GCF sampling sites were selected from the sites without BOP and plaque accumulation. GCF samples were obtained from buccal aspects of proximal sites in a single-rooted teeth in each individual participating in the present study. Paper strips† were carefully inserted 1 mm into the crevice for 30 seconds. Care was taken to avoid mechanical trauma. The absorbed GCF volume was estimated by a calibrated instrument. Then each strip from each patient were placed into one polypropylene tube before freezing at -40°C. The readings were converted to an actual volume (µl) reference to the standard curve. All GCF samples were stored at -40°C until the laboratory analyses.