Page 57 - My FlipBook

flas;kinc, vulcanizing and finishing. 45

in the [)laster. ]>y t]iis means the air is excluded, which
would nnt be the case if it were forced down horizontally
at once.
Fig. 20.

The height of the plaster about the denture determines
the division between the two sections of the flask. This
is regulated bv the character of the teeth invested. If they
are teeth (either gum or plain) that rest upon or are em-
bedded in the base plate, the case should be invested to
just above the margin of the wax (see Fig. 20). In this
way the teeth and nearly all of the wax rim will be em-
bedded in the upper portion of the flask.
\\dien the necks of the teeth are to rest upon the natural
gum, as shown in Fig'. 19, the investing plaster should
extend to the cutting edges of these teeth so as to retain
them in the lower section of the flask. This is illustrated
in Fig\ 21.
^^'hile the plaster is setting, trim the surface up to the
shape or slant desired, avoiding undercuts, leaving it as
smooth as possible. After it is thoroughly set, varnish
this surface with shellac, and when dry give it a thin coat
of oil or the soap solution. Care should be taken not to
allow the varnish or oil to come in contact ^vith the teeth.
The ring or upper section of the flask should now^ be