Effect of sodium hypochlorite on primary dentin—A scanning electron microscopy (SEM) evaluation

Abstract 

Objective

The aim of this study was to evaluate the alterations of etched deciduous dentin when submitted to different time and concentrations of sodium hypochlorite (NaOCl), using scanning electron microscopy (SEM).

Material and methods

Forty deciduous anterior teeth were selected, cleaned and ground until expose a flat dentin area on the buccal surface. The specimens were randomly distributed into eight groups (n=5), according to dentin surface treatment (35% phosphoric acid etching for 7s—AE and/or NaOCl application), NaOCl solution concentration (5% or 10%), and time of application (0, 30, 60, and 120s), as follows: G1: control (without AE and NaOCl); G2: only AE; G3, G4, and G5: AE+5% NaOCl for 30, 60, and 120s, respectively; G6, G7, and G8: AE+10% NaOCl for 30, 60, and 120s, respectively. All specimens were prepared for SEM analysis and the photomicrographs (three for each specimen) were classified according to a score as follow: 0: presence of smear layer (SL); 1: absence of SL+non-altered collagen fibrils; 2: absence of SL+collagen fibrils slightly altered; 3: absence of SL+collagen fibrils severely altered; and 4: absence of SL and absence of collagen fibrils. Data were submitted to Kruskal–Wallis and Mann–Whitney tests (p<0.05).

Results

All groups treated with NaOCl solution were significant different from G1 and G2, and showed alterations on the collagen fibrils network. Collagen complete removal was only observed when a 5% NaOCl solution was applied for 120s and 10% NaOCl solution for 30, 60, and 120s.

Conclusions

The NaOCl action produced significant changes in the etched deciduous dentin. The higher NaOCl concentration, the lower the time required to completely removing the collagen fibrils network in deciduous dentin.

Keywords: Sodium hypochlorite, Deciduous dentin, Demineralization, Deproteinization