Dental Materials 6
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DENTAL MATERIALS 6 SOLUBLE PLASTER COMPONENTS
•
80% PLASTER OF PARIS o
•
•
•
main component
K2SO4 o
slow setting time and setting expansion
o
0.15% - setting expansion
POTATO STARCH o
Makes the plaster “soluble”
o
Swells when immersed in warm water bath making it easier to be removed
Coloring materials/pigments
*Final setting time of ordinary Plaster of Paris is 20mins *Final setting time of Soluble Plaster is 3-5mins *Initial setting time of Soluble Plaster is 1-3mins WATER – POWDER RATIO OF SOLUBLE PLASTER 50cc – 75cc of water per 100g of soluble plaster COMPRESSIVE STRENGTH OF SOLUBLE PLASTER 580 (+/-) 290psi or 290 – 870psi SOLUBLE PLASTERS
•
Used as SECONDARY IMPRESSION MATERIAL o
•
Remove with teasing movement
Needed to have separating medium prior to cast construction
CAST CONSTRUCTION METHODS •
BOXING o
•
INVERSION o
•
Adding at least half an inch of base
Invert the tray
USE OF RUBBER BASE FORMER o
Shaped like the base of the cast and material is the same as of the rubber bowl
QUALITIES OF GOOD CAST •
Smooth but rigid appearance
•
No nodules, elevations or bubbles
•
Dimensionally stable
•
Good mechanical property (can withstand fracture from separation)
•
Able to copy the object accurately Rosette Go 120608
•
80% PLASTER OF PARIS o
•
•
•
main component
K2SO4 o
slow setting time and setting expansion
o
0.15% - setting expansion
POTATO STARCH o
Makes the plaster “soluble”
o
Swells when immersed in warm water bath making it easier to be removed
Coloring materials/pigments
*Final setting time of ordinary Plaster of Paris is 20mins *Final setting time of Soluble Plaster is 3-5mins *Initial setting time of Soluble Plaster is 1-3mins WATER – POWDER RATIO OF SOLUBLE PLASTER 50cc – 75cc of water per 100g of soluble plaster COMPRESSIVE STRENGTH OF SOLUBLE PLASTER 580 (+/-) 290psi or 290 – 870psi SOLUBLE PLASTERS
•
Used as SECONDARY IMPRESSION MATERIAL o
•
Remove with teasing movement
Needed to have separating medium prior to cast construction
CAST CONSTRUCTION METHODS •
BOXING o
•
INVERSION o
•
Adding at least half an inch of base
Invert the tray
USE OF RUBBER BASE FORMER o
Shaped like the base of the cast and material is the same as of the rubber bowl
QUALITIES OF GOOD CAST •
Smooth but rigid appearance
•
No nodules, elevations or bubbles
•
Dimensionally stable
•
Good mechanical property (can withstand fracture from separation)
•
Able to copy the object accurately Rosette Go 120608
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