Bacterial reduction compared betweeninstrumentation with K3TM rotary file andstainless steel K-file
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2010-11-03
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Khon Kaen University Dental Journal
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The purpose of this in vitro study was to compare the reduction of Enterococcus faecalis in teeth instrumented either with K3 rotary files or stainless steel hand K files. One hundred and ninety-one extracted human single-rooted teeth were cut to obtain the root length of 15 millimeters. These roots were coated with 2 layers of nail varnish, sterilized and allocated into 2 experimental groups (187 teeth), the positive control group (2 teeth) and the negative control group (2 teeth). Roots in the experimental groups and the positive control group were inoculated with E. faecalis in Todd–Hewitt broth at concentration 0.5 McFarland for 14 days. Two roots in the negative control group were not inoculated. In the experimental groups, ninety-two canals were instrumented using K3 rotary files with crown-down technique and ninety-five canals were instrumented using stainless steel hand K files with step-back technique until the master apical file was sized 30. Two roots in the positive control group were not instrumented. After instrumentation, each canal was dried, filled with 10 microliters of Todd–Hewitt broth and kept in 37OC for 24 hours under 100% humidity. The content in each canal was soaked up with a sterile paper point, transferred into Todd-Hewitt broth and incubated at 37OC for 24 hours. The presence of micro-organisms was evaluated by the turbidity of the broth. If the broth was turbid, aliquots of 25 microliters were spread onto a blood agar plate and incubated at 37OC for 24 hours. Characteristic colonies of E. faecalis on plates were observed and confirmed by inoculation in bile esculin agar and 6.5% sodium chloride solution. The colony of E. faecalis changed bile esculin agar into black color and the sodium chloride solution became turbid. The results showed that K3 files reduced E. faecalis 64.13% (95%CI: 53.45%-73.86%) of the tested teeth whilst K-files reduced E. faecalis 62.1% (95%CI: 51.57%-71.86%) of the tested teeth. There was no statistically significantly difference in the ability to reduce E. faecalis between the two instrumentation techniques (Chi-square test, p \> 0.05). Keywords: Enterococcus faecalis / Rotary instrument
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Khon Kaen University Dental Journal; Vo.12 No. 2 July - Dec. 2009