PRF was developed in 2001 by Choukroun in France, it was the second generation fibrin adhesive, and was used to accelerate the soft and hard tissue healing. Many studies have shown beneficial effects of PRF on osteoconductive filler material in sinus lift operations, treatment of periodontal sulcus defect and treatment of furcation defects. Also PRF contains many growth factors. PRF accelerates periodontal regeneration through the gradually excreted growth factors and contributes to the bone regeneration. In this study, the investigators evaluated the effect of PRF on growth factors and its contribution to periodontal regeneration in subjects with chronic periodontitis.