Page 91 - REMOVABLE ORTHODONTIC APPLIANCES

Class III malocclusions 83
continued for at least 3 months. The screw can Anchorage
be covered with cold-cured acrylic to prevent The anchorage provided by the clasped teeth is
any unwanted movement. more than adequate.

An appliance to procline an instanding Baseplate
incisor (Figure.9.7) A bite plane will serve to clear the overbite
while the incisors are being proclined.
Active component Normally, posterior bite planes should be used
A double cantilever spring may be used (see and are best trimmed so that there is about
Figure 3.14, p. 20). For a narrow tooth, such as 1 mm clearance in the incisor area.
a lateral incisor, such springs are rather stiff and The ehmination of occlusal contacts will help
their range of action is limited, although this lower incisor irregularities to improve sponta-
can be partly overcome by the use of 0.35 mm
wire. (If two adjacent teeth are instanding, it is neously. A slight lingual movement of the most
that the
upper
incisors means
prominent
lower
often preferable to use a single spring to
procline both.) Alternatively, a cranked single incisor has only to be proclined by a very small
cantilever spring may be suitable, because the amount.
crank keeps the spring clear of the other teeth.
The coil should be positioned as far forward as Points to note
possible or the direction of action may be incor- Provided that the tooth is palatally inclined and
rect. Both types of spring may be protected by the overbite is adequate, this is one of the
being boxed-in under the baseplate, but as the simplest tooth movements and will normally be
tooth moves forward, full protection will be completed within a few weeks. Where there is
lost. This may allow a double cantilever spring a positive overbite, retention may not be neces-
to slip occlusally but a cranked finger spring sary. An instanding incisor may, however, be
will still be supported by the baseplate. only one feature of a more complex malocclu-
sion and a complete case assessment must be
Retention performed before treatment is started. Where
Most springs will displace the anterior part of there is no positive overbite, or where the
the appliance and so, where possible, teeth in incisor apex is palatally displaced, treatment
addition to the first molar should be clasped. In with a removable appliance may be unsatisfac-
the mixed dentition such teeth will be decidu- tory.
ous canines or deciduous first molars, which do If the skeletal pattern is too severe further
not offer good retention. In the older patient, labial movement of the upper incisors will often
canines or first premolars may be clasped. produce a traumatic relationship with the

Figure 9.7 An appliance to procline |l. A
cantilever spring (0.5 mm), Adams' clasps
6|6 (0.7 mm) and on D|D (0.6 mm). Molar
capping to disengage the occlusion.