AGD Dental Materials and Biomaterials 2

Question 1

Which polymerization shrinkage direction is most clinically significant in composite restorations?

Accepted Answer

Shrinkage toward the bonded cavity walls

Answer

Composites shrink toward bonded walls, creating stress that can cause cusp deflection, marginal gaps, and post-operative sensitivity.

Question 2

What is the primary purpose of a silane coupling agent in composite systems?

Accepted Answer

Bond the resin matrix to inorganic filler particles

Answer

Silane coupling agents create a chemical bridge between the inorganic glass filler and the organic resin matrix, improving mechanical properties.

Question 3

Which cement has the highest compressive strength and is most suitable for high-stress core buildups?

Accepted Answer

Composite resin

Answer

Composite resin offers the highest compressive strength (250–300 MPa) among core buildup materials, making it ideal for high-stress situations.

Question 4

The Vickers hardness test is most appropriate for measuring hardness of which dental material?

Accepted Answer

Dental ceramics

Answer

The Vickers hardness test uses a diamond pyramid indenter suitable for hard, brittle materials like ceramics.

Question 5

Which property of dental amalgam improves over time after placement due to corrosion products?

Accepted Answer

Marginal seal

Answer

Corrosion byproducts of amalgam (tin oxides, tin chlorides) accumulate at margins and improve the marginal seal over time.

(AGD) Academy of General Dentistry Certification Practice Test