Effects of sodium hypochlorite as endodontic irrigation on Enterococcus faecalis

[Objective]This experiment evaluates the efficacy of 5.25% sodium hypochlorite(NaClO) as endodontic irrigation solution against Enterococcus faecalis within root canals.[Methods] Roots inoculated with E faecalis were randomly and evenly divided into two groups,which underwent different root canal irrigation: 5.25% NaClO,0.9% sterile saline solution(NaCl).Canals were sampled after instrumentation using sterile paper points,and then incubated at 37 ℃.The colony forming units(CFU) grown were counted at 24 h,48 h and 1 week.[Results] At 24 hour,48 hour,Enterococcus faecalis in 5.25% NaClO group were completely killed,and the colony forming units were 0 CFU mL-1.The average colony forming units of the NaCl group were respectively 1.2×106 CFU mL-1,1.7×106 CFUmL-1.At 1 week,few Enterococcus faecalis were detected.The average colony forming units of the 5.25% NaClO group was 109 CFU mL-1 and the NaCl group was 3.8×106 CFU mL-1.There were significant differences between the two tested groups at three different time spots(P 0.01).[Conclusion] 5.25% NaClO endodontic irrigation solution can immediately kill Enterococcus faecalis,but it can not clean up the Enterococcus faecalis completely.Sodium hypochlorite only can reduce the amount of the Enterococcus faecalis,and make it in bacteriostasis within a period of time.