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

The Vickers hardness test uses a square-based diamond pyramid indenter pressed into the surface under a specific load, and hardness is calculated from the diagonal length of the indentation.

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

Base metal alloys create an electrochemical couple with amalgam due to their different electrode potentials, resulting in galvanic corrosion and potential sensitivity.

Question 3

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

Accepted Answer

Hygroscopic expansion that partially offsets polymerization shrinkage

Answer

Water sorption causes hygroscopic expansion of composite resins, which can partially compensate for the polymerization shrinkage that occurs during initial curing.

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

A low contact angle indicates good wettability, meaning the adhesive spreads readily over the surface and can penetrate microporosities to form a strong mechanical bond.

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 IV (extra hard) gold alloys have the highest strength and hardness due to the highest proportion of platinum-group metals, making them suitable for thin, high-stress restorations.

DMD - Doctor of Dental Medicine Practice Test

DMD - Doctor of Dental Medicine Practice Test

DMD Dental Materials Science 3