40
b
een timed the operator knows how
long to pause after the media has been
placed on the lower teeth before bring-
ing the mandible to centric relation. It is
desirable to bring the mandible to cen-
tric relation just before the set occurs.
For best results it is important that the
operator and assistant work with consis-
tent technique throughout this procedure.
TECHNIQUE FOR
DIAGNOSTIC CASTS
Checkbite records made of hard base
plate wax can be used to advantage
when mounting diagnostic casts. The
wax used should be of a hard, brittle
consistency and fracture without bend-
ing at room temperature. For obtaining
centric relation records develop wax
wafers composed of two thicknesses of
wax to the dimension illustrated in fig.
80. It is best not to include the anterior
teeth in the centric relation record if suf-
ficient posterior teeth are present to sta-
bilize the casts in the record.
To develop the wax wafers soften a
sheet of base plate wax in a water bath
or open flame. Flame one surface of the
wax and fold the wax over on itself on
the flamed surface to bond the wax into
a wafer consisting of two thicknesses of
wax. With a warm spatula trim the wax
slightly oversize of the desired dimen-
sion. With the wax slightly softened so
the wafer is pliable, position the wafer
on the maxillary teeth and using the
index fingers adapt the wax to the teeth
to obtain very light indexing impressions
of the cusps tips and to contour the
wafer to the plane of occlusion. Do not
impress the mandibular teeth into the
wax at this time. Chill the wax with air so
that it will maintain the shape of the
plane of occlusion and remove the wafer
from the mouth. With a warm scalpel
trim the wafer to the desired dimensions.
Check the wafer in the mouth or on a
maxillary cast to confirm that the wafer is
contoured to the plane of occlusion and
is stable on the maxillary teeth.
Soften the lateral edges of the wax in an
open flame until it is dead soft. Quickly
temper the wax in a water bath and
position the wafer on the dry maxillary
teeth to obtain light impressions of the
tips of the cusps as previously
described. Guide the mandible in cen-
tric relation closure to obtain light
impressions of the mandibular cusp tips
in the record. It is important that the
operator guides the mandible to the
desired position.The patient should not
be instructed to bite down or close. As
soon as the impressions are obtained,
chill the wax with air and remove it from
the mouth. The record is chilled in cool
water and returned to the mouth and
checked for accuracy. The wafer is
placed on the maxillary teeth and the
mandible is arced in centric relation clo-
sure to occlusal contact. The mandibu-
lar cusp tips should come into simulta-
neous even contact with their impres-
sions in the record. When the mandibu-
lar teeth are brought into extemely light
occlusal contact with the record the
patient should preceive no premature
contact or uneven pressure on ques-
tioning.
Lateral Checkbite Records
A technique for fabricating a right lateral
checkbite record is described. The left
lateral record is obtained in a similar
manner.
Train the patient to allow you to arc the
mandible in hinge retation with the
patient’s rotating condyle in its most
fig. 80
F
igure 80 courtesy
Dr. P. Dawson and C.V. Mosby Co.
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