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 (ΔWID) 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 (p < 0.001). Pn had the highest color stability, followed by Pr and Ac, with significant differences between each. ΔWID also varied by cement (p = 0.004), with Pn and Pr differing significantly from Ac. Ceramic thickness alone had no significant effect on ΔE00 or ΔWID, but its interaction with cement type was significant (p < 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.