Dental Materials and Biomaterials Flashcards

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

Answer: Shrinkage toward the bonded cavity walls

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

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

Answer: Bond the resin matrix to inorganic filler particles

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

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

Answer: Composite resin

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

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

Answer: Dental ceramics

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

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

Answer: Marginal seal

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

What is the setting reaction of zinc phosphate cement?

Answer: Acid-base reaction forming zinc phosphate salt

Zinc phosphate sets via an exothermic acid-base reaction between zinc oxide powder and phosphoric acid liquid, forming zinc phosphate salts.

Which factor most significantly reduces the working time of polyvinylsiloxane (PVS) impression material?

Answer: Sulfur contamination from latex gloves

Sulfur compounds from latex gloves inhibit the platinum catalyst in PVS, drastically reducing or preventing setting.