Diabetes and oral health

Many people know diabetes raises the risk of heart disease and heart attack, stroke, vision loss, infections, loss of sensation, gangrene and lower limb loss.

Fewer know the implications for dental and oral health. They are as follows.

This is the one link between mouth and body where the evidence runs firmly in both directions — diabetes and dental health: the two-way street sets out the mechanisms and the treatment studies in detail.

1. Periodontal disease (gum and jawbone disease)

Unchecked, this causes loosening, drifting and loss of teeth, along with gum shrinkage, recession and sometimes painful infections. The gums are often swollen and bleed easily — bleeding gums is the sign most people notice first.

An important distinction: periodontal disease is not caused by diabetes. Its causes are bacterial plaque and calculus (calcified plaque), and our immune system’s response to bacterial components. What is gum disease? and periodontal (gum) disease explain the disease itself.

What diabetes does — when poorly controlled — is act as a major risk factor, making the disease:

How much more likely? Preshaw and colleagues, reviewing the two-way relationship in a paper available through PubMed Central, put the risk of periodontitis at approximately threefold in people with diabetes compared with people without it. Glycaemic control is what drives that figure: in the US NHANES III survey, adults with an HbA1c above 9% had a significantly higher prevalence of severe periodontitis than people without diabetes — OR 2.90; 95% CI 1.40–6.03 — after controlling for age, ethnicity, education, sex and smoking.

Diabetes Australia states the encouraging half of the same finding: with optimum blood glucose management, the risk of developing periodontitis is the same as for a person without diabetes. It gives the recommended blood glucose range as 4–7 mmol/L. That is the sentence worth taking away from this page.

The awkward part: Diabetes Australia also describes periodontitis as a chronic disease requiring life-long care and professional treatment, and is explicit that the recession of gum and bone it causes is irreversible. Control is achievable. Undoing damage already done is largely not.

That distinction between cause and risk factor is worth holding onto, because it is where most popular writing on this subject goes wrong. Treatment is the same disease-control work it is for anyone — when do you need deeper cleaning?, dental cleans with our hygienists and, in advanced cases, a periodontist — but the margin for error is smaller and the recall intervals shorter.

What it is reasonable to look for between visits

Diabetes Australia lists the signs of periodontal disease as bleeding gums, bad breath, sensitive teeth, loose teeth, gum recession (or longer-looking teeth), and gaps opening up between the teeth where food then becomes stuck.

And then the warning that matters most. It points out that people assume they are in the clear because nothing hurts — but these diseases are often painless, and pain tends to arrive only with advanced disease or a sudden flare-up, by which stage it may be too late for treatment to save the tooth. Absence of pain is not evidence of health here. It is the ordinary state of the disease until late.

2. Bacterial tooth decay

A significant proportion of people with diabetes have reduced saliva flow, which is a major risk factor for decay — the soft, invasive kind that chiefly affects areas where teeth touch, and root surfaces, where there is no hard enamel covering. My mouth is always dry — why is this, and does it affect my teeth? and my mouth always feels dry! What can I do? cover what can be done about it.

Diabetes Australia adds a detail worth knowing if you are deciding whether this applies to you: reduced saliva production is more common in people who have diabetes complications, and in particular diabetic neuropathy. If you have neuropathy, treat dry mouth as a live risk and say so at your next appointment. Chewing sugar-free gum is one of the measures it lists for stimulating saliva flow — does chewing sugar-free gum really help prevent cavities? covers what that can and cannot do.

The two problems compound: gum recession from periodontal disease is itself a risk factor for root-surface decay, exposing surfaces that would otherwise be sealed away from bacteria by gum, bone and connective tissue. Root surfaces have no enamel, so they decay faster and at a higher pH than crowns do — how does tooth decay develop? and the stages of dental decay.

The glucose mechanism

When blood glucose is high, there is a corresponding increase in glucose in the saliva.

Glucose encourages bacterial plaque growth, and is broken down by plaque organisms into lactic acid — the acid that produces cavities. Sugar: what does it do to your teeth? explains that pathway, and the rule that goes with it: how often sugar reaches the teeth matters more than how much.

