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What HbA1c Actually Tells You About Your Periodontal Patients

9/14/2026 12:27:00 AM   |   Comments: 0   |   Views: 84



The relationship between periodontitis and diabetes runs in both directions. Patients with diabetes have roughly a 24% higher incidence of periodontal disease. Patients with periodontitis carry about a 26% higher relative risk of developing diabetes. HbA1c is the number connecting the two, and a meaningful share of the patients in your chair have an elevated one they know nothing about.


That last part is worth sitting with, because it changes what a periodontal exam is capable of catching.

The bidirectional evidence is unusually good

Plenty of claimed oral-systemic links rest on thinner ground than their advocates suggest. This one doesn't.


A meta-analysis of cohort studies found a 24% increased incidence of periodontal disease among patients with diabetes, and a 26% increased relative risk of developing diabetes among patients with periodontitis. The joint EFP and AAP review put the hazard ratio for developing type 2 diabetes in periodontitis patients somewhere between 1.19 and 1.33.


The mechanism holds up in both directions. Hyperglycemia drives advanced glycation end-product accumulation, impairs neutrophil function, and alters collagen metabolism, all of which worsen periodontal breakdown and slow healing. Running the other way, periodontitis produces chronic overexpression of IL-1ß, IL-6 and TNF-a. Those trigger hepatic acute-phase reactants, suppress pancreatic insulin production, and feed indirectly into insulin resistance.


Duration matters too. Cross-sectional data show attachment loss is greater and periodontal disease worse once diabetes duration passes five years, in both type 1 and type 2.


None of this is news to most periodontists. What has changed is the practical question of what to do about it on a Tuesday afternoon.

What the number actually represents

HbA1c reflects the percentage of hemoglobin that has become glycated, which tracks average blood glucose across roughly the preceding two to three months. That's the lifespan of a red blood cell.


It is not a snapshot. A patient who ate carefully the morning of their appointment has not moved their HbA1c by a decimal point, which is worth mentioning to the ones who think they have.


The standard bands:

HbA1c

Interpretation

Below 5.7%

Normal

5.7% to 6.4%

Prediabetes

6.5% or above

Diabetes, on confirmed repeat testing

Below 7%

Common glycemic target for many adults with diabetes



For periodontal purposes the practical threshold sits lower than most clinicians assume. Yes, patients above 9% show clearly higher periodontitis prevalence than non-diabetics. But periodontal risk starts climbing well before that, and the prediabetic range is not a safe zone.


One caution worth carrying into every interpretation: HbA1c gets unreliable in anything that alters red cell lifespan. Hemoglobinopathies, recent transfusion, iron deficiency anemia, advanced chronic kidney disease. If the number doesn't fit the clinical picture in front of you, question it rather than accept it.

The undiagnosed patient already in your chair

This is where the dental setting stops being merely interested in diabetes and starts being useful.


In a study of patients attending a periodontology clinic who met CDC screening criteria, 27.5% turned out to have previously unknown hyperglycemia at HbA1c of 5.7% or above. In a separate group, 40.7% of dental patients under 45 with no diabetes diagnosis had HbA1c around 5.7% or higher.



Read that second figure again with the age in mind. Under 45. That's a group that often has no regular physician, hasn't had bloodwork in years, and sees a hygienist more reliably than any other clinician. For a real slice of the population, the dental operatory is the most consistent point of medical contact they have.


The EFP and AAP guidance follows directly. Patients with periodontitis warrant screening consideration for diabetes. Every newly confirmed diabetic patient should be told their periodontal risk is elevated and that glycemic control gets harder in the presence of periodontitis. Every initial exam should include periodontal evaluation.

Does treating the perio actually move the HbA1c?

Here the evidence deserves a more careful reading than it usually gets, and overselling it does nobody any favors.


The direction of effect is consistent. The size of it is modest, and how long it lasts is genuinely unsettled.

Across the major meta-analyses, non-surgical periodontal therapy produces an HbA1c reduction somewhere around 0.27% to 0.48% at three to four months compared with no treatment. The most-cited figure, from Engebretson and Kocher, is 0.36% (95% CI 0.19 to 0.54) at three months. A more recent meta-analysis reported 0.64% at three months and 0.33% at six.


Now the caveats, and they're real:

  • One meta-analysis found the six-month effect was not statistically significant (0.30%, p = 0.13).

  • In another, studies with adequate sample size showed a change of 0.014%. Effectively nothing. The pooled figure across all studies in that same analysis was 0.27%.

  • A systematic review of systematic reviews concluded there is a significant effect on HbA1c, "although the effect size is extremely small," with mean differences across 13 meta-analyses ranging from 0.93 down to a positive 0.13.

  • Adjunctive systemic antibiotics and laser therapy added no statistically significant glycemic benefit over non-surgical therapy alone.

So what's the defensible position?

A reduction of 0.3% to 0.4% is not nothing in diabetes terms. UKPDS data indicate every 1% reduction in mean HbA1c corresponds to roughly a 21% reduction in risk of any diabetes-related endpoint. On that scale, 0.4% is a real contribution, in the range of what some adjunctive drug interventions manage.


