What’s the Connection Between Diabetes and Oral Health?

Emerging evidence suggests that oral health, often overlooked by clinicians, is closely connected with overall health — and this connection has important consequences for individuals with type 2 diabetes (T2D). While most studies are observational and can’t prove cause and effect, the associations are robust enough for researchers to conclude that the connection is real.

Endocrinologists and other specialists, as well as primary care physicians, should ask about oral health, if not look in the mouth directly, experts say. “One of the most important things to ask people with diabetes is when their last dental visit was and if they have a follow-up,” Robert Gabbay, MD, PhD, Chief Scientific and Medical Officer of the American Diabetes Association (ADA) told Medscape Medical News. The ADA advocates for attention to oral health through its 2024 standards of care.

Systemic Impact

“Periodontitis is a probable risk factor for various problems connected to the cardiovascular, pulmonary, endocrine, musculoskeletal, central nervous, and reproductive systems,” wrote the authors of a recent review on the effects of periodontitis on major organ systems. While not specific to the diabetes connection, the review pinpoints some of the latest evidence that “oral health affects overall health, and…dental health should never be considered a distinct, remote, and lower significant part of health.”

In line with this perspective, and looking specifically at T2D, a recent study of more than 17,000 patients with T2D participating in a screening program in Korea found that periodontitis and an increased number of teeth with cavities were independent risk factors for cerebral or myocardial infarction (adjusted hazard ratios, 1.17 and 1.67, respectively).

Dental disease and poor oral hygiene were also associated with an increased risk for heart failure among people with T2D in a large cohort study, and the authors suggested that managing oral health may prevent heart failure development.

A recent review suggested that periodontitis exacerbates and promotes the progression of chronic kidney disease, a disorder that affects 1 in 3 people with diabetes.

Studies also have shown that diabetes is associated with cognitive decline, and a review of oral health and dementia progression concluded, “collectively, experimental findings indicate that the connection between oral health and cognition cannot be underestimated.”

Bidirectional Effects

Research has shown that the association between periodontal disease and T2D is likely bidirectional, although there is little awareness of this two-way relationship among patients and providers.

A recent review of this bidirectional relationship focused on microvascular complications, oral microbiota, pro- and anti-inflammatory factors in T2D and periodontal disease and concluded that “these two diseases require specific/complementary therapeutic solutions when they occur in association, with new clinical trials and epidemiological research being necessary for better control of this interdependent pathogenic topic.”

Yet an Australian study showed that 54% of 241 participants in a survey never received any information regarding the bidirectional relationship between periodontal disease and diabetes and lacked understanding of the association.

What’s the Mechanism?

How does T2D affect the teeth and vice versa? “Basically, people with T2D have high blood sugar, and the sugar comes out in the saliva and that promotes bacterial growth in the mouth and plaque formation on the teeth and gum disease,” Samir Malkani, MD, clinical chief of endocrinology and diabetes at UMass Chan School of Medicine in Worcester, Massachusetts, told Medscape Medical News.

“Patients get gingivitis, they get periodontitis, and since the gums and the jaw are a single unit, if the gum disease gets very severe, then there’s loss of jawbone and the teeth could fall out,” he said. There’s also inflammation in the mouth, and “when you have generalized inflammation, it affects the whole body.”

Recent research in Europe suggested that “although the mechanisms behind these associations are partially unclear, poor oral health is probably sustaining systemic inflammation.” Common oral infections, periodontal disease, and cavities are associated with inflammatory metabolic profiles related to an increased risk for cardiometabolic diseases, and they predict future adverse changes in metabolic profiles, according to the authors.

Awareness, Accessibility, Collaboration

Despite the evidence, the connection between oral health and diabetes (any type) is not front of mind with clinicians or patients, Malkani said. He pointed to a systematic review that included 28 studies of close to 28,000 people in 14 countries. The review found that people with diabetes have “inadequate oral health knowledge, poor oral health attitudes, and fewer dental visits, [and] rarely receive oral health education and dental referrals from their care providers.”

Social determinants of health have a “huge impact” on whether people will develop T2D and its related complications, including poor oral health, according to the National Clinical Care Commission Report presented to the US Congress in 2022. The commission was charged with making recommendations for federal policies and programs that could more effectively prevent and control diabetes and its complications.

