Abstract: OBJECTIVE To observe the changes of Porphyromonas gingivalis and Streptococcus sanguinis in gingival crevicular fluid of patients with peri-implantitis and analyze their relationship with probing depth of implant periodontal pocket, modified plaque index, modified sulcus bleeding index and bone loss index.METHODS Totally 30 patients with peri-implantitis who received the implant restoration for more than one year in department of stomatology of the First People 's Hospital of Yongkang from Jun 2013 to Dec 2015 were chosen as the peri-implantitis group, and 30 patients who had healthy implants were set as the healthy implant group.The contents of P.ingivalis and S.anguinis in gingival crevicular fluid were determined by using electrochemical method.RESULTS The content of the isolated P.ingivalis in gingival crevicular fluid was significantly higher in the peri-implantitis group than in the healthy implant teeth (P＜0.05); the content of the isolated P.ingivalis in gingival crevicular fluid was significantly higher in the peri-implantitis group than in the healthy implant group (P＜0.05).The content of the isolated S.anguinis in gingival crevicular fluid of the peri-implantitis group was significantly lower than that of the healthy implant teeth (P＜0.05); the content of the isolated S.anguinis in gingival crevicular fluid of the peri-implantitis group was significantly lower than that of the healthy implant group(P＜0.05).The probing depth of implant periodontal pocket, modified plaque index, modified sulcus bleeding index and bone loss index were significantly higher in the peri-implantitis group than in the healthy implant group (P＜0.05).The P.ingivalis in gingival crevicular fluid was positively correlated with the probing depth of implant periodontal pocket, modified plaque index, modified sulcus bleeding index and bone loss (P＜0.05); the S.anguinis in gingival crevicular fluid was negatively correlated with the probing depth of implant periodontal pocket, modified plaque index, modified sulcus bleeding index and bone loss (P＜0.05).CONCLUSIONThe content of the P.ingivalis in gingival crevicular fluid of the patients with peri-implantitis is increased, while the content of the S.anguinis is reduced. The P.ingivalis in gingival crevicular fluid of the patients with peri-implantitis is positively correlated with the clinical indexes, while the S.anguinis is negatively correlated with the clinical indexes.