A Comparative Effect of Nano-Zirconia and Nano-Zinc Oxide on Color Stability of Pigmented Maxillofacial Silicone Under Accelerated Aging

This in vitro study was designed to assess and compare the color stability of pigmented maxillofacial silicone elastomers reinforced with nano-zirconia and nano-zinc oxide with silicone without nanoparticles following accelerated weathering at various time intervals. A total of 150 disc-shaped pigmented maxillofacial silicone specimens were prepared and classified into one control group of 50 silicone elastomers pigmented without nanoparticles and two experimental groups of 50 nano-zirconia (ZrO₂) and 50 nano-zinc oxide (ZnO). The samples were then exposed to artificial weathering for 200, 400, and 600 h of accelerated weathering. All color measurements were performed at baseline and after aging using same specimens assigned to each interval with a spectrophotometer in the Commission Internationale de l'Eclairage (CIELAB) color space. Color differences (ΔE) were analyzed using two-way repeated measures ANOVA with Greenhouse-Geisser correction (p < 0.05). Color change values of both groups increased markedly with time aging, indicating that nanoparticle reinforcement significantly influenced the color change over time. At all aging intervals, the ZrO₂ group demonstrated the lowest ΔE values, followed by ZnO, while the control group exhibited the highest discoloration. After 600 h of accelerated aging, mean ΔE values were 3.23 for the control group, 2.82 for ZnO, and 2.16 for ZrO₂, exhibiting a superior color stability of zirconia-reinforced silicone. Nano-ZrO₂ showed better color change stability than nano-ZnO at all aging periods, indicating that it may be used to increase the esthetic longevity of maxillofacial silicone prosthesis.