Aim: A discoloration existing under tooth restoration can affect the final restoration color, and various techniques can be used to address this. The aim of this study was to investigate the masking ability of the substructure color of different hybrid CAD/CAM ceramics in various thicknesses. Methodology: A total of 120 samples were produced from 4 different CAD/CAM hybrid ceramic blocks (Cerec blocs, GC Cerasmart, Vita Enamic, 3M Lava Ultimate) in 1-, 1.5-, and 2-mm thicknesses. The samples were sliced at a pressure of 100 N with a low-speed precision cutting device under water cooling. The specimens were placed over a neutral grey background for initial spectrophotometric measurements. A three-color posterior nanohybrid composite (14x7x1 mm) was preferred to mimic discoloration in the substructure. The cementation procedure of the composite and the CAD/CAM hybrid ceramic complex was standardized under 10 N continuous pressure and was performed using a dual-cured resin cement. All samples were incubated at 37°C for 24 hours after cementation. The second spectrophotometric measurement was done via the L*, a*, and b* color attributes of the complex specimens. Additionally, ΔE* values were calculated to determine the color differences between each group. A Kruskal Wallis test was used for statistical analysis, and a Dunn’s test was used for group comparison. Significance was evaluated at p<0.05.

Results: It was found that as the thickness of the ceramics increased, the substructure color was better masked, the thickness making a statistically significant difference in the masking ability (p<0.01). For 1- mm-thick samples, the highest ΔE* value was found in in Lava Ultimate (11.59) while the lowest value was found in GC Cerasmart (4.27). Conclusion: Within the limitations of this study, it was concluded that the tested CAD/CAM hybrid ceramics showed better masking ability than Cerec blocs.