Page 53 - REMOVABLE ORTHODONTIC APPLIANCES

Anchorage 45
the upper incisors (so that it does not contact
them) and be at the level of the active lip line.
Its length can be adjusted at the 'U' loops (see
Figure 6.8). The 'U' loops may also need to be
adjusted to lengthen the inner bow during
treatment. The outer bow should he just clear
of the lips and cheeks with the hooks for the
elastics at the level of the mesial surfaces of the
Figure 6.11 An extraoral tube soldered to an first molars, about 4 cm anterior to the head
Adams' clasp.
cap hooks. When headgear is used with fixed
appliances, the level and length of the outer
arms determines the force vector applied to the
and will be fitted into tubes (1.15 mm internal teeth and thus affects their movement. With
diameter) soldered to the bridges of clasps on removable appliances the main concern must
either the molars or premolars (Figure 6.11). be that the direction of pull does not tend to
The tube should be soldered to the upper part unseat the appliance.
of the bridge of the clasp and the ends carefully
chamfered to minimize discomfort to the 'J' hooks provide an alternative to facebows
patient. Bending a loop in the bridge of the for connecting extraoral traction to an appli-
clasp provides an alternative method of attach- ance (see Figure 6.9). They can be attached to
ment but this is less stable. The facebow must be spurs soldered to clasps on the upper incisors or
adjusted so that it is readily inserted into the canines. In fixed appliance treatment 'J' hooks
tubes and does not tend to spring out. Facebows can be valuable as a means of intruding the
are available commercially and come in a vari- upper labial segment, but this is of questionable
ety of sizes. It is best to standardize on an inner efficacy with removable appliances. To make
bow of 1.15 mm wire diameter to fit the tubes the hooks as safe as possible it is recommended
and with short or medium length outer arms. A that the end be turned into a complete circle,
selection of four inner bow lengths will fit most which will still engage the hook on the appli-
appliances. ance. The term 'O' hook is suggested.
It is possible to fit bands to the upper first
molars to accept a facebow and fit a removable Headgear force
appliance over the bands. In this instance
flyover clasps (Figure 6.12) must be used For anchorage reinforcement the tension in the
instead of Adams' clasps. elastics needs to be sufficient to balance the
force of reaction generated by the active
components. For active retraction of buccal
Fitting a facebow segments, the traction force per side should be
at least 500 g. High pull headgear, which incor-
The inner bow must match the arch form and
length. It should lie a few millimetres labial to porates springs, can be obtained with tension
gauges that are integral in the springs so that
the force level can be measured. When elastic
force is used, latex elastics, which are more
uniform in size than commercial elastic bands,
can be obtained from orthodontic supply
companies. As a rule of thumb the elastic bands
should be stretched to approximately twice
their length. The patient should change the
elastic bands every third day or before if they
break.

Figure 6.12 Where molar bands are fitted to first
molars a flyover clasp (0.8 mm) should be used, the
clasp engages the buccal tube on the molar band. Headgear wear
This allows a removable appliance to be used in
conjunction with an extraoral facebow applied to the Once the initial training period with the extra-
buccal tubes on the bands. oral appliance has been completed (see