Review Flashcards
What is a defining characteristic of a solid
That it has shape and volume and
Two ways to measure hardness
Knopf test, Rockwell test
Ultimate strength
The maximum amount of stress a material can withstand without breaking
What does modulus mean?
Stiffness
What is proportional limit
The greatest stress a structure can withstand without permanent deformation
What is ductility
The amount of dimensional change a material can withstand without breaking
Materials with poor ductility are classified as brittle
Viscosity
Is the resistance of a liquid to flow
Thin fluids have low viscosity
Thick fluids have high viscosity
Thixotropic materials
Are liquids that flow more easily under mechanical force
Therapeutic materials
Used in the treatment of disease
Would liquid be considered the catalyst or the base?
Catalyst
Manipulation stage
Mixing and working time
Reaction stage
Initial and final set
Initial set time
This time begins when the dental material no longer can be manipulated in the mouth
What happens if you increase the amount o liquid or water
Final product might become weaker
Is and impression a negative or positive reproduction
Negative
What are the two forms of impression material
Elastic and inelastic(rigid)
Which ones are rigid impression materials
ZOE
COMPOUND
PLASTER
Which ones are elastic impression materials
Polysulfide Polyether Silicone Agar Alginate
Hydrocolloids
Hydrocolloids are water based colloids that function as elastic impression materials
What are the two types of hydrocolloids
Irreversible
And reversible
Liquid state in which colloidal particles are suspended by cooling or chemical reaction it can change into a gel
Sol
A semisolid state in which colloidal particles form a framework that traps liquid
Gel
What is a retarder in alginate
Trisodium phosphate
Used in regular set
80% H2O contains potassium sulfate, borax, alkyl benzoate
Agar
Reversible hydrocolloid
Agar
Which impression material changes from a sol phase to a gel phase via chemical reaction and is a irreversible hydrocolloid?
Alignate
Which impression material has poor tear strength?
Irreversible hydrocolloid
Alginate
Syneresis
Shrinkage
When would you use an alginate impression material
When you are working in a wet environment
Preliminary
When you need impression of subgingival tissues
Have to pour models
You don’t need to much detail in the impression
What are disadvantages of alginate
Shrinkage
Swelling
Poor tear strength
Burning tissues-client care
Imbibition
Swelling
What details do you want in an upper maxillary impression material
Palatial vault and Hamular notch