Comparison of the effect of four common irrigants on microbial leakage in obturated root canals

Cleaning the root canal is not possible without proper irrigation. After total debridement of the root canal, the final irrigants may affect microleakage. The aim of this study was to evaluate the effect of 2% chlorhexidine, doxycycline (100 mg/mL), sodium hypochlorite and distilled water as final irrigants on bacterial leakage of the root canal. In this in vitro study, 84 extracted single-rooted human teeth were instrumented using #15-40 K-files, irrigated with 1.3% NaOCl and divided into four experimental groups (n=19) and two positive and negative control groups (n=4). After removing the smear layer with 17% EDTA the root canals were irrigated with distilled water. The final irrigation was performed with NaOCl in group 1, doxycycline in group 2, distilled water in group 3 and 2% CHX in group 4. The teeth in each group were obturated with gutta-percha cones and AH-26 sealer. After ethylene oxide sterilization, the coronal portion of each root was placed in contact with Enterococcus faecalis inocula in brain-heart infusion (BHI) broth. The samples were checked every 3 days for turbidity, which continued for 90 days. Data were collected and Kaplan-Meier survival curves of SPSS 11.5 were constructed based on the microleakage in specimens over the study period. The mean turbidity days were calculated for each group and compared between the four groups using the log-rank test (α=0.05). Kaplan-Meier curves showed different tendencies for microleakage between the four groups and log-rank test showed statistically significant differences between group 2 and groups 1 (p value = 0.002) and 3 (p value = 0.002). In addition, there were significant differences between group 4 and groups 1 (p value = 0.043) and 3 (p value = 0.021). Under the limitations of the present study, there was a decrease in bacterial microleakage after the use of all the four irrigation solutions compared to the control groups, with more significant decreases in the doxycycline and chlorhexidine groups.