Objectives: Due to the important influence of glycemic control on oral health, this study aimed to compare the gingival index and decayed, missing, filled teeth (DMFT) in participants with type 2 diabetes mellitus receiving insulin and metformin. Materials and Methods: In this cross-sectional study, 130 participants with type 2 diabetes mellitus treated with insulin and metformin were studied in two groups based on the type of treatment. The information for DMFT and gingival indices were obtained using the oral examination. In the insulin group, participants received insulin Lantus 0.2 unit/kg once daily, and in the metformin group, participants received metformin tablets 500 mg every 12 hours. Glycosylated hemoglobin A1c (HbA1c) was measured by lab test in all participants. Finally, HbA1c, the information of DMFT, and gingival indices were compared between the two groups. Results: The results showed that there were no statistically significant differences in decayed, missed, and restored teeth, as well as the overall DMFT index between the two groups. The gingival index was significantly higher in the insulin group (P=0.046). Conclusions: Gingival health of insulin users is poorer than metformin users, but it seems that type of diabetes treatment does not affect the DMFT index