Colorimetric Evaluation of Internal Coloration Characteristics of New Silicone Epithesis

Objectives:
For the color reproduction of epithesis in a patient with a partially lost face, either the internal or external coloration is adopted.
Methods:
To determine the colorimetric characteristics of newly developed silicone epithesis materials together with a colorant, we tested the colorimetric parameters of various combinations of silicones (KRS-10-2 and KRS-10F-2; GC) and colorants (CA-R, CA-Y, CA-B, CA- P1, CA-P2, CA-B1, and CA-B2) with different thicknesses. A silicone and a colorant were mixed following manufacturer’s instructions using a vacuum stirrer (VM-113，Morita). Then, sample materials of thickness 5, 10 and 20mm were selected. Each sample was crosslinked in a constant-temperature dryer (EO-300B，As One) at 100°C. The color of samples set on a standard white board was determined using a spectrophotometer (CM-700d, Konica Minolta).
Results: No color difference was observed between KRS-10-2 and KRS-10F-2 with matched thickness when the same colorant was used (ΔE ＜ 1.91). In the case of the color difference between the 5-mm and 20-mm thick samples, ΔE values were 8.73, 24.13, and 3.20 for red (CA-R), yellow (CA-Y), and blue (CA-B), respectively. In contrast, pinkish (CA-P1 and CA-P2) and brownish (CA-B1 and CA-B2) colorants showed unrecognizable color difference between any combination of thicknesses (ΔE ＜ 1.61).
Conclusions:
Although the color difference of the pinkish and brownish sample materials showed little variation regardless of thickness, that of the red, yellow, and blue sample materials exhibited a significant difference as a function of thickness. Because pinkish and brownish colorants are lighter in color than the red, yellow, and blue ones, the former colorants exert a weaker effect on the samples than the latter ones regardless of thickness. The results in this study provide important information for modifying the coloration of epithesis in terms of the tone of colorants.