Page 86 - REMOVABLE ORTHODONTIC APPLIANCES

78 Removable Orthodontic Appliances
Even a reversed overjet on four incisors may be - ula. Once an overbite has been established this
treatable if there is a displacing activity. measure is not usually successful and an appli-
ance will be required. Provided there is a
displacing activity, it is sensible to consider
Incisor angulation early appliance treatment to avoid traumatic
The upper incisors should, ideally, be slightly occlusion with the lower incisors. This may be
retroclincd or of average axial inclination. associated with gingival recession and unsightly
Retroclined upper incisors are suited to procli- attrition to the labial faces of the upper incisors.
nation with removable appliances. The lower Early treatment also reduces the chance that
labial segment should have an average axial later erupting teeth may develop in lingual
inclination or be slightly proclined. occlusion.
When early treatment is to be carried out,
the parents should be informed that this is an
Buccal crossbite
interceptive phase of treatment which aims to
A unilateral crossbite often accompanies a mild deal with local problems and that further treat-
class III occlusion. If there is an associated ment may be required when the permanent
displacement of the mandible to one side, the dentition is established.
patient should be examined with the mandible Upper lateral incisors, which erupt palatally,
in the non-displaced position. A unilateral are a sign of crowding. If this is detected early,
crossbite associated with a mild skeletal class extraction of the deciduous canines, while the
III pattern and with only one incisor in cross- lateral incisors are erupting may .allow sponta-
bite, may still be favourable for correction. neous correction. Usually, however, the lateral
incisors will need to be proclined with an appli-
ance. Such movement should be undertaken
Lower arch considerations when the unerupted canines are still high and
Ideally, the lower arch should be well aligned - before they have moved down labial to the
this is a common feature of class III occlusions roots of the lateral incisors. If this has already
and relates to the size of the mandible. In some happened, correction of the lateral incisors
cases, where the reverse overjet is largely a must be delayed until such time as it is possible
feature of crowding, lower canine and incisor to retract the canines.
crowding may be sufficient to justify first Correction of a reverse overjet can be consid-
premolar extractions. Spontaneous alignment ered in the later stages of the mixed dentition
of the crowded lower incisors will occur in the but, as the permanent dentition becomes estab-
growing patient. This is aided by the fitting of lished there is an increasing chance of an under-
an upper removable appliance with molar lying marked skeletal discrepancy becoming
capping which will help to eliminate the apparent.
displacement and allow crowded and labially Surprisingly, some adult patients may still
placed incisors to align lingually. have an untreated reverse overjet associated
with a displacement. Correction with a remov-
able appliance may still be appropriate.
Age factors
One of the commonest interceptive treatments
in the early mixed dentition is the correction of Unfavourable factors
a reverse overjet on recently erupted central
incisors. Skeletal pattern
An upper central incisor may erupt in lingual Where there is no displacing activity, the
occlusion because it has been deflected underlying skeletal pattern will be a more
palalally by delayed shedding of its predeces- definite class III, which may be due to over-
sor, or because of a slightly abnormal path of development of the mandible, under-develop-
eruption. If the palatal deflection is recognized ment of the maxilla, or a combination of
before the tooth has reached the occlusal level, both. The Frankfort mandibular planes angle
it may be possible to correct it simply by is frequently high in the more severe skeletal
extracting the retained deciduous tooth and III patterns and such patients are more likely
instructing the patient to bite on a tongue spat- to grow unfavourably during adolescence.