Effect of enamel thickness and dentin shade of resin composite on the final color reproduction.

Aim: To evaluate the effect of different dentin shades and different enamel shade thicknesses on the final color reproduction in class IV anterior resin composite restorations restored using the bilaminar technique. Materials and methods: 54 resin composite discs of 10mm diameter were prepared in this study. The discs were equally divided into 9 groups (n = 6) according to the two levels of the study, Level-1: Dentin shade (A1, A2 and A3) and Level-2: A3 enamel shade thickness (0.25mm, 0.5mm, 0.75mm). Each group had a 3mm-thick core layer of dentin shade either A1, A2 or A3 (ceram.x® duo, Dentsply Sirona, Germany) followed by the designated enamel shade thickness . Clinical spectrophotometer (VITA Easyshade® V, Germany) was used to measure the L*, a* and b* values of reference A1, A2 and A3 VITA classical shade tabs and resin composite discs. CIEDE2000 color difference formula (ΔE00) was adopted to calculate the color difference between the resin composite discs and their corresponding VITA classic shade tab. Data were analysed using two-way ANOVA followed by Tukey’s post hoc test. Comparison of main and simple effects were done utilizing one-way ANOVA followed by Tukey’s post hoc test. Results: Two-way ANOVA showed that the dentin shade and the enamel layer thickness as well as their interaction had a statistically significant effect on color difference (ΔE00) compared to the VITA classical reference tabs(p<0.001). Best shade matching to the control was obtained when A3 dentin shade was used with both 0.25mm and 0.75mm enamel thickness (3.13±0.48 and3.04±0.39, respectively) while least shade matching was obtained when A1 dentin shade was combined with 0.5mm enamel shade (6.07±0.41). Conclusions: When using the bilaminar technique in vertical anatomical layering of resin composite restorations, the thickness of the outer enamel composite together with the dentin shade used demonstrated a significant effect on the final shade. The lighter the dentin shade used the thicker the enamel thickness needed for better shade reproduction and matching.