the color masking ability of a zirconia ceramic on the substrates with different values

background. the color masking ability of a restoration plays a significant role in coveringa discolored substructure; how-ever, this optical property of zirconia ceramics has not been clearly determined yet. the aim of this in vitro study was to evaluate the color masking ability of a zirconia ceramic on substrates with different values. methods. ten zirconia disk specimens,0.5 mm in thickness and 10 mm in diameter, were fabricated by a cad/cam sys-tem. four substrates with different values were prepared, including: white (control), light grey, dark grey, and black. the disk specimens were placed over the substratesfor spectrophotometric measurements. a spectrophotometer measured the l*, a*, and b* color attributes of the specimens. additionally, δe values were calculated to determine the color differences betweeneach group and the control,and were then compared with the perceptional threshold of δe=2.6. repeated-measures anova, bonferroni, and one-sample t-testwere used to analyze data. all the tests were carried out at 0.05 level of significance. results. the means and standard deviations of δe values for the three groups of light grey, dark greyand black were 9.94±2.11, 10.40±2.09, and 13.34±1.77 units, respectively.significant differences were detected between the groups in the δe values (p 2.6) (p<0.0001). conclusion. within the limitations of this study, it was concluded that the tested zirconia ceramic did not exhibit sufficient colormasking ability to hide thegrey and black substrates.