Objective: To spectrophotometrically evaluate the effect of minor variation in outer enamel composite layer thickness on the final color of anterior resin composite restorations layered by a 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: Final 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. VITA Easyshade® V 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. Data were analyzed 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: Closest shade matching to control occurred in groups: A3E(0.25- and 0.5mm)/A1D, A3E(0.75mm)/A2D, and A3E(0.5- and 0.75mm)/A3D. ΔE00 values for different final shades were: 8.78±0.72 for A1, 6.67±1.04 for A2, and 4.60±0.99 for A3 (p < 0.001).
Conclusions: The manufacturer's recommendation of 0.5mm for the thickness of outer enamel composite layer applies well to reproduce shades A1 and A3 but needs to be increased to reproduce shade A2. The lighter the shade, the less the match when color recipes adopting grayish universal enamel shade are used.