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Orthodontics · single question

Tooth #19 is displaced lingually out of the arch, and the arch shows a corresponding space deficiency. What is the appropriate management?

  1. A finger spring alone will correct it easily
  2. The arch must first be expanded or space regained, because the tooth needs room to be moved into alignment
  3. Extract the tooth and close the space
  4. Observe, as lingual displacement of a first molar self-corrects with growth
Show answer and explanation

Correct answer: B. The arch must first be expanded or space regained, because the tooth needs room to be moved into alignment

  • A. A FINGER SPRING is a simple removable auxiliary suited to tipping a single tooth a short distance INTO EXISTING SPACE. Where there is a space deficiency it has nothing to move the tooth into.
  • B. CORRECT. This is fundamentally a SPACE problem, not simply a tooth position problem. A tooth that is out of the arch is out of the arch because there is nowhere for it to go. Moving it buccally without first creating space produces a relapse, a crossbite, or crowding transferred elsewhere in the arch. The sequence is SPACE ANALYSIS first, then space creation — arch expansion, molar distalisation, interproximal reduction, or extraction — and only then alignment.
  • C. Extraction of a permanent FIRST MOLAR is a significant decision reserved for teeth of poor prognosis. It is not the answer to a malpositioned but sound tooth.
  • D. A lingually displaced permanent molar does not self-correct. Left alone it establishes a lingual crossbite, which can drive a functional mandibular shift and asymmetric growth.

Note: The governing orthodontic principle: SPACE BEFORE ALIGNMENT. Perform the arch length analysis, quantify the discrepancy, then decide how to resolve it before any appliance is placed.

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