NDAEB Dental Materials and Equipment 2

Question 1

Alginate impression material is classified as which type of impression material?

Accepted Answer

Irreversible hydrocolloid

Answer

Alginate is an irreversible hydrocolloid because once it undergoes its chemical setting reaction, it cannot be returned to its original state by heating.

Question 2

What is the correct storage method for an alginate impression before it can be poured with stone?

Accepted Answer

Wrapped in a damp paper towel sealed in a plastic bag

Answer

Alginate impressions must be wrapped in a damp paper towel and sealed in a bag to prevent syneresis (shrinkage from drying) or imbibition (swelling from absorbing water).

Question 3

Polyvinyl siloxane (PVS) is classified under which category of impression materials?

Accepted Answer

Elastomeric impression material

Answer

PVS is an addition silicone and belongs to the elastomeric category, meaning it sets to a flexible, rubber-like consistency that allows accurate reproduction of undercuts.

Question 4

Which type of gypsum product is MOST appropriate for fabricating dies used in crown and bridge construction?

Accepted Answer

Type IV die stone

Answer

Type IV die stone has the highest compressive strength and lowest setting expansion, providing the accuracy and hardness required for crown and bridge die fabrication.

Question 5

How does increasing the water-to-powder ratio of alginate primarily affect the mix?

Accepted Answer

Lengthens the setting time and produces a thinner mix

Answer

Adding more water to alginate dilutes the reaction, lengthening the setting time and producing a thinner, more fluid consistency that is weaker when set.

(NDAEB) National Dental Assisting Examination Board Practice Test

(NDAEB) National Dental Assisting Examination Board Practice Test

NDAEB Dental Materials and Equipment 2