ADAP Dental Materials 2 — Questions and Answers
Question 1: Which type of impression material is considered irreversible hydrocolloid?
- Alginate (Correct answer)
- Agar
- Polyvinyl siloxane
- Zinc oxide eugenol paste
Correct answer: Alginate
Alginate is an irreversible hydrocolloid because its chemical gel cannot be re-liquefied after setting.
Question 2: What is the primary purpose of a cavity varnish in restorative dentistry?
- To bond composite resin to enamel
- To seal dentinal tubules and reduce microleakage under amalgam (Correct answer)
- To etch the enamel surface before bonding
- To stimulate secondary dentin formation
Correct 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.
Question 3: Type IV gypsum (die stone) differs from Type III dental stone primarily in its:
- Color
- Higher strength and lower expansion (Correct answer)
- Setting time
- Powder-to-water ratio being lower
Correct 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.
Question 4: Which component of composite resin provides the filler-matrix bond?
- Bisphenol A glycidyl methacrylate (Bis-GMA)
- Silane coupling agent (Correct answer)
- Camphorquinone photoinitiator
- Diurethane dimethacrylate (UDMA)
Correct answer: Silane coupling agent
The silane coupling agent chemically bonds the inorganic filler particles to the organic resin matrix in composite materials.
Question 5: A patient's custom tray is fabricated with relief wax over the edentulous ridge. What is the purpose of this relief?
- To add bulk to the tray material
- To create space for a controlled thickness of final impression material (Correct answer)
- To prevent the tray from seating too deeply
- To allow airflow during impression taking
Correct 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.
Question 6: Glass ionomer cement releases which ion that provides an anticariogenic benefit?
- Calcium
- Phosphate
- Fluoride (Correct answer)
- Zinc
Correct answer: Fluoride
Glass ionomer cement releases fluoride ions over time, which inhibit bacterial metabolism and remineralize adjacent tooth structure.
Question 7: When mixing zinc phosphate cement, spreading the powder over a large, cool glass slab serves to:
- Increase the powder-to-liquid ratio
- Dissipate the exothermic heat of reaction and extend working time (Correct answer)
- Improve the cement's color match
- Reduce the film thickness
Correct 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.
ADAP Dental Materials 2
Which type of impression material is considered irreversible hydrocolloid?