POSTERIOR OPEN BITE

Posterior open bite occurs more rarely than anterior open bite and the aetiology is less well understood.

In some cases an increase in the vertical skeletal proportions is a factor, although this is more commonly

associated with an anterior open bite which also extends posteriorly. A lateral open bite is occasionally

seen in association with early extraction of first permanent molars, possibly occurring as a result of lateral

tongue spread.

Posterior open bite is also seen in cases with eruption disturbances. Primary failure of eruption is a

condition which almost exclusively affects molar teeth and has recenty been linked to a specific gene.

Affected teeth may erupt and then cease to keep pace with vertical development becoming relatively

submerged or may fail to erupt at all. Althought these teeth are not ankylosed they do not respond

normally to orthodontic force and indeed usually become ankylosed if traction is applied. Extraction is the

only treatment alternative.

More rarely, posterior open bite is sees in association with unilateral condylar hyperplasia, which also

results in facial asymmetry. If this problem is suspected, a bone scan will be required. If the scan indicates

excessive cell division in the condylar head region, a condylectomy alone, or in combination with surgery

to correct the resultant deformity, may be required.