Inconclusive results were reported about the cleaning and disinfection accomplished by the two irrigation methods .
There is insufficient evidence to cl aim general superiority of any one of these methods .
The aim of this study was to systematic ally review and critically analyse the published data on the treatment outcome ( primary outcome ) and on the  cleaning and disinfection of root canals  ( secondary outcomes ) achieved by negative pressure irrigation as compared to syringe irrigation .
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 m and ibular molars were instrumented to produce either a non-tapered or tapered preparation , sterilized , inoculated with E. faecalis for 30 days , and then r and omly 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 sample d before and after final irrigation and sample s 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
Inconclusive results were reported about the cleaning and disinfection accomplished by the two irrigation methods .
There is insufficient evidence to cl aim general superiority of any one of these methods .
The aim of this study was to systematic ally review and critically analyse the published data on the treatment outcome ( primary outcome ) and on the  cleaning and disinfection of root canals  ( secondary outcomes ) achieved by negative pressure irrigation as compared to syringe irrigation .