Colour parameters and shade correspondence of CAD-CAM ceramic systems

Objectives: To evaluate colour differences between (1) CAD-CAM ceramic systems considering shades A1, A2 and A3 and the corresponding nominal shade of VC (Vita Classical shade guide) and (2) shades A1-A2, A2-A3 and A1, A2 and A3 within the same ceramic system. Methods: Samples of shades A1, A2 and A3 were fabricated (n = 5) from CAD-CAM ceramic blocks (IPS e.max (R) CAD LT and HT, IPS Empress (R) CAD LT and HT, Paradigm (TM) C, and VITABLOCS (R) Mark II) and polished to 1.0 +/- 0.01 mm in thickness. Spectral reflectance and colour coordinates were measured using a spectroradiometer inside a viewing booth using the CIE D65 illuminant and the d/0 degrees geometry. Spectral reflectance curves were compared using VAF coefficient and were statistically analyzed using Kruskal-Wallis and the Mann-Whitney U test (alpha = 0.05). Colour coordinates were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (alpha = 0.001). All colour differences (Delta E-ab* and Delta E-00) were analyzed through comparisons with the PT-perceptibility and AT-acceptability thresholds for dental ceramics. Results: Delta E between ceramic systems and its corresponding shade ranged from 6.32 to 13.42 (Delta E-ab*) and 4.48 to 9.30 (Delta E-00). DE between shades A1-A2, A2-A3 and A1, A2 and A3 ranged, respectively, 1.93-4.82, 1.22-5.59 and 3.63-8.84 (Delta E-ab*); 1.54-3.87, 1.03-3.90 and 2.95-6.51 (Delta E-00). Conclusions: Considering the corresponding nominal shade from VC, none of the ceramic systems showed colour differences below the AT. In addition, some ceramic systems showed colour differences below AT (shades A1-A2 and A2-A3) and below PT (shades A2-A3). Clinical significance: Careful adjustments should be made to the final shade of CAD-CAM ceramic restorations to reach a clinically acceptable shade match. (C) 2015 Elsevier Ltd. All rights reserved.