Abstract: Abstract：　Objective　 To compare the inhibitory effect of three endodontic irrigating reagents (NaOCl, H2O2, PVP-I) on four kinds of bacteria (E.f, F.n, P.g, P.e) in human root canals after chemo-mechanical preparation. Methods　60 single root teeth with chronic apical periodontitis were randomly divided into three groups. The first group (n=20) was irrigated with 2.5% NaOCl. The second group (n=20) was irrigated with 3% H2O2. The third group (n=20) was irrigated with 1% PVP-I. Clinical periapical indexes was presented by the diameter of image shadows. The symptoms of pain and swelling were documented and measured before and after the root canal treatment. Real-time quantitative-polymerase chain reaction (qRT-PCR) was used to compare the positive rates and quantities of four bacteria (E.f, F.n, P.g and P.e) in different groups. Statistical analysis was performed using the Mann–Whitney test. Results The symptom of pain and swelling was significantly decreased and relieved in all three groups after root canal treatment. The bacteria load was reduced significantly after treatment in three gourps. There was no significant inhibitory effect on P.e in three groups（P >0.05）,whereas the numbers of E.f, F.n and P.g were reduced significantly (P<0.05). The numbers of E.f, F.n and P.g were reduced significantly in both NaClO-group and the (PVP-I)-group comparing to the H2O2-group (P<0.05). The detection rate of P.e in the (PVP-I)-group was lower than the H2O2-group (P<0.05). Conclusions 2.5% NaClO, 1% PVP-I and 3% H2O2 can effectively inhibit the growth of E.f, F.n, P.g and P.e in infectious root canals. There was no significant inhibitory effect on these four bateria between 2.5%NaClO and 1% PVP-I, but both showed inhibitory effect on E.f, F.n and P.g comparing to 3% H2O2. 1% PVP-I showed better inbitory effect on P.e than 3% H2O2.

Key words: Irrigations, Chronic periodontitis, bacteria, Real-time fluorescence quantitative polymerase chain reaction