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Investing and casting
Dr. Linninger Mercedes
assistant professor
Semmelweis University, Department of Prosthodontics
Casting investments:
• Lost-wax process
– In use for many thousands of years
– Jewellery, ornaments, decorated objects
– Bronze, gold etc. (ages)
• Investing: wrapping the pattern
• Investment agent: material used for it
Preparation of teeth
Impression taking
Gipsum cast
Wax pattern
Framework
Veneered framework
Cementation of FPD
Precisional dental
casting technique
Wax pattern
Framework
Precisional dental
casting technique
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Lost wax technique
Sprueing the wax pattern
Sprue
Lost-head
(reservoire)
For
preventing
cavities and
porosities, due to the
thermal
contraction
Images from Bego Virtual Academy
Sprueing the wax pattern
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Wax pattern: the preformed applience, we want to cast
Mold: the form we want the molten alloy to cast in
Investing the wax pattern
The casting ring The casting ring with the wax pattern
• Wax shrinkage: 0,3-0,4 %
• Alloy shrinkage: 1,3-1,6 % (noble)
2.0 – 2,3 % (base alloys)
Casting shrinkage
Investing the wax pattern
Investment materials
plaster-
bonded
gypsum
Liquid:
Powder:
Sulfate contained sublimates - toxic
Water ( no controll of the expansion )
Used in case of gold
and acrilyc works
Investing the wax pattern
Investment materials
silica-
bonded
phosphate-
bonded
Heat-resistant particles (quartz, cristobalite)
Bonding agent (plaster- or silica- or phosfate based component)
Liquid
Powder
Total expansion = setting + thermal expansion
(controls the expansion )
Contraction – expansion:
• Liquid contraction: cooling molten metal
• Erectile contraction: during cristallization
• Solid contraction: chilling to room
temperature
Must be compensated by the investment
Expansion of investments
• Setting expansion
– Mixing powder and liquid
• Thermal expansion
– Preheating
Vacuum mixing
Investing the wax pattern
Investing the wax pattern
Investing the wax pattern
Setting
expansion
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Burning out the wax pattern
… in the furnace
Thermal
expansion
Images from Bego Virtual Academy
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
The casting technique
Melting the alloy
Casting the alloy
• Open flame
• Induction melting
• Vacuum pressure casting
• Centrifugal casting
Casting the dental alloy
The molten mass
Hot zone
Crucible (melting pot)
Casting mould
Casting the dental alloy
Images from Bego Virtual Academy
Casting the dental alloy
Images from Bego Virtual Academy
Casting the dental alloy
Images from Bego Virtual Academy
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Deflasking the cast
Long cooling time
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Sandblasting the framework
Sprueing the wax pattern
Investing the wax pattern
Burning out the wax pattern
Casting the dental alloy
Deflasking the cast
Sandblasting the framework
Finishing the framework
Finishing the framework
Preparation of teeth
Impression taking
Gipsum cast
Wax pattern
Framework
Veneered framework
Cementation of FPD
Precisional dental
casting technique
Thank You for Your attention!
