Diabetes and periodontitis: a two-way link, with the figures

Two chronic diseases that feed each other

HbA1c (glycated haemoglobin) reflects average blood glucose over the previous two to three months; it is the figure your doctor follows. Periodontitis is a chronic inflammation, triggered by plaque bacteria, that destroys the bone and attachment of the teeth: hence loosening and receding. The 2018 EFP–IDF consensus describes both as chronic non-communicable diseases, associated with increased mortality and linked in both directions ^[1].

From diabetes to the gums

When blood glucose stays high, gum tissues hold more pro-inflammatory mediators (IL-1β, TNF-α, IL-6), which contribute to greater periodontal destruction ^[1]. Poorly controlled diabetes goes hand in hand with more frequent, more severe periodontitis and a less favourable response to treatment ^[6]. Glycaemic control is what matters most: the better the diabetes is controlled, the closer the periodontal risk comes to that of a person without diabetes, without erasing it ^[1].

This is why the European guideline for treating periodontitis (EFP S3, 2020) recommends diabetes-control interventions in patients undergoing periodontal therapy (recommendation R1.7) ^[7]. The periodontist therefore asks about diabetes control and encourages the patient to raise it with their doctor, without ever taking the doctor's place.

The warning signs for a person with diabetes are those of any periodontitis: gums that bleed on brushing, look red or swollen, persistent bad breath, teeth that seem longer or feel loose, gum abscesses. As periodontitis is often painless, a periodontal examination is worthwhile even without discomfort.

From the gums to blood sugar

Ulcerated periodontal pockets let bacteria and inflammatory mediators into the bloodstream. This low-grade inflammation may hamper the action of insulin, a phenomenon known as insulin resistance; the mechanism has mainly been shown in experimental models ^[8]. Observational studies associate periodontitis with poorer glycaemic control and more complications in people with diabetes ^[1].

Does periodontal treatment lower HbA1c?

The 2022 Cochrane review pooled the trials comparing periodontal treatment (cleaning the roots below the gumline, known as root surface debridement) with no treatment or usual care, in people with diabetes, mostly type 2 ^[2]:

All these figures come from the Cochrane review ^[2]. To give a sense of scale, the EFP likens a reduction of about 0.4 points to the effect of adding a second glucose-lowering drug ^[6]. It is an average: some patients will see no change, others a clearer fall, depending on the initial inflammation and the response to treatment.

Trials that disagree

In 2013, a multicentre American trial (514 patients with type 2 diabetes) found no improvement in HbA1c six months after non-surgical treatment: +0.17 points in the treated group and +0.11 in the control group ^[3]. The trial drew published methodological criticism, notably over the intensity of treatment and the persistence of gum inflammation in treated patients ^[11].

In 2018, a twelve-month British trial (264 patients) compared intensive periodontal treatment with minimal treatment: HbA1c was 0.6 points lower (95% CI 0.3–0.9) in the intensively treated group ^[4].

These differences probably reflect the intensity of treatment, how well inflammation was controlled and the populations studied. The Cochrane synthesis remains favourable, with moderate certainty ^[2]. These trials mainly follow HbA1c, from three months to a year; the effect of treatment on diabetes complications (retinopathy, kidney damage, cardiovascular disease) calls for longer studies.

How to read these results

Three precautions avoid misunderstandings. First, an average masks very different individual responses: someone whose gums stop bleeding and whose pockets close is not in the position of someone whose inflammation persists. Second, HbA1c depends above all on diet, physical activity and medication: periodontal treatment adds to these levers without replacing them. Finally, the effect lasts only as long as inflammation stays under control, hence the role of periodontal maintenance.

Periodontal treatment also lowers, on average, CRP, a blood marker of inflammation ^[10]. This fall is consistent with the inflammatory link between the gums and blood sugar. The place of this marker and of other blood tests is discussed in the article on blood tests and supplements.

What this changes at the practice

• If you have diabetes: a full periodontal examination is worth having, followed by regular maintenance.
• If you have periodontitis without known diabetes but have risk factors (excess weight, family history, high blood pressure), Dr Hazout suggests raising it with your GP. The EFP estimates that 20 to 40% of patients with periodontitis, depending on the study, have diabetes or prediabetes, often unrecognised, especially where prediabetes is concerned ^[6].
• Coordination: with your consent, the practice sends a periodontal report to your GP or diabetes specialist, as the EFP–WONCA consensus recommends ^[5].

At the examination, at the practice in Levallois-Perret, Dr Hazout examines the gums around each tooth (bleeding, inflammation, mobility), then reviews the radiographs. The international classification of periodontitis factors in diabetes when estimating the risk of progression (the 'grade'): knowing your HbA1c therefore helps to adjust the treatment plan and the follow-up interval.

The treatment itself is described on the periodontitis treatment page: the whole mouth treated in a single session, a one-month follow-up, then six-monthly follow-up. For a person with diabetes the procedure does not change; what changes is the attention paid to glycaemic control, healing and the maintenance interval.

Frequently asked questions

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