Color interaction of dental materials: blending effect of layered composites

To evaluate the in vitro blending effect (BE) of layered resin composites related to material, shade, and differences in color and translucency between compared materials.

Specimens made of two composites (2CS, n=5) consisted of the outer composite with an outer diameter of 10mm, 4mm thick and an inner diameter of 4mm, 2mm thick for the inner composite. Thus, the inner composite was encircled by a 3mm outer composite around its circumference and backed by a 2mm thick outer composite, to simulate a dental restoration surrounded by hard dental tissues. The outer composite was Palfique Estelite (PE, C2 shade, standard shade), while the inner composites were PE A2, B2 and C2 shades and corresponding shades of Point 4 (P4), Tetric Ceram (TC) and Filtek A110 (FA) composites (batch shades). Single-composite, disk-shaped specimens (1CS) of all five shades (D=10mm, 2mm thick, n=5) were made as well. Visual color assessments were done by six observers using a lightbooth and 1 (mismatch) to 5 (perfect match) scale. The BE was calculated as a difference in scores between corresponding 2CS and 1CS. Z-scores and corresponding BE values (BE(Z)) were calculated. 1CS were also evaluated using a spectrophotometer.

Blending effect ranged from -0.4 to 2.2, while BE(Z) ranged from -0.6 to 3.0. Mean visual scores for 1CS and 2CS were 1.8 (1.2) and 2.2 (1.3), respectively. BE increased with a decrease in color difference (r=0.41) and increase of translucency parameter (TP, r=0.77). High agreement was recorded among pairs of observers for both 1CS, r=0.95 (0.03) and 2CS, r=0.96 (0.02).

Blending effect is composite and shade dependent. Quantifying of blending potential of dental materials might provide useful clinical information for dental professionals.