Polymerisation Shrinkage — MFDS Part 1 MCQ

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ModerateDental MaterialsPolymerisation ShrinkageMFDS Part 1

During light curing of a bonded posterior resin-composite restoration, polymerisation contraction is constrained by adhesion to the cavity walls. Which clinical problem is most directly associated with the resulting shrinkage stress?

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

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Correct answer: C — Marginal gap formation with microleakage

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

A is correct. Resin composite contracts during polymerisation. Because the material is bonded to the cavity walls, free contraction is restricted and stress develops at the tooth–restoration interface. If that stress exceeds local bond strength, interfacial debonding can produce marginal gaps and microleakage. An oxygen-inhibited layer (B) results from atmospheric oxygen interfering with surface polymerisation. Inadequate depth of cure (C) is primarily related to insufficient irradiance, exposure time, or excessive increment thickness. Occlusal wear (D) depends mainly on material properties, restoration location, and functional loading. Transient colour mismatch after dehydration (E) reflects changes in the optical appearance of tooth tissue rather than polymerisation shrinkage.

Reference: Ferracane JL, Hilton TJ. Polymerization stress—is it clinically meaningful? Dental Materials. 2016;32(1):1–10. https://pubmed.ncbi.nlm.nih.gov/26220776/