Diabetes and periodontitis: understanding a two-way link

Two chronic inflammatory diseases that reinforce 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: it is what causes teeth to loosen and gums to recede. 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 contain 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 and more severe periodontitis, and with a less favourable response to treatment ^[6]. The risk depends above all on glycaemic control: well-controlled diabetes brings the periodontal risk close to that of a person without diabetes, without cancelling 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]. In practice, this means the periodontist asks about diabetes control and encourages the patient to discuss it with their doctor, without taking the doctor's place.

The warning signs for a person with diabetes are those of any periodontitis: gums that bleed on brushing, are red or swollen, persistent bad breath, teeth that look 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 interfere with the action of insulin, a phenomenon known as insulin resistance; this 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 compares a reduction of about 0.4 points to the effect of adding a second glucose-lowering drug ^[6]. This 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]. This trial has been the subject of published methodological criticism, notably concerning 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]. However, no trial has shown that periodontal treatment reduces diabetes complications (retinopathy, kidney damage, cardiovascular disease): this is an open question, not an established benefit.

How to read these results

Three precautions help avoid misunderstandings. First, an average hides very different individual responses: someone whose gums stop bleeding and whose pockets close is not in the same situation as someone whose inflammation persists. Second, HbA1c depends above all on diet, physical activity and medication: periodontal treatment adds to these levers, it does not replace them. Finally, the effect only lasts if inflammation stays under control, hence the importance of periodontal maintenance.

Periodontal treatment also lowers, on average, CRP, a blood marker of inflammation ^[10]. This fall is consistent with the inflammatory hypothesis, without on its own proving a long-term health benefit. The place of this marker and of other blood tests is discussed in the article on blood tests and supplements.

In practice at the clinic

• If you have diabetes: a full periodontal examination is worthwhile, 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 discussing 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 in the case of prediabetes ^[6].
• Coordination: with your consent, the practice sends a periodontal report to your GP or diabetes specialist, as recommended by the EFP–WONCA consensus ^[5].

At the examination, at the practice in Levallois-Perret, Dr Hazout measures bleeding, pocket depth and loss of attachment around each tooth, and reviews the radiographs. The international classification of periodontitis takes diabetes into account when estimating the risk of progression (the 'grade'): knowing your HbA1c therefore helps to tailor the treatment plan and the follow-up interval.

The treatment itself is described on the periodontitis treatment page: full-mouth treatment in a single session under local anaesthesia, then re-evaluation. For a person with diabetes the procedure is the same; what changes is the attention paid to glycaemic control, healing and the maintenance interval.

Frequently asked questions