11/6: Definitive Casts 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
defintive (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
what are the requirements for a good cast?
bubble and distortion free
captures both the prep and unprepped surfaces
all occlusing surfaces must allow for appropriate articulation
all soft tissues be captured
what are the Die requirements?
reproduce the prepared tooth
all surfaces
uprepared tooth structure apically to finish line
adequate access for carving wax pattern margins
what is the primary material used for dies?
gypsum
what is the advantage to using gypsum?
compatible with all impression material
can replicate fine details
dimensional accuracy and stability
easy to use
what is negative about gypsum?
abrasive can affect it
ADA die classification
type 1 and 2: Impression plaster and mounting plaster
type 3: dental stone
type 4: high strength/low expansion
type 5: high strength/high expansion
what types of gypsum are die stone?
type 4 and 5
what are the desirable properties of die materials?
accuracy
reproduce fine detail
strength and durability
color
what strength and durability do we want in die materials?
dry versus wet strength
resistance to shearing forces (edge strength)
abrasion resistance
why is color important in die materials?
so CAD/CAM can scan it
should you add powder to water or water to powder?
powder to water
what is directly proportional to water?
setting time and fluidity