title: Tubular sclerosis rather than the smear layer impedes dye penetration into the dentine of endodontically instrumented root canals.
abstract: OBJECTIVE
  To evaluate the effect of different root canal irrigating regimes on dentine penetration of Patent Blue dye.
  
  
  METHODS
  Eighty extracted single-rooted human mandibular premolar teeth with narrow root canals were prepared using ProFile instruments. After each instrument, canals were irrigated with 1% sodium hypochlorite. Subsequently, teeth were randomly assigned to receive a 10 mL rinse of aqueous 17% (w/v) ethylenediaminetetraacetic acid or tap water for 2 or 10 min, followed by a final rinse with a 2% Patent Blue dye solution for 2 or 10 min (eight groups, n = 10 teeth per group). Teeth were then horizontally sectioned 3, 6 and 9 mm from the apex. Sections were digitally photographed and dye penetration was calculated as percentage of total dentine area using NIH Image J. Values were compared using one-way anova and Bonferroni correction with the alpha-type error set at <0.05. Representative tooth sections from all groups were further analysed using scanning electron microscopy.
  
  
  RESULTS
  No significant impact of irrigating protocols on dye penetration was found. Dye penetration was significantly (P < 0.001) greater in the coronal than middle, and in middle than in apical root thirds. When observed microscopically, irrigant penetration was independent of the presence of a smear layer, but was rather a function of tubular sclerosis.
  
  
  CONCLUSIONS
  Tubular sclerosis, a physiological phenomenon that starts in the third decade of life in the apical root region and advances coronally with age, was the main factor influencing penetrability of root dentine.
authors.affiliation: Division of Endodontology, Department of Preventive Dentistry, Periodontology, and Cariology, University of Zürich Center for Dental Medicine, Zürich, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Paqué
authors.forename: H U
authors.initials: HU
authors.lastname: Luder
authors.forename: B
authors.initials: B
authors.lastname: Sener
authors.forename: M
authors.initials: M
authors.lastname: Zehnder
mesh_terms: D000704:Analysis of Variance; D004396:Coloring Agents / Q000008:administration & dosage; D003804:Dentin / Q000737:chemistry* / Q000473:pathology; D004492:Edetic Acid / Q000008:administration & dosage; D006801:Humans; D012388:Root Canal Irrigants / Q000008:administration & dosage; D012598:Sclerosis; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D014092:Tooth Root / Q000737:chemistry / Q000473:pathology
chemical_list: D004396:Coloring Agents; D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite