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Public Health · single question

Regarding the DMF index, all of the following are true EXCEPT:

  1. DMFT counts affected teeth
  2. It is a reversible measure that decreases when disease is treated
  3. It is applied to the permanent dentition
  4. DMFS counts affected surfaces
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Correct answer: B. It is a reversible measure that decreases when disease is treated

  • A. IS true. DMFT is the tooth-level index; each tooth contributes at most 1.
  • B. CORRECT — this is the EXCEPTION and the false statement. The DMF index is IRREVERSIBLE and CUMULATIVE. Once a tooth is decayed, missing or filled it stays in the count permanently; restoring a carious tooth simply moves it from the D column to the F column without lowering the total. This is the index's best-known limitation — it measures lifetime caries EXPERIENCE, not current disease activity.
  • C. IS true. Uppercase DMF is used for the permanent dentition; lowercase dmf (or def) is used for the primary dentition.
  • D. IS true. DMFS is the surface-level index, giving a maximum of 128 surfaces and greater sensitivity to small changes.

Note: Other recognised limitations: DMF gives equal weight to a tiny lesion and a grossly destroyed tooth, and it cannot distinguish teeth lost to caries from teeth lost to periodontal disease or trauma.

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