Abstract: Objective: To study the transparency of two Nacera zirconia systems and their color difference with A2 color of Vita classical shade guide. Methods: The Nacera Pearl and Nacera Shell zirconia blocks were processed by CAD/CAM systems into disc-shaped core porcelain with different thicknesses (0.5mm, 0.8mm, 1.0mm, 1.5mm), then veneered correspondingly with 1.0 mm, 0.7 mm, 0.5 mm, 0.0 mm thick veneer porcelain(Noritake Kizai Co., Nagoya, Japan) of A2 color and glazed. A total of 40 copings of φ10.0 mm, 1.5mm thick zirconia-based ceramic specimens were produced for this study (n=5). PR-655 spectrophotometer was used to measure the color parameters of the specimens against standard black and white plates and 4.0mm thick dentin color resin. Then the relative transparency (TP) and the color difference (ΔE) with A2 color (Vita Lumin Vacuum shade guide) were calculated. Results: TP values of Nacera Shell were significantly smaller than Nacera Pearl. As the core thickness of the Nacera Pearl core increases, ΔE values between specimens and A2 color film became larger, and the color of Nacera Shell changed relatively small. Conclusion: Both systems of Nacera zirconia simulate the A2 color well. However, compared to high transparent zirconia, the color of low transparent zirconia is more stable.

Key words: Thickness, Color difference, Zirconia, Veneer porcelain