A total of 108 gingival crevicular fluid samples were taken from the Group 5 (18 subjects x 6 sites) and 90 samples from each of the remaining 5 groups (15 subjects per group x 6 sites). All samples were collected between 8-10 am on the day following periodontal status assessment. Samples were collected from the sites in the chronic periodontitis group that fit the following criteria: pocket probing depth≥5mm, clinical attachment level≥5mm and ≥30% radiographic alveolar bone loss. Accordingly, gingival crevicular fluid samples were collected from 2 molar teeth, 2 premolar teeth and 2 incisors. Gingival crevicular fluid samples were collected from the same 6 sites in the gingivitis and periodontally healthy groups in order to maintain consistency of sampling.