Many studies have demonstrated an increased inci­dence of apical periodontitis in patients who suf­fer from type 2 diabetes mellitus. According to a report issued last year by the Centers for Disease Control and Prevention, >10% of Americans have type 2 diabetes mellitus; thus, this relationship may have a major impact on dental health. However, no researchers had studied this patient group using a sufficiently large U.S. population and controlling for possible confounding variables.

Recently, Yip et al from the University of North Carolina at Chapel Hill published a case-controlled study of >15,000 patients to determine (1) whether apical periodon­titis is independently associated with type 2 diabetes mel­litus after controlling for confounding variables and (2) whether varying levels of glycated hemoglobin (HbA1c) were associated with apical periodontitis. From the records of 7 dental clinics at hospitals spread throughout North Carolina, the researchers identified 7749 patients with diagnoses of both apical periodontitis and type 2 diabetes mellitus. They then created a control group of the same number of patients from the same hospital clinics, matched by age, race and sex, who did not have a diagnosis of apical periodontitis.

In addition to periodontal and diabetes status, the follow­ing variables for each patient were recorded:

  • HbA1c
  • oral cellulitis
  • body mass index (categorized as obese or nonobese)
  • primary and secondary hypertension
  • atherosclerosis
  • chronic kidney disease
  • smoking status
  • use of metformin (a drug commonly prescribed to treat type 2 diabetes mellitus)
  • use of statins (a class of drugs commonly prescribed for hypercholesterolemia)

Several regression models were created to determine whether an association exists between periodontal disease and type 2 diabetes mellitus, and what (if any) impact any of the studied vari­ables had on that association.

Nearly twice as many patients with api­cal periodontitis also had a diagnosis of type 2 diabetes mellitus. This rela­tionship held even after controlling for demographic factors and potential confounding variables. Interestingly, patients taking either statins or met­formin had significantly lower odds of developing apical periodontitis (Table 1). Patients with poorly con­trolled HbA1c levels (defined as HbA1c >8.0) had significantly greater odds of developing apical periodontitis, as did current and former smokers and patients diagnosed with atherosclerosis or hypertension.


While it is impossible for a study like this to establish a direct cause-and-effect relationship between type 2 diabetes mellitus and apical peri­odontitis, this study’s large sample size and strict control of potential confounding variables allowed it to show a strong independent associa­tion between the 2 conditions, with higher HbA1c levels significantly associated with apical periodonti­tis. Patients on metformin therapy, which is frequently prescribed to control HbA1c, were less likely to be afflicted with apical periodontitis.

Yip N, Liu C, Wu D, Fouad AF. The associa­tion of apical periodontitis and type 2 diabetes mellitus: a large hospital network cross-sectional casecontrolled study. J Am Dent Assoc 2021; 152:434-443.