ADC Dental Materials Science

Question 1

Which property of dental amalgam describes its slow, permanent deformation under sustained compressive load?

Accepted Answer

Creep

Answer

Creep is the time-dependent plastic deformation of amalgam under sustained stress, which can lead to marginal failure if excessive.

Question 2

Delayed expansion in zinc-containing amalgam is primarily caused by:

Accepted Answer

Contamination of the mix with moisture during condensation

Answer

Moisture contamination of zinc-containing amalgam causes a delayed expansion reaction due to hydrogen gas production, which can lead to postoperative pain and restoration failure.

Question 3

Which composite resin type provides the best surface polish due to its very small filler particle size?

Accepted Answer

Microfill composite

Answer

Microfill composites contain colloidal silica particles (0.04–0.4 µm) that allow a very smooth, highly polishable surface, though at the cost of reduced strength.

Question 4

The setting reaction of conventional glass ionomer cement (GIC) is best described as:

Accepted Answer

Acid-base reaction between polyacrylic acid and fluoroaluminosilicate glass

Answer

Conventional GIC sets via an acid-base reaction where polyacrylic acid attacks the glass powder, releasing ions that cross-link the polymer chains and harden the cement.

Question 5

Among commonly used luting cements, which has the highest compressive strength?

Accepted Answer

Zinc phosphate cement

Answer

Zinc phosphate cement has the highest compressive strength (~100 MPa) of the classical luting cements, making it suitable for high-stress applications despite its lack of adhesion.

ADC - Australian Dental Council Practice Test

ADC - Australian Dental Council Practice Test

ADC Dental Materials Science