Effect of thickness of CAD/CAM materials on light transmission and resin cement polymerization using a blue light‐emitting diode light‐curing unit

Objective 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 ( R p max ) of a light‐cured resin cement (LCC). Material and methods 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 R p max 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 ( α = 0.05). Results 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. R p max decreased with the decrease in IR. Conclusions Although the HT CAD/CAM materials reduced the irradiance from the LCU, minor effects were observed in the LCC's DC. Clinical significance 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.