Influence of Cement Opacity on the Translucency and Related Optical Properties of High Translucency Monolithic Zirconia

Objectives: The objective of this study was to evaluate the effects of cement opacity on the resulting optical properties of a colored high translucency zirconia and a stained high translucency zirconia and compare these to that on a lithium disilicate material.
Methods: Two types of high translucency zirconia (BruxZir Anterior 250 A2 and Lava Plus) were used. Lithium disilicate E-max CAD (LT A2) was included as the control (n=21/group). The samples in the dimension of 12mm x 12mm x 1mm were fired according to the manufacturers’ recommendation. Lava Plus samples were then colored using Lava Plus A2 coloring liquid. The samples in each group were further divided into three groups (n=7) according to cement color: clear, opaque, and A2. After cementing on resin block, the CIE-L*a*b*for all specimen assemblies were measured and the color difference (ΔE) between the samples and the Vita classic A2 shade guide were calculated. The data were analyzed with one-way ANOVA.
Results: E-max CAD lithium disilicate cemented with opaque cement was found to show significantly higher L* value and lower a* value (p<0.001) compared to E-max CAD assemblies with clear and A2 cement, which led to a significantly higher ΔE with Vita A2. On the contrary, Bruxzir samples cemented with opaque cement showed a significantly lower ΔE with Vita A2 shade guide when compared to the Bruxzir assemblies using clear and A2 cements. E-max CAD assemblies with clear and A2 cement, as well as Bruxzir opaque cement assembly, show ΔE lower than the clinically perceptible level. All assemblies in the Lava group show very high L* value and close-to-zero a* and b* values.
Conclusions: Cement color shows different effects on the color and value of E-max CAD lithium disilicate and Bruxzir high translucency zirconia. The staining protocol on Lava was ineffective in changing the white color of the sample.