39
c
one is cut with a scissors to produce
an opening at the apex approximately
1/8 inch in diameter (fig. 77B).
Mix record media and gather it into one
mass on the end of the cement spatula.
Load the media into the bottom of a
paper cone (fig. 77C). Squeeze the
paper cone behind the record media to
capture the media near the apex of the
cone and to clean the spatula as it is
withdrawn (fig. 77D). After the spatula is
removed the cone is squeezed with the
index finger and thumb of both hands to
push all the media to the apex of the
cone and then the cone is folded back
on itself to prevent movement of the
media toward the large end of the cone
when it is compressed (fig. 77E).
The cone is squeezed to dispense the
media into the central groove of the
mandibular teeth (fig. 78). As soon as a
cone is loaded the operator can pro-
ceed to apply the media to the teeth as
the assistant immediately begins to mix
another batch of material for securing
additional centric relation records.
An inexpensive file jacket is used as a
mixing pad and provides for convenient
disposal of the record media after use. It
is good procedure to obtain three cen-
tric relation records. One is used to
mount the mandibular cast and the
remaining two are used to double check
the mounting for accuracy with the
Denar
®
Vericheck technique presented
in Appendix B of this manual.
The setting times of zinc oxide eugenol
record medias vary with temperature,
humidity, spatulation time and batch
number. Under certain conditions the
material will set very rapidly and the
operator must work quickly to get the
material to place before the set occurs.
Alternately the material may set slowly.
Since it is difficult for the operator to
maintain the patient’s mandible in cen-
tric relation for extended periods of
t
ime,
time, the operator using a slow setting
record media should wait for a period of
time after the media is placed on the
mandibular teeth until the set is about to
occur before manipulating the patient’s
mandible to centric relation. Therefore,
the operator should dispense record
media for four batches of material on
the mixing pad (fig. 79). The first batch is
use to time the set of the media and is
discarded. The remaining three batches
are used to obtain the centric relation
records.
To time the set, mix the first batch of
material according to the manufacturers
recommendations. Load the cone and
apply the first batch of record media to
the mandibular teeth. Do not bring the
mandible to centric relation. The opera-
tor should then start to count slowly
until the set occurs. Once the set has
fig. 78
fig. 79
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