Assessing tooth color differences in digital facial portraits

Although a large body of scientific literature shows that background color and luminance affect color perception, previous measurements of tooth color difference thresholds have not taken the effects of viewing context into account. The present study tested the hypothesis that differences in skin/gingival color influence individuals' judgments of tooth color differences. Perceptibility and acceptability thresholds were determined in 10 individuals using a signal detection paradigm. They evaluated 500 pseudo-random presentations of two facial portraits: an African-American and a Caucasian. These portraits varied trial-to-trial only in the direction (CIELAB +L*, +a*, or +b*) or magnitude of the color difference between a portrait's two central incisors. The individuals were significantly less sensitive to tooth color differences in the +L* direction in the Caucasian portrait than for any other combination of color direction or portrait type. Furthermore, comparable perceptibility and acceptability thresholds were generally not statistically significant from each other.