the position of the first molar. If the second molar has erupted before the extraction it
still migrates forward, taking up most or all of the space depending on the degree of
crowding, and it usually tilts mesially and rotates mesiopalatally about the palatal
root. However, compensating extraction of the lower first molar is not indicated (911HFig.
14.9 (a) and (b)).
Balancing extractions of the contralateral first permanent molars are not routinely
necessary unless they also are in poor condition. Where the arch is crowded an
extraction on the opposite side is usually needed to relieve crowding and prevent any
shift of the centreline, but if the first permanent molars are in good condition the
extraction of first premolars may well be more appropriate.
Key Points
First permanent molar extractions
- These are never the teeth of choice for orthodontic extraction.
- The best age for loss is 8 1/2 - 9 1/2 years.
- Extraction of the upper first molar may reduce occlusal disturbance where the lower
first molar has to be extracted. - There is no need to extract the lower first molar if the upper first molar has to be
extracted. - Contralateral extractions depend on the degree of crowding.
Extraction of first permanent molars where orthodontic treatment is planned
Where future appliance treatment is anticipated, the objective is to try to avoid
complicating it. It is difficult to give hard and fast rules as the management strategy
will differ for each patient, but the main factor to consider is the amount of space that
will be needed. Where the extraction space is to be used to relieve crowding or reduce
an increased overjet, unwanted mesial drift of the second permanent molars must be
minimized. On the other hand, where there will be excess space, mesial drift of the
second permanent molars should be encouraged.
In the lower arch the extractions are managed according to severity of crowding.
Where there is little or no crowding the extraction should, if possible, be carried out at
the 'ideal' age of about 8 1/2 - 9 1/2 years, so as to encourage mesial migration of the
second molar. Where there is significant crowding it is better to delay the extraction,
if possible, until after the lower second molar has erupted, so that the space is
available for alignment of the arch.
The upper arch is also managed according to space requirements, but these are
determined not only by the amount of crowding but also by the class of malocclusion.
Where there is significant crowding the upper first molars should be preserved if
possible until after the upper second molars have erupted and can be included in an
appliance. Similarly, in a class II malocclusion space will be useful to reduce an
increased overjet and, again, where possible the extractions should be delayed. If the
upper first molar has to be removed earlier it is sometimes possible to start treatment
with appliances before the upper second molars have erupted, but the treatment tends
to be more complex, with headgear to move the upper premolars distally.
Conversely, excess upper arch space in a class III malocclusion complicates