Tooth intrusion occurs when the tooth has been driven into the alveolar process due to an axially directed impact. This is the most severe form of displacement injury. Pulpal necrosis occurs in 96% of intrusive displacements and is more likely to occur in teeth with fully formed roots. Immature root development will usually mean spontaneous re-eruption. Mature root development will require repositioning, surgery, and splinting or orthodontic extrusion. Treat relatively quickly since the pulp usually becomes necrotic – this can be treated with temporary filling of calcium hydroxide paste followed by root canal therapy.