Thickness Influence on Optical Behavior, Surface Microhardness, and Polymerization of One-Shade Resin Composites with Different Light-Matching Technologies

Objectives:This study compared two one-shade resin composites based on different light-matching technologies with a conventional nano-hybrid composite in terms of light transmittance, color blending ability, surface microhardness, and degree of monomer conversion at different restoration thicknesses.Methods: One-shade composites using smart chromatic technology (Omnichroma; SCT) and adaptive light-matching technology (Charisma Diamond One; ALT), and a nano-hybrid composite (Filtek Z550; NHC) were evaluated at 1-mm and 2-mm thicknesses. Standardized specimens were prepared for light transmittance, surface microhardness, and degree of monomer conversion analyses. Tooth color blending was assessed on extracted maxillary incisors. Data were analyzed using appropriate parametric or non-parametric statistical tests (p < 0.05).Results: Light transmittance did not differ significantly among materials of the same thickness (p > 0.05), but significant differences were observed in overall comparisons (p < 0.001). Color blending was similar at 1 mm, whereas at 2 mm NHC showed lower ΔE values than ALT (p = 0.001). After water storage, ΔE values decreased only in SCT-1 and NHC-1 groups (p < 0.05). NHC showed the highest microhardness, while SCT exhibited the highest monomer conversion (p < 0.05).Conclusions: Composite formulation and restoration thickness influence optical behavior, surface microhardness, and polymerization-related outcomes.