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CROWN- AND BRIDGE-WORK. 1 89

of the porcelain facing"; for without tliis protection the
porcelain would he almost certain to he hroken. The con-
cave surface of these tips is filled as descrihed inider crown-
work with solder of a little lower carat. This surface is
then ground smooth and fitted to the squared surface of the
porcelain facing and waxed in position. Triangular pieces
of platinum are then cut of the proper size to fit the sides
of the tooth, waxed in position, and the whole invested,
leaving- the hack open, which is filled with i8 k. solder or
coin-gold.
These teeth are then fitted into position in the hridg^e, as
previously described.
Fig. 164 shows the completed work in the mouth.
Where only one molar or bicuspid is
Fig^^S.
lost, sufficient support may be gained
by the cap, which is made to pass over
the adjoining molar. If the first molar
and second bicuspid are lost, the an-
terior end of the bridge may receive sufficient support from
a strong spur ( h'ig. 165), which may rest in a cavity in the
first bicuspid, and around wdiich a filling is placed.
Fig. 166 illustrates a device for obviating the necessity
for removing the crowns of natural teeth in preparing the
mouth for bridge-work. Crowns are fitted in the mouth to
the points of attachment in the usual manner. An impres-
sion is taken, bringing the crowns away in their proper
positions. From this the cast or model is obtained. Heavy
bands of half-round gold or platinum wire are now fitted
around the necks of the natural teeth on their lingual sur-
faces. These bands, being waxed in position, serve to con-
nect the different parts of the bridge, uniting them in one
piece without the loss of any of the natural crowns. This
will be found a highly satisfactory method of inserting
both small and more extensive bridges. Fig. 167 shows