Restorative and Impression Materials Flashcards
6 cards from real RDA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Restorative and Impression Materials flashcards as text
What is the setting reaction of amalgam?
Answer: Reaction between silver-tin alloy and mercury (trituration) forming gamma-1 and gamma-2 phases
Amalgam sets through a reaction between the silver-tin alloy particles and mercury (during trituration/mixing) to form gamma-1 (Ag2Hg3) and gamma-2 (Sn7-8Hg) crystalline phases. Modern non-gamma-2 alloys are stronger and more corrosion-resistant.
Which type of impression material is used for final impressions of crown and bridge preparations due to its high dimensional accuracy?
Answer: Polyvinyl siloxane (PVS/addition silicone)
Polyvinyl siloxane (PVS, addition-cured silicone) provides excellent dimensional stability, high detail reproduction, and can be poured multiple times, making it the material of choice for crown and bridge final impressions.
What is the purpose of bonding agent in composite resin restorations?
Answer: To chemically bond the composite resin to acid-etched enamel and/or dentin
Bonding agents (adhesives) form a chemical and micromechanical bond between composite resin and the acid-etched tooth structure (enamel and/or dentin), creating a durable interface that resists microleakage.
What is the purpose of the zinc oxide eugenol (ZOE) temporary restoration?
Answer: Temporary coverage and sedative effect on the pulp between appointments
ZOE temporary restorations provide a sedative (soothing) effect on the pulp due to eugenol's analgesic and anti-inflammatory properties, temporary cavity coverage, and a seal between appointments.
When mixing type III gypsum dental stone for a diagnostic model, what does an increased water-to-powder (W:P) ratio result in?
Answer: Weaker model with decreased strength and increased porosity
Too much water (high W:P ratio) produces excess porosity as water evaporates, resulting in a weaker, softer model with poor surface detail and lower compressive strength.
Which cement is most appropriate for the final cementation of a porcelain-fused-to-metal (PFM) crown on a vital tooth?
Answer: Resin-modified glass ionomer (RMGI) cement
Resin-modified glass ionomer (RMGI) cement is widely used for final crown cementation because it provides good adhesion, fluoride release, low solubility, biocompatibility, and reduced postoperative sensitivity compared to zinc phosphate.