The fluorescence property of human teeth under UV light has long been studied in dentistry and is now used in the diagnosis of anomalies, such as dental decays. Its role in the appearance of teeth and dental restorations has also been demonstrated, and fluorescence, even under daylight, may sensibly modify the color of dental restorations. As such, dental resin composites used in aesthetic restorative dentistry include fluorescent agents which aim to reproduce the natural fluorescence of teeth. While several studies have measured the fluorescence properties of dental biomaterials and a few other studies have focused on predicting the color of samples, the influence of fluorescence on color prediction models remains to be assessed. In this paper, we propose a prediction model for the spectral emission of slices of a dental biomaterial as a function of their thicknesses, in reflection and in transmission modes, in order to improve color prediction models for these materials.
It can be easily observed that a white support printed with halftone ink layers changes color when coated with a clear layer. The color change can be explained by purely optical phenomena, for example the perception of a different amount of light scattered by the ink-matter interface if the observer is not too far from the specular direction. But color change can be also observed far from the specular direction, especially with halftone colors, where the support has not a homogeneous reflectance at the mesoscopic scale. This is due to subsurface optical phenomena investigated only recently in the case of uniformly colored support. In the present paper, thanks to an original optical model dedicated to halftone colors, we show that this subsurface phenomenon tends to increase the chance for light to meet several ink dots, therefore the chance to be absorbed.