Evaluation of the different irrigation regimens with sodium hypochlorite and EDTA in removing the smear layer during root canal preparation

ObjectivesThe aim of this study was to compare, by scanning electron microscopy analysis, the cleaning efficacy of a 2.5% sodium hypochlorite (NaOCl) and a 17% ethylenediaminetetra-acetic acid (EDTA) solution with the two solutions either applied alternately or mixed together for smear layer removal after the use of each endodontic file in different root thirds.Materials and methodsFifty-four single-rooted human maxillary premolars were used and divided into three groups. Manual instrumentation was performed with K-Flexofiles with the crown-down technique; and divided in Group 1: canal preparation was performed with 2.5% NaOCl mixed with 17% EDTA in the root canal. Group 2: irrigation was performed alternately with 2.5% NaOCl and 17% EDTA. Group 3: only 2.5% NaOCl was used during all instrumentation and EDTA for 3 min at the final. The mean scores for the smear layer by SEM after the use of each file were calculated and analysed.ResultsA statistically significant difference (P < 0.05) was found among the instrumentation groups between the apical third and the middle and coronal thirds. In the apical third, the canal walls were often contaminated by inorganic debris and smear layer.ConclusionsThe alternate or mixed use of EDTA during instrumentation with 2.5% sodium hypochlorite was the most effective form of irrigation for the removal of smear layer on the cervical and middle thirds. No form of irrigation was sufficiently effective to remove the smear layer in the apical third.Clinical relevanceThe importance of the alternating use of 17% EDTA and 2.5% sodium hypochlorite during root canal instrumentation.