Free RDA Restorative and Impression Materials Questions and Answers

Question 1

When mixing alginate impression material, using water that is warmer than the recommended temperature will:

Accepted Answer

Cause it to set faster

Answer

Alginate undergoes a chemical reaction called gelation, which is temperature-dependent. Using warmer water accelerates this reaction, causing the material to set much faster and reducing the available working time.

Question 2

The mechanical mixing of dental amalgam alloy powder and mercury is known as:

Accepted Answer

Trituration

Answer

Trituration is the specific term for the process of mixing the liquid mercury with the metal alloy powder to form amalgam. This process is done in an amalgamator (or triturator) to ensure a consistent and properly mixed restorative material.

Question 3

Zinc phosphate cement is mixed on a cool, dry glass slab primarily to:

Accepted Answer

Dissipate the exothermic heat

Answer

The chemical reaction of mixing zinc phosphate cement is highly exothermic, meaning it releases a significant amount of heat. Mixing on a cool glass slab helps dissipate this heat, which slows down the setting reaction and allows for a longer working time.

Question 4

The process by which a light-cured composite resin material is changed from a pliable state to a hardened restoration is known as:

Accepted Answer

Polymerization

Answer

Polymerization is the chemical process in which small monomer molecules link together to form long polymer chains, resulting in the hardening of the material. In dentistry, this is often initiated by a high-intensity curing light for composite resins.

Question 5

Which type of elastomeric impression material is known for having the best dimensional stability over time, allowing a delay before pouring the model?

Accepted Answer

Polyvinyl siloxane (PVS)

Answer

Polyvinyl siloxane (PVS) has excellent dimensional stability because it does not produce any by-products during its setting reaction that could evaporate and cause shrinkage. This stability allows the impression to be poured up to a week later without significant distortion.

(RDA) Registered Dental Assistant Practice Test

(RDA) Registered Dental Assistant Practice Test

Free RDA Restorative and Impression Materials Questions and Answers