RDA Restorative and Impression Materials 5

Question 1

A patient bites through an alginate impression before it has fully set. What is the MOST likely result?

Accepted Answer

Permanent deformation and inaccurate reproduction of the arch

Answer

Applying pressure to alginate during gelation causes permanent deformation (tearing or distortion) because the material cannot recover elastically until fully set.

Question 2

What property of polyether impression material makes it advantageous in humid clinical conditions?

Accepted Answer

It is hydrophilic and wets oral tissues well

Answer

Polyether is hydrophilic, which allows it to flow into moist sulcular areas and wet oral tissues effectively, producing detailed impressions even in humid conditions.

Question 3

When preparing an amalgam restoration, the dental assistant mixes the amalgam and notices it is crumbly and dry. What is the MOST likely cause?

Accepted Answer

Undertrituration

Answer

Undertrituration results in insufficient mercury-alloy contact, producing a crumbly, grainy mix with reduced strength and poor adaptation.

Question 4

Which composite resin curing light wavelength range is needed to activate camphorquinone, the most common photoinitiator?

Accepted Answer

400–500 nm (blue light)

Answer

Camphorquinone is activated by blue light in the 400–500 nm range, with peak absorption at approximately 468 nm.

Question 5

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?

Accepted Answer

Bis-acryl generates less exothermic heat during setting

Answer

Bis-acryl provisional materials produce significantly less exothermic heat during polymerization compared to PMMA, reducing risk of pulpal irritation.

(RDA) Registered Dental Assistant Practice Test

(RDA) Registered Dental Assistant Practice Test

RDA Restorative and Impression Materials 5