Perceptibility and acceptability thresholds for color differences of light and dark maxillofacial skin replications

Abstract

The aim of this study was to assess the perceptibility and acceptability thresholds of maxillofacial silicones for light and dark skin colors and to evaluate the effect of gender and professional experience on these thresholds. Two different sets of specimens (as light and dark) each, consisting of 14 (25 × 25 × 6-mm³) silicone skin replications, were produced. Four specimens of each set were produced from the same silicon mixture of the relevant set and polymerized simultaneously to provide standardized fabrication conditions. These 4 light/dark specimens were assigned as “baseline color specimens (BCs)” in each set, while the other 10 specimens were produced with a color difference level that increased gradually from BC. These stepped levels were obtained by controlled increasing of the pigment concentration in the relevant baseline silicon mixture. Color difference levels of specimens were calculated by using the CIELAB and CIEDE2000 formulas. Observers comprised of 3 different professional experiences as first-year dental students, interns, and dentists (n = 30/group, gender-balanced) were included. Combinations consisting of 5 specimens with 4 BCs and 1 different color were shown to the observers to assess whether the color difference was perceptible or acceptable. Perceptibility and acceptability percentages were regressed with color difference levels to estimate the best fit curve and confidence intervals were calculated (α = 0.05). The highest estimation of the coefficient of determination (R²) was found in the cubic curve for all parameters. A significant difference was found between the light and dark colors. The perceptibility thresholds (ΔE*_ab/ΔE₀₀) were 0.8/0.59 and 2.63/1.75 for light and dark colors, respectively. The acceptability thresholds (ΔE*_ab/ΔE₀₀) were 3.35/2.25, 10.07/7.04 for light and dark colors, respectively. No significant differences were found between gender and among experience groups concerning visual thresholds. Regardless of gender and experience, observers could perceive color differences more easily in light skin colors.