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Restorative & Materials · single question

Which statement best describes remineralised (arrested) enamel compared with the surrounding sound enamel?

  1. It is more soluble in acid because of its higher carbonate content
  2. It contains smaller crystals and is softer than the surrounding enamel
  3. It contains larger crystals and is more resistant to subsequent acid attack
  4. It is identical in composition and hardness to the original enamel
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Correct answer: C. It contains larger crystals and is more resistant to subsequent acid attack

  • A. Remineralised enamel has LOWER carbonate content, which is precisely why it is less soluble.
  • B. This reverses the finding — the crystals are larger and the tissue harder, not smaller and softer.
  • C. CORRECT. Remineralisation does not simply restore what was lost — it deposits mineral that is CHEMICALLY SUPERIOR. The new crystals are LARGER, and where fluoride is present the mineral formed is fluorapatite or fluoride-enriched hydroxyapatite, which dissolves at a lower pH (around 4.5) than the original carbonated hydroxyapatite (around 5.5). Remineralised enamel is therefore harder, darker and MORE acid-resistant than it was before.
  • D. It is not identical; the mineral phase is altered and its acid resistance is improved.

Note: This is the rationale behind fluoride therapy and behind leaving arrested lesions alone. A dark, hard, shiny arrested lesion is a treatment SUCCESS, not a restoration waiting to happen.

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