Page 89 - REMOVABLE ORTHODONTIC APPLIANCES

Class III malocclusions 81
Aims of treatment extraction of permanent teeth. Residual extrac-
tion space towards the front of the arch may
The aims of treatment are the correction of allow relapse of a corrected incisor position and
reverse overjet, alignment of the labial because of this, first premolar extractions
segments, elimination of any displacing activity should only be considered when the crowding is
and a stable result. marked. In the mildly crowded case, premolar
A critical factor in the stability of a corrected extractions may be best avoided and the extrac-
class III incisal relationship is the degree of tion of upper second molar teeth may some-
overbite. The aim of treatment is generally to times be considered.
maintain the existing overbite and not to It is wise to be cautious about lower arch
reduce it. Appliances should be designed to extractions. Where crowding is severe, the
minimize overbite reduction. The use of molar extraction of lower first premolars may be
capping to disengage the occlusion while a considered to relieve canine and incisor crowd-
displacing activity is corrected has the advan- ing, but in mildly crowded cases, fixed appli-
tage of inhibiting vertical growth of the poste- ance treatment is indicated. Very occasionally.
rior teeth and thus helping to maintain a
positive overbite.
The proclination of an upper incisor will tend
to reduce its vertical height and so to reduce the
overbite (Figure 9.5). Because the upper incisor
has a sloping palatal surface, a spring, which is
designed to move the tooth forward, will also
produce an intrusive component of force. The
correct choice of spring or the use of a screw
can minimize this.

Extraction considerations
In the mixed dentition stage, one or two
incisors in crossbite are often associated with
upper arch crowding. Extraction of the upper
deciduous canines is often desirable to allow
for temporary relief of upper labial segment
crowding. Early correction can be worthwhile
because it is more easily carried out before the
eruption of successive teeth provides further Figure 9.5 Where the overbite is reduced,
obstruction. Such cases frequently require proclination of the upper incisors will result in a
extraction of the lower deciduous canines to further reduction in overbite and may produce an
unstable incisor relationship.
allow for some temporary relief of the lower
incisor crowding, which assists any correction.
It must be made clear to the parents that, ulti-
mately, extraction of permanent teeth may be extraction of a lower incisor may be appropri-
necessary. ate; particularly if, as a result of a crossbite, it is
In the established dentition, proclination of labially displaced with reduced buccal bone and
the upper incisors and expansion of the upper gingival recession. In such a case specialist
arch moves the teeth onto an arc of wider advice should be sought.
circumference, which effectively reduces In the upper arch, in some very crowded
crowding. Extractions may therefore need to be cases, with the canines forward and labial to the
further back in the arch than in a cass I or mild lateral incisors, it may be possible to extract a
class II case with an equivalent degree of totally excluded lateral incisor and allow the
crowding. Where there is doubt, it may be wise canine to erupt into contact with the central
to commence arch expansion, either anteropos- incisor. Again, specialist advice should be
teriorly or laterally, before deciding upon sought before proceeding with such a plan.