DANB Dental Materials & Laboratory Procedures — Questions and Answers

Question 1: Which dental material is commonly used for taking final impressions?

Zinc oxide eugenol
Alginate
Polyvinyl siloxane (Correct answer)
Plaster of Paris

Correct answer: Polyvinyl siloxane

Polyvinyl siloxane (PVS) is a highly accurate elastomeric impression material commonly used for final impressions due to its excellent dimensional stability, tear strength, and ability to capture fine details. These properties make it ideal for fabricating precise crowns, bridges, and other indirect restorations. Its accuracy ensures a well-fitting restoration.

Question 2: What is the primary purpose of a dental liner?

To etch the tooth
To hold the restoration in place
To protect the pulp (Correct answer)
To polish the surface

Correct answer: To protect the pulp

A dental liner is a thin layer of material, often calcium hydroxide, applied to the deepest portion of a cavity preparation. Its primary purpose is to protect the dental pulp from chemical irritation, thermal changes, and bacterial invasion. This promotes pulpal health and aids in secondary dentin formation, preventing sensitivity and damage.

Question 3: Which material is typically used to create study models?

Acrylic resin
Composite
Zinc phosphate cement
Dental plaster (Correct answer)

Correct answer: Dental plaster

Dental plaster, specifically Type II gypsum, is commonly used to create study models (diagnostic casts) because it is economical, easy to mix, and sets relatively quickly. While not as strong or abrasion-resistant as dental stone, it provides sufficient detail and strength for diagnostic, educational, and treatment planning purposes.

Question 4: What is the purpose of triturating dental amalgam?

To disinfect the material
To shape the restoration
To reduce curing time
To mix mercury with alloy powder (Correct answer)

Correct answer: To mix mercury with alloy powder

Trituration is the mechanical process of mixing the liquid mercury with the powdered alloy in a dental amalgam capsule. This process initiates the chemical reaction that forms the amalgam, creating a plastic mass that can be condensed into the cavity preparation. The material then hardens into a durable restoration.

Question 5: What is the ideal storage condition for alginate impression material before use?

Refrigerated and moist
Warm and dry
Cool and dry (Correct answer)
In direct sunlight

Correct answer: Cool and dry

Alginate impression material is sensitive to moisture and temperature fluctuations, which can affect its shelf life and working properties. Storing it in a cool, dry environment, away from direct sunlight and humidity, helps prevent premature degradation. This ensures consistent setting times and accurate impressions when the material is used.

Question 6: Which cement is commonly used for permanent crowns?

Zinc oxide eugenol
Calcium hydroxide
Glass ionomer (Correct answer)
Cavity varnish

Correct answer: Glass ionomer

Glass ionomer cement is frequently used for permanent cementation of crowns, bridges, and other indirect restorations due to its chemical adhesion to tooth structure and metal, as well as its fluoride-releasing properties. Its biocompatibility and low solubility make it a reliable choice for long-term restorations. It also helps prevent secondary caries.

DANB Dental Materials & Laboratory Procedures

Which dental material is commonly used for taking final impressions?