourne VIC 3000 — getting here. Phone 13 13 96, contact us, or theteam@smilesolutions.com.au. Monday–Friday 8.00am–6.00pm, Saturday 8.30am–1.30pm, Sunday by appointment.

Published 22 February 2018. The evidence base described continues to develop. General information only — it is not a diagnosis or a treatment plan, and it does not replace advice from your treating practitioner or doctor. No medication should be started or stopped on the basis of this page.

Smile Solutions trades under ABN 28 193 514 103.