Light‐activation of resin cement through ceramic: Relationship between irradiance intensity and bond strength to dentin

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 ( α ≤ 0.05), and failure scores with the Kruskal–Wallis test ( α ≤ 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. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008