Comparison of the antibacterial effectiveness of four different endodontic irrigation techniques (conventional syringe irrigation, passive ultrasonic irrigation, EndoVac® irrigation, RinsEndo® irrigation) against Enterococcus faecalis on the basis of an intracanal biofilm model

OBJECTIVE: The failure of primary root canal treatments is mostly due to persisting bacteria. Several irrigation techniques have been introduced with the main objective of improving root canal disinfection. The aim of this in vitro study was the comparison of the effectiveness of four different endodontic irrigation techniques (conventional syringe irrigation, passive ultrasonic irrigation, EndoVac® irrigation, RinsEndo® irrigation) in reducing intraradicular Enterococcus faecalis biofilms. METHODS: 70 extracted single-rooted human teeth were used for the in-vitro model. After a standardized root canal preparation the smear layer was removed with EDTA 17% and NaOCl 1%. Distribution to a total of eight experimental groups was made: two groups (each n = 5) served for analyzing the smear layer removal (SL) and the grown biofilm (BF) by means of scanning electron microscopy. Four groups (each n = 10) served for analyzing the four irrigation techniques. Furthermore, a positive and a negative control group (each n = 10) were analyzed. An E. faecalis biofilm was grown in the root canals of the conventional syringe irrigation, passive ultrasonic irrigation, EndoVac® irrigation, RinsEndo® irrigation, positive control and BF groups for 72 hours with repeated injection of a fresh standardized E. faecalis solution after 24 and 48 hours. Those groups were then disinfected with 6 ml of NaOCl 1% for 3 Minutes, with the exception of the RinsEndo® system which used about 18 ml of NaOCl 1%. Dentin particles were removed with endodontic instruments and incubated on an agar culture medium. After 24 hours the colony forming units (CFU) were counted and statistically evaluated. RESULTS: The removal of the smear layer and the growth of a biofilm were confirmed by means of the SEM analysis. All irrigation techniques significantly reduced the number of E. faecalis in root canals (p < 0,0001). No disinfection measure led to a complete elimination of E. faecalis from the root canal system. There was no significant difference in the effectiveness of the four different endodontic irrigation techniques. CONCLUSION: There was no evident antibacterial superiority of any of the four irrigation techniques evaluated in the present in vitro study. The use of an effective antibacterial rinsing solution like NaOCl 1% seems to be most important.2018-02-2