Translucency Parameter and on-Dentin Color Behavior of Enamel Composites

Objectives: In esthetic layered restorations, enamel shades are usually recommended to be applied on dentin at reduced thicknesses (around 0.5mm) to avoid a “low value grayish appearance”. However, some new materials market the possibility of using enamel shades in a “natural” thickness. This study aimed to measure translucency parameter(TP) and assess “on-dentin" color parameters of different enamel shades at varying thicknesses.
Methods: 0.5mm, 1.0mm and 1.5mm disks of the 3M Supreme Ultra XWE, WE, EA1, EA2 and EA3 and of the GC Essentia LE and DE composites were produced. 3mm disks of the 3M DA2 and the GC MD composites were used as dentin substrates. For the TP measurement the enamel disks were photographed under standard conditions using a digital camera with polarizing filters on white and black backgrounds. Images were taken with a gray reference card with known color coordinates for color/exposure calibration, and color coordinates were measured using the CIELAB system. On-dentin color parameters were measured using the same photographical method with enamel disks positioned on dentin substrates using an optical integration liquid. Data were evaluated using ANOVA and Tukey(α=0.05).
Results: Increasing thicknesses of the enamel shades reduced the TP, ranging from 40.8-48.6 at 0.5mm, 28.6-35.8 at 1mm and 20.9-28.3 at 1.5mm. DE composite present a tendency to higher TP values while EA1 to lower. On dentin substrates, all CIELAB color coordinates were affected by the composite shade. Increasing thickness of enamel shades promoted the most significant color changes on the b* color axis. The LE composite presented the lowest b* values.
Conclusions: Increasing the tested enamel shades thickness did not reduce the final value as usually accepted. It mainly affected the yellow-blue(b*) axis. More knowledge of composites' optical properties could increase success of esthetic layered restorations.