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The LightSpeed root canal instrument is similar in design to the Canal Master instrument with the exception of being engine driven and fabricated from nickel-titanium alloy. The purpose of the design of these instruments is to reduce apical transportation of the canal during cleansing and shaping procedures. Twenty extracted human molar teeth with roots of varying degrees of curvature were used in this study. A double exposure radiographic technique was used to assess the presence or absence of apical transportation resulting between the initial instrument and the final instrument, a size 50 LightSpeed. Only one of the 20 teeth examined exhibited apical transportation. Results of this study suggest that little or no apical canal transportation could be expected when curved canals are instrumented using the LightSpeed root canal instruments.

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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.