Which type of dental traumatic injury has the worst prognosis?

Intrusion (apical displacement of the tooth into the alveolar bone) has the worst prognosis among luxation injuries because it causes severe crush injury to the periodontal ligament fibers, compression of the apical vessels (leading to pulp necrosis in 88-98% of teeth with closed apices), and damage to the alveolar bone. Complications include pulp necrosis, inflammatory root resorption, ankylosis, and marginal bone loss. Prognosis depends on the degree of intrusion and root development stage. Extrusion and luxation injuries have better prognosis as they allow PDL preservation. Subluxation (loosened but not displaced) has the best prognosis.