Color Match of Single-Shade and Group-Shade Resin Composites: A Visual and Instrumental Analysis

Objective: Single-shade materials are favored for simplifying clinical workflows without compromising the esthetics of restorations, although evidence supporting their use remains limited. Therefore, this laboratory evaluated color match of single-shade versus group-shade resin composites. Methods: Sixty sound human molars were divided into three subgroups (n = 20), based on the tooth-shade correspondence for the tested group-shade resin composite: L (light) including A1, B1, B2, C1 and D2; M (medium) including A2, A3, C2, D3 and D4, and D (dark) including A3.5, A4, B3, B4, C3 and C4 shaded teeth. Standardized class V cavities (4 × 4 × 2 mm) were prepared. Half of the specimens within each subgroup were restored with single-shade (Omnichroma), while the other half was restored with group-shade resin composite (SimpliShade). Tooth/restoration ΔE00 color differences were calculated at 24 hours (T1), and after seven days (T2) by a spectrophotometer (VITA Easyshade V). A visual analysis was performed after 14 days (T3). Also, a novel computer vision algorithm (CVA) analysis, was employed to evaluate color match at three weeks (T4). Student's t-test was used to compare the two groups within each subgroup and time point and one-way ANOVA was used to compare the values between subgroups, within each group and time point. Results: Instrumental analysis at T1 showed higher mean ΔE00 for single-shade compared to group-shade resin composites (p < 0.05), within each subgroup. Within single-shade specimens, significantly higher mean ΔE00 differences were found at T2 between D (8.24 ± 1.85) vs L (5.65 ± 2.24) (p = 0.007) and M (6.49 ± 2.5) (p = 0.03). Within group-shade specimens, a significant difference was found between L (4.16 ± 2.19) and M (2.17 ± 1.05) at T1 (p = 0.034). Visual analysis reported a significant difference (p = 0.0153) between L-group shade (1.03 ± 1.04) and L-single shade (1.97 ± 0.78) restorations (p = 0.0153). No significant differences were detected when CVA analysis was employed. Conclusions: Overall, group-shade showed better color match than single-shade resin composites, especially when spectrophotometric and visual evaluation were employed.