Page 81 - REMOVABLE ORTHODONTIC APPLIANCES

Class II malocclusions 73
Figure 8.12 An appliance to retract a
pronninent upper central incisor.

Figure 8.13 Once the retraction has
commenced, it may be necessary to add
bayonet bends mesial and distal to the
central incisor to ensure that the force of
the 'U' loop labial bow is applied to the
incisor.

8.13) on either side of the prominent tooth. Appliance design
This ensures that the bow acts only on the A variety of appliance designs may be used. All
prominent incisor. Subsequently the bow may of them must make provision for the intermo-
be activated at the 'U' loops.
lar width to be increased during distal move-
ment to compensate for the shape of the arch
and to prevent a crossbite from developing. An
Treatment in second molar extraction appliance may either incorporate screws or
cases springs with headgear support, or else rely
solely on extraoral force to achieve the move-
Distal movement
ment (an 'en-masse' appliance). The third
Where the lower arch is uncrowded, or exhibits method, using fixed appliance techniques, is to
only very mild crowding, the buccal segment cement molar bands and apply the extraoral
relationship may best be corrected by the use force directly to these.
of extraoral force to move the upper buccal
segments distally. It is not practical, however, to
move the buccal segments more than half a unit An appliance to retract upper first molars:
in this manner. The movement of the upper twin screw appliance (Figure 8.14)
buccal segments can be facilitated by the extrac- Active components
tion of upper second molars (providing the This appliance incorporates two screws, placed
upper third molars are present and well placed). at a slight angle to allow for upper arch width