Page 358 - My FlipBook

356 COMBINATION FILLINGS.
fillings can be finished as soon as the last piece of gold is consolidated,
without the least danger of mercury coating.
In preparing the cavity for a filling of this kind, almost no tooth
substance has to be cut away shnjjly to get access to the cavity, to prop-
erly start and pack the filling, as is often necessary if an entire gold
filling is to be made. As a consequence, much valual)le tooth substance
is saved, for, so long as the decay is removed and frail edge walls are
cut away, the amalgam can be perfectly packed, no matter how irregular
the surface to which it is to be adapted. Of course, the excavation
must be planned so that a filling of proper contour can be made, and
walls cut back when by so doing future decay can be better guarded
against. There will be many cases encountered, however, where, by
this method, much of a tooth structure can be left, whereas if gold
were to be used it would be necessary to cut, often causing severe
pain, in order that the part might be properly filled.
For the jiurpose of describing a simple combination filling of this
kind, a cavity involving the occlusal and distal surface of an upper sec-
ond bicuspid is selected as an example. In the first place, sufficient
space must be secured for a filling of the right contour, and to allow
for passing in a very thin strip for finishing the filling. It is best to
secure this room by previous wedging. Space having been secured, the
cavity is prepared with proper undercuts, and the walls of the approxi-
mal part, to be filled with gold, made at as nearly a right angle to the
matrix as possible. This is in order to facilitate packing the gold, it
being very difficult to obtain a satisfactory margin if the walls form a
very acute angle with the matrix.
A matrix so adjusted that it will stand the pressure of putting in
the filling without moving is an absolute necessity for this combination.
It having been put on as described under the head of " Cement and
Amalgam " fillings (page 349), enough amalgam is carefully packed at
the cervical wall to fill one-fourth or one-third of that portion of the
cavity. It should l)e thoroughly consolidated by using properly shaped
instruments and sufficient force to drive it into every part of the cav-
ity. It is a good plan to use small pellets of bibulous paper, forcing
them against the amalgam with medium-sized instruments. The free
mercury which rises to the surface should be carefully removed. It is
well to put in considerably more amalgam than is to be left, cutting
out the surplus, which method leaves a good surface upon which to
begin with the gold. Before the gold is added, however, care should
be taken to remove every chip of soft amalgam from the folds of the
dam, or any that may be clinging to the matrix, or in any position
where it might be brought in contact with the gold when finishing the
filling. These chips will remain for a long time soft enough to coat