So inadequately controlled diabetes does not just weaken the defences; it feeds the bacteria directly.

The preventive response is the ordinary one, done properly: the ideal daily routine for oral hygiene, flossing, fluoride — often at high concentration where root surfaces are exposed — the right toothpaste, and keeping sugar and acid to mealtimes. On fluoridated tap water, Diabetes Australia is unusually direct for a diabetes organisation: it calls water fluoridation "the safest and most effective way to reduce tooth decay", and cites reductions of 26% to 44% in children and adolescents, and 27% in adults. Can you reverse tooth decay? explains the narrow window in which early damage can still be undone; past it, the answer is a filling.

Diabetes Australia also suggests asking your dentist whether interdental brushes suit you — small bristled brushes for the spaces between teeth — alongside or instead of floss. That is a question for someone who has looked at your mouth, not a general recommendation.

3. Oral thrush

Thrush is an infection by Candida albicans, a fungus. Most people carry it harmlessly, but it is opportunistic — multiplying harmfully when conditions encourage it, and diabetes is one of those conditions.

As well as affecting skin, nails and genitalia, in the mouth it causes:

Diabetes Australia describes the same infection as creamy white patches, often on the tongue or inside the cheeks, and attributes its occurrence in diabetes to three things at once: less saliva being produced, more glucose in the saliva for Candida to live and grow on, and a weakened immune system. The mechanism, in other words, is the same glucose-in-saliva pathway that drives the decay.

Where the palatal tissue becomes thin and fragile, it may over-grow, creating hygiene problems and difficulties with removable dentures.

Until treated successfully, the infection can complicate, delay or prevent oral surgical procedures such as implants to replace missing teeth — which is why it is dealt with before, not during, treatment planning. What are the replacement options for missing teeth? sets out the alternatives.

One caution that applies to any persistent patch in the mouth, thrush or otherwise: an ulcer, lump, or red or white patch that has not healed within two weeks should be examined. See oral cancer: signs, risk factors and how your dentist can help and the cause of mouth ulcers and their usual treatments.

4. Impaired healing

Accidental or surgical wounds, including those from oral surgery, often heal more slowly in people with diabetes, and may be more likely to become infected.

This is understood to be due to:

Diabetes Australia gives the same two causes — changes in blood flow, and a weakened immune system — and names mouth ulcers specifically among the wounds in the mouth that are slow to heal.

It is one of the reasons wisdom teeth removal and other procedures under an oral and maxillofacial surgeon are planned differently for diabetic patients, and why implant timelines are sometimes longer.

5. Resilience to dental procedures

This is the practical constraint patients least expect.

Some dental conditions and procedures interfere with your usual eating schedule, which makes stable blood glucose harder to maintain.

Some procedures are physiologically or emotionally stressful, and stress releases adrenal hormones that counteract the regulatory effect of insulin. If dental anxiety is part of the picture, it is worth raising in advance rather than on the day — how can I ease my anxiety about visiting the dentist? and dental anxiety.

Consequently:

That coordination is not bureaucracy — it is what makes the procedure safe. Understanding your treatment explains how a plan is put together, and why would I need to see a dental specialist? covers when specialist input is involved.

6. Altered taste

This one is rarely mentioned and is worth naming, because people tend to assume it is unrelated to the mouth’s health. Diabetes Australia lists altered taste among the oral complications of diabetes: the ability to taste food and drink can be affected.

It is candid that the reason is not settled. The underlying cause is not clear; it may be that taste receptors in the mouth renew more slowly, or it may be associated with diabetic neuropathies.

We have no more to add than that, and will not pretend otherwise. What matters practically is the second-order effect: when food tastes of less, sweeter and stronger-tasting food tends to get chosen, which feeds straight back into the decay risk above. If your sense of taste has changed, mention it — to your dentist and to whoever manages your diabetes.

