Intrusion Root Resorption — NDEB AFK MCQ
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Correct answer: C — Intrusion
Intrusion (apical movement of the root apex) is the orthodontic tooth movement most strongly associated with external apical root resorption. The concentrated stress at the root apex during intrusive forces causes osteoclastic (and cementoclastic) resorption of the root surface. Other risk factors for orthodontic root resorption include heavy forces, long treatment duration, root morphology (blunted, pipette-shaped, or dilacerated roots), and individual susceptibility. Light, intermittent forces and careful monitoring with periapical radiographs minimise this risk.
Reference: Proffit – Contemporary Orthodontics, 6th ed., 2019