Dental Dental Materials 1 — Questions and Answers
Question 1: Which type of dental material is classified as an irreversible hydrocolloid impression material?
- Agar
- Alginate (Correct answer)
- Polyvinyl siloxane
- Polysulfide
Correct answer: Alginate
Alginate is an irreversible hydrocolloid because its gelation is a chemical reaction that cannot be reversed by heating.
Question 2: What is the primary purpose of a cavity liner placed in a deep preparation?
- To improve aesthetics of the final restoration
- To provide pulp protection from chemical and thermal irritation (Correct answer)
- To increase the retention of the restoration
- To prevent marginal leakage
Correct answer: To provide pulp protection from chemical and thermal irritation
A cavity liner is placed over the pulp to protect it from the chemical and thermal stimuli that restorative materials may transmit.
Question 3: Which gypsum product has the highest compressive strength and is used for dies?
- Plaster of Paris (Type I)
- Model plaster (Type II)
- Dental stone (Type III)
- Die stone (Type IV) (Correct answer)
Correct answer: Die stone (Type IV)
Type IV die stone (high-strength stone) has the highest compressive strength due to its low water-to-powder ratio, making it ideal for dies.
Question 4: What is the setting reaction of zinc phosphate cement?
- Polymerization of resin monomers
- Acid-base reaction between zinc oxide and phosphoric acid (Correct answer)
- Chelation reaction between polyacrylic acid and zinc oxide
- Light activation of photoinitiators
Correct answer: Acid-base reaction between zinc oxide and phosphoric acid
Zinc phosphate cement sets via an acid-base reaction where phosphoric acid reacts with zinc oxide powder to form zinc phosphate salt.
Question 5: Which of the following composite filler types provides the best combination of strength and polishability?
- Macrofill composite
- Microfill composite
- Nanofill composite
- Hybrid composite (Correct answer)
Correct answer: Hybrid composite
Hybrid composites combine large and small filler particles, offering superior strength compared to microfills and better polishability than macrofills.
Question 6: What is the major advantage of glass ionomer cement over zinc phosphate cement?
- Higher compressive strength
- Chemical adhesion to tooth structure and fluoride release (Correct answer)
- Longer working time
- Superior aesthetics
Correct answer: Chemical adhesion to tooth structure and fluoride release
Glass ionomer cement chemically bonds to enamel and dentin and releases fluoride, providing cariostatic benefits that zinc phosphate lacks.
Question 7: Which component of dental amalgam is primarily responsible for its corrosion resistance?
- Mercury
- Tin
- Copper (Correct answer)
- Zinc
Correct answer: Copper
High copper content in modern amalgam alloys reduces the formation of the corrosion-prone gamma-2 phase (Sn8Hg), improving corrosion resistance.
Dental Dental Materials 1
Which type of dental material is classified as an irreversible hydrocolloid impression material?