RESEARCH AND EDUCATION Comparing the color match of monolithic CAD-CAM dental ceramics with the VITA Classical shade guide

Abstract

Statement of problem. Matching the shade selected and the final color of a ceramic restoration is challenging, and studies on matching monolithic ceramics to the shade selected are lacking. Purpose. The purpose of this in vitro study was to compare the color match of monolithic lithium disilicate (LDS), zirconia-reinforced lithium silicate (ZLS), presintered zirconia-reinforced lithium silicate (PS-ZLS), polymer-infiltrated ceramic network (PICN), and multilayer zirconia with the 3 modes of the VITA Classical shade guide. Material and methods. This study was performed on 50 rectangular plates (14x12x1 mm) of 5 types of ceramics with A2 shade (n=10). Zirconia specimens were evaluated in 3 locations: incisal, medial, and cervical thirds. The color coordinates of the specimens of all 7 groups were measured on #3 and #8 Ivoclar Natural Die Color material by using a reflective spectrophotometer. The color coordinates of A2 VITA shade were measured in 5 modes: without backing placed in specimen holder, shade tab on the backgrounds #3 and #8, and 1-mm-thick shade tab on the backgrounds #3 and #8. The color difference of each specimen with 3 modes of A2 shade (without backing and on similar backgrounds) was calculated by using the DE00 formula, and comparison among groups was performed by using 2-way ANOVA and Tamhane post hoc tests. The comparison of DE00 between the values obtained from backgrounds #3 and #8 was performed by using the independent t test (a=.05). Results. In both backgrounds, statistically significant differences were found between the studied groups and VITA shade (P<.001). In most situations, the amount of color difference was lowest for the "shade tab on the backgrounds" mode. On background #3, the highest color difference was related to ZLS (6.48 +/- 0.23), and the lowest values were observed in the PICN group (1.02 +/- 0.31). On background #8, the highest color difference was related to ZLS compared with the "without backing" mode (8.62 +/- 0.27), and the lowest values were reported for ZLS compared with the "shade tab on the backgrounds" mode (1.27 +/- 0.44). The independent t test showed a statistically sign ificant color difference on the 2 different backgrounds for all situations (P<.001). Conclusions. Color selection of monolithic ceramics with the VITA Classical shade guide is improved by placing the VITA tabs on a similar background. Background color has a significant effect on the final shade of the monolithic ceramics. Choosing the correct color for LDS, ZLS, and PS-ZLS requires more care than for PICN and zirconia.