RDA Restorative and Impression Materials 4

Question 1

Which impression material is most affected by the presence of moisture or blood during the impression-taking procedure?

Accepted Answer

Polyvinyl siloxane (PVS)

Answer

Polyvinyl siloxane (PVS) is hydrophobic and is significantly affected by moisture, blood, or saliva contamination, leading to voids and inaccurate impressions.

Question 2

When mixing glass ionomer cement for a base, what is the ideal powder-to-liquid ratio compared to a luting consistency?

Accepted Answer

Higher powder ratio than luting

Answer

A base consistency of glass ionomer requires a higher powder-to-liquid ratio to achieve a stiffer, more viscous mix that can withstand condensation forces.

Question 3

What is the purpose of applying a cavity varnish before placing an amalgam restoration?

Accepted Answer

To reduce microleakage and protect the pulp from irritants

Answer

Cavity varnish seals dentinal tubules to reduce microleakage and protects the pulp from chemical irritants until the amalgam has fully set.

Question 4

A custom tray for a final impression should be constructed to leave how much space for impression material between the tray and the tissues?

Accepted Answer

2–3 mm

Answer

A uniform 2–3 mm space between the custom tray and tissues allows for an adequate thickness of impression material for dimensional accuracy.

Question 5

Which restorative material undergoes the LEAST thermal expansion and contraction, making it most dimensionally stable in the oral cavity?

Accepted Answer

Ceramic (porcelain)

Answer

Ceramic/porcelain has a coefficient of thermal expansion very close to that of natural tooth structure, making it the most dimensionally stable under temperature changes.

(RDA) Registered Dental Assistant Practice Test

(RDA) Registered Dental Assistant Practice Test

RDA Restorative and Impression Materials 4