A Shade Guide Model Based on the Color Distribution of Natural Teeth

摘要

The objectives were to determine the color distribution of natural teeth sorted by the parameters of Value, Chroma, and hue angle measured with a colorimeter, and to suggest a shade guide model. The color of maxillary and mandibular 12 anterior teeth was measured with a tristimu-lus colorimeter for 47 subjects (n = 564). The color of teeth was grouped initially by Value (CIE L~*) by the interval of 3.3 units. After then, within each main group, the color of teeth was subgrouped by Chroma by the interval of 3.3 units. Chroma was calculated as C_(ab)~* = (a~*2 + b~*2)~(1/2). Since the hue angles were in the first or fourth quadrant, subgroups were further sorted by the first or fourth quadrant hue angles. Hue angle was calculated as h° = arctan (b~*/a~*). Mean color difference (ΔE_(ab)~*) between the color of an individual tooth and the mean color of each main group was 2.5-3.3, which was lower than acceptable limit (ΔE_(ab)~* < 3.3), and that in each subgroup was 0.9—3.1. The number of subgroups was 22, which was comparable to those of conventional shade guides. A shade guide model based on the color distribution of natural teeth sorted by Value in six main groups, three or four subgroups within each main group sorted by Chroma, and further sorted by hue angle (first or fourth quadrant values) was suggested.