Objective: Periodontitis is one of the most widespread chronic infectious disease in humans,which ultimately leads to tooth loss.It is characterized by progressive destruction of periodontal supporting tissues including periodontal ligament and alveolar bone due to microbial plaque accumulation and consequently unbalanced immune response.Recently,periodontitis is considered as a risk factor of systemic disease such as cardiovascular disease,diabetes,premature birth and low birth weight,rheumatoid arthritis etc.Although increasing evidences in support of the notion that peridontitis may be considered as an autoimmune disease,its detail mechanism is still unclear.Insulin-like growth factor-binding protein-5(IGFBP5)is a member of the insulin-like growth factor axis(IGFs axis)which was proved to be vital in promoting bone formation,inhibiting inflammation,increasing proliferation and differentiation of gingival epithelial cells and human periodontal ligament fibroblasts.Accumulated evidences suggest that IGFBP5 play an important role in anti-inflammation and tissue regeneration,here we hypothesis that IGFBP5 may involve in the maintenance of periodontal health and tissue regeneration.The purpose of this study was to investigate the potential biological mechanism of IGFBP5 in periodontitis by comparing the level of IGFBP5 in gingival crevicular fluid from patient with periodontitis.