Purpose: To produce CAD/CAM reference samples for shade communication milled from the restoration materials zirconia (ZrO2) and zirconia-reinforced lithium silicate (ZLS) and evaluate the color difference with the corresponding conventional VITA Classical (VC) shade tab. Furthermore, to verify the color consistency of the materials. Materials and Methods: In total, 55 samples were milled out of ZrO2 and ZLS in five different colors, and their color parameters were compared to the corresponding VC tabs both visually and digitally. For digital evaluation, images were taken of the samples and VC tabs and analyzed in Adobe Photoshop to extract L*a*b* values. Color difference (ΔE00) was calculated using the CIEDE 2000 formula. Multilevel mixed-effects linear regression model was used to derive estimates of the mean ∆E00. Results: Color difference was significantly higher than 1.8 in the case of all the ZrO2 samples and for the ZLS A3, B2, and C2 samples. Color difference was also found during the visual comparison. Comparing the same color samples, the ΔE00 exceeded 0.8 in some cases but stayed under 1.8 in every case and showed no color difference visually. Conclusions: When comparing CAD/CAM samples and VC shade tabs, visible and measurable color differences (ΔE00 > AT50:50%) were found in the case of all ZrO2 samples and in three out of five evaluated shades of ZLS samples. The color consistency of the blocks was acceptable. Better shade communication and more reliable shade reproduction is achieved when reference photos are sent with a color sample made from the restoration material.
