Recommendations for sprue positioning, heating

and casting temperatures not observed.                   
 

See points 2, 4, 5 and 6 in the instructions for use of dental alloys       

Shades are too light and not transparent enough

Porcelain has porosities

Pre-heating temperature is too high

Firing temperature is too low

Vacuum pump sets in too late

Vacuum levels are too low

Reduce Pre-heating temperature

Increase firing temperature

Reduce Pre-heat/Vacuum start temperature

Check furnace/pump for leakage
 

Porcelain has rough surface

Not enough glaze on the surface

Pre-heating temperature too low

Holding time too short

Increase firing temperature

Lengthen holding time

Too much glaze on the surface

Ridges and contours are round
 

Firing temperature too high

Holding time too long

Lower firing temperature

Shorten holding time

Pressure stress cracks: horizontal cracks in the incisal

area or at the pontics

Long-term cooling or tempering (3 min, 720 °C)

Increase tempering
temperature

Lengthen cooling phase
 

Tensile stress cracks: craquelé cracks on the surface

(crazing)

Wrong alloy

Porcelain’s CTE is too high due to wrong long-

term cooling or heat rate

Wall thickness of framework too thin
 

Check the compatibility of the alloy

Observe minimum wall thickness levels

false burs

Paste opaque dried incorrectly

Air trapped whilst layering

Too much opaque thinner

Paste applied too thickly
 

Only use burs which are specifically designed for

use in metall ceramics 
 

Only use cross cut tungsten carbide burs

Lengthen pre-drying time