The effect of ultraviolet induced fluorescence on visually perceived tooth color under normal light conditions.

OBJECTIVE: Restorative and prosthetic materials should provide an appearance similar to natural teeth under all light conditions, including UV-rich environments and daylight. Various studies claim that UV-induced fluorescence makes teeth whiter and brighter in daylight. The aim of this paper is to determine experimentally the significance of tooth fluorescence in natural sunlight on perceived tooth color. METHODS: A total of 35 extracted, hydrated teeth without restorations or endodontic treatments were evaluated in an experimental setup. A UV/VIS spectrometer using a reflectance/backscattering probe was used to collect the reflected spectrum. Unfiltered and filtered sunlight was used for irradiation of the samples so as to use the combined ultraviolet and visible spectrum (UV/VIS) and the visible spectrum (VIS) exclusively. Color coordinates for each group were measured using the CIE L*a*b* 1976 system, averaged, and compared. RESULTS: The average color difference between both groups (UV/VIS and UV) was ΔE* 0.527. The average tooth color for the VIS group was L*VIS 72.21, a*VIS -2.42, and b*VIS 22.35, and for the UV/VIS group was L*UV/VIS 72.00, a*UV/VIS -2.47, and b*UV/VIS 22.44. SIGNIFICANCE: UV induced fluorescence from sunlight does not make teeth whiter and brighter.

Effect of ethylene oxide sterilization on enamel and dentin demineralization in vitro.

For in situ studies into caries prevention, sterilization of tooth samples is essential. However, sterilization may influence the caries process itself. The aim of this study was to assess the effect of sterilising sound human enamel and dentin with ethylene oxide on lesion depth and mineral loss before and after in vitro demineralization. Lesion depth and mineral loss were measured using transversal microradiography (TMR). The experiment was carried out with 32 enamel and 32 dentin samples. We found a significant reduction of lesion depth due to sterilization in demineralized enamel (-9.8microm; 95% CI: -15.1 to -4.4microm). The small effect of sterilization on demineralized enamel is considered to be irrelevant for in situ studies of de- and remineralization.

Optical path-length spectroscopy of incipient caries lesions in relation to quantitative light-induced fluorescence and lesion characteristics.

A basic understanding of the light-scattering processes that take place inside the dental tissue (either sound or carious) is obtained both with measurements of the photon path-length distribution of light inside such media and with Monte Carlo simulations. Furthermore, the following is investigated: the correlations between different momenta of the photon path-length distribution of light inside caries lesions, the fluorescence loss determined with quantitative light-induced fluorescence, and/or the demineralization and depth of caries lesions determined with transversal microradiography. It is concluded that (i) the light paths inside both carious and sound enamel are considerably influenced by the refractive-index contrast at the tooth surface; (ii) contrary to a previous hypothesis, the fluorescence loss is larger in lesions in which the average photon path length is longer; (iii) very good correlations are obtained between the optical characteristics and the physical parameters of lesions when the optical measurements are performed such that there is high refractive contrast at the tooth surface.