very lengthy when started early. Progress can be slow in prepubertal children because
of their relatively slow growth rate, and dwindling co-operation with these demanding
appliances can become a real problem during prolonged treatments. The appliance
should be worn as a retainer until after the pubertal growth spurt, which in boys may
be 15 or 16 years of age⎯a long time if treatment started at the age of 9. Treatment
for crowding can usually only begin after the premolars start to erupt, and the patient
effectively has two courses of treatment⎯one to reduce the overjet and one to align
the arches. A potential difficulty of this approach is that the overjet reduction must be
retained while the crowding is being treated, which can make management complex.
Early treatment is often justifiable for patients with severe overjets, but the possible
disadvantages must be balanced carefully against the potential benefits.
927H
Fig. 14.13 (a) An 11-year-old boy with a class II, division I malocclusion. (b) A 10-
mm overjet and class II molar relationship. (c) Functional appliance in place with
sectional fixed appliance to assist upper incisor alignment. (d) The functional
appliance:a type of activator. (e) Slight overcorrection. (f) Post-treatment facial
profile.
14.4.4 Space maintenance
It is often important that drifting of teeth into an extraction space is prevented, such
as: following loss of a primary molar (928HSection 14.3.3); following loss of an upper
incisor (929HSection 14.7.2); where the crowding is severe enough that extractions give
only just enough space.
In these situations a space maintainer is indicated. In the upper arch this can be a
simple acrylic appliance with clasps, but in the lower a lingual arch is better tolerated
(930HFig. 14.14 (a) and (b)).