Abstract
The purpose of this study was to evaluate the color and translucency of multi-shade layered composites. To simulate a class IV direct composite restoration, 4 mm-thick disc-shaped specimens (15 mm in diameter) were prepared. Z250 (A2) or Z350XT (A2 enamel (E), body (B), and dentin (D)) were bulk-filled. Both Z350XT/A2E and Z350XT/A3D were bi-layered, in which the thickness of Z350XT/A2E was increased from 1.0 mm to 3.0 mm with an increment of 1.0 mm while the thickness of Z350XT/A3D was decreased. Total thicknesses of the sandwiched specimens were maintained at 4 mm. The CIELAB parameters (L*, a*, and b*) of specimens were measured using a spectrophotometer to calculate the color difference (ΔE) without background, and to calculate translucency parameter (TP) on a white or black background. One-way ANOVA and post-hoc Tukey’s test were employed for statistical analysis. ΔE between Z250 (A2) and three different shades of Z350XT (A2E, A2B, and A2D) were greater than 3.3, that was an unacceptable level. ΔE between a bulk-filled specimen with Z350XT/A2B and layered specimen with the Z350XT/A2E and Z350XT/A3D was the lowest in a specimen of A2E 2 mm + A3D 2 mm (p0.05). Statistically significant difference was found between the TP values of bulk-filled specimens (p0.05). The TP values of layered specimens increased with increasing the thickness of enamel shade (p0.05). Within the limitation of this in vitro study, the combined layering with 2 mm-thick A2E and 2 mm-thick A3D is recommended for the class IV direct composite restoration with a Z350XT/A2 shade.
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