CDT Dental Materials Science 3

Question 1

Which investment material is used for casting high-fusing noble and base metal alloys due to its ability to withstand higher burnout temperatures?

Accepted Answer

Phosphate-bonded investment

Answer

Phosphate-bonded investments tolerate burnout temperatures above 700°C, necessary for high-fusing metal alloys used in crowns and bridges.

Question 2

The Shore A hardness scale is most commonly used to measure the hardness of:

Accepted Answer

Elastomeric impression materials

Answer

Shore A hardness is appropriate for soft, flexible materials like elastomeric impression materials (silicones, polyethers).

Question 3

When a zirconia coping is sandblasted prior to veneering, the primary purpose is to:

Accepted Answer

Improve surface wettability and mechanical bonding for porcelain

Answer

Sandblasting creates surface roughness on the zirconia coping that improves micromechanical retention and wettability for the veneering porcelain.

Question 4

Which phenomenon explains why dental porcelain fired in a vacuum produces fewer surface bubbles and higher translucency than air-fired porcelain?

Accepted Answer

Air is evacuated so gas bubbles cannot be trapped within the material

Answer

Vacuum firing removes air from the furnace chamber, preventing gas entrapment within molten porcelain and resulting in a denser, more translucent restoration.

Question 5

In the lost-wax casting process, what is the purpose of the sprue former?

Accepted Answer

To form a channel through which molten metal flows into the mold

Answer

The sprue former creates the channel (sprue) that guides molten metal from the crucible into the mold space vacated by the wax pattern.

(CDT) Certified Dental Technicians Practice Test

(CDT) Certified Dental Technicians Practice Test

CDT Dental Materials Science 3