CDC Ceramic Firing & Kiln Operations Flashcards

What is the primary purpose of the 'pre-drying' stage at the beginning of a porcelain firing cycle?

Answer: To slowly remove moisture from the wet porcelain to prevent cracking

Pre-drying removes residual moisture from the condensed porcelain at low temperatures to prevent steam expansion that could cause cracking.

In dental porcelain firing, which atmospheric condition inside the kiln is recommended for most feldspathic porcelains?

Answer: Oxidizing atmosphere (vacuum released before peak temp)

Most feldspathic porcelains are fired under vacuum to reduce porosity and then completed in an oxidizing atmosphere to ensure proper crystallization.

Which term describes the temperature at which a dental ceramic softens and begins to flow during firing?

Answer: Fusion temperature

The fusion temperature is the point at which the ceramic softens and begins to flow, allowing particles to bond and the surface to become glassy.

Why must zirconia restorations be fired on a dedicated zirconia tray or firing pin setup?

Answer: Zirconia must not contact metal trays to prevent contamination and discoloration

Zirconia in contact with metal firing trays can absorb metal ions, causing discoloration (particularly yellowing or greening) of the restoration.

After a porcelain firing cycle, the restoration should be allowed to cool:

Answer: Slowly at room temperature away from drafts and cold surfaces

Rapid cooling of ceramic restorations can introduce thermal shock, causing micro-cracks or fractures that may not be immediately visible.

Which of the following best explains why porcelain 'shrinks' during firing?

Answer: Burnout of organic binders and sintering of ceramic particles

During firing, organic binders burn away and ceramic particles sinter (fuse together), reducing overall volume and causing dimensional shrinkage.