Effect of the diffusion of bleaching agents through enamel on dentin bonding at different depths.
OBJECTIVE
To evaluate the influence of two concentrations of bleaching agents applied over enamel surfaces on the dentin bonding at different depths.


METHODS
Twenty-four bovine incisors were sectioned, obtaining three fragments per tooth (4x4 mm). Each fragment presented a 0.7 mm enamel thickness; and the dentin thickness varied according to the experimental group: 0.5 mm, 1 mm or 1.5 mm. Fragments from each dentin-thickness were allocated into three groups (n=8): G1: Control (no bleaching); G2: 16% carbamide peroxide (6 hours/14 days); G3: 35% hydrogen peroxide (three 15-minute treatments). 24 hours after enamel bleaching, the adhesive system was applied and dentin surfaces were restored with resin composite cylinders (2 mm diameter and 1 mm height). The micro-shear testing was performed immediately after restorative procedures, at a speed of 0.5 mm/minute until failure. Bond strength values, in MPa, were statistically analyzed (split-plot ANOVA/Tukey alpha=0.05).


RESULTS
Means obtained were: G1-0.5 mm: 13.5, G1-1 mm: 9.48, G1-1.5 mm: 9.01; G2-0.5 mm: 9.64, G2-1 mm: 9.44, G2-1.5 mm: 9.27; G3-0.5 mm: 11.68, G3-1 mm: 11.64, G3-1.5 mm: 7.63. Regardless of the dentin thickness, bleached groups presented bond strengths similar to that of control groups. Nevertheless, significant differences among dentin depths were detected (P=0.02); and the lowest bond strength was observed on the deepest dentin (1.5 mm). The diffusion of bleaching agents through enamel surfaces did not affect the bond strength to dentin, which is highly dependent on the morphology/depth of the substrate.
Lima
Adriano Fonseca
AF
Department of Restorative Dentistry, Piracicaba School of Dentistry, State University of Campinas, Piracicaba, Brazil.
Fonseca
Fabrício Maurílio da Silva
FM
Cavalcanti
Andrea Nóbrega
AN
Aguiar
Flávio Henrique Baggio
FH
Marchi
Giselle Maria
GM
D000704:Analysis of Variance; D000818:Animals; D000077463:Carbamide Peroxide; D002417:Cattle; D001840:Dental Bonding; D003745:Dental Enamel Permeability; D003799:Dental Stress Analysis; D003804:Dentin / Q000033:anatomy & histology / Q000187:drug effects*; D004058:Diffusion; D006861:Hydrogen Peroxide / Q000009:adverse effects; D016877:Oxidants / Q000009:adverse effects; D010545:Peroxides / Q000009:adverse effects; D033081:Shear Strength; D018709:Statistics, Nonparametric; D014073:Tooth Bleaching / Q000009:adverse effects*; D014508:Urea / Q000009:adverse effects / Q000031:analogs & derivatives
D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide