Antimicrobial efficacy of two irrigation techniques in tapered and nontapered canal preparations: an in vitro study

The aim of this in vitro study was to determine whether irrigation with apical negative pressure was more effective than traditional positive-pressure irrigation in eradicating Enterococcus faecalis from preshaped root canals. Fifty-four extracted mandibular molars were instrumented to produce either a non-tapered or tapered preparation, sterilized, inoculated with E. faecalis for 30 days, and then randomly assigned into the following groups: group 1--non-tapered preparation and negative-pressure irrigation, group 2--non-tapered preparation and positive-pressure irrigation, group 3--tapered preparation and positive-pressure irrigation, and group 4--tapered preparation and negative-pressure irrigation. Mesial canals were sampled before and after final irrigation and samples incubated aerobically for 48 hours at 37 degrees C. Scanning electron microscopic analysis confirmed dense bacterial colonies in the positive control, consistent with biofilm formation. A statistically significant difference was evident when comparing apical negative-pressure irrigation to positive-pressure irrigation (p=0.004). There was no statistically significant difference in colony-forming units (CFUs) between sizes #35 and #45, nor between tapered and non-tapered preparation. The results of this in vitro study showed that apical negative-pressure irrigation has the potential to achieve better microbial control than traditional irrigation delivery systems.