Whitening Concentration Conversion — ORE Part 1 MCQ

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ModerateDental MaterialsWhitening Concentration ConversionORE Part 1

A dentist is comparing concentrations stated on two vital tooth-whitening products. Approximately what concentration of hydrogen peroxide is equivalent to a product containing 10% carbamide peroxide?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — 3.5% hydrogen peroxide

Explanation lettering: B = shown as A · D = shown as B · A = shown as D

The correct answer is A. In whitening products, 10% carbamide peroxide is conventionally regarded as equivalent to approximately 3.5% hydrogen peroxide, the active oxidising bleaching component. This follows the approximate one-third conversion of carbamide peroxide concentration to hydrogen peroxide concentration; the remainder is principally urea. Option B incorrectly treats the carbamide peroxide concentration as though it were the hydrogen peroxide concentration. Option C is too high and may result from confusing the urea proportion with hydrogen peroxide. Options D and E are substantially below the expected equivalent concentration. The question concerns concentration equivalence, rather than comparing clinical protocols, contact times, or legal limits for whitening products.

Reference: Duschner H, et al. High levels of hydrogen peroxide in overnight tooth-whitening formulas: effects on enamel and pulp. 2005. The abstract explicitly states that 10% carbamide peroxide is equivalent to 3.5% hydrogen peroxide. https://pubmed.ncbi.nlm.nih.gov/15934684/