Final Colour of Ultratranslucent Multilayered Zirconia Veneers, Effect of Thickness, and Resin Cement Shade

Abstract

Background. Aesthetic restorations should be able to mimic the natural colour depth of teeth, affected by several factors including material properties. There is a lack of information regarding the effect of cement shade and material thickness on the final colour of ultratranslucent multilayered zirconia veneers. Objectives. This study evaluated the effect of ceramic thickness and resin cement shade on the final colour of different layers of ultratranslucent multilayered (UTML) zirconia veneers. Methods. This in vitro study produced 90 rectangular-shaped specimens with nonsintered Katana UTML monolithic zirconia (Kuraray Noritake Dental, Tokyo, Japan), shade A1 blocks. Ceramic samples were prepared in two groups of 0.7 mm and 0.5 mm thicknesses, 45 of each (a: $8\times 11\times 0.5\text{mm}$ ; b: $8\times 11\times 0.7\text{mm}$ ). Specimens of each thickness were further divided into 5 groups: universal, clear, brown, white, and opaque ( $n=9$ ). Each adhesive resin cement (Panavia V5) was applied between the ceramic samples and composite substrate. The colour values were measured using a spectrophotometer in baseline and after resin cement application according to the CIELab system. For all samples, $\Delta \text{E}00$ values were obtained. Data were evaluated with SPSS 25 using the three-way ANOVA test ( $p<0.05$ ). Results. The factors of cement shade, ceramic thickness, and ceramic layers have statistically significant effect on $\Delta \text{E}00$ values ( $p<0.001$ ). The results showed lower $\Delta \text{E}00$ values with thicker ceramic veneers. Tukey test results showed that the opaque and brown shade had a significantly greater $\Delta \text{E}00$ values comparing to universal ( $p=0.004$ ), clear, and white shades ( $p<0.001$ ). Conclusion. The colour change was greater in lower ceramic thickness. Different shades of resin cement and layers of UTML zirconia differently affected the final colour.