Agradecimentos: We would like to thank Braden Sullivan for the technical assistance, and Dr. Veber L. B. Azevedo and Oswaldo S. de Andrade for the donation of some of the CAD/CAM blocks tested in this study. This research was supported in parts by grants from the São Paulo Research Foundation (Sprint process 2017/50131-5), the National Council for Scientific and Technological Development (process 304692/2018-2), Brazil and CALDO (Consortium of Alberta, Laval, Dalhousie and Ottawa Universities), Canada. Consortium of Alberta, Laval, Dalhousie and Ottawa Universities, Grant/Award Numbers: IR&DRef, PAP17-08 Ver menos

Abstract: Evaluate the effect of thickness of high-translucency (HT) CAD/CAM materials on irradiance and beam profile from a blue light-emitting diode light-curing unit (LCU) and on the degree of conversion (DC) and maximum polymerization rate (Rpmax ) of a light-cured resin cement (LCC). The direct output from the LCU, the light transmission and irradiance ratio (IR) through one conventional composite and nine HT CAD/CAM materials (0.5, 1.0, 1.5, or 2.0-mm thick; n = 5) were measured with a integrating sphere coupled to a spectrometer. The light beam was assessed with a beam profiler camera. The DC at 600 s and the Rpmax of one LCC was determined using a Fourier transform infrared spectrometer (n = 5). Data were analyzed by ANOVA followed by Tukey's tests, and Dunnett's test was also used for irradiance data ('alpha' = 0.05). A significant decrease in irradiance through all materials occurred as thickness increased. Thin CAD/CAM materials improved light homogeneity, which decreased with the increase in thickness. The DC of the LCC directly exposed to light was the same as when exposed to 45%, 25%, 15%, or 5% IRs. Rpmax decreased with the decrease in IR. Although the HT CAD/CAM materials reduced the irradiance from the LCU, minor effects were observed in the LCC's DC. Despite the light attenuation of blue light through different CAD/CAM materials that were up to 2-mm thick, the degree of conversion of one brand of light-cured resin cement was clinically acceptable when the LCU was used for 30 s Ver menos