title: Smear Layer Removal in the Apical Third of Root Canals by Two Chelating Agents and Laser: A Comparative in vitro Study.
abstract: BACKGROUND
  Smear layer (SL) is produced as a result of mechanical instrumentation of the canal(s). Despite the controversies regarding its removal, the evidence-based trend has shifted towards removing and eliminating the SL. Different methods have been used to remove the SL and the aim of this in vitro study was to evaluate the ability of 17% ethylenediaminetetraacetic acid (EDTA), 18% etidronate and Er: YAG on effective removal of the SL.
  
  
  METHODS
  Fifty straight single-rooted teeth were divided into three experimental groups (n=15) and one control group of five. The canals were instrumented with HERO 642 rotary files up to 30/0.06. In group 1, canals were irradiated with Er: YAG laser; in groups 2 and 3, canals were irrigated with 17% EDTA and 18% etidronate, respectively. In group 4 (control) distilled water was used for canal irrigation. The amount of remaining SL was quantified according to Hulsmann's method with scanning electron microscopy (SEM). Data was analyzed by the Kruskal-Wallis and Mann-Whitney U tests (P<0.05).
  
  
  RESULTS
  The results showed statistically significant differences in terms of SL removal among the groups (P<0.05). The amount of removed SL by EDTA was significantly greater followed by Er: YAG laser and 18% etidronate.
  
  
  CONCLUSIONS
  Within the limitations of this study, EDTA was more effective in removing SL compared to Er: YAG and etidronate.
authors.affiliation: Department of Endodontics, Dental School, Iranian Center for Endodontic Research, Research Institute for Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hengameh
authors.initials: H
authors.lastname: Ashraf
authors.affiliation: Department of Endodontics, Dental School, Iranian Center for Endodontic Research, Research Institute for Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Asnaashari
authors.affiliation: Department of Endodontics, Dental School, Iranian Center for Endodontic Research, Research Institute for Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Soheila
authors.initials: S
authors.lastname: Darmiani
authors.affiliation: Department of Periodontology and Torabinejad Dental Research Center, Dental, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Birang
keywords: EDTA; Er; Etidronate; Scanning Electron Microscopy; Smear Layer; YAG Laser