title: Is the presence of the smear layer a limiting factor for root dentin permeability in primary teeth?
abstract: OBJECTIVE
  The purpose of this study was to correlate the dye permeability to the morphological aspect (presence or absence of a smear layer) of the primary root dentin wall, using scanning electron microscopy, regarding the endodontic preparation and irrigation methods. The hypothesis evaluated was that there was a correlation between the dye permeability and the morphological aspect of the primary root dentin.
  
  
  METHODS
  A total of 112 extracted primary roots were distributed into the following groups: Dakin's liquid, Dakin+hydrogen peroxide; 2% chlorhexidine gel; and saline solution. Manual (MI) or Ultrasonic irrigation (UI) was performed. The roots were made impermeable, filled with dye (2% methylene blue), and longitudinally sectioned. The halves were divided in cervical, middle, and apical thirds for dye penetration measurement. The samples were observed under a scanning electron microscope. The data were submitted to linear regression analysis with a dummy variable (P<.05).
  
  
  RESULTS
  The data revealed a relationship between decreasing permeability and the presence of a smear layer on root canal dentin walls for MI in the middle third (P=.0147). Regarding UI, no statistically significant relation was observed (P>.05).
  
  
  CONCLUSIONS
  The presence of a smear layer on root canal dentin walls was not a limiting factor to dye penetration in all groups except the middle third for manual irrigation.
authors.affiliation: Piracicaba Dental School, University of Campinas, Piracicaba, São Paulo, Brazil.
authors.forename: Fernanda Miori
authors.initials: FM
authors.lastname: Pascon
authors.forename: Kamila Rosamilia
authors.initials: KR
authors.lastname: Kantovitz
authors.forename: Mario Alexandre Coelho
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: Regina Maria
authors.initials: RM
authors.lastname: Puppin-Rontani
mesh_terms: D002710:Chlorhexidine; D004396:Coloring Agents; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D003806:Dentin Permeability; D004338:Drug Combinations; D006801:Humans; D006861:Hydrogen Peroxide; D016014:Linear Models; D008751:Methylene Blue; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants; D018915:Root Canal Preparation / Q000379:methods; D016369:Smear Layer; D017693:Sodium Bicarbonate; D012973:Sodium Hypochlorite; D014094:Tooth, Deciduous / Q000033:anatomy & histology*; D014465:Ultrasonics
chemical_list: D004396:Coloring Agents; D004338:Drug Combinations; D012388:Root Canal Irrigants; C069467:modified Dakin's solution; D017693:Sodium Bicarbonate; D006861:Hydrogen Peroxide; D012973:Sodium Hypochlorite; D002710:Chlorhexidine; D008751:Methylene Blue