ORE Part 1 Dental Materials Science 3

Question 1

Which property of commercially pure titanium (grade 4) makes it most suitable as a dental implant material?

Accepted Answer

Exceptional biocompatibility enabling osseointegration

Answer

High thermal conductivity similar to dentine

Answer

Elastic modulus identical to cortical bone (17–20 GPa)

Answer

Extremely low density reducing implant weight

Question 2

The fluoride release profile of conventional glass ionomer cement (GIC) is best described as:

Accepted Answer

Initial high burst release followed by sustained lower-level long-term release

Answer

Constant steady-state release throughout its entire lifespan

Answer

No fluoride release until the cement is mechanically stressed or cracked

Answer

Progressively increasing fluoride release as the cement fully matures

Question 3

At the molecular level, polymerisation shrinkage in composite resins occurs because:

Accepted Answer

Van der Waals intermolecular distances are replaced by shorter covalent bond lengths as monomers link

Answer

Heat generated during curing causes thermal contraction of the polymer

Answer

Inorganic filler particles contract under high-intensity light exposure

Answer

Water sorption into the matrix displaces residual monomer causing collapse

Question 4

Galvanic corrosion in the oral cavity most commonly occurs when:

Accepted Answer

A newly placed amalgam restoration contacts an existing gold crown in the opposing or adjacent arch

Answer

Two restorations made from the same alloy are in occlusal contact

Answer

A composite resin restoration contacts a metallic crown

Answer

A ceramic crown is cemented over a metallic post-core

Question 5

Which mechanical test is most appropriate for measuring the wear resistance of dental restorative materials?

Accepted Answer

Pin-on-disk tribology test

Answer

Charpy impact test

Answer

Three-point bending (flexural strength) test

Answer

Diametral tensile strength test

Question 6

The glass transition temperature (Tg) of a dental polymer such as PMMA refers to:

Accepted Answer

The temperature at which the polymer transitions from a rigid glassy state to a rubbery state

Answer

The temperature at which the polymer melts and flows freely

Answer

The boiling point of the liquid monomer used in polymerisation

Answer

The optimal processing temperature for heat-cure polymerisation cycles

Question 7

Which dental casting alloy is classified as a base-metal alloy?

Accepted Answer

Nickel-chromium alloy (Ni ~70–80%)

Answer

Type III gold alloy (Au ~75%)

Answer

Palladium-silver alloy (Pd ~60%)

Answer

Gold-platinum alloy (Au ~85%)