The Japan Diabetes Complications and its Prevention (JDCP) prospective study was conducted to analyze the association between glycemic control and oral conditions in a large database of Japanese patients with diabetes. It included a total of 6,099 patients with diabetes (range, 40-75 years) who were treated as outpatients between 2007 and 2009. The mean number of teeth at baseline was 19.8 and women had fewer teeth than men in type 2 diabetes. Within the previous year, 17 % had lost teeth. At baseline, 32 % had experienced gingival swelling, 69 % brushed more than twice a day, 37 % used interdental devices, and 43 % received dental regular checkups. A multiple logistic regression analysis indicated that type 1 diabetic patients with HbAlc 7.0 % had a higher risk having fewer than 20 teeth (odds ratio [OR]: 2.38; 95 % confidence interval [CI]: 1.25-4.78), and type 2 diabetic patients with HbAlc 8.0 % also had a high risk having fewer than 20 teeth (OR: 1.16; 95 % CI: 1.00-1.34), after adjusting for 9 possible confounders. In conclusion, diabetic patients had a high risk of tooth loss and the poorer the glycemic control, the higher the risk of tooth loss.