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216, OPERATIVE DENTISTRY

caused by its application as it is a most powerful escharotic and
the clear arsenic applied to a pulp will often cause great pain. One
of the most popular mixtures is here given:

Arsenic trioxide gr. v.
Cocaine gr. xv.
Creosote Q. S. ft. stiff paste.
To this should be added enough lamp black to make the above a
dark gray color so that it will have a contrasting color with that of
the tooth to assist in placing it in the exact location desired.
The Technic of its application is as follows: The cavity should
be thoroughly protected and dried, preferably under the rubber dam.
Foreign matter should be removed from the cavity and the same
thoroughly sterilized, the softened dentine removed and the pulp ap-
I)roached to as near exposure as possible without causing the patient
pain. Complete exposure is not necessary. Again sterilize the cavity
and dry. Bathe cavity with phenol and again dry. With the enamel
hatchets secure a definite cavity margin, particularly if cavity is in
the gingival third. In cavities that are sub-gingival build in amal-
gam as high as the gum line or at least one or two millimeters high,
being sure not to let this approach the pulp exposure or the point
Ashcre the application is to be made. Take, of the above paste on
the point of a flat excavator, a quantity equal to about one-fourth
the size of a common pin head and apply very close to, but not di-
rectly on the exposed pulp. B.y very close is meant within one-half
millimeter. Place over this a piece of spunk the size of a pin head,
or larger if cavity is large and roomy, which has been dipped in
creosote and then pinched in a napkin to dryness, putting into place
in such a manner as not to cause pressure on the pulp. The retain-
ing filling may now be completed with amalgam, cement or temporary
stopping.
Amalgam as a Retainer of arsenic has the advantages of making
a tight filling at the margins. Nothing will pass through it and it
is the most easily removed if it is applied where there are frail over-
hanging enamel walls which a chisel will easily cleave; or if the
amalgam has been but partially mixed with not enough mercury,
resulting in a mealy filling or where a great excess of mercury has
been used, that is to say where a most poorly manipulated amalgam
has been used resulting in its being cut with a bur much more easily
than cement, an advantage in cases where a tooth becomes sore to
pci'cnssion.