Glycemic control and number of natural teeth: analysis of cross-sectional Japanese employment-based dental insurance claims and medical check-up data

Aim Diabetes mellitus is a well-known risk factor for onset and progression of periodontal disease. However, the continuous relationship between glycemic control and the number of natural teeth has not been well characterized in large-scale studies. We aimed to determine whether the glycated hemoglobin A1c (HbA1c) level and fasting plasma glucose (FPG) are associated with the number of natural teeth. Methods A cross-sectional study: A database comprising employment-based health insurance claim and medical check-up data from 706,150 participants between April 2015 and March 2016 in Japan. The exclusion criteria included missing data regarding dental receipts, number of natural teeth, HbA1c, smoking status, and age < 20 years. Ultimately, 233,567 individuals were analyzed. The participants were allocated to five groups according to their HbA1c and three groups according to their FPG, and then the number of natural teeth were compared. Results Higher HbA1c was associated with fewer teeth in participants ≥ 30 years of age ( P for trend < 0.001). Higher FPG was associated with fewer teeth between 30 and 69 years of age ( P for trend < 0.001). Participants with impaired fasting glucose was already at risk for fewer teeth between 40 and 69 years of age than those with normal FPG. Conclusions Glycemic control is strongly associated with the number of natural teeth in the real-world setting. Furthermore, there are continuous relationships of HbA1c and FPG with number of natural teeth including individual with impaired fasting glucose. These data emphasize the importance of glycemic control and appropriate oral care for the protection against tooth loss.