Application Modes of Different Root Canal Irrigants in Removing Smear Layer of Root Canals:A Comparative Study

Objective To compare the effects of application modes of different root canal irrigants on removing the smear layer of root canals.Methods 40 human teeth with a single root canal were randomly divided into 5 groups after the amputation of the crowns of these teeth.All of the root canals were irrigated with six different root canal irrigants when the canals were prepared with crown-down technique.The teeth in Group A were irrigated with 20 g/L chlorhexidine acetate solution (CHX),and Group B with 25 g/L sodium hypochlorite solution (NaOCl).In the specimens of Group C the root canals were irrigated with 20 g/L CHX + EDTA gel,and those of Group D with 25 g/L NaOCl+EDTA gel.The control specimens in Group E were irrigated with distilled water.After the teeth were split into two buccal-lingually,the cleaning effects of all the specimens from the 5 groups on the removal of smear layer in the middle third of the root canal and debris was observed with a scanning electron microscope,and analyzed statistically.Results Compared with Group E,there was significant difference among Group A,B,C and D (P0.05).Group B and D had significantly less smear layer and more visible open dentinal tubules compared with Group A and C(P0.05).Paired comparison showed that Group C was superior to Group A (P0.05).There was no significant difference between Group B and D (P0.05).Conclusion Either chlorhexidine or NaOCl,used alone or in combination with EDTA gel,can remove smear layer.The group with NaOCl+ EDTA gel has the best cleaning effect.Chlorhexidine solution as a root canal irrigant cannot remove all the smear layer from the root-canal system.Combined with EDTA gel,however,its performance in the removal of smear layer has obviously improved.