Patient population Criteria for selection Patients of both sexes (aged >18 to 70 years) with a diagnosis of chronic periodontitis according to the 1999 International World Workshop for a Classification of Periodontal Diseases and Conditions and a history of type 2 diabetes with a HbA1C < 8 % and a fasting plasma glucose (FPG) < 180 mg/dL. Patients with aggressive periodontitis, pregnant or lactating females, required antibiotic pre-medication for the performance of periodontal examination and treatment or received antibiotic treatment in the previous 3 months were excluded. A history of anti-inﬂammatory therapy within preceding six months or that had received a course of periodontal treatment within the last 6 months, allergies to penicillin, metronidazole or clindamycin, and were not able to provide consent to participate in the study were also criteria for exclusion.