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

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.

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.

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).

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.