Composite Radiopacity — MFDS Part 1 MCQ

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ModerateDental MaterialsComposite RadiopacityMFDS Part 1

A posterior resin-based composite is designed to be distinguishable from tooth structure and recurrent caries on bitewing radiographs. Which constituent primarily provides this radiopacity?

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Correct answer: C — High-atomic-number inorganic filler

The correct answer is C. Composite radiopacity is principally provided by inorganic fillers containing relatively high-atomic-number elements, such as barium, strontium, zirconium or ytterbium. These elements attenuate X-rays more strongly, allowing the restoration to be distinguished from tooth tissue and adjacent caries. Bis-GMA forms the principal resin matrix, while TEGDMA reduces resin viscosity; neither is the main radiopacifier. Camphorquinone initiates light-activated polymerisation. The silane coupling agent chemically links the inorganic filler to the organic resin matrix and improves stress transfer, but it does not itself provide clinically significant radiopacity.

Reference: Mendoza LCL et al. Radiopacity and Filler Content of Dual-Cure Resin Core Material, Dual-Cure Resin Cement, and Bulk-Fill Resin Composites Used for Restoring Endodontically Treated Teeth. Operative Dentistry. 2025;50(2):175-184. https://pubmed.ncbi.nlm.nih.gov/40193557/