ORE Part 1 Dental Materials Science 2

Question 1

Which ADA/ISO type of gypsum product has the highest compressive strength?

Accepted Answer

Type V — high-strength, high-expansion stone

Answer

Type V gypsum (high-strength, high-expansion die stone) has the highest compressive strength of all gypsum types, exceeding 35 MPa, making it suitable for precision die work.

Question 2

Which monomer is the primary liquid component in heat-cured PMMA denture base resins?

Accepted Answer

Methyl methacrylate (MMA)

Answer

Methyl methacrylate (MMA) is the primary liquid monomer in conventional PMMA denture base resins; when polymerised it forms polymethyl methacrylate (PMMA).

Question 3

Which elastomeric impression material has the best dimensional stability after removal from the mouth?

Accepted Answer

Addition silicone (polyvinyl siloxane, PVS)

Answer

Addition silicone (PVS) has the best dimensional stability because its hydrosilylation setting reaction produces no volatile by-products, resulting in negligible post-set dimensional change.

Question 4

The primary mechanism by which 4th-generation dentine bonding agents achieve adhesion is:

Accepted Answer

Micromechanical interlocking through hybrid layer formation in demineralised dentine

Answer

4th-generation bonding agents use a separate etch-prime-bond sequence to form a 'hybrid layer' — resin monomers infiltrate the acid-demineralised collagen network and polymerise, achieving micromechanical retention.

Question 5

What stabilises the tetragonal crystal phase of zirconia in yttria-stabilised tetragonal zirconia polycrystal (Y-TZP) ceramics?

Accepted Answer

Yttrium oxide (yttria) doping

Answer

Yttrium oxide (yttria, Y2O3) is added in small amounts (3 mol%) to stabilise the tetragonal phase at room temperature, enabling transformation toughening when cracks propagate through the material.

ORE Part 1 Practice Test

ORE Part 1 Practice Test

ORE Part 1 Dental Materials Science 2