DMD Dental Materials Science 3

Question 1

The Vickers hardness test measures dental material hardness using which type of indenter?

Accepted Answer

A square-based diamond pyramid

Answer

A hardened steel ball

Answer

A tungsten carbide cone

Answer

A Brinell hardened ball

Question 2

Which metal restorative system is most likely to cause galvanic corrosion when placed adjacent to existing dental amalgam restorations?

Accepted Answer

Base metal alloy containing nickel and chromium

Answer

High-gold Type III alloy

Answer

Gold-palladium alloy

Answer

Commercially pure titanium

Question 3

Water sorption by dental composite resins results in which dimensional change?

Accepted Answer

Hygroscopic expansion that partially offsets polymerization shrinkage

Answer

Permanent contraction that worsens marginal gaps

Answer

No dimensional change at physiologic water concentrations

Answer

Rapid volumetric shrinkage causing bulk fracture

Question 4

A low contact angle (θ approaching 0°) of an adhesive resin on a conditioned tooth surface indicates:

Accepted Answer

Good wettability and favorable adhesion potential

Answer

Poor wettability and weak adhesion potential

Answer

High viscosity that prevents penetration

Answer

Incomplete polymerization of the adhesive

Question 5

According to ADA classification, which type of gold casting alloy has the highest strength and is indicated for long-span fixed partial dentures and removable partial denture frameworks?

Accepted Answer

Type IV (extra hard)

Answer

Type I (soft)

Answer

Type II (medium)

Answer

Type III (hard)

Question 6

The diametral tensile strength test is used to evaluate brittle dental materials because:

Accepted Answer

Direct uniaxial tensile testing of brittle specimens is technically problematic and unreliable

Answer

These materials are always stronger in tension than in compression

Answer

It more accurately simulates masticatory loading patterns

Answer

It requires less specialized equipment than direct tensile testing

Question 7

Which mechanical property describes a dental material's ability to fully recover its original dimensions after removal of the deforming force?

Accepted Answer

Elasticity

Answer

Plasticity

Answer

Resilience

Answer

Ductility