overeruption of the opposing first molar and reduces the mesial tilting of the lower
second molar.
916H
Fig. 14.8 (a) and (b) Extraction of the first molars when the bifurcation of the roots
of the lower second molar is starting to calcify, usually 8 1/2 - 9 1/2 years of age,
gives the best chance of a good result.
917H
Fig. 14.9 (a) and (b) Extraction of the upper first molar does not need to be
compensated with extraction of the lower first molar.
14.4 APPLIANCE TREATMENT IN THE MIXED DENTITION
14.4.0 Introduction
The great majority of orthodontic treatments are carried out during the late mixed and
early permanent dentitions, to avoid prolonged appliance wear while permanent teeth
erupt. However, a few conditions can benefit from earlier intervention.
14.4.1 Anterior cross-bite
Although it may be a sign of a developing class III problem, a local anterior cross-bite
involving one or two incisors is often simply due to the positions of the developing
tooth-germs causing the teeth to erupt into cross-bite. Possible complications of a
localized anterior cross-bite include a premature contact with the tooth in cross-bite,
which causes the mandible to displace forwards as the teeth come into maximum
intercuspal position, or one lower incisor in cross-bite may be driven labially through