Degradation Resistance of Next-Generation Dental Composites Under Bleaching and Immersion: A Multiscale Investigation

Background/Objectives: In the oral environment, tooth-colored restorations are frequently exposed to staining agents, affecting their aesthetic and physical properties. This study assessed the impact of stains and bleaching agents on the surface roughness, microhardness, and color stability of four different composite materials (Omnichroma, Charisma, Z350, and TPH). Methods: Based on group distribution, the discs of all the composite material samples were prepared. All the ninety-six-disc specimens (n = 96) were then randomly divided into four different groups based on different composite resin groups. The samples were then immersed into four different immersing media [each group had twenty-four-disc samples (n = 24)]. Finally, all the samples then faced the challenge of a bleaching agent application. Measurements were taken at baseline, post-immersion, and post-bleaching stages. Results: Red wine caused increased roughness in Filtek™ Z350 and significant color change in Omnichroma, while coffee increased roughness in Omnichroma and altered the color of TPH spectra. Soda led to increased roughness and significant color change in TPH spectra. Additionally, Filtek™ Z350 experienced reduced microhardness across all solutions after bleaching. Conclusion: This study concluded that staining and bleaching adversely affected the tested composites, with increases in surface roughness, color change, and microhardness reduction observed. Overall, Charisma diamond demonstrated the greatest resilience to staining and bleaching challenges, whereas Filtek™ Z350 XT exhibited the most pronounced degradation, indicating that composite formulation critically governs both aesthetic and mechanical stability under clinically relevant conditions.