Dental Materials & Equipment Maintenance Flashcards
7 cards from real EFDA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Dental Materials & Equipment Maintenance flashcards as text
Which property of dental amalgam is described as the tendency to expand or contract under stress without fracturing?
Answer: Creep
Creep is the slow plastic deformation of amalgam under sustained compressive load, which can lead to marginal breakdown and ditching over time.
Why must etchant (phosphoric acid) be completely rinsed from enamel before applying bonding agent?
Answer: Residual acid continues to demineralize enamel and disrupts bonding chemistry
Residual phosphoric acid must be thoroughly rinsed because it can continue etching and prevent proper resin infiltration into the enamel tubules.
Which type of gypsum product is used to pour final working casts requiring high strength and hardness?
Answer: Type IV die stone
Type IV die stone (improved high-strength stone) has the highest compressive strength and lowest expansion, making it ideal for working casts and dies.
What is the purpose of applying cavity varnish before placing zinc phosphate cement?
Answer: Seal dentinal tubules to reduce pulpal irritation from cement acidity
Cavity varnish seals dentinal tubules to protect the pulp from the low pH of freshly mixed zinc phosphate cement.
When is biological monitoring (spore testing) of an autoclave required at minimum?
Answer: Weekly
The CDC and OSAP recommend weekly spore testing of sterilizers to verify that sterilization conditions are being achieved.
Which characteristic distinguishes polyvinyl siloxane (PVS) from polysulfide impression materials?
Answer: PVS has superior dimensional stability and no offensive odor
PVS (addition silicone) offers excellent dimensional stability and no byproducts, while polysulfide releases hydrogen byproduct and has a characteristic sulfur odor.
What does the term 'film thickness' refer to when selecting a luting cement?
Answer: The minimum thickness of the set cement layer between the restoration and tooth
Film thickness is the minimum thickness of cement between two parallel surfaces under load, and a low film thickness is critical to ensure complete seating of cast restorations.