Ceramic materials for porcelain veneers. Part I: Correlation between translucency parameters and contrast ratio.

STATEMENT OF PROBLEM

Different parameters are used in the literature to describe translucency, making it difficult for clinicians to find clear information on ceramic translucency and compare studies.

PURPOSE

The purpose of this study was to assess the correlation between the contrast ratio (CR) and translucency parameter (TP) when the translucency of different types of ceramic systems is compared.

MATERIAL AND METHODS

Disks 13 mm in diameter and 0.7 mm thick were fabricated for the following materials (n=5): VITA VM9, VITA PM9, IPS Empress CAD, IPS e.max CAD, IPS e.maxPress, and Lava Zirconia. VITA VM9 served as positive control, while Lava Zirconia served as negative control. The luminous reflectance (Y) and color coordinates (CIE L* a* b*) of the specimens were measured with a tristimulus colorimeter. The CR (CR=Yb/Yw) was calculated from the reflectance of the light of the material on a black backing (Yb) to the reflectance on a white backing (Yw). The TP (TP=(LbLw)(2+)(ab*-aw*)(2+)(bb*-bw*)(2) ) was calculated from the color difference of the material on a black versus a white background. One-way ANOVA based on ranked data and the Pearson and Spearman rank correlation tests were used to analyze the data (α=.05).

RESULTS

A significant correlation between CR and TP was found when all specimens were included (P<.001). The coefficient of -0.99 indicated a strong decreasing relationship between the 2 variables.

CONCLUSIONS

Either CR or TP can be used to evaluate the relative translucency of ceramic systems.