Primary failure of eruption.

Failure of eruption may be due to mechanical interference or to a failure in the eruption mechanism of the tooth. The etiology of the primary failure of eruption is unknown, but it could be due to an alteration in either metabolism or blood flow to the periodontal ligament. Therapy of patients with this condition is extremely difficult; orthodontic treatment causes ankylosis and probably the only way to move unerupted teeth into occlusion is to reposition them surgically with a small segment alveolar osteotomy.