The commission “approached its charge through the lens of a socioecological and an expanded chronic care model,” the report authors wrote. “It was clear that diabetes in the US cannot simply be viewed as a medical or healthcare problem but also must be addressed as a societal problem that cuts across many sectors, including food, housing, commerce, transportation, and the environment.”

Diabetes also is associated with higher dental costs, another factor affecting an individual’s ability to obtain care.

A recent questionnaire-based study from Denmark found that people with T2D were more likely than those without diabetes to rate their oral health as poor, and that the risk for self-rated poor oral health increased with lower educational attainment. Highest educational attainment and disposable household income were indicators of a high socioeconomic position, and a lower likelihood of rating their oral health as poor, again pointing out inequities.

The authors concluded that “diabetes and dental care providers should engage in multidisciplinary collaboration across healthcare sectors to ensure coherent treatment and management of diabetes.”

But such collaborations are easier said than done. “One of the challenges is our fragmented health system, where oral health and medical care are separate,” Gabbay said.

For the most part, the two are separate, Malkani agreed. “When we’re dealing with most complications of diabetes, like involvement of the heart or eyes or kidneys, we can have interdisciplinary care — everyone is within the overall discipline of medicine, and if I refer to a colleague in ophthalmology or a cardiologist or a vascular surgeon, they can all be within the same network from an insurance point of view, as well.”

But for dental care, referrals are interprofessional, not interdisciplinary. “I have to make sure that the patient has a dentist because dentists are usually not part of medical networks, and if the patient doesn’t have dental insurance, then cost and access can be a challenge.”

A recent systematic review from Australia on interprofessional education and interprofessional collaborative care found that more than a third of medical professionals were “ignorant” of the relationship between oral health and T2D. Furthermore, only 30% reported ever referring their patients for an oral health assessment. And there was little, if any, interprofessional collaborative care between medical and dental professionals while managing patients with T2D.

Treat the Teeth

“We always talk to our T2D patients about the importance of getting an eye exam, a foot exam, and a kidney test,” Malkani said. “But we also need to make sure that they’re going to the dentist. Normally, people get their teeth cleaned twice a year. But if you have diabetes and poor oral health, you might need to get your teeth cleaned every three months, and insurance often will pay for that.”

Furthermore, in keeping with the bidirectional connection, treating periodontitis can help glycemic control. The authors of a 2022 update of a Cochrane review on treating periodontitis for glycemic control wrote that they “doubled the number of included studies and participants” from the 2015 update to 35 studies randomizing 3249 participants to periodontal treatment or control. This “led to a change in our conclusions about the primary outcome of glycemic control and in our level of certainty in this conclusion.”

“We now have moderate‐certainty evidence that periodontal treatment using subgingival instrumentation improves glycemic control in people with both periodontitis and diabetes by a clinically significant amount when compared to no treatment or usual care. Further trials evaluating periodontal treatment vs no treatment/usual care are unlikely to change the overall conclusion reached in this review.”

“Dentists also have a responsibility,” Malkani added. “If they see someone with severe gum disease or cavities, especially at a younger age, they need to tell that person to get their blood sugar checked and make sure they don’t have T2D.”

In fact, a recent review found that complications of T2D such as xerostomia and periodontal problems adversely affect well-being, and that “dentists can play an essential role in the awareness of diabetic patients about these problems and improve their quality of life.”

Key Stats

The US Centers for Disease Control and Prevention highlighted these facts about diabetes and oral health:

• Adults aged 20 years or older with diabetes are 40% more likely to have untreated cavities than similar adults without diabetes.
• About 60% of US adults with diabetes had a medical visit in the past year but no dental visit.
• Expanding healthcare coverage for periodontal treatment among people with diabetes could save each person about $6000 (2019 US dollars) over their lifetimes.
• Adults aged 50 years or older with diabetes lack functional dentition (have fewer than 20 teeth) 46% more often and have severe tooth loss (eight or fewer teeth) 56% more often than those without diabetes.
• Adults aged 50 years or older with diabetes are more likely to report that they have a hard time eating because of dental problems.
• Annual dental expenditures for an adult with diabetes are $77 (2017 US dollars) higher than for an adult without diabetes. This cost translates to $1.9 billion for the United States.