In Vitro Comparison of Mechanical and Esthetic Properties of Different Universal-Shade Resin Composites After Simulated Aging

Background: Universal-shade resin composites (USRCs) have gained popularity for their simplified shade-matching and reduced chairside time. However, their long-term performance under oral environmental stresses remains uncertain. This study aimed to compare the mechanical and esthetic properties of five commercially available single-shade resin composites and one conventional micro-hybrid resin composite (MHRC) after simulated aging. Methods: A total of 18 disc-shaped specimens (10 mm circular × 3 mm thick) were prepared from five USRCs (Omnichroma, Zenchroma, A-Uno, TRANSCEND, and Ecosite One) and one MHRC (Clearfil AP-X). The polymerized specimen disk was polished using 2500 grit SIC paper. The mechanical properties, Vickers microhardness (HV), elastic modulus (EM) and creep (CR), and the esthetic properties, color and gloss, were measured after 24 h water storage and after 1-year stimulated aging. The data was analyzed using SPSS 27.0 software. A significance level of α = 0.05 was used for all statistical analyses. Results: Both the aging and types of material showed a significant effect on the mechanical and esthetic properties of the tested resin composite materials. The MHRC showed a significantly higher HV and EM compared to the USRC (p < 0.05). The MHRC showed significantly lower CR compared to USRC (p < 0.05). The color retention of USRCs was comparable to the MHRC (p > 0.05) and some USRCs showed superior gloss values compared with MHRC (p < 0.05). The solubility of USREs were comparable to MHRC (p > 0.05) except A-Uno which showed significantly higher solubility compared to MHRC (p < 0.05). Conclusions: Within the limitations of this in vitro study, it concludes that the USRC possesses inferior mechanical properties compared with the convention MHRC. Thus, their use should be limited when strong and durable mechanical properties are required under heavy occlusal stress. The use of USRCs could be beneficial for achieving a highly esthetic outcome of the restoration that does not includes the area that comes under heavy occlusal stress.