But a contribution is not a treatment. Periodontal therapy is not diabetes management, and framing it that way to a patient or a physician colleague costs you credibility the underlying evidence never required you to spend. The honest version is that treating periodontitis appears to modestly improve short-term glycemic control, on top of the periodontal benefits that justify the treatment on their own.

That version survives a skeptical endocrinologist. The oversold one doesn't.

Chairside screening, and the questions that actually stop people

Point-of-care HbA1c testing in the dental setting is technically simple and reasonably well studied. Chairside aMMP-8 oral rinse immunotests have also been looked at as a cheaper screening adjunct, using periodontal inflammation itself as the flag for further glycemic testing.


The barriers are almost never technical. They're these:


Scope and licensure. What counts as permissible screening varies by state and by license type. Confirm it locally before you implement anything, especially for hygienist-performed testing.


Where does the result go? A screening program with no defined route into primary care generates anxiety and resolves nothing. The value sits in the handoff, not in the number.

How you frame it. Screening is not diagnosis. A chairside HbA1c of 6.8% means this needs medical follow-up. It does not mean you have diabetes. The diagnosis isn't yours to make, and being clear on that protects the patient and the practice both.


Documentation. Record the value, the advice you gave, and the referral you made.


If you're not ready to implement testing, there's a version that costs nothing. Ask every periodontitis patient whether they've had bloodwork in the past year, and refer the ones who haven't. That alone catches a good share of the same population.

Talking to patients about the number

A percentage is an abstraction. Tell most patients their HbA1c is 7.4% and you'll get a nod that means nothing.


Converting it to estimated average glucose tends to land better, because it maps onto numbers they already recognize from finger-stick readings. An HbA1c of 7% works out to an eAG of roughly 154 mg/dL. An 8% is about 183 mg/dL. Patients who check their glucose daily but have never connected those readings to their quarterly lab value often find that translation genuinely useful.


HealthCalculator has a free A1C calculator that converts an HbA1c percentage into estimated average glucose, which is handy when you're explaining a lab value at the chair.


There's also decent evidence the conversation itself does something. In one study of adults with diabetes, participants who understood the effect of periodontal disease on diabetes were about three times more likely to have an HbA1c below 7% than those who didn't. Daily flossers were roughly six times more likely. You can argue about causality in observational data like that, and you should. But the association fits the mechanism and acting on it costs you nothing.

Working with the medical side

The most common failure in this whole area is parallel care with zero communication. The physician manages the diabetes. You manage the periodontitis. Neither of you knows what the other is doing


A few things that measurably improve on that:


Request the HbA1c instead of asking the patient. Patient-reported values are wrong or out of date more often than not. A release and a fax to the physician's office gets you better data than a question at the chair ever will.


Send your findings back. A short note covering periodontal status, treatment provided, and the modest glycemic contribution you'd expect puts you in the room as a clinical collaborator. Most physicians hear nothing at all from dentistry, so the bar here is low and the return is good.


Time treatment around control where you can. Elective periodontal surgery in a patient at 10% with no medical follow-up is a different risk calculation than the same procedure at 7%. That's a coordination question, not a refusal.


Know the cost argument. Markov modeling of combined periodontal and diabetes management found the integrated approach was cost-saving in patients with uncontrolled diabetes at HbA1c of 7% or above. If you're in a value-based or integrated arrangement, that's a number worth having ready.

The short version

Screen the periodontitis patient who hasn't had bloodwork. The undiagnosed rates in dental populations are high enough to justify it, and for a lot of these patients you're the only clinician they see.


Know 5.7% and 6.5%, and remember periodontal risk starts rising before either one.


Be accurate about the treatment effect. Roughly 0.3% to 0.4% at three months, durability uncertain, meaningful as a contribution and not as a substitute for diabetes care.



Translate the number when you discuss it. Estimated average glucose means more to most patients than a percentage does.


And talk to the physician. The bidirectional evidence is strong enough now that parallel, non-communicating care doesn't reflect what we know.



This article is intended for dental professionals and is for general clinical information. Screening protocols, scope of practice and licensure requirements vary by jurisdiction and should be confirmed locally.

Selected sources

  1. Preshaw PM, et al. Periodontitis and diabetes: a two-way relationship. Diabetologia.

  2. Engebretson S, Kocher T. Evidence that periodontal treatment improves diabetes outcomes: a systematic review and meta-analysis. J Clin Periodontol, 2013.

  3. Madianos PN, Koromantzos PA. An update of the evidence on the potential impact of periodontal therapy on diabetes outcomes. J Clin Periodontol, 2018.

  4. Graziani F, et al. Bidirectional association between periodontal disease and diabetes mellitus: systematic review and meta-analysis of cohort studies. Scientific Reports, 2021.

  5. Sanz M, et al. EFP/AAP consensus: scientific evidence on the links between periodontal diseases and diabetes.

  6. Teeuw WJ, et al. Chairside screening for undiagnosed diabetes and prediabetes in patients with periodontitis.

  7. UK Prospective Diabetes Study (UKPDS 35): association of glycaemia with macrovascular and microvascular complications.





Category: Cosmetic Dentistry
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