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Evaluation of the effectiveness of two irrigation systems in reducing bacterial load in root canals in vitro by quantitative real-time polymerase chain reaction Zhang, Duo


Introduction: Irrigation is regarded as having a key role in one of the main goals of endodontic treatment, the killing and removing bacteria from the infected root canal. Different methods and techniques have been used to deliver irrigating solutions and to facilitate the effectiveness of irrigation. The purpose of this in vitro study was, by using quantitative real-time PCR to determine the effectiveness of two irrigation and cleaning systems in removing multispecies oral biofilms from root canals. Methods: Fifteen extracted human molars were instrumented to size #15/.02 and then cleaned with the GentleWave System (GW; Sonendo Inc, Laguna Hills, CA). The teeth were autoclaved to provide the same sterile baseline. The molars were filled with mixed plaque suspended in brain-heart infusion broth and centrifuged to help the bacteria spread all over the root canal system. After two weeks of incubation, samples were divided randomly into two treatment groups and instrumented into size #15/.04 (GW) and #35/.04 (PiezoFlow group) under needle irrigation with sterile water. The teeth were then cleaned either with GentleWave System or ProUltra PiezoFlow Active Ultrasonic System (Dentsply Tulsa, Tulsa, OK) using 3% NaOCl, 8% EDTA and sterile water as irrigants. Root canals were sampled with paper points before and after instrumentation (S1, S2) and after GW or PF cleaning (S3). Quantitative real-time PCR was performed, the presence of microorganism in the samples was determined by using universal bacterial, a genus specific and species-specific primers. Statistical analysis was performed using the Mann-Whitney U test with the significance level set at P < 0.05. Result: A highly significant bacterial reduction was recorded for both groups (P < 0.001). GW group showed a significantly higher reduction than the PF group of total microbes (P < 0.01), Enterococcus faecalis (P < 0.01) and Streptococcus species (P < 0.05). GW resulted predictably in high reduction of over 99% of the microbes in every canal, whereas in the PF group the reduction of microbes varied between 87% and 99.99%. Conclusion: While both systems demonstrated effective reduction of intracanal bacteria, a high level of over 99% was more predictably achieved in the GW group.

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