Restorative and Impression Materials Flashcards
7 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 7 Restorative and Impression Materials flashcards as text
A patient bites through an alginate impression before it has fully set. What is the MOST likely result?
Answer: Permanent deformation and inaccurate reproduction of the arch
Applying pressure to alginate during gelation causes permanent deformation (tearing or distortion) because the material cannot recover elastically until fully set.
What property of polyether impression material makes it advantageous in humid clinical conditions?
Answer: It is hydrophilic and wets oral tissues well
Polyether is hydrophilic, which allows it to flow into moist sulcular areas and wet oral tissues effectively, producing detailed impressions even in humid conditions.
When preparing an amalgam restoration, the dental assistant mixes the amalgam and notices it is crumbly and dry. What is the MOST likely cause?
Answer: Undertrituration
Undertrituration results in insufficient mercury-alloy contact, producing a crumbly, grainy mix with reduced strength and poor adaptation.
Which composite resin curing light wavelength range is needed to activate camphorquinone, the most common photoinitiator?
Answer: 400–500 nm (blue light)
Camphorquinone is activated by blue light in the 400–500 nm range, with peak absorption at approximately 468 nm.
A bis-acryl composite provisional material was used to fabricate a temporary crown. What is an important property that distinguishes it from PMMA provisional materials?
Answer: Bis-acryl generates less exothermic heat during setting
Bis-acryl provisional materials produce significantly less exothermic heat during polymerization compared to PMMA, reducing risk of pulpal irritation.
An impression is removed from the mouth and a void is found at the margin of the preparation. Which of the following is the MOST likely cause?
Answer: Air was trapped during syringing of light-body material
Voids at critical margin areas are most commonly caused by air entrapment during injection of the light-body material around the preparation.
Which of the following describes the correct storage condition for elastomeric impression materials to maintain their shelf life?
Answer: Room temperature (68–77°F) away from heat and sunlight
Elastomeric materials should be stored at room temperature (68–77°F), away from heat and direct sunlight, which can accelerate premature polymerization.