Journal of Dental Research, Vol 64, 74-77, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Spectrometric analysis of the influence of metal substrates on the color of metal-ceramic restorations
J. D. Brewer, C. K. Akers, D. A. Garlapo and S. E. Sorensen
The development and use of ceramic alloys have created the potential for
variation in the color of dental porcelain. In order to define the nature
of the alterations, it is necessary to examine quantitatively the color of
dental porcelain baked onto ceramic alloys. The purpose of this study was
to examine spectrometrically where color differences occur in the
fabrication process. One shade of Vita porcelain was baked onto coupons of
three ceramic alloys (high gold, palladium-silver, base metal). Eight
replications were made in each alloy at seven fabrication steps: prepared
metal, oxide, first opaque, second opaque, first dentin, second dentin, and
glaze. Spectrometric analyses were performed for each replication at each
step. Data were tabulated every 10 nm over the recorded 380-750-nm range,
for conversion to the CIE color measurement system. Tristimulus values X,
Y, and Z and chromaticity coordinates x and y were calculated. Differences
from spectrographic inspection were seen among the metal substrate series.
The greatest variation appeared at the first dentin step between the
palladium-silver and high-gold alloys and between the palladium-silver and
base metal alloys. Mean tristimulus values were significantly different (p
less than 0.0001) for all steps and alloys. The distribution of plotted
values followed the same pattern of spectral changes throughout the seven
fabrication steps. Analysis of these data shows that color differences of
metal-ceramic coupons based on dissimilar metal substrates can be
quantified, and that spectral reflectance values can be converted to CIE
notation. As depicted spectrally, notable color differences appeared with
the first dentin porcelain layer.
