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PORCELAIN AND GOLD INLAYS. 337

allow of a somewhat acute cavo-surface angle that will be strong
and safe. See Figures 105-107. In that case, the porcelain, after
rounding over the cusp, may have a strong obtuse angle against
the enamel. Other cases will not ])e favorable for this and will
require that more of the cusp be cut away in order to give suffi-
cient strength, possibly to one-third or one-half the length of the
tooth. In this latter case, unless the pulp of the tooth has been
removed, it will become very difficult to obtain sufficient anchor-
age in bicuspids because of the lack of sufficient tooth sub-
stance. It will sometimes be better to remove the pulp in order to
use the pulp chamber for additional anchorage. Then the horns
of the pulp chamber may be cut out to the occlusal for the pur-
pose of forming the anchorage, and the whole length used to a
level with the gingival wall.
If there is a mesio-occluso-distal cavity in a bicuspid from
which the pulp has been removed, both cusps may be cut away
about one-third the length of the tooth and a porcelain inlay
built up that will replace the entire occlusal surface. In such a
case, the greatest care must be exercised in forming the anchor-
age, and also in so arranging the detail of the cavity form that
the body of the porcelain inlay will be particularly thick and
strong.
In these cases it is supposed that the operator has destroyed
and removed the pulp of the tooth himself under conditions that
will certainly prevent the future discoloration of the remain-
ing parts of the tooth ; or under conditions in which no products
of decomposition have found their way into the dentin. In any
case where there has been abscess, or in which the pulp chamber
has been open to the fluids of the mouth, we may expect that
products of decomposition have been absorbed into the dentin
which will cause more or less discoloration and destroy the
esthetic effect of a nicely fitted inlay. AVith the condition last
mentioned, it is better to cut away the crown and replace it with
a porcelain crown. This will be stronger, if well done, and will
not be subject to discoloration. As a general principle, it is
wrong to place porcelain in any pulpless tooth, because of the
liability of the tooth changing color. A gold filling or gold inlay
is better. It is a principle, as has been stated above, in esthetic
appearance that a thing off the normal that declares its true
character at once is better than one that places the observer in
doubt. This is just what a porcelain restoration a little off color
always does.
Gold inlays. The preparation of proximal cavities in the