Page 45 - REMOVABLE ORTHODONTIC APPLIANCES

The baseplate 37
When anterior bite planes are used in adults, the Posterior bite planes need to be thinner
initial bite plane should be very thin, because it posteriorly than anteriorly and should contact
is often more difficult for an adult to tolerate the the opposing teeth on both sides of the mouth.
same degree of bite opening as a younger They are difficult to construct accurately unless
patient. the models have been set up on an articulator.
If this is done in the laboratory then consider-
able time will be saved at the fitting appoint-
Posterior bite plane
ment.
Posterior bite planes can be used to eliminate a
lateral or anterior displacement of the
mandible. Posterior bite planes will assist in the Adjustments o the acrylic
t
correction of a buccal crossbite or an anterior
crossbite by preventing interference by the
opposing teeth and allowing the mandible to Initial fitting of the appliance
adopt a centric position (Figure 5.3).
Removable appliances should ideally be fitted
within 2 weeks of the impressions being taken.
Provided that no tooth movement has occurred
in the meantime, the baseplate should fit with-
out adjustment. If this is not the case any trim-
ming should be done with care and should be
carried out from the fitting surface, because
small gaps between the baseplate and the teeth
encourage food packing.
If there is any difficulty in seating the appli-
ance it may be best to bend the clasps gently
away from the teeth to check whether the resis-
tance is from the baseplate or from the wires. If
there are undercuts, the acrylic should be care-
fully trimmed from them without touching the
edge of the polished surface of the appliance so
that this still contacts the teeth.
Once the appliance can be fitted, it should be
examined in the mouth to ensure that the
acrylic is clear of the teeth that are to be moved.
The appliance should be removed and retried if
necessary to ensure that there is no interference
with the intended movement and that gingival
hyperplasia will not be encouraged.

Anterior bite planes
Anterior bite planes should be horizontal trans-
versely and anteroposteriorly, so that when the
appliance is in place the premolars are sepa-
rated by 2 or 3 mm. Ideally the bite plane
should be flat but, if the lower incisors are irreg-
ular, it may be necessary to adjust it to contact
at least three of them. As overbite reduction
Figure 5.3 A posterior bite plane. A unilateral occurs the bite plane can be built up and
crossbite may be corrected by arch expansion. levelled with the addition of cold-cured acrylic.
Posterior bite planes are incorporated to free the Overbite reduction should be evident within
occlusion and eliminate any associated displacing
activity. the first 2 months of fitting the appliance. Some