Page 51 - REMOVABLE ORTHODONTIC APPLIANCES

Anchorage 43
Extraoral anchorage

This is provided by a headgear, which can take
the form of a full headcap or a high pull head-
gear. The direction of pull should be horizontal
(occipital anchorage) or higher than this
(Figure 6.6). Cervical anchorage provided by
means of a neck strap cannot be used satisfac-
torily with a removable appliance and is not
recommended unless bands have been fitted to
the first molars.
Extraoral forces may be used to reinforce
intraoral anchorage, but may also serve as the
sole source of anchorage, for example when
upper buccal segments are being retracted
(Figure 6.7). When the extraoral force is the
active component for tooth movement, it is
referred to as extraoral traction. Extraoral
force may be generated by elasticity in the
headgear, by elastics connecting it to the appli-
ance or by springs. The connection between the
headgear and appliance is made by a facebow
(Figure 6.8) or occasionally by 'J' hooks (Figure
6.9). It must be emphasized that these devices
are potentially hazardous to the patient and to
other children so the precautions discussed
below must be adopted.
Figure 6.7 A mild class II case with minimal overjet
and less than 1/2 unit class II molar relationship. In
this situation, distal movement by means of
headgear force to correct the molar relationship and
reduce the slight overjet is often indicated. This may
be associated with loss of the upper second molars.

Figure 6.6 An adjustable headgear attached to a
facebow by means of elastics. The direction of the Figure 6.8 A detachable facebow. Note the re-
force applied is slightly superior, which aids curved ends, which are designed to avoid possible
retention of the appliance. injury.