All clinical and radiological examinations, sampling site selections were performed by one examiner and the samples were collected on the day after clinical examination of patients. This was to prevent contamination of GCF with blood associated with the probing of inflamed sites. The deepest two pocket sites of single-rooted teeth were selected for the collection of GCF in both periodontitis groups, and also two pocket sites with an absence of inflammation were sampled to ensure the collection of an adequate amount of GCF in control groups. In patients from CP and DM-CP groups, sites showing greatest PD when measured with a periodontal probes and signs of inflammation, along with radiographic conformation of bone loss were sampled. GCF samples were collected at baseline and after 8 weeks from baseline sampling in both periodontitis groups, and only at baseline in control groups. To avoid salivary contamination, the sites to be sampled were rinsed with water, isolated by cotton rolls and gently air dried. Paper strips (Periopaper; Oraflow Inc.,Smithtown, NY, USA) were gently inserted 1-2 mm into the sulcus/pocket for 30 seconds. Care was taken to avoid mechanical injury of the gingival tissues. All samples containing blood and saliva were discarded. The two strips from two sites of each individual were placed into coded sealed plastic eppendorf tubes and pooled before freezing at -80 degree