Definitive Casts & 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 and 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 cast 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 will all impression materials
- ability to reproduce fine detail & sharp margins
- dimensional accuracy & stability
- easy to use
What is the disadvantage of gypsum products?
Susceptibility to abrasion
ADA Type I & II gypsum products:
Impression plaster/ model & 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 automixing of gypsum product?
- homogenous
- more strength
- intended expansion
What is directly proportional to the water:powder ratio of gypsum products?
Setting times & manipulation
Regarding the water:powder ratio of gypsum products:
Describe the directly proportional ratio to increased water
Increased water= increased setting time; increased fluidity
What is indirectly proportional to the water:powder ratio of gypsum products?
Compression strength & 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 to replace them accurately in the original position:
Die pin
Definitive cast die requirements:
- bubble free
- distortion free
- must reproduce both prepared & unprepared tooth surfaces
- all occluding surfaces must allow for precise articulation of the opposing casts
- all relevant soft tissues should be reproduced
Die requirements:
- reproduces the prepared tooth exactly
- all surfaces must be accurately duplicated
- no bubbles
- no voids
- finish line should be especially accurate
- unprepared tooth structure 0.5mm apical to finish line should be visible
- adequate access for carving wax pattern margin
- correct cervical contour of restoration
Types I-V 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 cast)
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 detail
- strong & durable (strength resistance & 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 & fluidity
INCREASED water INDIRECTLY leads to DECREASED:
Compressive strength & setting time
May result in unset or powdery gypsum on the surface:
disinfectant
Dry strength is _______ x stronger than wet strength
2
When gypsum is immersed in water (per every 20 min of immersion) linear dimension decreases, this describes:
solubility
What happens to the gypsum material when immersed in water with calcium sulfate slurry?
Solubility decreases
Surfaces impregnation of gypsum products uses:
cyanoacrylate cement
