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 DeltaE(00) formula, and comparison among groups was performed by using 2-way ANOVA and Tamhane post hoc tests. The comparison of DeltaE(00) between the values obtained from backgrounds #3 and #8 was performed by using the independent t test (alpha=.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 significant 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.