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°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.