Optical properties of pre-colored dental monolithic zirconia ceramics

The purposes of this study were to evaluate the optical properties of recently marketed pre-colored monolithic zirconia ceramics and to compare with those of veneered zirconia and lithium disilicate glass ceramics.

Various shades of pre-colored monolithic zirconia, veneered zirconia, and lithium disilicate glass ceramic specimens were tested (17.0×17.0×1.5mm, n=5). CIELab color coordinates were obtained against white, black, and grey backgrounds with a spectrophotometer. Color differences of the specimen pairs were calculated by using the CIEDE2000 (ΔE₀₀) formula. The translucency parameter (TP) was derived from ΔE₀₀ of the specimen against a white and a black background. X-ray diffraction was used to determine the crystalline phases of monolithic zirconia specimens. Data were analyzed with 1-way ANOVA, Scheffé post hoc, and Pearson correlation testing (α=0.05).

For different shades of the same ceramic brand, there were significant differences in L^*, a^*, b^*, and TP values in most ceramic brands. With the same nominal shade (A2), statistically significant differences were observed in L^*, a^*, b^*, and TP values among different ceramic brands and systems (P<0.001). The color differences between pre-colored monolithic zirconia and veneered zirconia or lithium disilicate glass ceramics of the corresponding nominal shades ranged beyond the acceptability threshold.

Due to the high L^* values and low a^* and b^* values, pre-colored monolithic zirconia ceramics can be used with additional staining to match neighboring restorations or natural teeth.

Due to their high value and low chroma, unacceptable color mismatch with adjacent ceramic restorations might be expected.