Page 364 - My FlipBook

362 COMBINATION FILLINGS.

*' fiber/' so to speak, the particles not directly under the point are not
drawn down as the pressure is applied. This is why this preparation
of gold is so useful for starting fillings.
Now take a cylinder made of gold foil, ])lace it on blotting paper as
before, and with the same instrument press on the centre of it. It will
be noticed that the instrument does not make a clean cut through the
cvlindei', as was the case with the piece of mat gold, and, instead of
remaining flat on the blotting paper, it is inclined to curl up. The
fibrous quality of the foil is an advantage when a corner is to be built
on to a tooth, or in any place where toughness of the material assists in
its manipulation.
By using these golds for starting cavities, the peculiar qualities just
referred to will be exhibited. For illustration, we will take an extreme
case—that of a shallow circular cavity in the buccal surface of a lower
molar. This cavity is entirely without angles or undercuts, its walls
flaring outward, the bottom being flat,
Fig. 344.
or as nearly so as it can be made with
a large bur (see Fig. 343). A piece of
plastic gold a little larger than the
cavity is placed in position, then with

Fig. 343.

Royce pluggiug instruments.

a flat, very slightly serrated instrument (rr, Fig. 339) it is carefullv and
gently worked into place. When it is condensed al)out even with the
outer edge of the cavity, a smaller instrument is used to condense
around the edge. As (mly the portion of gold under the point is dis-
turbed, this can be done quite readily without dislodging the whole piece.
Soon sufficient force can be used to thoroughly condense the whole.
Care must be used in selecting a first piece that it be not too large, but
large enough, so that it will not chop up as it is being manipulated.
After getting the first piece in place, the filling can be finished with the
same or any other preparation of gold. If of the same, it is well to
use oval points (Fig. 344) and work the gold toward the sides of the
cavity with a sort of rotary motion, keeping the edges of the filling
higher than the centre.
This gold is very soft and takes a very sharp impression of the sur-