CCE Substructure for Ceramics 4

Question 1

Which casting defect in a metal substructure is caused by gas entrapment during solidification?

Accepted Answer

Gas porosity

Answer

Gas porosity results from dissolved or entrapped gases released during metal solidification, leaving voids within the casting.

Question 2

A full-contour zirconia substructure (monolithic) differs from a veneered zirconia substructure in that it:

Accepted Answer

Has no veneering ceramic and relies on zirconia's intrinsic color

Answer

Monolithic full-contour zirconia is milled to final shape and stained/glazed without a separate veneering ceramic layer, eliminating chipping risk.

Question 3

When adjusting an occlusal contact on a fired PFM crown, what instrument is preferred to avoid damaging the ceramic surface?

Accepted Answer

Fine diamond bur with water cooling

Answer

Fine diamond burs used with water coolant minimize heat generation and micro-crack propagation in the ceramic during occlusal adjustment.

Question 4

In the lost-wax casting technique for metal substructures, which material is used to create the investment mold?

Accepted Answer

Gypsum-bonded or phosphate-bonded investment

Answer

Phosphate-bonded or gypsum-bonded investments are used to create high-temperature molds for casting metal copings via the lost-wax process.

Question 5

The process of 'airborne particle abrasion' on a completed metal coping before porcelain application serves to:

Accepted Answer

Remove oxides and create micro-retention

Answer

Particle abrasion removes excess surface oxides and creates microscopic roughness that enhances the mechanical retention of opaque porcelain.

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