Influence of Dark Aging on the Mechanical Properties of Zirconium Silicate Nanoparticle-Reinforced Maxillofacial Silicone Prostheses

Background/Objectives: Silicone elastomers are widely used in maxillofacial prostheses, but their service life is typically limited to 6–24 months due to progressive degradation. Reinforcement with zirconium silicate (ZrSiO4) nanoparticles has been proposed to improve durability, yet evidence on their long-term performance under storage remains limited. This study evaluated the effect of two years of dark storage on the mechanical properties of room-temperature-vulcanized (RTV) silicone reinforced with 1.5 wt% ZrSiO4 nanoparticles. Materials and Methods: Zirconium silicate (ZrSiO4) nanoparticles at 1.5 wt% were incorporated into A-2186 RTV silicone specimens, which were randomly divided into two equal groups: baseline specimens stored for 24 h and aged specimens stored for 24 months under dark conditions. Mechanical properties were assessed by measuring tensile strength, elongation at break, tear resistance, and Shore A hardness in accordance with standardized protocols. Fourier transform infrared (FTIR) spectroscopy was performed to verify the structural characteristics of the ZrSiO4 nanopowder. Statistical analysis was conducted using independent-samples t-tests, with significance set at p < 0.05. Results: After 24 months of dark storage, tensile strength and elongation at break decreased significantly (p < 0.05), indicating reduced elasticity. Tear resistance and hardness showed slight but non-significant reductions. FTIR confirmed the preservation of ZrSiO4 structural features. Conclusions: Dark storage selectively reduced reinforced silicone’s tensile and elongation properties, while tear resistance and hardness remained relatively stable. ZrSiO4 nanoparticles provided partial reinforcement, enhancing stability but not entirely preventing RTV silicone aging.