title: A comparative scanning electron microscopic investigation of the smear layer after the use of sodium hypochlorite gel and solution forms as root canal irrigants.
abstract: BACKGROUND
  The effect of sodium hypochlorite (NaOCl) gel along with EDTA on the removal of the smear layer has not been studied; therefore, the aim of the present study was to compare the efficacy of gel and solution forms of NaOCl in removal of the smear layer from root canal walls.
  
  
  METHODS
  A total of 40 single-rooted teeth with minimum curvature (<5 degrees) were selected and divided into two experimental groups, each containing 15 teeth and one positive control group containing 10 teeth. The canals of all the teeth were prepared with rotary RaCe instruments up to #35. In the NaOCl solution group, the root canals were flushed with 2.5% NaOCl solution during instrumentation and in NaOCl gel group, the instruments were coated with gel form of NaOCl and used inside the root canals; then saline was used for root canal irrigation. Finally, 1 mL of 17% EDTA was used to rinse inside the root canals and remained in the root canals for 2 minutes in the both experimental groups; in the saline group, only saline was used for irrigation. The amount of the smear layer was quantified according to the Torabinejad method using a scanning electron microscope. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests. All the statistical analyses were set with a significance level of alpha = 0.05.
  
  
  RESULTS
  There were no significant differences between NaOCl gel and solution forms in the coronal, middle, and apical thirds of root canals. There were significant differences between NaOCl solution and saline groups in the three parts of root canal walls and between NaOCl gel and saline in the coronal, middle, and apical thirds.
  
  
  CONCLUSIONS
  The use of NaOCl gel can be as effective as NaOCl solution along with EDTA in smear layer removal in the three parts of root canal walls.
authors.affiliation: The Department of Endodontics, Tabriz Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Zand
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Lotfi
authors.forename: Saeed
authors.initials: S
authors.lastname: Rahimi
authors.forename: Hadi
authors.initials: H
authors.lastname: Mokhtari
authors.forename: Ali
authors.initials: A
authors.lastname: Kazemi
authors.forename: Vahideh
authors.initials: V
authors.lastname: Sakhamanesh
mesh_terms: D002614:Chelating Agents / Q000008:administration & dosage; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D004492:Edetic Acid / Q000008:administration & dosage; D005782:Gels; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D016369:Smear Layer; D012965:Sodium Chloride / Q000008:administration & dosage; D012973:Sodium Hypochlorite / Q000008:administration & dosage*; D012996:Solutions; D019227:Tooth Apex / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D002614:Chelating Agents; D005782:Gels; D012388:Root Canal Irrigants; D012996:Solutions; D012965:Sodium Chloride; D004492:Edetic Acid; D012973:Sodium Hypochlorite