This study analyzed the difference in color caused by different thickness in enamel layer of composite resins when applied with single and layering placement technique, and evaluated if the results agreed with the shade guide from the manufacturers to verify reliability of the color matching process of the manufacturers.

For single composite resin samples, 6 mm diameter and 4 mm thickness cylindrical samples were fabricated using Ceram-X mono (DENTSPLY DeTrey) and CIE L^*a^*b^* values were measured with spectrophotometer. Same process was done for layering composite resin samples, making 3 dentinal shade samples, 4 mm thickness, for each shade using Ceram-X duo (DENTSPLY DeTrey) and enamel shade resins were layered in 2 mm thickness and CIE L^*a^*b^* values were measured. These samples were ground to 0.2 mm thickness each time, and CIE L^*a^*b^* values were measured to 1 mm thickness of enamel shade resin.

Color difference (ΔE^*) between single and layering composite resin was 1.37 minimum and 10.53 maximum when layering thicknesses were between 1 mm and 2 mm and 6 out of 10 same shade groups suggested by manufacturer showed remarkable color difference at any thickness (ΔE^* > 3.3).

When using Ceram-X mono and duo for composite resin restoration, following the manufacturer's instructions for choosing the shade is not appropriate, and more accurate information for Ceram-X duo is needed on the variation and expression of the shades depending on the thickness of the enamel.