Objective: To explore the effect of full-mouth disinfection (FMD) on glycemic control and insulin resistance in type 2 diabetes mellitus (DM). Method and Materials: Sixty dentate patients who were never-smokers with type 2 diabetes mellitus were recruited for the study. Based on clinical examination they were divided into two groups: one with chronic periodontitis and the other without chronic periodontitis. Periodontal parameters Plaque Index (PI), Gingival Index (GI), and probing pocket depth (PPD) were evaluated. Blood samples were assessed for the levels of fasting glucose (FG), insulin, and C-reactive protein (CRP), and insulin glucose ratio was calculated using a mathematical equation (HOMA-IR). All parameters were assessed at baseline, and at 3 months and 6 months after FMD. Results: The results showed a significant reduction in PI, GI, PPD, FG, and HOMA-IR from baseline to 6 months. The CRP levels were constant throughout the study period. Conclusion: Within the limitations of the present study it can be concluded that FMD contributes to significant reduction in insulin resistance, thereby improving the glycemic control in type 2 diabetes mellitus patients. Schlagwörter: insulin resistance, full-mouth disinfection, glucose level, type 2 diabetes mellitus