Metameric effect between natural teeth and the shade tabs of a shade guide.

The objective of this study was to evaluate metameric effects, that is, the dependence of the colours of teeth and shade tabs on the illuminant used. The colours of 49 teeth of 37 participants and of the corresponding shade tabs of the 3D-Master (VITA Zahnfabrik; colour match DeltaE(ab)< 2) were measured using an intra-oral spectrophotometer (VITA Easyshade). Spectral reflectance data (from 400 to 700 nm) were recorded. Commission Internationale de l'Eclairage (CIE) L*a*b* values were calculated for D65 (reference daylight), A (incandescent light), and TL84 (store/office light) as reference illuminants. A modified metamerism index (Mod-M) and hue-angle ratios were calculated to express differences between tooth and tab colour relative to the difference observed under D65 illumination. The Mod-M for teeth and tabs was greater than unity (indicating a greater colour difference relative to D65) by 57.1% for A and by 49.3% for TL84. Hue-angle ratios of teeth and tabs using the test illuminants were different from those obtained using the standard illuminant D65. If teeth and shade tab matching is conducted using daylight illumination, the colour difference may not be the same under other lighting conditions, leading to perceptible, or even unacceptable, colour differences under these conditions.

Differences in lightness, chroma, and hue in the anterior teeth of quinquagenarians and septuagenarians.

The purpose of this study was to evaluate, for both genders and two elderly age groups, differences in lightness, chroma, and hue of pairs of natural anterior teeth, so that more accurate information on color would be available for the production of dentures with a natural appearance. The subjects in the younger group (YG) were 54 to 56 years of age, those in the older group 73 to 75 (N = 195, 48% women). Tooth color was measured using a spectrophotometer. Mixed models were calculated for each pair of teeth, with gender as a fixed factor. Gender did not have a significant effect in either age group. In both groups, differences in chroma between upper canines and lateral incisors and in lightness and hue between upper and lower canines were observed. In the YG, additional differences were found, with the only exception of the comparison between upper central and lateral incisors. The nongender-specific color differences observed should be considered when producing denture teeth for these groups of patients, in order to come as close as possible to the natural color ideal.