Effect of sodium hypochlorite on primary dentin--a scanning electron microscopy (SEM) evaluation.
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).


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 120 s), as follows: G1: control (without AE and NaOCl); G2: only AE; G3, G4, and G5: AE+5% NaOCl for 30, 60, and 120 s, respectively; G6, G7, and G8: AE+10% NaOCl for 30, 60, and 120 s, 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 120 s and 10% NaOCl solution for 30, 60, and 120 s.


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.
Correr
Gisele Maria
GM
Department of Restorative Dentistry, Dental Materials Area, Piracicaba Dental School, University of Campinas, Piracicaba, São Paulo, Brazil.
Alonso
Roberta Caroline Bruschi
RC
Grando
Maria Fernanda
MF
Borges
Ana Flávia Sanches
AF
Puppin-Rontani
Regina Maria
RM
D000134:Acid Etching, Dental; D003094:Collagen / Q000187:drug effects / Q000648:ultrastructure; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D003808:Dentin Solubility / Q000187:drug effects; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000008:administration & dosage / Q000494:pharmacology*; D010756:Phosphoric Acids / Q000494:pharmacology; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors; D014094:Tooth, Deciduous / Q000187:drug effects* / Q000648:ultrastructure
D016877:Oxidants; D010756:Phosphoric Acids; D003094:Collagen; D012973:Sodium Hypochlorite; C030242:phosphoric acid