ORE Part 1 Dental Materials Science

Question 1

Which phase in conventional dental amalgam is most susceptible to corrosion?

Accepted Answer

Gamma-2 phase (Sn8Hg)

Answer

Gamma phase (Ag3Sn)

Answer

Gamma-1 phase (Ag2Hg3)

Answer

Beta phase (Ag2Hg)

Question 2

What is the approximate working time of zinc phosphate cement when mixed at room temperature (23°C)?

Accepted Answer

3–5 minutes

Answer

1–2 minutes

Answer

7–9 minutes

Answer

10–12 minutes

Question 3

Which impression material is classified as an irreversible hydrocolloid?

Accepted Answer

Alginate

Answer

Agar

Answer

Polysulfide

Answer

Condensation silicone

Question 4

What is the primary clinical advantage of resin-modified glass ionomer cement (RMGIC) over conventional GIC?

Accepted Answer

Reduced sensitivity to moisture during initial setting

Answer

Significantly higher fluoride release

Answer

Greater compressive strength

Answer

Better translucency and aesthetics

Question 5

Which type of composite resin contains the smallest filler particle size?

Accepted Answer

Microfilled composite (0.04–0.4 μm)

Answer

Macrofilled composite (10–50 μm)

Answer

Hybrid composite (0.4–5 μm)

Answer

Packable composite (0.7–3.5 μm)

Question 6

What is the role of the silane coupling agent in composite resin?

Accepted Answer

Forms a chemical bond between the organic resin matrix and inorganic filler particles

Answer

Initiates the polymerisation reaction when light-activated

Answer

Prevents discolouration of the restoration over time

Answer

Reduces volumetric polymerisation shrinkage

Question 7

The Vickers Hardness (VHN) test measures which material property?

Accepted Answer

Resistance to permanent surface indentation

Answer

Tensile strength

Answer

Elastic (Young's) modulus

Answer

Fracture toughness