Dental Materials Flashcards

Which type of impression material is considered irreversible hydrocolloid?

Answer: Alginate

Alginate is an irreversible hydrocolloid because its chemical gel cannot be re-liquefied after setting.

What is the primary purpose of a cavity varnish in restorative dentistry?

Answer: To seal dentinal tubules and reduce microleakage under amalgam

Cavity varnish seals dentinal tubules to reduce microleakage and postoperative sensitivity, particularly under amalgam restorations.

Type IV gypsum (die stone) differs from Type III dental stone primarily in its:

Answer: Higher strength and lower expansion

Type IV die stone has higher compressive strength and lower setting expansion than Type III, making it ideal for accurate dies.

Which component of composite resin provides the filler-matrix bond?

Answer: Silane coupling agent

The silane coupling agent chemically bonds the inorganic filler particles to the organic resin matrix in composite materials.

A patient's custom tray is fabricated with relief wax over the edentulous ridge. What is the purpose of this relief?

Answer: To create space for a controlled thickness of final impression material

Relief wax creates uniform spacing between the tray and tissues so the impression material flows evenly and records details accurately.

Glass ionomer cement releases which ion that provides an anticariogenic benefit?

Answer: Fluoride

Glass ionomer cement releases fluoride ions over time, which inhibit bacterial metabolism and remineralize adjacent tooth structure.

When mixing zinc phosphate cement, spreading the powder over a large, cool glass slab serves to:

Answer: Dissipate the exothermic heat of reaction and extend working time

Spreading zinc phosphate powder over a cold slab dissipates the exothermic reaction heat, slowing the set and extending working time.