Applicability of CIELAB/CIEDE2000 formula in visual color assessments of metal ceramic restorations

Abstract Objectives To investigate the applicability of color-difference formula (CIELAB or CIEDE2000) in visual color assessments of metal-ceramic specimens in small color-difference ranges. Methods Metal-ceramic specimens using mixture of gradient ratio porcelain powders were fabricated to create a color pool. Color differences of specimen pairs were calculated using the CIELAB ( Δ E ab ∗ ) and CIEDE2000 (Δ E 00 ). A questionnaire, composed of 1 target and 3 enactment specimens, was designed. For formula-determination, the enactment specimen with the minimum Δ E to the target specimen was registered as FS. For visual-assessment, twenty participants were asked to finish the questionnaire by choosing the most color-matched enactment specimen to the target. The percentage of the FS been selected ( P FS ) was calculated, which was used to represent the consistence of formula-determination and visual-assessment. Binomial Tests were used to compare the differences between P FS values and 33% (the randomized probability of the FS been selected was one out of three, approximate 33%). Regression analysis was used to determine the correlation between Δ E ab ∗ and Δ E 00 values. Results A linear regression equation was drawn as Δ E 00 = − 0.049 + 0.619 × Δ E ab ∗ . There were no significant differences between P FS values and 33% within the range of Δ E ab ∗ 2.0 , whereas P FS values were significantly higher than 33% when Δ E ab ∗ > 2.0 ( P L * values and higher b * or C ′ values, within the range of 1.0 Δ E ab ∗ 2.0 . Conclusions CIE color-difference formulas were not applicable for visual color assessments of metal-ceramic specimens within the color-difference range of Δ E ab ∗ 2.0 .