Page 74 - REMOVABLE ORTHODONTIC APPLIANCES

66 Removable Orthodontic Appliances

Figure 8.3 A class II division 1 occlusion with a well Figure 8.4 Molar relationship more than half unit
aligned lower arch and a molar relationship of half a class II, but a well aligned lower arch. In such cases it
unit class II or less. Premolar extractions in this type is sometimes possible to extract the upper first
of occlusion would give too much space. Extraction premolars only, finishing with a class II molar
of upper second molars, the use of extraoral traction relationship.
to move back the buccal segments and reduce the
overjet, is more appropriate treatment.

movement of the upper buccal segments Molar relationship more than half a
(Figure 8.3). In the presence of well-placed unit class II
upper third molars this movement may be facil-
itated by the extraction of the upper second Where there is an uncrowded lower arch it may
molars. be possible to extract the upper first premolars,
If the lower arch is mildly crowded the retract the canines and reduce the overjet. This
extraction of all four first premolars may be will allow the first molars to establish a class II
indicated, depending upon the age and sex of buccal segment relationship, which will be
the patient. If the second molars have erupted acceptable because units have only been lost
fully and the occlusion is well established, then from the upper arch (Figure 8.4). In the treat-
extraction of the lower first premolars may ment of such a case, extraoral anchorage may be
leave residual space. In such cases, the extrac- needed to prevent excessive forward movement
tion of lower second premolars may well be the of the upper first molars during treatment.
better choice but will necessitate the use of If the lower arch is mildly crowded and the
fixed appliances. patient is of an appropriate age, the extraction