Free RDA Restorative and Impression Materials Questions and Answers 1 — Questions and Answers
Question 1: When mixing alginate impression material, using water that is warmer than the recommended temperature will:
- Cause it to set slower
- Cause it to set faster (Correct answer)
- Prevent it from setting at all
- Make the final impression stronger
Correct answer: Cause it to set faster
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:
- Amalgamation
- Condensation
- Spatulation
- Trituration (Correct answer)
Correct answer: Trituration
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:
- Incorporate more powder into the liquid
- Accelerate the setting time
- Dissipate the exothermic heat (Correct answer)
- Prevent moisture contamination
Correct answer: Dissipate the exothermic heat
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:
- Polymerization (Correct answer)
- Galvanism
- Trituration
- Amalgamation
Correct answer: Polymerization
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?
- Polysulfide
- Polyether
- Condensation silicone
- Polyvinyl siloxane (PVS) (Correct answer)
Correct answer: Polyvinyl siloxane (PVS)
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.
Question 6: A primary advantage of using glass ionomer cement as a restorative material is its ability to:
- Achieve a very high polish
- Release fluoride (Correct answer)
- Withstand high occlusal forces in posterior teeth
- Be used without a bonding agent
Correct answer: Release fluoride
Glass ionomer cements contain fluoride within their glass particle composition. After placement, they slowly release this fluoride into the surrounding tooth structure, which helps to inhibit recurrent decay and can aid in remineralization.
Free RDA Restorative and Impression Materials Questions and Answers 1
When mixing alginate impression material, using water that is warmer than the recommended temperature will: