Evaluation of the efficiency of smear layer removal during endodontic treatment using scanning electron microscopy: an in vitro study

Background: The smear layer formed during root canal instrumentation negatively affects root canal irrigation activity, which in turn can affect the treatment prognosis of endodontic treatment. Aim: The aim of this study is to compare the efficiency of smear layer and debris removal in root canals using different irrigation protocols using scanning electron microscopy (SEM). Materials and methods: The quality of smear layer removal throughout the root canal was assessed in 30 intact extracted teeth divided into 3 groups according to the irrigation protocol: Group 1: 3% sodium hypochlorite (NaOCL) alternately with 17% ethylenediaminetetraacetic acetate (EDTA) was used. Group 2: 3% NaOCL alternately with 9% etidronate solution diluted with distilled water and Group 3: 9% etidronate solution diluted in 3% NaOCL. The quality of smear layer removal was assessed using scanning electron microscopy (SEM). The nonparametric Mann-Whitney test was used to compare the protocols of irrigations. Results: The study showed significant differences in the quality of smear layer removal in the apical part of the root canal. The best results were obtained in the groups using 9% etidronate and 9% etidronate solution diluted in 3% sodium hypochlorite. Conducting a comparative evaluation of the effectiveness of removing the smear layer using 3% NaOCL + 17% EDTA, 3% NaOCL + 9% etidronic acid diluted with distilled water, 3% NaOCL + 9% etidronic acid diluted with 3% hypochlorite showed greater effectiveness of protocols using etidronate. When comparing statistical data, protocols using etidronate were 4 times more effective than EDTA. Conclusion: The smear layer formed during mechanical treatment of the root canal was better removed during irrigation with etidronate solution. © The Author(s) 2025.