Tooth Color and Reflectance as Related to Light Scattering and Enamel Hardness

Abstract

Tooth color is determined by the paths of light inside the tooth and absorption along these paths. This paper tests the hypothesis that, since the paths are determined by scattering, a relation between color and scattering coefficients exists. One hundred and two extracted incisors were fixed in formalin, mounted in a standardized position in brass holders, and pumiced. A facet was prepared near the incisal edge on the labial plane to allow for Knoop hardness measurements with a 500-gram load. Light scattering by the enamel was measured in a 450/00 geometry; light scattering by both enamel and dentin was measured in a 00/00 geometry. The reflection spectrum of the tooth was measured from the labial plane with a spectroradiometer in a 450/O°geometry, with standard illuminant A and standard illuminant D65. To include all volume-reflected light, we used entire-tooth illumination and small-area measurement. CIELAB color coordinates were calculated from the spectra. Neither spectra nor coordinates showed evidence of a contribution of fluorescence to tooth color. Averaged values and standard deviations for L*,a*,b* were 69.9 (4.1), 1.22 (1.4), and 17.9 (2.9), respectively. Both scattering coefficients averaged to 0.6 (0.4) mm'l; Knoop hardness number was, on average, 271 (39) kg/mm2. L* correlated with a* (r = -0.51), with the enamel scattering coefficient (r = 0.60), and slightly with hardness (r = 0.17, p = 0.03). The colors of 28 teeth from which the enamel was removed correlated strongly with the colors of the complete tooth. This study quantitatively confirms that tooth color is determined mainly by dentin, with enamel playing only a minor role through scattering at wavelengths in the blue range.

Prevalence of Tooth Shade and its Correlation with Skin Colour - A Cross-sectional Study

“…Within the groups, tab arrangement is based on increasing chroma-the more chromatic tabs are marked with higher numbers. Group A consists of five tabs (A1, A2, A3, A3.5, A4); Groups B and C consist of four tabs each (B1, B2, B3, B4 and C1, C2, C3, C4, respectively); and Group D consists of three tabs (D2, D3, D4) [10]. A single examiner who has evaluated the skin colour matched the shades of tooth in a bright natural light according to manufacturer's instructions.…”

Chromatic Influence of Value Resin Composites

“…[8][9][10] The application of enamel resin over dentin resin was responsible for the increased light dispersion. When this dispersion occurs, the energy is reflected diffusely, returning randomly from the specimen surface, commonly beyond the observation range of the spectrophotometer.…”

In vitro assessment of the effectiveness of whitening dentifrices for the removal of extrinsic tooth stains

“…The greater the increase in the amount of these pigments, the greater is the absorption of the incident light and the darker the tooth becomes. 14,15 Many methods are currently used to assess tooth color, the objective methods such as reflectance spectrophotometer analysis being the most reliable. 16,17 Spectrophotometers and colorimeters are instruments commonly used to measure the color of an object.…”