Page 57 - REMOVABLE ORTHODONTIC APPLIANCES

Class I malocclusions 49
years following the successful eruption of
delayed incisors. A removable appliance
may provide an appropriate first treatment
phase which can be followed by a period of
part-time retention before definitive fixed-
appliance treatment is considered.
• Space closure - Although the inflexible
baseplate of a removable appliance makes
general space closure difficult, if not impos-
sible, it is occasionally helpful to move
together a number of spaced incisor teeth in
order to collect space nearby for erupting
teeth, such as canines. Closure of a substan-
tial mid-line diastema is rarely appropriate, Figure 7.2 (a) A median diastema which could be
as this generally requires precise control closed with a removable appliance by tipping of the
crowns mesially. (b) A diastema that would require a
over the position of the apices of teeth if an fixed appliance for space closure.
aesthetically pleasing and stable result is to
be achieved.
Short-term retention is usually all that is developing dentition which will often close
required following treatment of class I cases. spontaneously with the eruption of the perma-
Long-term retention is contraindicated when nent canines. A persistent median diastema
the prolonged use of an appliance will maintain may be due to a mid-line supernumerary tooth
extraction spaces in situations where natural which must be removed before appliance treat-
space closure is desired after treatment.
ment commences. Radiographs should be
obtained before closure is considered.
Where upper incisors are crowded the lateral
Upper removable appliances incisors may need to move distally so that
alignment can proceed. If retraction of the
The following appliances may also have an canines has to be carried out before this the
application in the treatment of class II or class lateral incisors will often follow them, provided
III occlusions and relevant comments are that the appliance does not interfere with this
included where appropriate. movement.
Incisors may need to be moved round the
arch where there is a shift of centre-line, usually
Tooth movements in the tine of the following asymmetric loss of a deciduous
arch canine or first molar. Fixed appliances are
usually necessary to correct significant centre-
In general, single cantilever springs, boxed line discrepancies.
and guarded, are most satisfactory. The design
of these springs has been discussed on p. 19.
They can be used to move a tooth buccally as Appliance to open space for 1|1 (Figure 7.3)
well as mesially or distally, but it is not gener- Retention
ally possible to obtain appreciable palatal Adams' clasps on 6|6.
movement.
Anchorage
The other teeth in the arch provide adequate
Incisors
anchorage.
Movement of incisors in the line of the arch is
not commonly required but if the distance is Baseplate
small simple tooth movement may suffice. Normal full palatal coverage.
Closure of a median diastema may sometimes
be necessary (Figure 7.2), but it should be Springs
remembered that this is a natural feature of the Cantilever springs to move 2|2 distally.