Bioactive Resin Cement Color Stability and Restoration Thickness as Determinants of the Final Shade in a Glass–Ceramic CAD/CAM Material

Bioactive resin cements are gaining popularity for their clinical benefits, but concerns remain regarding their color stability. This study evaluated the color change (ΔE₀₀) and whiteness change (ΔWI_D) in bioactive resin cements and how their potential discoloration affects the shade of bonded CAD/CAM glass-ceramics at different ceramic thicknesses. VITA Mark II blocks were prepared in three thicknesses (0.5, 0.8, and 1.0 mm) and divided by resin cement: Panavia SA Universal (Pn), Predicta Bioactive Cement (Pr), and ACTIVA BioACTIVE Cement (Ac) (n = 10). Additionally, 10 specimens (10 × 2 mm) of each cement alone were prepared. Color was measured before and after 24 days of coffee immersion. Cement type significantly affected ΔE₀₀ (<i>p</i> < 0.001). Pn had the highest color stability, followed by Pr and Ac, with significant differences between each. ΔWI_D also varied by cement (<i>p</i> = 0.004), with Pn and Pr differing significantly from Ac. Ceramic thickness alone had no significant effect on ΔE₀₀ or ΔWI_D, but its interaction with cement type was significant (<i>p</i> < 0.001). While ceramic thickness does not directly affect the final shade, its combination with resin cement does. Choosing the right resin cement is key for long-term esthetic outcomes.