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Restorative & Materials · single question

The 'C-factor' (configuration factor) of a composite restoration refers to:

  1. The ratio of bonded to unbonded surfaces, which drives polymerization shrinkage stress
  2. The intensity of the curing light
  3. The percentage of filler by weight
  4. The coefficient of thermal expansion
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Correct answer: A. The ratio of bonded to unbonded surfaces, which drives polymerization shrinkage stress

  • A. Correct. The C-factor is the ratio of bonded to free (unbonded) surfaces. A higher ratio (e.g., a deep Class I) concentrates shrinkage stress and raises the risk of marginal debonding.
  • B. Incorrect. Light intensity affects degree of cure, but is not the configuration factor.
  • C. Incorrect. Filler loading affects physical properties, not the cavity configuration ratio.
  • D. Incorrect. Thermal expansion is a separate material property unrelated to bonded:unbonded surface ratio.

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