NBDHE NBDHE Dental Materials and Procedures 2

Question 1

Which type of gypsum product has the highest compressive strength and is used for dies?

Accepted Answer

Die stone (Type IV)

Answer

Type IV die stone has the highest compressive strength and lowest setting expansion, making it ideal for accurate die fabrication.

Question 2

What is the primary advantage of using polyvinyl siloxane (PVS) impression material over polysulfide?

Accepted Answer

Greater dimensional stability over time

Answer

PVS impression materials are addition silicones that exhibit excellent dimensional stability and can be poured multiple times without significant distortion.

Question 3

When cementing a metal crown with zinc phosphate cement, why must the tooth be kept dry?

Accepted Answer

Moisture increases solubility in oral fluids

Answer

Moisture contamination increases the solubility of zinc phosphate cement in oral fluids, reducing the longevity of the restoration.

Question 4

Which dental alloy classification contains at least 25% gold and is used for crowns requiring high strength?

Accepted Answer

Type IV

Answer

Type IV gold alloy has the highest hardness and strength due to its composition, making it suitable for thin restorations like inlays, partial denture frameworks, and clasps.

Question 5

What causes the 'orange peel' surface texture sometimes seen on processed acrylic denture bases?

Accepted Answer

Insufficient pressure during processing

Answer

Insufficient pressure during processing allows porosity to develop at the surface, creating the characteristic orange peel appearance.

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NBDHE NBDHE Dental Materials and Procedures 2