Abstract: Abstract：　Objective　To evaluate the effect of nonsurgical periodontal therapy on gingival crevicular fluid (GCF) of C-reactive protein (CRP) levels in different tooth-site of subjects with severe chronic periodontitis, to help to diagnose the type of the activity of periodontitis and to assess the outcome of periodontal therapy. Methods　 GCF samples were collected by filter paper strip and weighed by tooth-site from 60 severe periodontitis ( probing depth≥6mm) sites and 60 mild periodontitis ( probing depth≤4mm) sites of 30 severe chronic periodontitis patients at baseline and at 1, 3, 6, 12 months after nonsurgical therapy. 30 healthy sites of 15 subjects with healthy periodontium were obtained as a control. The periodontal clinical parameters were recorded and the C-reactive protein levels in GCF were assessed by enzyme-linked immunosorbent assay (ELISA). Results　The levels of CRP in GCF in deep pocket sites were (968.06±360.54pg/ml)significantly higher than shallow pocket sites(291.65±65.62pg/ml), and the levels of CRP in GCF of all diseased sites were higher than healthy subjects(33.47±24.53pg/ml). Positive correlations existed between CRP concentration and probing depth(0.825,P<0.05),clinical attachment loss(0.833,P<0.05),plaque index(0.741,P<0.05). Moreover, the concentration of CRP in disease sites showed a statistically decrease after nonsurgical therapy and were related to the condition of oral hygiene. Conclusions　 The concentration of CRP in GCF may correlate with the degree of periodontal tissue destruction, the levels of CRP reduced after nonsurgical therapy in diseased sites.

Key words: 　severe chronic periodontitis, gingival crevicular fluid, C-reactive protein