Second molars

Thomas et al.21 provided a succinct summary on the role of loss of second molars in orthodontic treatment. They state that all other teeth should be present with the third molars of normal size, shape and in a good position to erupt. Mild lower labial segment crowding may be effectively treated by loss of second molars, however they should not be considered in the treatment of moderate or severe crowding. Second molar loss may be undertaken under the following circumstances:

• To facilitate the eruption of the third molars obviating the need for surgical removal at a later stage.

• To allow relief of premolar crowding (especially where second premolars are impacted)

• May prevent crowding in a well-aligned lower arch (Fig. 13).

• Distal movement in the upper arch is more reliable and more stable.

However, the potential disadvantages of second molar extraction are:

• Eruption of third molars especially in the lower arch is unpredictable. About 30% of these teeth require uprighting.

• The teeth are remote from the site of crowding making alignment unpredictable.

Where second molars are considered for extraction, the timing is important. Satisfactory third molar alignment is less likely if the second molars are extracted after the third molar roots are more than one third formed.

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