After a hypo: what it does to your teeth

Treating hypoglycaemia means getting fast-acting carbohydrate in quickly — which, from the teeth’s point of view, is a sugar and acid exposure at a moment when nobody is thinking about teeth. That is unavoidable, and treating the hypo comes first, always.

Diabetes Australia’s practical advice for afterwards is simple. The fast-acting options it names are jellybeans, soft drink, fruit juice or sugar taken directly. Once you feel well again, drink water to rinse the sugar and acid off the teeth — and if you want to brush, wait 60 minutes before you do.

The waiting is not fussiness. Brushing enamel that has just been acid-softened removes more of it — the same reason the general advice about acidic food and drink runs the way it does. See what is acid wear and how can I avoid it?, how does acidic food affect your teeth? and should I brush my teeth before or after breakfast?.

If hypos are frequent, that is a conversation for your diabetes team rather than your dentist — but tell your dentist they are happening, because it changes how your decay risk is assessed.

The gap in the standard diabetes checklist

Worth knowing, because it explains why nobody may ever have raised any of this with you.

Diabetes Victoria points out that dental visits are not formally included in the Annual Cycle of Care for diabetes in Australia. That cycle typically covers blood pressure, HbA1c, cholesterol, kidney function, podiatry and eye examinations — oral health is missing from the checklist. Diabetes Victoria has added periodic dental checks to its own downloadable checklist, and notes that advocacy groups and health professionals have long argued for dental care to be included in chronic disease management plans.

So the dental side of diabetes is not something your diabetes team is prompted to ask about. Until that changes, raising it is largely up to you.

The common thread

For every oral health aspect of diabetes described here, severity and prevalence are reduced when the diabetes is well controlled, with demonstrably stable blood glucose levels.

Good glycaemic control is the single measure that improves all of them at once. Smoking works in the opposite direction on every one of them — the Preshaw review names smoking as a major risk factor for periodontitis in its own right, and Diabetes Australia asks that you tell your dentist if you are a current or previous smoker. On the vaping question, are e-cigarettes bad for my teeth? sets out what is known and what is not yet.

What about the traffic in the other direction — does treating the gums help the diabetes? Honestly: a little, and not for long, on the evidence as it stands. The Preshaw review reports HbA1c reductions of approximately 0.4% following treatment of periodontitis. Diabetes Australia is more cautious still: professional periodontal treatment has been shown to produce a mild improvement in blood glucose levels, but the documented improvement lasted only about three months, with longer-term studies ongoing. Treat your gums because losing teeth is bad; any glycaemic dividend is a bonus, not the plan.

Common questions

I have pre-diabetes, not diabetes. Does any of this apply yet?

Some of it, and the honest answer is that the evidence running in that direction is weaker than the evidence running the other way.

Diabetes Australia states it broadly: “people with periodontitis exhibit a higher chance of developing prediabetes and diabetes,” and that those with periodontitis have poorer glycaemic status — a higher HbA1c — than people without it.

The underlying research is more equivocal, and worth seeing in full rather than in summary. The Preshaw review describes a seven-year prospective study of 5,848 people aged 30 to 59 who did not have diabetes, which assessed whether periodontitis predicted new cases. In the unadjusted analysis, both moderate periodontitis (pockets of 3.5–5.5 mm) and severe periodontitis (pockets over 5.5 mm) were significantly associated with an increased risk of developing diabetes. But that significance was lost once the researchers adjusted for sex, smoking, BMI, triacylglycerol, hypertension, HDL-cholesterol and gamma-glutamyl transpeptidase.

Which is the interesting part, not a reason to dismiss it. Those adjustment variables — weight, smoking, blood pressure, lipids — are the same things that raise the risk of both conditions. The association may be real and shared rather than causal, and the study cannot separate the two.

So the fair statement is this. Gum disease is not established as a cause of diabetes. It does travel with the same risk profile, and it is the one item in that cluster that a dentist can measure at a routine appointment. If you have been told you have pre-diabetes, that is a good reason to have your gums charted properly — pocket depths recorded, not a glance — and to treat what is found. You would be doing that anyway; this simply moves it up the list.

