Objective: It has been clinically observed that color differences between teeth and some restorations are smaller than if they are viewed in isolation. The objective was to evaluate in vitro the influence of restoration size, initial color difference and translucency on blending effect (BE) of resin composites.
Methods: Specimens were made of two composites (2CS, n = 5). The outer ring (D=10 mm, 2-mm thick) was made of Palfique Estelite (PE, C2 shade), while the inner composites (D = 2-, 4-, and 6-mm, 2-mm thick) were PE and Esthet-X (EX, A2 and B2 shades of both materials). Single-composite specimens (1CS) of all five shades (D = 10 mm, 2-mm thick, n = 5, batch) were made as well. Visual color assessments were done by six observers using a 1-5 scale. The BE were calculated as a difference in visual scores between corresponding 2CS and 1CS. 1CS were additionally evaluated using a spectrophotometer (D55, 10 degrees). Intra-and inter-observer agreements were tested.
Results: The blending effect for comparisons of PE/A2 for 2-, 4- and 6-mm inner composite was 2.7, 1.7, and 1.7, respectively. Lower values were recorded for PE/B2 (1.7, 1.2, and 1.1), EX/A2 (0.3), 0.0, and 0.1) and EX/B2 (-0.2, -0.1, and -0.1). The correlation coefficient (r) among BE for 2-, 4-, and 6-mm inner composite (2CS) and deltaE* among batch shades and PE/C2 (1CS) were 0.98, 0.95, and 0.97, respectively.
Significance: Discovering and quantifying mechanisms of color shift of dental materials towards color of surrounding teeth may improve the esthetics of restorations and simplify shade matching.