Fluorescence of dental porcelain.

This study of the fluorescence of natural enamel and of dental ceramics shows the fluorescence of ceramics not containing rare earths decreases when the color saturation increases; the fluorescence of samples of the same shade guide are not homogenous; some guides show a strong green fluorescence; and two shade guides of the same origin can present completely different fluorescence. The cementing medium can affect the fluorescence of a ceramic prosthesis.

[Fluorescence of shade guides]. / Fluorescence des nuanciers.

The experimental protocol developed in the previous article (4) has been modified to permit the investigation of the fluorescence of shade guides. The following will be traced out on each graphic display: a reference spectrum using full lines; a sample spectrum using dotted lines; the chromaticity triangle of the X Y Z CIE 1931 system; the chromaticity of the sample to be tested, represented by the sign +; the chromaticity of the reference, represented by the sign -. The shade guides without any rare earth have spectra in the form of wide bands; their intensity decreases when the degree of colour purity in white light of the buttons increases. The shade guides containing rare earth have spectra with both a wide band and thin lines. It has been shown that: the same shade guide can contain different fluorescence components; two shade guides from the same source can have very different fluorescences for buttons of the same reference; two shade guides from different sources can have identical fluorescent components. This study reveals: that unadapted fluorescences of shade guide may be the cause of an error in the choice of the colour of a ceramic restoration; that the comparison of spectra appears to prove that shade guides are not manufactured by the ceramic manufacturers which recommend them and are, in fact, of the same origin.

[Fluorescence of dental porcelain: material and methods]. / Etude de la fluorescence de la porcelaine dentaire: matériel et méthodes.

Dental porcelain emits some fluorescence under the action of ultra-violet rays. This emission may be at the origin of errors in the choice of the colour of a crown. In order to study this fluorescence phenomenon, the following experimental protocol has been developed: 363.8 nm exciting radiation isolated from the emission by an Argon laser; Fluorescence emitted by the sample and dispersed via a spectrometer, protected by a stop-U.V. filter; Influx collected by a photomultiplier, then directed, after passage in a picoamperemeter, toward a mini-computer programmed to print the spectra; Correction of the spectra by a tungsten lamp used at the 2,600 K colour temperature; Use of reference spectra. On the same graph, the sample spectra are represented in solid lines, while the spectrum of the enamel used as a reference is shown as a dotted line. The results show that: Enamel has a fluorescence spectrum which has the shape of a wide band, with a maximum of 450 nm (characteristic of a blue-green shade) and a slow decrease up to 680 nm. The enamel fluorescence does not depend on the colour of the tooth; Dentine has a distribution spectrum which is similar to that of enamel but is three times fuller; The spectra of the ceramic samples reveal: a wide band due to transition metals, fine lines due to rare earth (terbium and europium). When the saturation degree of the ceramic increases, its fluorescence colour varies due to the relative increase in the amplitude of the lines in relation to the bands. Thus, when the sample colour progresses from B1 to B4, its fluorescence colour becomes greener.(ABSTRACT TRUNCATED AT 250 WORDS)