Effect of different techniques on removal of smear layer in dental canal

Objective: To evaluate the ability of different techniques on removal of smear layer in dental canal.Methods: Forty extracted single-rooted human teeth were randomly distributed into 4 groups.The teeth were prepared by ProTaper rotary instruments and subjected to different techniques for the removal of smear layer in dental canals.Hydrogen peroxide(H2O2) and normal saline(NS) were used in group A;5.25% sodium hypochlorite(NaClO) and ethylenediamine tetraacetis(EDTA) gel in group B;ultrasonics in group C;5.25% NaClO and EDTA gel with ultrasonics in group D.Samples were examined under the scanning electron microscope and scored for smear layer removal and the erosion on the surface of the root canal walls.Results: The whole surfaces of root canals in group A were covered by smear layer.The smear layer of root canals in group B,C and D was removed.Statistical analysis showed that the removal effect in group B,C and D was significantly better than that in group A at coronal,middle and apical portions.There were not significant differences among group B,C and D.In group D the surface of root canal at coronal,middle portion was eroded.Conclusion: 5.25% NaClO with EDTA gel,ultrasonics with 5.25% NaClO,EDTA gel and ultrasonic can effectively remove the smear layer in root canal,but the dentin can be eroded by using 5.25% NaClO with EDTA gel and ultrasonics.