Elastomers Flashcards
Advantage of speed set alginate?
High level of patient comfort
Define thixotrophy
Progressive decrease viscosity
Advantage of enhanced thixotrophy?
Gives greater accuracy of impression without excessive flow
Advantage of high elasticity in relation to undercuts?
Copes with the most severe undercuts
What limits syneresis (release of water)
Dimensional stability (controlled by pH balance in the formula)
Examples of elastomeric impression materials? (2)
- Polyether
2. Addition silicones
Accessing material properties checklist includes (8)
- Flow/viscosity
- Surface detail
- Wettability
- Elastic recovery
- Stiffness
- Tear strength
- Mixing time
- Working time
Name an example of an addition silicone
Polyvinylsiloxane
What is the purpose of ISO standards
Assesses properties of a product to see if it meets acceptable requirements for safe and effective use
What is the ISO standard for impression materials?
That grooves/indentations of either 20um or 50um (depending on material viscosity) are replicated
List 3 of the best features of the virtual Polyvinylsiloxane
- Excellent detail reproduction
- Superior elastic recovery
- High tear strength
What does superior elastic recovery mean in response to virtual impressions?
Easy to remove from the patients mouth and elastically recover from the deformation of removal
What properties lead to impression accuracy? (2)
- Surface reproduction
2. Visco-elasticity/elastic recovery
What properties allow us to deal with removal and undercuts? (2)
- Tear/tensile strength
2. Rigidity (removal)
Define viscosity
A materials ability to flow
Determines a materials potential for how well it records surface detail (making close contact with hard/soft tissue surfaces)
