Page 79 - REMOVABLE ORTHODONTIC APPLIANCES

Class II malocclusions 71
deliver a palatal component of force (see buccal drift of the canines but it is better to
Figure 3.6, p. 18). This can be a retractor, made ensure that the springs are correctly made and
from 0.5 mm wire supported in tubing, or a self- adjusted. Palatal springs should be activated by
supporting spring made from 0.7 mm wire. just less than half a canine tooth width (3 mm).
Care must be taken not to overactivate
Retention buccal springs because they are capable of
Clasps will be needed on first permanent generating large forces which may overload the
molars. A double Adams' clasp or a Southend anchorage, causing loss of space and an
clasp may be used on the central incisors. This increase in overjet. Self-supporting buccal
is most important if anchorage is to be supple- springs should only be activated by about
mented by extraoral traction. 1 mm. Supported buccal springs may be acti-
vated by 2 mm.
Anchorage
Retraction of canines places demands on
anchorage. It is difficult to avoid some anchor- Incisor retraction
age loss without the use of headgear. Unless In class II, division 1 cases, overjet reduction is
there is space to spare, extraoral support will one of the main treatment objectives. Space
probably be necessary either with a facebow to must first be created by retraction of the upper
tubes on the molar clasps, or with 'J' hooks to canines. If the incisors are irregular or the over-
the anterior part of the appliance. jet is small (less than 4 mm), alignment may be
carried out on the same appliance as canine
Baseplate retraction (see Figure 3.25, p. 27) by the incor-
Usually an anterior bite plane will be required poration of a labial bow. After canine retrac-
in class II division 1 cases to reduce the overbite tion, the bow is modified (see Figure 3.23,
and occasionally to clear the occlusion. p. 25) to retract the incisors. Overbite reduction
is undertaken during canine retraction but the
Points to note biteplate continues in use during overjet reduc-
The spring should not be activated until the tion to maintain the lower incisor depression
tooth is close to the occlusal level otherwise its (and to reduce the overbite further, should this
eruption will be impeded. The point of contact be necessary).
of the spring with the tooth is important and, Where the overjet is large (more than 4 mm)
particularly with palatal springs, unwanted it is preferable to use a second appliance to
buccal movement should be watched for. Some reduce it with a light flexible bow such as
orthodontists incorporate a labial bow (see Roberts' retractor (Figure 8.11). This has a
Figure 3.25, p. 27) into this appliance to prevent range of action sufficient to permit continuous

Figure 8.11 An appliance to retract the
upper incisors. A Roberts' retractor
(0.5 mm) sheathed in tubing (0.5 mm ID).
Stops on 3|3. Cribs on 6|6 (0.6 mm). A
bite plane to maintain overbite reduction.