Although periodontitis does not belong to clinical manifestations of any type of diabetes mellitus, it is still being labeled as “the sixth chronic complication of diabetes. It has been confirmed that, in individuals with diabetes, there is about a three times higher risk of periodontitis. Thus, diabetes is considered to be a predisposing factor for periodontitis .In the diabetic patients, the periodontal disease develops at a younger age than in the healthy population. The aim of this study was to prove the bidirectional relationship between periodontal diseases and diabetes type 1 in children. Patients and Methods: this study was conducted on 40 children with age range from 8-13 years, for evaluation of periodontal diseases “Gingival Index (GI), Plaque Index (PI) and Clinical Attachment Loss (CAL)" were used, and “Glycosylated hemoglobin (HbA1c %)" for the evaluation of blood glucose level and after application of the dental treatment program the patients were reevaluated after 3months, 6months and 9months. Results: the results show that both periodontal diseases and diabetes type 1 had a bidirectional relationship.