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the Selection and TIpplication of Porcelain.
Building in Layers. Building in Sections. Mixing Colors. Technique of Applying
Porcelain to the Matrix.

In selecting the colors for an inlay, note the variation of color in
the natural tooth, in which three or more colors, or hues of colors, are
usually found. If the tooth is a vital one, the foundation, which should
be constructed of a coarsely ground porcelain and be fired only to a
high biscuit, should be a hue of yellow. Dentin is but slightly trans-
lucent and transmits light feebly ; it should be replaced with a porcelain
which approximates it in density, and which presents an unglazed sur-
face. Such porcelain will cause the diffusion of the transmitted light,
and this will cause less light to be transmitted to the cement and less
reflected light to be transmitted through the porcelain.
A study of the colors of the teeth should be made before the por-
celain for an inlay is selected. While the color of a tooth is due mainly
to its pigments, the thickness of the dentin and enamel and the density
of these tissues, with their power to absorb, transmit, refract, and re-
flect light, are also factors. The colors of most teeth containing no for-
eign pigments are hues of yellow, blue, brown, and gray, with a yellow-
ish or bluish hue.
The first point to consider in the selections of colors is the varia-
tions of hues seen in different sections of the natural tooth. Under nor-
mal conditions dentin, which forms the body of the tooth, is some hue
of yellow. The color of the enamel varies, and the variation of the
thickness of the layer of the enamel, in different sections of the tooth,
gives it a variety of hues of colors. A careful study of the colors of a
tooth shows that the gingival third is usually some hue of yellow, mod-
ified by a hue of brown or gray, that the middle third generally appears
to be a gray, having a yellowish or a greenish hue, and that the incisal
third usually has a predominance of blue or gray.

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