The axial displacement of a tooth. A tooth may be intruded into its tooth socket due to a failure of the tooth to fully erupt, a pathological condition, trauma, or intentionally as part of orthodontic treatment. Intruded teeth with immature roots (open apices) are likely to erupt without treatment; intruded teeth with closed apices are likely to require orthodontic treatment or surgical repositioning and splinting in severe cases. Intrusion due to trauma may require surgical repositioning followed by flexible splinting for 1–2 weeks. See also luxation.