Impact of Aging on the Optical and Mechanical Properties of Universal Resin Composites.

Purpose: The clinical use of universal resin composites for direct restorations has increased significantly in recent years due to their versatility and simplified shade-matching approach. However, limited long-term data exist on their stability under aging conditions. This study evaluated the optical and mechanical properties of six universal resin composites (Omnichroma, Charisma Topaz One, Vittra APS Unique, OptiShade, G-aenial A'Chord, and Neo Spectra ST) after six months of artificial saliva aging, while examining the influence of spectrophotometer type and inorganic filler composition on their performance. Methods: Color differences [CIEDE2000 (ΔE00)], translucency (TP00), gloss (GU), surface roughness (Ra, μm), and flexural strength (MPa) were measured before and after six months of artificial saliva aging. Statistical analysis was performed using non-parametric tests, including Kruskal Wallis, Mann Whitney U, and Wilcoxon signed-rank tests, with a significance level set at α < 0.05. Results: Statistically significant differences were observed in color differences (ΔE00), translucency (TP00), gloss (GU) and flexural strength among the tested resin composites following aging (p < 0.05). Vittra APS Unique exhibited the highest translucency (TP00 = 55.35) and flexural strength (initial = 140.0 MPa, aged = 99.7 MPa), while G-aenial A'Chord demonstrated the lowest surface roughness (Ra = 0.124 μm) and highest gloss (56 GU). The type of spectrophotometer used significantly impacted the color differences (p < 0.05). Conclusions: Optical and mechanical properties of universal resin composites varied significantly after six months of artificial saliva aging. Moreover, this study showed that the type of spectrophotometer utilized had a significant effect on color differences.