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56 Removable Orthodontic Appliances
Figure 7.10 An appliance to expand the upper
arch. Adams' clasps 64|46 (0.7 mm), a mid-line
screw and molar capping to eliminate
mandibular displacement.
• to help seat the appliance, particularly after Rotations
activation.
A mildly rotated upper central incisor can be
Anchorage corrected with a removable appliance. Rota-
The arch is to be expanded symmetrically, so tions of other teeth and multiple rotations can
anchorage is reciprocal. only be corrected by using a fixed appliance.
Many rotations are associated with an element
Points to note of apical displacement and will be difficult to
The patient should open the screw by one quar- correct with a removable appliance. Rotations
ter-turn each week. If the appliance is adjusted are also particularly liable to relapse.
more frequently it may not seat home fully and
will become difficult to wear. The molar An appliance to derotate an upper central
capping should be removed after the expansion incisor (Figure 7.11)
has been completed and the appliance should
continue to be worn as a retainer for at least 3 Active component
months. It is wise to cover the screw with cold- A force-couple must be applied to the tooth.
cured acrylic to prevent any unwanted move- A labial bow and a palatal spring can gener-
ment during this stage. ate this. If the palatal aspect of the tooth is
already in the line of the arch, contact with
Upper arch contraction
Only if there is a buccal crossbite of the upper
teeth will contraction of the upper arch be
necessary. This is an unusual finding associated
with a broad maxillary base and a narrow
mandibular base. Treatment is difficult and is
best left to the orthodontic specialist. It may
involve the use of an upper appliance similar to
that for upper arch expansion except that the Figure 7.11 A rotated |l to be aligned with a 'U'
screw is opened before it is incorporated into loop labial bow (0.7 mm). The labial bow is activated
progressively. The acrylic must be cleared away from
the appliance and is closed by the patient.
the mesial aspect of the central but maintained in
Simultaneous expansion of the lower arch will contact with the disto-palatal aspect of the central
usually be required. incisor.