title: Light-activation of resin cement through ceramic: relationship between irradiance intensity and bond strength to dentin.
abstract: This study investigated the relationship between the irradiance transmitted through ceramic and the bond strength of a resin cement to dentin. After application of an adhesive system, elastomer molds with cylindrical orifices (1.2 mm in diameter) were placed onto bovine dentin surfaces and filled with a photoactivated luting agent (Enforce; Dentsply Caulk). Light-activation was performed through a 0.6-mm-thick ceramic disc using different intensities: 250, 400, 550, 700, or 850 mW/cm(2). Control specimens were irradiated without ceramic (1050 mW/cm(2)). The radiant exposure was kept at 30 J/cm(2). Light spectral distribution was analyzed with a spectrometer. Microshear test was conducted and modes of failure were classified under SEM. Bond strength data were analyzed with ANOVA and Student-Newman-Keuls' test (alpha < or = 0.05), and failure scores with the Kruskal-Wallis test (alpha < or = 0.05). A linear regression model assessed the relationship between irradiance and bond strength. Groups light-cured at 250 and 400 mW/cm(2) presented lower bond strengths than groups activated at 850 and 1050 mW/cm(2). The linear regression showed that a decrease in light irradiance predicts a decrease in bond strength (r(2) = 0.955; p = 0.004). A predominance of mixed failures was observed. No significant alteration in the spectral wavelengths was observed. Despite the constant energy dose, the bond strength was dependent upon the irradiance level.
authors.affiliation: Department of Restorative Dentistry, Dental Materials Area, Piracicaba School of Dentistry, State University of Campinas, SP, Brazil.
authors.forename: Rafael R
authors.initials: RR
authors.lastname: Moraes
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: Mário A C
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: Regina M
authors.initials: RM
authors.lastname: Puppin-Rontani
authors.forename: Fabrício A
authors.initials: FA
authors.lastname: Ogliari
authors.forename: Evandro
authors.initials: E
authors.lastname: Piva
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D002417:Cattle; D002516:Ceramics / Q000737:chemistry*; D001840:Dental Bonding / Q000295:instrumentation / Q000379:methods; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength