Periodontal disease is a multifactorial disease associated with multiple risk factors.Diabetes mellitus is a hormonal disease characterized by changes in carbohydrate, protein, and lipid metabolism. The main feature of diabetes is an increase in blood glucose levels (hyperglycemia). Numerous cross-sectional and longitudinal prospective clinical studies provide evidence for a bidirectional relationship.This book deals with association between both of them and the mechanisms that associated with it.