Dental Materials Flashcards
6 cards from real MFDS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Dental Materials flashcards as text
The polymerisation shrinkage of conventional composite resins is approximately:
Answer: 1–3%
Conventional methacrylate-based composites shrink by approximately 1–3% by volume during polymerisation as monomers convert to a polymer network.
Which component of amalgam is primarily responsible for its corrosion resistance?
Answer: Copper
High-copper amalgam alloys suppress the corrosion-prone tin-mercury (gamma-2) phase by converting it to copper-tin (eta) phase, greatly improving corrosion resistance.
What does the term 'thixotropic' mean when applied to impression materials?
Answer: Becomes less viscous under shear stress
Thixotropic materials decrease in viscosity when subjected to shear stress (e.g. mixing or syringing) and return to a gel-like state at rest, aiding injection and flow.
Galvanic corrosion in the mouth most commonly occurs between:
Answer: Two dissimilar metals in contact
Galvanic corrosion occurs when two dissimilar metals are in contact in the presence of saliva as electrolyte, causing the less noble metal to oxidise.
Which property is most important when selecting a luting cement for a post with a long, parallel preparation?
Answer: Low film thickness
Low film thickness is critical for long parallel-sided posts to allow full seating; excess thickness prevents the post from reaching full depth.
The process of 'stress relaxation' in impression materials refers to:
Answer: Decrease in internal stress over time under constant strain
Stress relaxation describes how a viscoelastic material that is held in a deformed state gradually reduces its internal stress without further change in strain.