Efficacy of irrigating solutions in removing radicular smear layer from anterior primary teeth

Objective: in vitro evaluation of the effect of three irrigation systems used during instrumentation of anterior deciduous teeth canals on the SL removal and dentinal permeability, using two types of instrumentation. Methods: 32 anterior deciduous teeth had their apices sealed, and the first 24 teeth were divided at random into 2 groups of 12 according to canal manipulation: Kerr files up to size 25 (Phase I - G1 to G4) or files up to size 40 (Phase II - G5 to G8). The irrigating systems used were: G1 and G5 – distilled water (control); G2 and G6 – Endo-PTC activated by Dakin's Liquid; G3 and G7 - 4% sodium hypochlorite alternating with 3% hydrogen peroxide; and G4 and G8 - 1% sodium hypochlorite; final washing with 10% citric acid aqueous solution. The teeth were dried, the crowns removed, and the radicular part cleaved longitudinally. The samples were examined by MEV and blindly evaluated according to the criteria of Rome et al. (1985). The methodology used for G5 to G8 was employed on the 8 remaining teeth, divided at random into 4 groups of two teeth each (G9 to G12, respectively). The roots were impermeabilized and 50% silver nitrate aqueous solution was injected into the canal (2 hours). The roots were washed and packed in epoxy resin. After 24 hours, the sets were sectioned for observation under stereoscopic microscope. The area infiltrated was obtained by AutoCAD 14 software and data tabulated on Epi Info 6.04. Results: The efficiency of the irrigating systems in removing SL were, in decreasing order: G4 and G8; G2 and G6; and G3 and G7; and for permeability to silver nitrate: G12, G10 and G11. Conclusions: The sequence of sodium hypochlorite and citric acid is beneficial, as it removes SL and increases dentinal permeability in deciduous teeth, in vitro.