MFDS Dental Materials 2

Question 1

The polymerisation shrinkage of conventional composite resins is approximately:

Accepted Answer

1–3%

Answer

Conventional methacrylate-based composites shrink by approximately 1–3% by volume during polymerisation as monomers convert to a polymer network.

Question 2

Which component of amalgam is primarily responsible for its corrosion resistance?

Accepted Answer

Copper

Answer

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.

Question 3

What does the term 'thixotropic' mean when applied to impression materials?

Accepted Answer

Becomes less viscous under shear stress

Answer

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.

Question 4

Galvanic corrosion in the mouth most commonly occurs between:

Accepted Answer

Two dissimilar metals in contact

Answer

Galvanic corrosion occurs when two dissimilar metals are in contact in the presence of saliva as electrolyte, causing the less noble metal to oxidise.

Question 5

Which property is most important when selecting a luting cement for a post with a long, parallel preparation?

Accepted Answer

Low film thickness

Answer

Low film thickness is critical for long parallel-sided posts to allow full seating; excess thickness prevents the post from reaching full depth.

MFDS Part 1 Practice Test

MFDS Part 1 Practice Test

MFDS Dental Materials 2