Page 183 - My FlipBook

CROWN- AND BRIDGE- WORK. 171
tlie band and meet the mars^-in of the ginn. It should also
be ground out at the center of the base (b), so as to form a
slight space just over the base of the pin.
The tooth is then backed with either thin
Fig. 136.
platinum or gold-plate (gold will give a slight
yellow shade to the tooth while platinum will give
a bluish tint). The upper edge of the backing,
brought down thin with a file or stone, should
extend as far as possible under and between the
tooth and the cap, so that the solder will more
readily flow in and fill what space there may be.
Waxing the Tooth in Position.—A perfect joint and the
proper length and angle of the tooth having been secured,
the pieces, that is, the tooth, cap, and pin, should now be
thoroughly dried, then held together in the proper relation-
ship, and secured in this position by running warm adhesive
(resin) wax over the palatal portion of the tooth, attaching
the backing to the cap. It should then, before the wax
gets very hard, be carefully carried to position upon the
root, when any correction in the position of the tooth can
readily be made. Now apply a drop or two of cold water
from the syringe or on a pledget of cotton; this will harden
the wax, so that the crown may be removed without chang-
ing" the position of the tooth upon the cap. It will then be
ready to be invested for soldering.
Investing.—A most suitable investment for crown work
is marble-dust and plaster, ecjual parts, with a small cjuan-
tity of fine asbestos fiber thoroughly
Fig. 137. incorporated. After the investment
has thoroughly set, the wax may be re-
moved and the surface of the backing
and cap cleansed by directing upon it
a small stream of boiling water. The
investment should be cut away so as to