The aim of this study is to evaluate the pre-heating effects on the degree of conversion (DC) of dual-cured resin cements (RC) submitted to different activation modes simulating the cementation of indirect ceramic restorations. The low and high viscosity versions of two dual RCs will be used: Nexus2 Low and High (Kerr Corp.,CA, USA), and Variolink II LV and HV (Ivoclar Vivadent). The products will be placed on mixing pad and will be kept at 25 C or pre-heated in oven at 35 C and 60 C. The RCs will be mixed according to the manufacturers' instructions and will be applied to the horizontal diamond surface of an attenuated total reflectance (ATR) unit (Satandard Golden Gate, Specac) coupled to the infrared spectroscope (Tensor 27, Bruker Comp). The following activation modes will start the polymerization of the RCs: light activation through glass slide or through 1.5 / 3-mm thick ceramic discs (2 mm in diameter), which will be placed on the RC layer; the RCs will be allowed to self-cure. Fourier Transformed Infrared (FTIR) spectra will be obtained between 1680 and 1500 cm-1 before the activation of polymerization as well as 10 minutes after the beginning of the reaction of polymerization. The DC results (%) will be analyzed using 3-way ANOVA (viscosity, temperature, and activation mode) and post-hoc Tukey's test (alpha=5%).
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