Definitive Casts and Dies Flashcards
A replica of the tooth surfaces, residual ridge areas, and/or other parts of the dental arch and/or facial structures used to fabricate a dental restoration or prosthesis:
Definitive (master or working) cast
Definitive cast =
master or working cast
The positive reproduction of the form of a prepared tooth in any suitable substance:
die
A metal pin used in some stone casts to remove die sections and replace them accurately in the original position
die pin
In a die, the unprepared tooth structure apical to the finish line should be easily visible at:
0.5-1.0mm
Advantages of gypsum products:
- compatible with all impression materials
- ability to reproduce fine detail and sharp margins
- dimensional accuracy and stability
- easy to use
What is the disadvantage of gypsum products?
Susceptibility to abrasion
ADA Type I & II Gypsum productions
Impression plaster/ model and mounting plaster
(PLASTER)
ADA Type III Gypsum products:
Dental stone
(general purpose cast)
ADA Type IV Gypsum products:
High strength/Lowest expansion
(Die stone)
ADA Type V Gypsum products:
High strength/ High expansion
(Die stone)
What are the advantages of auto mixing a gypsum product?
- homogenous
- more strength
- intended expansion
What is directly proportional to the water powder ratio of gypsum products?
setting times and manipulation
Regarding the water to powder ratio of gypsum productions:
Describe the directly proportional relationship with increased water:
Increased water = increased setting time; increased fluidity
What is indirectly proportional to the water powder ratio of gypsum products?
compression strength and setting expansion
Describe the inverse relationships of gypsum products with an increase in water
Increased water= decreased compressive strength; decreased setting expansion
Surface hardness DOES NOT equal:
abrasion resistance
A replica of the tooth surfaces, residual ridge areas, and/or other parts of the dental arch and/or facial structures used to FABRICATE a dental restoration or prosthesis:
Definitive (master or working) cast
The positive reproduction of the form of a PREPARED tooth in any suitable substance:
Die
A metal pin used in stone casts to remove die sections and replace them accurately in the original position:
Die pin
Definitive cast die requirements:
- bubble free
- distortion free
- must reproduce prepared and unprepared tooth surfaces
- all occluding surfaces must allow for precise articulation of the opposing casts
- all relevant soft tissues should be reproduced
Gypsum stones:
Type I:
Type II:
Type III:
Type IV:
Type V:
Type I: impression plaster
Type II: model/mounting plaster
Type III: dental stone (general purpose casts)
Type IV: high strength/ low expansion (die stone)
Type V: high strength/ high expansion (die stone)
Desirable properties of die materials:
- accuracy
- ability to reproduce fine detal
- strong and durable (strength resistance and abrasion resistance)
- color (should contrast with wax, scanning visibility for CAD/CAM)
Water-powder ratio= the _____ amount of water necessary to obtain proper manipulation of stone. You should use the manufacturers recommendations. Add powder to liquid (allows for proper wetting)
LEAST
INCREASED water DIRECTLY leads to INCREASED:
setting time and fluidity
INCREASED water INDIRECTLY leads to DECREASED:
compressive strength and setting time
May result in unset of powdery gypsum on the surface:
disinfectant
Dry strength is ____x stronger than wet strength
2x
When gypsum is immersed in water (per every 20 min of immersion), linear dimension decreased this describes:
solubility
What happens to the gypsum material when immersed in water with calcium sulfate slurry?
solubility decreases
Surface impregnation of a gypsum produced uses:
cyanoacrylate cement
