Page 278 - My FlipBook

27fi THE OPERATION OF FILLING CAVITIES.

to conserving tooth structure, and w hcii lie lias given it a sliapc to please
liini he can select, from the nuiiiy, a special form of gold that will meet
his requirements.
There are certain ])rinciples involved in the packing oi" gold which
must be borne in mind, and the oj)erator should study these before
introducing his filling. The first of these is force, and the direction and
relation of that force to the object to be attained. If a given cavity is
to be filled with non-cohesive gold the operator must take into consid-
eration the strength of the cavity walls, and must determine whether by
the wedging process which he will exercise in the effort to adapt the
gold to the walls of the cavity he will run the risk of breaking them.
Non-cohesive gold is usually introduced by what is known as hand
pressure. Each layer of gold is carried to the floor and the walls of
the cavity by a process of wedging, and the mechanical arrangement of
each piece of gold should be such that no portion of the gold can es-
cape when the filling is completed. It will be shown later on, when
considering the various types of cavities to be filled, that in small cav-
ities of simple shape the gold prepared in the form of tape is best
suited, whereas in compound cavities or those of greater size the gold
may be introduced in the form of compact cylinders or blocks.
When it is desirable to use a combination of non-cohesive and cohe-
sive gold, the former is generally introduced first and the cohesive is in-
corporated with it by driving or forcing layers of cohesive into the non-
cohesive. This is best effected by using single layers of heavy foil or
rolled gold of a thickness equal to 20, 30, or 40 grains to the leaf. If
the filling is to be made of but one kind of gold and that the cohesive
variety, both hand pressure and percussion by means of the mallet
may advantageously be employed. The operator who has learned to
combine the two forms of gold and is not restricted to either method
of packing is best qualified for the requirements which are presented in
general practice. Perfect adaptation to the walls may be effected by
either method, but greater celerity and the attainment of equal excel-
lence may be reached by combining the two.
Plugging Instruments.—In the selection of instruments for pack-
ing gold the operator should have a sufficient number to meet his every
need. They should be of such a variety of patterns that every part of
every cavity, however remote, can be reached with ease. It is a mis-
taken notion that a large number of instruments (if well selected) is
confusing. The operator should study his instruments and know their
uses as thoroughly as he knows the letters of the alphabet, and if this
be done and they be arranged in an orderly manner in his case, the
confusion will be manifest in their absence, not in the possession of
them.