BackgroundPeriodontitis is a common chronic inflammatory disease and one of oral complications in diabetes. Diabetes-related microvascular complications and periodontitis are also closely related to systemic inflammation. We hypothesized that periodontitis and oral hygiene markers might increase the risk of microvascular complications in diabetes mellitus. MethodsWe enrolled 11,353 diabetes participants without prior microvascular complications who received complete oral health checkups in the National Health Insurance Service-National Health Screening Cohort in 2003–2004. The primary outcome was the first development of diabetes-related microvascular complications, including nephropathy, neuropathy, and retinopathy. ResultsThe age of all participants was 55.27 ± 9.46 years, and 7833 (68.99%) participants were male. Periodontitis was noted in 8.37%. During the 7.03 ± 4.30 year of the mean follow-up period, 7227 patients experienced diabetes-related microvascular complications (2645 with nephropathy, 2513 with neuropathy, 2069 with retinopathy). Multivariable Cox regression analyses revealed that periodontitis was an independent risk factor for diabetes-related microvascular complications (adjusted hazard ratio (HR):1.13; 95% confidence interval (CI):1.04–1.23; p = 0.004). In the secondary analysis for individual microvascular complications, periodontitis was an independent risk factor for retinopathy (adjusted HR: 1.21; 95% CI: 1.04–1.40; p = 0.013). ConclusionsThe presence of periodontitis was associated with an increased risk of microvascular complications in diabetes patients.