Thresholds of perceivable color difference in silicone: A pilot study

Purpose: The relationship of instrument measured color difference to observer perception of color difference is not currently well-defined in applications related to color for facial prosthetic devices. Determining the threshold of perceivable color difference (∆E) in silicone will improve the quality of patient treatment and allow for better applications of technology in the production of facial prostheses. The purpose of this study is to determine the threshold of perceivable color difference in silicone and to examine if this threshold varies with light versus dark colors, and/or among three different observer groups.
Material and Methods: Two sets of 40 silicone samples (one simulating light skin and one simulating dark skin) were compared to one standard sample. Sample color was measured using a portable spectrophotometer, and ∆E values between each sample and a standard sample were calculated (Commission Internationale de l’Eclairage CIE (L*a*b*)). Samples were shown to 29 subjects from three groups (12 professionals who work with color, 6 patients with a facial prosthesis, and 11 laypeople) in random order next to a standard sample under controlled viewing conditions. Subjects were asked “Do these samples appear to be the same color?†and responses were analyzed to calculate the ∆E value of the threshold of perceivable color difference in silicone for each subject. Subject thresholds were used to determine average thresholds for each subject group, and for all participants.
Results: No significant difference in the thresholds of perceivable color difference among the three subject groups, or between light and dark sample sets was found. ∆E = 1.025 was calculated as the average threshold of perceivable color difference.
Conclusion: The results of this study indicate that ∆E = 1.0 can be used as a threshold of perceivable color difference in silicone used in facial prosthesis fabrication. Understanding this threshold will be useful in evaluating and integrating technology into the color-matching process of prosthesis production. It can also be used as a clinical standard for color difference comparisons and quality control in prosthetic outcomes. (Int J Maxillofac Prosthetics 2020;3:12-22)