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METHODS OF TAKING IMPRESSIONS. 1
ill hot water; when the latter method is employed the mois-
ture should always be absorbed from the surface with a
towel or napkin before manipulating" with the hands.
The cup should then l)e filled with the softened material
and impression taken. The position of both patient and
operator, and the manner of introducing the cup into the
mouth is the same as has been directed for taking impres-
sions in plaster. But it must be remembered that these
materials will not flow as plaster does, so it is very necessary
that firm and steady pressure should be used against the
cup in order to secure a good impression of every desirable
part, and to aid in this the patient should be directed to
draw down the lip, and the impression material should be
pressed in all around above the rim, the pressure on the
surface of the cup must at the same time be kept firm and
steady. The hardening of these materials may be hast-
ened by dipping the corner of a napkin or a piece of cotton
in cold water, and passing it over the surface of the cup.
When it is firm enough to remove it must be done with
great care, and the direction of its removal must be deter-
mined by the position of any remaining teeth, or the pro-
jection of the ridge. And though much care is taken the
impression is never as sharp as where plaster is used, and
there exists such a probability of imperfection from bend-
ing or dragging due to undercuts, that plaster should be
the material used in all cases possible, the more difficult
the case the more reason wdiy it should be employed.
Preparing the Vacuum Chamber.—In full cases it is not
necessary, as a rule, to make a vacuum chamber in the plate.
Vacuum chambers are of temporary service only, as they
are soon perfectly filled with soft tissue. All that is re-
quired to secure sufficient adhesion is to have the plate
come in close contact with the palate and ridge at every
point, that is, to have the pressure equally distributed. (See
carving of models.
METHODS OF TAKING IMPRESSIONS. 1
ill hot water; when the latter method is employed the mois-
ture should always be absorbed from the surface with a
towel or napkin before manipulating" with the hands.
The cup should then l)e filled with the softened material
and impression taken. The position of both patient and
operator, and the manner of introducing the cup into the
mouth is the same as has been directed for taking impres-
sions in plaster. But it must be remembered that these
materials will not flow as plaster does, so it is very necessary
that firm and steady pressure should be used against the
cup in order to secure a good impression of every desirable
part, and to aid in this the patient should be directed to
draw down the lip, and the impression material should be
pressed in all around above the rim, the pressure on the
surface of the cup must at the same time be kept firm and
steady. The hardening of these materials may be hast-
ened by dipping the corner of a napkin or a piece of cotton
in cold water, and passing it over the surface of the cup.
When it is firm enough to remove it must be done with
great care, and the direction of its removal must be deter-
mined by the position of any remaining teeth, or the pro-
jection of the ridge. And though much care is taken the
impression is never as sharp as where plaster is used, and
there exists such a probability of imperfection from bend-
ing or dragging due to undercuts, that plaster should be
the material used in all cases possible, the more difficult
the case the more reason wdiy it should be employed.
Preparing the Vacuum Chamber.—In full cases it is not
necessary, as a rule, to make a vacuum chamber in the plate.
Vacuum chambers are of temporary service only, as they
are soon perfectly filled with soft tissue. All that is re-
quired to secure sufficient adhesion is to have the plate
come in close contact with the palate and ridge at every
point, that is, to have the pressure equally distributed. (See
carving of models.
