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 II — dental plaster

Answer

Type III — dental stone

Answer

Type IV — die stone (improved stone)

Question 2

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

Accepted Answer

Methyl methacrylate (MMA)

Answer

Ethyl methacrylate (EMA)

Answer

Bisphenol A-glycidyl methacrylate (Bis-GMA)

Answer

Urethane dimethacrylate (UDMA)

Question 3

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

Accepted Answer

Addition silicone (polyvinyl siloxane, PVS)

Answer

Polysulfide

Answer

Polyether

Answer

Condensation silicone

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

Direct chemical bonding to calcium in hydroxyapatite

Answer

Ionic exchange with calcium ions at the dentine surface

Answer

Covalent bonding directly to exposed collagen fibres

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

Aluminium oxide additions

Answer

Rapid sintering at high temperature

Answer

Lithium disilicate glass matrix

Question 6

Which component in ZOE-based root canal sealers is primarily responsible for periapical tissue cytotoxicity?

Accepted Answer

Eugenol

Answer

Zinc oxide powder

Answer

Rosin

Answer

Titanium dioxide

Question 7

What is the primary setting reaction of addition silicone (PVS) impression material?

Accepted Answer

Platinum-catalysed hydrosilylation of Si-H groups across vinyl groups

Answer

Radical chain-growth polymerisation initiated by benzoyl peroxide

Answer

Polycondensation releasing ethanol as a volatile by-product

Answer

Acid-base neutralisation between base and catalyst pastes