Color accuracy of different types of monolithic multilayer precolored zirconia ceramics

Statement of problem: The use of monolithic multilayer precolored zirconia facilitates the production of esthetic restorations in a convenient and straightforward manner. However, the accuracy of the final color is not clear. Purpose: The purpose of this in vitro study was to determine the color accuracy of different types of monolithic multilayer precolored zirconia ceramics of varying thicknesses. Material and methods: Eighty cubical A2-shade monolithic multilayer precolored zirconia ceramic specimens (15×15 mm) of 2 different thicknesses (1.0 mm and 1.5 mm) and 4 zirconia brands (UPCERA EXPLORE [UPEX], KATANA Zirconia STML [STML], Enamel ZR Multi-5 [EZM5], and Aidite 3D Pro Zir [A3DM]) were fabricated and divided into 8 groups (n=10). The Commission Internationale de l'Eclairage (CIELab) values were measured against 3 different backing substrates (gray, transparent, and A2) by using a spectrophotometer. The color difference (ΔE) between the backing substrates of each group and the Vita A2 Shade Guide, translucency parameter (TP), and chroma (C) values were calculated to evaluate the accuracy of the final color. Statistical analysis was performed by using ANOVA and the post hoc Tukey HSD tests (α=.05). Results: The ΔE values for UPEX and STML exceeded the clinically acceptable thresholds for gray and transparent backing substrates (ΔE>3.7) and were higher than those for the A2 backing substrate. A3DM showed less ΔE from the shade guide for all the backing substrates (P<.05), and the corresponding ΔE values were within the clinically acceptable threshold (ΔE<3.7). The TP value was inversely proportional, and the C value was proportional to thickness. For the zirconia ceramics with identical thicknesses, UPEX and STML exhibited the highest TP values, and A3DM showed the lowest C value (P<.05). Conclusions: At a specific thickness, color accuracy was mainly affected by the type of monolithic multilayer precolored zirconia ceramic, and the high transparency of ceramics will cause color differences.