title: Effect of the diffusion of bleaching agents through enamel on dentin bonding at different depths.
abstract: 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.
authors.affiliation: Department of Restorative Dentistry, Piracicaba School of Dentistry, State University of Campinas, Piracicaba, Brazil.
authors.forename: Adriano Fonseca
authors.initials: AF
authors.lastname: Lima
authors.forename: Fabrício Maurílio da Silva
authors.initials: FM
authors.lastname: Fonseca
authors.forename: Andrea Nóbrega
authors.initials: AN
authors.lastname: Cavalcanti
authors.forename: Flávio Henrique Baggio
authors.initials: FH
authors.lastname: Aguiar
authors.forename: Giselle Maria
authors.initials: GM
authors.lastname: Marchi
mesh_terms: 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
chemical_list: D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide