Composite Depth of Cure — ORE Part 1 MCQ
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Correct answer: E — Maximum 2 mm per increment
Explanation lettering: C = shown as A · D = shown as B · B = shown as C · E = shown as D · A = shown as E
The correct answer is A: maximum 2 mm per increment for conventional light-cure composite resin. This is supported by extensive microhardness and ISO 4049 testing showing that at 2 mm depth, polymerization is adequate, but beyond 2 mm depth, hardness declines significantly and cure becomes unreliable. Option B (5 mm) applies only to bulk-fill composites, a distinct newer category not covered by this question. Options C (10 mm) and D (no limit) are clinically unsafe and result in inadequate polymerization of deeper layers. Option E (0.5 mm) is overly restrictive; whilst 1 mm is ideal, 0.5 mm is impractically thin and not evidence-based as a requirement.
Reference: Depth of cure of light-cured composite resin with light-curing units of different intensity. PubMed (PMID: 9461955), 1997. https://pubmed.ncbi.nlm.nih.gov/9461955/