Tubular sclerosis rather than the smear layer impedes dye penetration into the dentine of endodontically instrumented root canals.
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.
Paqué
F
F
Division of Endodontology, Department of Preventive Dentistry, Periodontology, and Cariology, University of Zürich Center for Dental Medicine, Zürich, Switzerland.
Luder
H U
HU
Sener
B
B
Zehnder
M
M
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
D004396:Coloring Agents; D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite