Color stability of multilayer resin composite versus feldspathic ceramics after immersion in different beverages

The objective of this study was to assess the color stability of multilayer resin composite (RC) blocks by immersing them in staining solutions. Four RC blocks, Cerasmart Layer (CL), Block HC Hard AN (HC), KZR-CAD HR4 E-VA (EV), and Katana Avencia N (KA), were tested, with a ceramic block, Vita Mark II, serving as the control. All specimens were prepared using #2000 SiC paper and stored in ultrapure water. The immersion tests were performed using five staining solutions (coffee, Coke, tea, red wine, and Milli-Q) at 37 °C, with measurements taken at 24 h; 1, 2, 3, and 4 weeks; and 3, 6, 9, and 12 months. Color parameters (L*, a*, b*) were measured, and the color differences (∆E) were calculated using the color parameters obtained before immersion tests and at each interval. Statistical analysis was performed using three-way ANOVA (α = 0.05). Results showed that red wine caused the most significant ΔE (16.6) across all materials, followed by tea (2.19), Coke (1.94), coffee (1.73), and Milli-Q (0.99), with significant differences (p < 0.05). Several RCs demonstrated color differences compared with ceramic, particularly EV and KA in coffee, all RC blocks in Coke, CL in tea, CL and KA in red wine, and EV and KA in Milli-Q. The changes in color parameters over time differed between the solutions; notably, red wine showed the most significant color changes in all beverages. These findings suggest that multilayer RC blocks exhibit discoloration resistance comparable to that of ceramic materials.