The effectiveness of Hero (taper 4% & 6%) instrumentation techniques on the elimination of Enterococcus faecalis from root canal

Due to the deeper penetration of bacteria like Enterococcus faecalis into dentinal tubules in pulp diseases, different tapering in root canal therapies leads in different dentinal removal from root canal wall. Then, root canals with higher tapering will contain lower microbial microbial contents. Furthermore, together with higher prevalence of root fractures in teeth with more tapering, the aim of this study is comparing the effect of different tapering of Hero Rotary files (6% versus 4%) in reduction of Enterococcus faecalis bacteria from the root canal of human extracted teeth. Seventy human extracted teeth were divided in two equal experimental (Hero 4%as group 1and Hero 6% as group 2) (n=27) and the control group (n=6).Two extra control group (positive n=5 and negative n=5) took for confirmation the canal reinfection, too. All of the samples prepared by K file No 20 and Gates Gilden No 2 & 3 before sterilization. Then the teeth were autoclaved and were infected with Enterococcus faecalis. The experimental groups were instrumented either with Hero 4% or with Hero 6% files up to #30. Bacteriological samples were taken after instrumentation to determine the level of remaining bacteria. In the group 1 two samples and in the group 2 six samples represented complete reduction of bacteria. There was not statistically significant different between the two groups. Aggressive preparation with an instrumentation technique removing substantial amounts of dentin (Hero 6%) did not reduce the intracanal bacteria more effectively than a more conservative instrumentation technique (Hero 4%) (P>0.05).