Page 62 - REMOVABLE ORTHODONTIC APPLIANCES

54 Removable Orthodontic Appliances
patient to insert. A cranked finger spring may Buccally crowded canines have to be moved
be used for buccal movement of a canine. palatally as well as retracted and a buccal
canine retractor (see Figure 7.4, p. 50) should
Retention be used. If a canine being retracted with a
Clasps on 6|6 and 1|1 or the contralateral first palatal spring has inadvertently been moved
premolar. buccally, palatal movement will be required. It
may be possible to modify the existing appli-
Baseplate ance by adding a buccal spring, soldered
A bite plane is usually required to clear the directly to the bridge of a molar clasp (Figure
occlusion. Unless the overbite is reduced or the 7.9). If the molar clasp has to be adjusted the
overjet reversed, an anterior bite plane is best spring will be moved and will need its own
and should be just high enough to clear the adjustment.
occlusion. If the overbite is reduced, thin molar
capping should be used instead of an anterior
bite plane. A spring to move a premolar palatally
(see Figure 7.8)
Anchorage A self-supporting buccal arm in 0.7 mm wire
This is not a problem as a large number of teeth entering the acrylic behind the molar clasp.
are contacted by the baseplate and pitted
against the single tooth to be moved. Retention
This spring does not tend to displace the appli-
Points to note ance so retention is not a problem. Clasps on
The 'T' spring should be curved so that it is clear 6|6 are adequate.
of the palatal mucosa and should contact the
tooth quite close to the cusp. If appreciable Baseplate
tooth movement is required, adjustment loops Where occlusal interference may limit tooth
should be included (Figure 7.8) so that the spring movement an anterior bite plane should be
may be progressively lengthened. The spring is included.
adjusted by pulling it away from the baseplate.
Excessive activation should be avoided because Anchorage
the spring will catch on the cusp of the tooth and The other teeth on the same side of the arch are
make the appliance difficult to insert. contacted by the baseplate and should provide
adequate anchorage.

Palatal movement Points to note
During appliance construction the tags of
Occasionally, a premolar erupts into a buccal clasps and springs must be kept well clear of the
crossbite and has to be moved palatally. tooth to be moved to allow later trimming.

Figure 7.9 A buccally placed spring (0.7 mm)
to move a canine palatally. Note the acrylic
must be trimmed well clear of the palatal
aspect of the tooth.