Correction Of Overbite

Space closure with fixed appliances tends to increase the overbite and therefore extractions in the lower arch in deep bite cases should be undertaken with caution. In some malocclusions, where the anterior face height is reduced, extractions can make space closure difficult and great care must be taken in diagnosis before this decision is made. It is important to recognise whether a case is genuinely crowded or whether the teeth are displaced lingually as in a Class II Division 2 case. Lingually displaced lower labial segments are frequently not crowded, even though they may appear to be so.

Proclination of the lower labial segment also reduces the overbite, as well as overjet, and may obviate the need for extractions. However, this treatment approach should be undertaken cautiously as uncontrolled and excessive proclina-tion of the lower incisors can be unstable and should only be undertaken in selected cases by experienced clinicians. Flattening of an accentuated curve of Spee in order to reduce an over-bite, where proclination is contraindicated, does require space, for which the extraction of lower teeth can sometimes be considered. The space required to flatten a curve of Spee has historically been over rated, the amount of space required is

Fig. 2 A supplemental lower incisor (a) was removed, resulting in spontaneous correction of crowding in the lower labial segment (b)

Fig. 3 This case presented with missing upper first premolars and lower right third molar, with vertically impacted lower second premolars. (a) Both lower first molars are heavily filled and would be ideal for extraction to allow eruption of the second premolars. However the missing third molar on the right resulted in extraction of the lower right first premolar and the lower left first molar. Spontaneous alignment occurred (b) with both impacted premolars erupting successfully into the occlusion with no active treatment

Fig. 3 This case presented with missing upper first premolars and lower right third molar, with vertically impacted lower second premolars. (a) Both lower first molars are heavily filled and would be ideal for extraction to allow eruption of the second premolars. However the missing third molar on the right resulted in extraction of the lower right first premolar and the lower left first molar. Spontaneous alignment occurred (b) with both impacted premolars erupting successfully into the occlusion with no active treatment

Fig. 4 In this case, the erupting upper second premolars showed some resorption of the mesial roots of the upper first molars. (a) Progressive resorption of the mesial roots of the molars was seen on subsequent radiographs (b), which progressed to such an extent (c) that both upper first molars required extraction, allowing eruption of the second premolars

1-2 mm when the curve is severe and there is no crowding. It is difficult then to justify extracting teeth purely for the sake of creating space to flatten an occlusal curve. The greatest challenge is the mechanical control of the teeth to prevent excessive proclination of the lower incisors. This usually occurs because the intrusion force is at some distance labial to the centre of resistance of the incisors and lingual crown torque is needed to prevent the labial movement of the incisors.

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