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Orthodontics · single question

What is the accepted rate for orthodontic forced eruption (extrusion) of a tooth?

  1. Approximately 2 mm per week
  2. Approximately 1 mm per month
  3. Approximately 4 mm per month
  4. Approximately 1 mm per week
Show answer and explanation

Correct answer: D. Approximately 1 mm per week

  • A. 2 mm per week exceeds biologic tolerance and risks pulp necrosis, root resorption, and relapse.
  • B. 1 mm per month is unnecessarily slow and prolongs treatment without benefit.
  • C. 4 mm per month is too aggressive for controlled extrusion with attachment following.
  • D. CORRECT. Forced orthodontic eruption for crown lengthening is usually performed at roughly 1 MM PER WEEK using light continuous force (about 15–30 g). This rate allows the periodontal attachment apparatus to follow the tooth without producing hyalinization, root resorption, or pulpal injury. Total extrusion of 3–4 mm typically takes 4–6 weeks, followed by 8–12 weeks of stabilization before restorative work.

Note: ⚠️ Rates cited in the literature vary (some sources quote 2–3 mm per month). Confirm with your group. The principle that matters: LIGHT continuous force + a stabilization period equal to or longer than the active phase.

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