Comparison of the efficacy of three chelating agents in smear layer removal.

The purpose of this study was to compare the efficacy of SmearClear (Sybron Endo, Orange, CA), 17% EDTA, and 10% citric acid in smear layer removal. Forty-eight extracted single-rooted human teeth were randomly divided into 4 groups (n = 12) and instrumented using Mtwo nickel-titanium rotary instruments. Each canal was subsequently irrigated with one of the following solutions: 5.25% NaOCl (control), SmearClear, 17% EDTA, or 10% citric acid. After that, all the specimens were subjected to irrigation with 5.25% NaOCl. The teeth were then processed for scanning electron microscopy (SEM), and the removal of the smear layer was examined in the coronal, middle, and apical thirds. The results showed that there were no significant differences in the efficacy of three chelating agents at all levels of the root canals. The comparison of three one thirds in each group showed no significant difference in the SmearClear and EDTA groups. However, the efficacy of citric acid was significantly less in the apical third compared with the coronal and middle thirds of the canals. In conclusion, the protocol used in this study was not efficient to completely remove the smear layer especially in the apical third of the canal.