My gums have already receded and I have lost some bone. Can any of it come back?

No, and it is better to know that plainly than to spend money finding out.

Diabetes Australia is explicit: the changes periodontitis causes — the gum and bone receding away from the tooth — are irreversible, and it describes periodontitis as a chronic disease requiring life-long care and professional treatment. What treatment does is stop the loss and hold the position, not rebuild what has gone. A dentist or periodontist can check for signs of the disease and treat it, and severe untreated disease ends with teeth becoming loose, painful and eventually lost.

Two things follow, and they are more useful than the disappointment.

The first is genuinely good news. Diabetes Australia's own finding is that with optimum blood glucose management, the risk of developing periodontitis is the same as for a person without diabetes — with the recommended blood glucose range given as 4–7 mmol/L. The risk is not a permanent surcharge attached to the diagnosis. It tracks control.

The second is that the exposed root changes your everyday care. A receded gum leaves root surface uncovered, and root surface has no enamel. As the decay section above sets out, it decays faster and at a higher pH than the crown of the tooth does — so the risk simply moves from gum disease to root caries. That is the reason for the things that get recommended at this point and can sound like upselling: higher-concentration fluoride, interdental brushes sized to the spaces that have opened up, shorter recall intervals, and keeping sugar and acid to mealtimes. Each of them targets a surface that was sealed away before and is not any more.

Ask for your pocket depths to be recorded and to be told the numbers, so that next year's reading means something. Stable is the goal, and stable is achievable. See when do you need deeper cleaning? and periodontists.

Does treating my gums actually reduce my risk of the other diabetes complications?

Possibly, by a small amount, and the arithmetic is worth doing openly rather than being gestured at.

The chain of reasoning runs through HbA1c. The Preshaw review cites the well-known finding that each 1% reduction in HbA1c has been associated with risk reductions of 21% for any endpoint related to diabetes, 21% for deaths related to diabetes, 14% for myocardial infarction and 37% for microvascular complications. Those are substantial numbers, and they are the reason lowering HbA1c matters at all.

Now put the gum treatment beside them. The same review reports HbA1c reductions of approximately 0.4% following effective periodontal therapy — less than half of one percentage point. So even taking the association at face value and assuming it scales, the expected benefit is proportionally smaller than those headline figures, not equal to them. Diabetes Australia is more cautious again, describing the improvement as mild and documented for only about three months.

The review's own conclusion is appropriately hedged. It states that “evidence suggests that resolution of periodontal inflammation can improve metabolic control (with reported HbA1c reductions of approximately 0.4%), though large, multi-centre, randomised controlled trials are needed to further validate these findings.” It also notes that the mechanism is not clear, though it probably relates to reduced systemic inflammation.

So the fair summary: treating periodontitis may contribute something to complication risk, and the size of that contribution is uncertain and probably modest. The strong reason to treat it is the local one — that severe gum disease costs teeth, and the damage does not come back. Any metabolic benefit is a second reason, not the case.

One genuinely useful side effect of the same literature, though. It reports that people with diabetes who managed their gum inflammation successfully tended to report better glycaemic control and had lower mean HbA1c than those who did not, and links this to self-efficacy — the confidence to manage one's own condition. Brushing, flossing and glucose management draw on the same habits. Getting one of them working well tends to help the other.

Further information

Related reading

Practical details

Written by Dr Peter Henderson, Smile Solutions.

Tell your dental team about your diabetes, your current medications, and your most recent HbA1c — all three affect treatment planning. Diabetes Australia puts the same request more broadly: make sure your dentist knows the names of all prescribed and over-the-counter tablets and medicines you take, and whether you are a current or past smoker. The clinical team is listed by name, and fee ranges are in the price guide.

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 11 March 2014. Study figures in the questions above are from the review Periodontitis and diabetes: a two-way relationship (Preshaw et al.) and the studies it cites, and describe those study populations rather than any individual's risk; consumer statements are attributed to Diabetes Australia and Diabetes Victoria. General information only; it does not replace advice from your treating practitioner, GP or endocrinologist.

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