Comparison of surface properties of universal shade and conventional resin-based composites after degradation and repolishing

Purpose: To investigate the discoloration, line roughness and gloss of conventional and universal shade resin-based composites. Methods: Clearfil AP-X (AP-X) and Estelite Sigma Quick (EQ) samples were prepared. Discoloration, roughness, and gloss were measured on mirror-polished, alkaline-degraded, and repolished surfaces. The superficial layer degraded by alkaline immersion (degraded layer) was ground off from the sample surface. After removing the degraded layer, the surface was polished with aluminum oxide powder (1.0 mu m and 0.3 mu m), to create a repolished specimen. Scanning electron microscopy observations were made of the specimens. Results: The results were compared with those for Omnichroma (OC) from a previous study. All the materials showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials.