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Objective: The aim of this study was to verify the effect of interposing different indirect restorative materials on the three-point flexural strength (FS), Knoop microhardness (KHN) and FT-Raman degree of conversion (DC) of a resin cement. Methods: Disks (2-mm thick and 11mm in diameter) were built using the indirect restorative materials IPS Eris (IvoclarVivadent glass-ceramic, E), IPS Empress 2 (Ivoclar-Vivadent framework ceramic) veneered by IPS Eris (EE), Sinfony (3M ESPE, micro-hybrid composite resin, S) and SR Adoro (Ivoclar-Vivadent microfilled composite resin, A). Initially, their relative transmittance (RT) was determined analyzing digital images obtained by a CCD camera and with visible light spectrometry. Then, bar-shaped specimens (sps, 10 x 2 x 1 mm) of the Nexus 2 resin cement (SDS Kerr) were prepared either with (dual) or without catalyst (light-cured), and photoactivated throught the different restorative materials disks using a halogen light curing unit (QTH, Optilux 501, SDS Kerr) or a light emitting diode (LED, L.E.Demetron 1, SDS Kerr). The sps were also light-cured without interposing the disks, keeping the curing unit light guide either in contact (S0) or 2 mm (S2) from the cement surface. For KHN and DC evaluation, each sp was divided in four regions: irradiated-center (IC), irradiated-edge (IE), non-irradiated-center (NC) and non-irradiated-edge (NE). Light curing unit spectral emissions were obtained with the relative (%) and absolute (mW/cm) irradiance values. Results: The spetrometry was more capable to detect the RT differences between the restoration materials than the CCD camera and indicated that the S resin (3,5%) transmitted more light and the E ceramic (1,6%) transmitted less light. ANOVA revealed higher FS, KHN and DC values for the cement in dual-cure mode compared to light-cure (p<0.001). The QTH (192 MPa) promoted higher FS than LED (164 MPa). On the other hand, the LED increased the KHN values in some interactions with the EE group and in other interactions there were not statistic differences between the curing units. The FT-Raman method was less sensitive than KHN to detect differences between the experimental groups. The ceramic materials reduced the lightcured cement’s FS and KHN compared to the S0 and S2 groups; however, when the catalyst was added to the cement these reductions did not occurred. The IC regions showed the highest KHN values and the NE, the lowest, indicating the non-uniform distribution of the light. A positive correlation was found between DC and KHN. Conclusion: It was possible to conclude that there was a tendency for the restorative materials which allowed more light transmission to provided better conditions for an efficient polymerization reaction and, consequently, desirable physical properties of the resin cement, more noticeable when used in light-cure mode.

Influência da atenuação da luz provocada por materiais restauradores indiretos estéticos sobre a polimerização de um cimento resinoso