the supporting tissues, causing localized gingival recession (918HFig. 14.10). Early
correction encourages development of a class I occlusion, and treatment in the mixed
dentition is often straightforward provided that these criteria are met:
- Normal skeletal pattern. Treatment of obvious class III problems should be delayed
until the nature of the patient's growth pattern becomes clearer. However, it is
essential to check for the presence of a forward displacement of the mandible, as this
can make a normal facial pattern appear to be slightly prognathic. - Adequate space in the arch. There must be enough space to accommodate the tooth
in alignment. In a crowded upper arch, space may be made for alignment of upper
lateral incisors by extracting the primary upper canines (see serial extraction, 919HSection
14.3.2). This treatment must be started fairly early while the permanent canine is still
high, because labial movement of the lateral incisor will be prevented if the canine
crown is labial to the root of the lateral. It is therefore essential to palpate the position
of the permanent canine crown, and, if it has come down too far, treatment must be
delayed until the first premolars have erupted. - Adequate overbite. Stable correction of the cross-bite depends on there being
positive overbite after treatment. Labial tipping of upper incisors with a removable
appliance tends to reduce overbite, and specialist advice should be sought where lack
of overbite is a problem.
There are many designs of removable appliance to correct anterior cross-bites and a
typical example is shown in 920HFig. 14.11 (a) and (b). Its essential features are:
- An active component such as a Z-spring or a screw palatal to the tooth to be moved.
- Retention as far anteriorly as possible to resist the tendency of the spring to displace
the front of the appliance. - Posterior capping to open the occlusion while the upper incisor moves labially over
the lowers.
921H
Fig. 14.10 Localized gingival recession
associated with incisor cross-bite.
922H
Fig. 14.11 (a) and (b) Appliance to
procline upper incisor. Note posterior
capping to disengage occlusion and
retention anterior to 6|6 to resist the
displacing force generated by the Z-