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MANIPULA TION OF AMAL CAMS. 6 1

which, being below the gum-line, is impossible to keep dry. This is
filled with amalgam until tho dam can be placed so that the rest of
the cavity may be dried thoroughly. The amalgam is allowed to
set, and at a subsequent sitting a portion of it removed, -leaving as
little within the cavity as possible, without risking the slipping of
the dam. The gold is then placed, being partly anchored into under-
cuts made in the amalgam. This is often advisable. Especial cases
arise where a large portion of an anterior approximal surface of a
bicuspid has been lost by caries. Restoration with amalgam alone
would be unsightly, and with gold alone impossible. The amalgam
may be placed along the gingival fourth or fifth of the cavity, and
covered with gutta-percha, till the next sitting, when it will be found
that the dam may be used and the gold packed into the remainder
of the cavity. When all is done, nothing shows but the gold.
The second method is to pack the gold upon the fresh amalgam.
To accomplish this a matrix is required, and the plastic golds are
preferable to form the contact with the amalgam. This kind of gold
may be readily packed against the amalgam, and will soon assert
itself by overcoming the efforts at amalgamation to such an extent
that the filling may be completed with cohesive foil at the same sitting.
A of this nature made in a tube an inch one-half of
filling glass long,
each metal, has been so successfully made that the resulting rod when
removed from the glass showed a perfect union, with great strength,
between the gold and the amalgam. The objection to this, in my mind,
is that the matrix must be used.
It will frequently occur that a cavity is so shallow and of such poor
shape for retention that it is questionable whether an amalgam filling
would be retained. Here we may frequently depend upon a method
which is useful with also. Mix oxyphosphate to a
exceedingly gold
and smear some the walls of the imme-
sticky consistency, upon cavity,
some Allow the to set
diately adding amalgam. phosphate thoroughly,
and the amalgam is practically cemented to place. The filling is then
continued by adding more amalgam, and will be more likely to remain
in place because of the underlying phosphate. Care must be taken,
before adding the second batch, that no phosphate be left overlapping
any of the margins, as that would leave a weak point.
In a similar way, in deep crown cavities, we may depend upon the
phosphate, not only as a protection to the nearly approached pulp but
we
as an additional retentive precaution, provided pack the amalgam
before the phosphate sets, instead of waiting till afterward, as is the usual
custom.
The mixing of an amalgam with a phosphate I have never tried, and
can see no advantage in. The mixing of the alloy with the phos-
phate, however, is totally different, and in many cases a practice