title: The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis.
abstract: OBJECTIVE
  To verify, under the scanning electron microscope (SEM), the influence of irrigation time with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on intracanal smear layer removal.
  
  
  METHODS
  Twenty-one extracted human permanent teeth with single straight root canals were included. The root canals of the teeth were instrumented and, at the end of preparation, were irrigated with 3 mL of 15% EDTA, followed by 3 mL of 1% NaOCl for 1 min (group 1), for 3 min (group 2), and for 5 min (group 3). The canals of teeth in group 4 (control) did not receive the final irrigation. The teeth were sectioned longitudinally and prepared for an SEM. The dentinal wall of cervical, middle and apical thirds was graded according to the amount of debris and smear layer remaining on the walls. The results were analysed using the Kruskal-Wallis and Conover-Inman tests.
  
  
  RESULTS
  In all the canals of experimental groups irrigation with EDTA and NaOCl completely removed the smear layer from the cervical and middle thirds. In the apical third, the dentine surface were partially covered, particularly in the teeth of group 1, where there was significantly more smear layer when compared with the other thirds in the same group (P<0.007). However, the Kruskal-Wallis test showed overall that there were no significant differences between groups 1, 2 and 3 (P>0.05).
  
  
  CONCLUSIONS
  In this limited laboratory study, canal irrigation with EDTA and NaOCl for 1, 3 and 5 min were equally effective in removing the smear layer from the canal walls of straight roots.
authors.affiliation: Dental School, Federal University of Santa Catarina, Florianópolis, Brazil. cleotex@uol.com.br
authors.forename: C S
authors.initials: CS
authors.lastname: Teixeira
authors.forename: M C S
authors.initials: MC
authors.lastname: Felippe
authors.forename: W T
authors.initials: WT
authors.lastname: Felippe
mesh_terms: D002614:Chelating Agents / Q000008:administration & dosage*; D003481:Cuspid; D003786:Dental Pulp Cavity / Q000187:drug effects / Q000648:ultrastructure; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D004492:Edetic Acid / Q000008:administration & dosage*; D006801:Humans; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D018915:Root Canal Preparation; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000008:administration & dosage*; D013997:Time Factors; D019227:Tooth Apex / Q000648:ultrastructure; D019237:Tooth Cervix / Q000648:ultrastructure
chemical_list: D002614:Chelating Agents; D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite