CCE Substructure for Ceramics 5

Question 1

For a three-unit PFM bridge, which area of the substructure is most susceptible to porcelain fracture under occlusal load?

Accepted Answer

Connector-pontic junction

Answer

The connector-pontic junction experiences the highest bending stress during occlusal loading, making it the most fracture-prone ceramic region.

Question 2

Which firing atmosphere is used during the oxidation/degassing cycle for base metal alloy substructures?

Accepted Answer

Air (atmospheric)

Answer

Degassing of base metal alloys is performed in air to allow controlled oxide layer formation on the metal surface.

Question 3

CAD/CAM-milled zirconia substructures must be sintered after milling because the pre-sintered blanks are in a:

Accepted Answer

Partially sintered (green or white) state

Answer

Zirconia is milled in a partially sintered (pre-sintered) state for easy machining, then sintered to full density and final hardness in a high-temperature furnace.

Question 4

What effect does repeated firing have on the veneering porcelain overlying a metal substructure?

Accepted Answer

It can cause devitrification and loss of translucency

Answer

Repeated high-temperature firings cause devitrification (crystallization) of the glass-ceramic matrix, resulting in a white, opaque, and weakened surface.

Question 5

When fabricating a PFM coping for a maxillary central incisor, which margin design best supports the facial porcelain while allowing an esthetic ceramic margin?

Accepted Answer

Shoulder or deep chamfer with ceramic butt joint

Answer

A shoulder or deep chamfer preparation supports a ceramic butt joint margin, providing strength for the porcelain edge while eliminating the visible metal collar.

(CCE) Certified Ceramist Practice Test

(CCE) Certified Ceramist Practice Test

CCE Substructure for Ceramics 5