Nowadays, a lot has been discussed about the interaction between periodontal disease and some systemic conditions, like diabetes mellitus. The objective of this review was to verify, by means of a review of clinical trials, if there is a positive association of periodontal disease on the glycemic control of type 2 diabetes mellitus (DM-2) patients. A search in PubMed baseline (www.pubmed.gov) was performed upon the terms “type 2 diabetes” and “periodontal disease”, with limits on “humans”, “clinical trials” and “randomized clinical trials”. Eleven articles fit the study criteria and were revised. It was concluded that periodontal disease seems to influence the metabolic condition of DM-2, and additional studies with greater sample sizes and time period are necessary to better clarify this issue.