Page 10 - REMOVABLE ORTHODONTIC APPLIANCES

2 Removable Orthodontic Appliances
use removable appliances successfully to deal
with simpler cases, but the specialist will still
find their use invaluable.

Action of removable appliances
Functional appliances are sometimes consid-
ered as 'removable appliances'. (They are, of
course, almost always removable) but they
depend for their effect on maintaining the
mandible in a postured position, influencing
both the orofacial musculature and dentoalve-
olar development. They are beyond the scope
of this volume, which will deal only with simple
removable appliances.

Spontaneous movement
Figure 1.1 Spontaneous uprighting of a mesially
inclined lower canine following extraction of a lower
Where extractions are carried out as part of
first premolar.
treatment, the relief of crowding may, on its
own, allow neighbouring teeth to upright
towards the extraction sites. Removable appli-
ances can enhance such tooth movement and inclined because uprighting can take place
treatment depends principally upon the ability towards the first premolar extraction sites. In
of the active components of the appliance to tip the lower arch this can be particularly benefi-
teeth. In many cases, spontaneous tooth move- cial.
ment can be relied upon to assist alignment and
this may be particularly important in the lower Labio-lingual movement
arch, where removable appliances are bulky
and are less efficient. (a) Anterior teeth
Because spontaneous tooth movement is so The lower labial segment may be influenced by
important as an adjunct to removable appliance soft tissue contact from the tongue and lips.
treatment, significant factors relating to sponta- The tongue provides an anterior component of
neous tooth movement are considered below. force to lingually displaced incisors while the
lips provide a lingually directed force to
proclined or labially crowded incisors (Figure
Eruption guidance
1.2). These forces may permit considerable
In the late mixed dentition stage, appropriate spontaneous alignment of imbricated lower
extractions allow an enhanced path of eruption incisors once crowding has been relieved. The
for crowded or misplaced teeth. Removable effect is much less marked in the upper arch
appliances have an important role to play as because the tongue does not contact the upper
space maintainers, following relief of crowding. incisors to the same extent.
This is considered fully in Chapter 7 on class I
malocclusions.
(b) Posterior teeth
There is limited soft tissue influence in the
Uprighting
bucco-lingual position of the upper posterior
When crowding is relieved a tooth may upright teeth but, in the lower posterior segments,
by movement of the crown towards an adjacent impacted second premolars are often uprighied
extraction space (Figure 1.1). This is commonly by the action of the tongue once crowding has
associated with crowding of canines and works been relieved, provided there is no cuspal inter-
most effectively when the crowns are mesially locking. Upper removable appliances often