Depth-Dependent Performance of Single-Shade Composite Resin: Assessing Color Adjustment Potential and Translucency

The blending effect refers to a phenomenon where the color difference between the restorative material and surrounding tooth structure appears smaller when they are adjacent to each other. The effect can be affected by the translucency of restorative material. This study evaluated the influence of cavity depth on the color adjustment potential (CAP) and translucency of a single-shade composite resin compared to multi-shade composite resins. A single-shade composite (Omnichroma) and two multi-shade composites (Filtek<sup>TM</sup> Z350 XT and Estelite® Sigma Quick) were tested in 1.5 mm and 3.0 mm cavity depths/thicknesses. CAP was assessed using the ΔE<sub>ab</sub>* color difference between single and dual specimens. Translucency was measured using the translucency parameter (TP). The single-shade composite demonstrated significantly higher CAP and TP values compared to multi-shade composites across all depths/thicknesses (<i>p</i> < 0.0167). CAP decreased with increasing cavity depth for all composites. In 1.5 mm cavities, the single-shade composite achieved a clinically imperceptible color match (ΔE<sub>ab</sub>* < 3.7). The higher translucency of the single-shade composite likely contributes to its enhanced blending effect and CAP. These results suggest that single-shade composites offer superior shade-matching ability due to their structural color phenomenon and high translucency. However, the decrease in CAP with increasing cavity depth indicates potential limitations in deeper restorations. Clinicians should consider appropriate techniques or additional products for optimal aesthetic outcomes in deeper cavities when using single-shade composites.