Root canal disinfection comparing conventional irrigation vs photon-induced photoacoustic streaming (PIPS) using a buffered 0.5 % sodium hypochlorite solution

Background: The purpose of this study was to assess the antimicrobial effect of a buffered 0.5 % sodium hypochlorite solution activated by photon-induced photoacoustic streaming compared to conventional irrigation. Methods: The canals on 48 single canal lower bicuspids were cleaned and shaped using rotary instrumentation. All roots were autoclaved for 20 min. Thirty-six of the roots were placed in glass flasks with blood heart infusion media and Enterococcus faecalis (ATCC 4082) for 4 weeks. The remaining 12 roots were placed in a sterile environment and served as negative controls. The contaminated roots were irrigated by conventional means using a buffered 0.5 % sodium hypochlorite solution with or without photon-induced photoacoustic streaming (PIPS) activation (n = 12 each group). The remaining 12 roots did not receive any treatment and served as positive controls. The apical 3 mm of each tooth was sectioned and pulverized. The pulverized samples were collected and placed in Eppendorf micro-centrifuge tubes with sterile phosphate-buffered saline. Thirty MicroLiters of the collected samples was then placed in the blood heart infusion media and incubated for 24 h at 37 °C. Colony forming units (CFU) were compared with Wilcoxon signed ranked test. Mann-Whitney U test was used to assess PIPS effectiveness in comparison with conventional irrigation. Results: Both regimens reduced significantly the number of CFU; however, reduction was significantly higher for the PIPS group (p = 0.002). Conclusion: Buffered 0.5 % sodium hypochlorite delivered by conventional method was effective in removing E. faecalis from contaminated root canals; however, activation of a buffered 0.5 % sodium hypochlorite solution by PIPS significantly increased its antimicrobial capacity.