DANB CDA Dental Materials — Questions and Answers
Question 1: What is the setting reaction of alginate impression material?
- An irreversible hydrocolloid reaction (Correct answer)
- A reversible thermal reaction
- An acid-base reaction with water
- A polymerization chain reaction
Correct answer: An irreversible hydrocolloid reaction
Alginate is an irreversible hydrocolloid that undergoes a chemical reaction (sol-gel transformation) when mixed with water, forming a gel that cannot return to its original state.
Question 2: Which type of cement is commonly used for permanent cementation of crowns?
- Glass ionomer cement (Correct answer)
- Zinc oxide eugenol
- Calcium hydroxide
- Temporary cement
Correct answer: Glass ionomer cement
Glass ionomer cement is widely used for permanent cementation because it chemically bonds to tooth structure, releases fluoride, and provides adequate strength for crown retention.
Question 3: What is the purpose of an etchant in bonding procedures?
- To create microscopic roughness on enamel for mechanical retention (Correct answer)
- To sterilize the cavity preparation
- To numb the tooth nerve
- To seal the restoration surface
Correct answer: To create microscopic roughness on enamel for mechanical retention
Acid etchant (typically 37% phosphoric acid) creates a microscopically rough surface on enamel by dissolving mineral crystals, allowing the bonding agent to flow into and mechanically lock onto the surface.
Question 4: What is the working time of a dental material?
- The time from start of mixing until the material becomes too stiff to manipulate (Correct answer)
- The total time until the material fully hardens
- The time the material remains in the patient's mouth
- The shelf life of the material
Correct answer: The time from start of mixing until the material becomes too stiff to manipulate
Working time is the period from when mixing begins until the material becomes too rigid to be properly shaped or placed, requiring all manipulation to be completed within this window.
Question 5: Which dental material releases fluoride and is used as a liner under restorations?
- Glass ionomer (Correct answer)
- Composite resin
- Amalgam
- Gold alloy
Correct answer: Glass ionomer
Glass ionomer cement releases fluoride over time, provides chemical bonding to tooth structure, and is commonly used as a liner or base under restorations to protect the pulp.
Question 6: What is the primary disadvantage of amalgam as a restorative material?
- Poor esthetics due to its silver/gray color (Correct answer)
- Inability to bond to tooth structure
- Low compressive strength
- Rapid deterioration in the oral environment
Correct answer: Poor esthetics due to its silver/gray color
Amalgam's main disadvantage is its metallic silver/gray appearance, which makes it esthetically unacceptable for visible tooth surfaces, leading many patients and dentists to prefer tooth-colored alternatives.
DANB CDA Dental Materials
What is the setting reaction of alginate impression material?