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Orthodontics · single question

What is the accepted rate of forced orthodontic extrusion of a tooth?

  1. Approximately 2 mm per month
  2. Approximately 5 mm per month
  3. Approximately 2 mm per week
  4. Approximately 0.2 mm per month
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Correct answer: A. Approximately 2 mm per month

  • A. Correct. Forced (rapid) orthodontic extrusion proceeds at roughly 2 mm per month using light continuous force, which moves the tooth without carrying the bone and gingiva coronally.
  • B. 5 mm per month vastly exceeds physiologic tolerance of the periodontal ligament.
  • C. 2 mm per week is far too fast and risks pulpal necrosis, root resorption and detachment.
  • D. 0.2 mm per month is slower than routine orthodontic tooth movement and would make the procedure impractical.

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