In vitro color stainability and relative translucency of CAD-CAM restorative materials used for laminate veneers and complete crowns

Statement of problem. Assessing the long-term stainability and durability of restorative materials is an important parameter for determining clinical success and longevity. Information remains limited regarding the color stainability and translucency of the recently introduced ceramic materials for restorative treatment. Purpose. The purpose of this in vitro study was to compare the effect of cyclic immersion in hot and cold coffee on the color stainability and translucency of 6 computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials at thicknesses which represent a laminate veneer and a complete crown. Material and methods. CAD-CAM restorative materials including zirconia-reinforced lithium silicate ceramic (Celtra Duo), lithium disilicate glass-ceramic (IPS e.max CAD), polymerized resin nanoceramic (Lava Ultimate), integrated ceramic and acrylate polymer network material (VITA ENAMIC), zirconia-reinforced lithium silicate (VITA SUPRINITY), and zirconia (VITA YZ HT) were studied in 2 thicknesses for laminate veneer (0.7 mm) and complete crown application (1.3 mm to 1.5 mm). For each specimen, color difference on a gray backing was calculated using a spectroradiometer between its baseline color and after 6000 cycles of coffee thermocycling. The colors of the specimens on the black and white backings were used to calculate the relative translucency parameter from the CIEDE2000 color difference formula. An ANOVA and the Bonferroni-corrected Student t tests were used for testing statistical significance (alpha=.05). Results. No difference was found among the means of color change after coffee thermocycling between any 2 materials for the crown thickness (P>.999), and no difference was found among the means of color change between the 2 thickness groups within each material (P >=.187). However, the mean color change of the resin nanoceramic material in laminate veneer application (0.7 mm) was greater than that of every other material in the veneer thickness group (P<.001), and the mean color change of the integrated ceramic and acrylate polymer network material was greater than that of the lithium disilicate glass-ceramic material studied at the veneer thickness (P=.014). Translucency was found to be lower for complete crown thickness compared with laminate veneer thickness within each combination of material and coffee thermocycling (P<.001). The translucency of the lithium disilicate glass-ceramic material studied at the laminate veneer thickness was also found to be higher after coffee thermocycling (P=.033). Furthermore, several differences among materials were found for each combination of thickness and coffee. Conclusions. Color change after coffee thermocycling of the resin nanoceramic material was beyond the acceptability threshold. The lower translucency found for crown thickness compared with veneer thickness was verified.