Page 60 - REMOVABLE ORTHODONTIC APPLIANCES

52 Removable Orthodontic Appliances
0.5 mm hard stainless steel wire, which contact Baseplate
the mesial surface of the second molars, close An anterior bite plane is required only if there
to the gingival margin. is occlusal interference with the appliance or
with tooth movement.
First permanent molars Anchorage
This is provided by the other teeth that are
If the first permanent molar has drifted forward contacted by the appliance and by the contact
following early loss of deciduous teeth, it may of the baseplate with the palatal vault. If only
need to be moved back to make space for the one molar is to be retracted, extraoral rein-
second premolar. This is most easily done forcement may not be required. If both first
before the second permanent molar has permanent molars are to be retracted, then
erupted (or possibly following its extraction). It extraoral reinforcement is usually necessary.
is difficult to retract both the first and second Tubes can be soldered onto the molar clasps.
permanent molars with this type of appliance As the first molars move distally, the facebow
without losing anchorage, even if extraoral should be adjusted at the 'U' loops to keep it
support is worn. Where the entire buccal clear of the incisors. An alternative is to use a
segment is to be retracted, an en-masse appli- headgear with 'J' hooks to spurs on a labial
ance can be used (see Figure 8.15, p. 75). This bow.
will retract the premolars at the same time.

An appliance to retract a first permanent
molar (Figure 7.6) Occlusal movement
Active component A removable appliance offers a considerable
A screw with its long axis parallel to the line of advantage in the occlusal movement of
the arch. This should be activated by one quar- partially erupted teeth because its contact with
ter-turn each week. (Alternatively, it is possible the vault of the palate provides better anchor-
to use a heavy single cantilever spring in age for such tooth movement than does a fixed
0.7 mm wire. This should be activated by about appliance. Occlusal movement is not possible
2 mm. The appliance is otherwise similar to that unless there is a point of application to allow
described except that the molar to be retracted the spring to apply an occlusally directed force.
is not clasped.) This is simply achieved by the addition of a
bonded attachment, usually to the labial
Retention surface of the tooth.
Clasps on first premolars and first permanent The method is particularly useful for
molars. partially erupted canines or central incisors.

Figure 7.6 An appliance to retract 6|.
Adams' clasps 63|46 (note that the screw is
placed parallel to the line of the arch).