Color matching and stability of single-shade paste, single-shade flowable bulk-fill, and simplified shade-system bulk-fill composites

Abstract

Background: The growing demand for efficient aesthetic restorations has driven the development of single-shade and simplified shade-system resin composites, which are designed to streamline clinical workflows without compromising optical integration. However, their initial color-matching capabilities and long-term stability following dietary staining remain critical clinical concerns. Therefore, this study aimed to evaluate the color matching and stability of a single-shade paste composite, a single-shade flowable bulk-fill composite, and a simplified shade-system paste bulk-fill composite. Materials and Methods: Thirty extracted human molars were allocated to three groups (n=10): Charisma Topaz One, Charisma Bulk Flow One, and Opus Bulk Fill APS. Standardized buccal cavities (4x4 mm) were prepared and restored following selective etching and universal adhesive application. Instrumental color (VITA Easyshade V) was recorded at baseline, 24 h post-restoration, after 7-day coffee staining, and after repolishing; visual matching (five calibrated observers, 5-point scale) was recorded at the last three of these time points. Data were analyzed using CIEDE2000 (ΔE00), ANOVA, Kruskal-Wallis, Friedman tests, and GEE models (α=0.05). Results: A significant intergroup difference occurred only at the post-restoration/baseline interval (p<0.001), where the simplified shade-system showed lower ΔE00 than both single-shade materials. No significant differences were found after staining or repolishing (p>0.05). All materials showed significant phase-related (ΔE00) changes (p<0.001). Repolishing significantly reduced the color change produced by staining in all groups. Visual acceptability remained high but showed significant time and group×time interactions. Conclusions: All composites exhibited similar staining susceptibility, with repolishing reversing much of the staining-related color change. Initial color matching differed among the materials but was influenced by baseline tooth color.