Patients and methods In this double-blind, randomized clinical trial, a total of 42 patients with chronic periodontitis and type 2 diabetes were included in a 24-months follow-up. Patients were randomly assigned to treatment with either amoxicillin/metronidazole or clindamycin every for 7 days. Clinical determinations (depth of probing, bleeding at the probe and plaque index) were performed to determine the extent and severity of periodontitis before and after the pharmacological treatment. The intra-group differences were calculated with Wilcoxon rank test. The inter-group differences were calculated with Mann-Whitney test. Sex, bacterial plaque, and bleed to the sounding were summarized using proportions and analyzed with the chi-square method. In all analyses, a P-value of <0.05 (two tailed) was considered statistically significant