Colour parameters and shade correspondence of CAD–CAM ceramic systems

Abstract

ObjectivesTo 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. MethodsSamples of shades A1, A2 and A3 were fabricated (n=5) from CAD–CAM ceramic blocks (IPS e.max® CAD LT and HT, IPS Empress® CAD LT and HT, Paradigm™ C, and VITABLOCS® Mark II) and polished to 1.0±0.01mm 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° geometry. Spectral reflectance curves were compared using VAF coefficient and were statistically analyzed using Kruskal–Wallis and the Mann–Whitney U test (α=0.05). Colour coordinates were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α=0.001). All colour differences (ΔEab* and ΔE00) were analyzed through comparisons with the PT – perceptibility and AT – acceptability thresholds for dental ceramics. ResultsΔE between ceramic systems and its corresponding shade ranged from 6.32 to 13.42 (ΔEab*) and 4.48 to 9.30 (ΔE00). ΔE 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 (ΔEab*); 1.54–3.87, 1.03–3.90 and 2.95–6.51 (ΔE00). ConclusionsConsidering 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 significanceCareful adjustments should be made to the final shade of CAD–CAM ceramic restorations to reach a clinically acceptable shade match.