OBJECTIVETo evaluate the possible effects of apical periodontitis (AP) on cardiac function, structure, and oxidative stress (OS) in rats with diabetes mellitus type 2 (T2DM).DESIGNForty-eight (Wistar albino, male) rats were randomized into four groups: control healthy (CTRL), normoglycemic with AP (AP), T2DM, and T2DM with AP (T2DM+AP). T2DM was induced by streptozotocin and a high-fat diet. AP was induced by pulp exposure to the oral environment for 4 weeks and analyzed radiographically. In the blood samples insulin and glucose were established. In vivo, cardiac function was evaluated by echocardiography. Ex vivo cardiac function was assessed by the Langendorff technique. Heart tissue was analyzed pathophysiologically. OS was determined in cardiac tissue homogenate and coronary venous effluent, spectrophotometrically.RESULTSImpaired glycoregulation was observed in the T2DM+AP group compared to the T2DM, AP, and CTRL groups. The T2DM+AP group was associated with disturbed echocardiography and cardiodynamic parameters. The levels of superoxide anion radical, nitrite, and index of lipid peroxidation were significantly increased, while the superoxide dismutase and catalase were significantly decreased in the T2DM+AP group compared to T2DM, AP, and CTRL groups. The radiographic AP area was significantly larger in the T2DM+AP compared to the AP group.CONCLUSIONAP was associated with increased glucose levels, impaired cardiac function, structure, and OS in diabetic rats. Diabetes was related to an increased radiographic AP area. The study may be a starting point for further research to clarify the effects of AP on cardiac function in various models of systemic diseases.