Page 317 - My FlipBook

USE OF AMALGAM. 315

Use of Amalgam.
It is to be understood that amalgam is to be employed onlv in those
conditions and situations which clearly indicate it as the proper mate-
rial. As a general rule, it is excluded from the ten anterior teeth of
each jaw, although this rule is open to exceptions. Its anterior limit
of application is usually regarded as the distal surface of the first bicus-
pid. Its more general employment has been greatly reduced in many
places since the introduction of what are known as combination fillings
(see Chapter XIV.), and by improyement in the forms and character of
artificial crowns.
The first class of cayities to which amalgam is applied are those
which extend beneath the gum margin ; the second, buccal cayities ; the
third, compound cayities ; the fourth, approximal cayities ; the fifth,
cavities upon the masticating faces of the teeth. These are the classes
in wdiich gold is most difficult of introduction and of proper shaping
and finishing, in the order named. Amalgam should rarely or neyer be
packed against dentinal or enamel walls without the interposition of a
layer which will prevent either the discoloration of the dentin or the
bluish apjiearance noted when amalgam underlies enamel.
The shaping of cavities for the reception of amalgam fillings (see
Chapter VIII.) should be done M'ith such care as will 2:iye assurance
of the permanent retention of the filling and the perfect sterilization of
the dentin before and during its introduction.
The separation of the teeth, removal of gum overhanging cavity
margins, and breaking down of frail enamel walls by means of chisels,
precede the filling.
The rubber dam is to be adjusted where and when possible, with such
care that an exclusion of the fluids of the mouth is assured durino- the
shaping, sterilizing, and filling of the cavity. As Dr. Black has shown,^
much of the permanency of form of an amalgam mass depends upon
the even distribution of the constituents ; it is evident that every aid to
this end should be utilized, an important one being that the mass should
be packed into a cavity having but one orifice, that for the introduction
of the filling.
AVith the data relative to dental amalgams which have been given,
it is evident that a dental amalgam mass is by no means simple, but is
a very complex body. If sufficient mercury has been used to effect
solution of the alloy particles the mass will consist, first, of a quantity
of a chemical amalgam— /. e. one in which the metals are united in
atomic ratios—this being surrounded by one or more other distinct
^ Dental Cosmos, 1895, vol. xxxvii. p. 553.