Elastomeric Impression Materials Flashcards
What are the main elastomers
Polyethers
Addition silicone
What is the ideal elasticity of an elastomer
High elasticity to negotiate the undercut shape and to recover its shape upon removal of the impression tray
Which characteristics should elastomers be assessed upon (8)
Flow/viscosity Surface detail Wettability Elastic recovery Stiffness (flexibility) Tear strength Mixing time Working time
What is the ISO standard for IMs
That grooves/indentations of either 20um or 50um (depending on material viscosity) are replicated
How does distinguishing the margins between the tray material and wash relate to how precise the impression is
It doesn’t
How will viscosity and surface wetting capability affect an IM
Will affect the quality of surface interaction between materials and tooth/soft tissue surfaces
Which properties affect the accuracy of an IM
Surface reproduction (ISO) Visco-elasticity/elastic recovery
How will the tear/tensile strength and rigidity (flexibility) of an IM affect its performance
Will effect if it remains intact when removal and if it can overcome the bulbous aspects of teeth
What does the ISO standard tell us about a product
It is safe for use, not necessarily the best
What levels of viscosity are elastomers available in
Low
Medium
High
What is the ideal viscosity for an IM
Low viscosity as the material will flow and make contact with dental tissues so the surface detail is recorded more accurately
What is surface wetting
How well the elastomer makes interfacial contact with dental tissues
The better the surface wetting, the less likely there will be any bubbles or voids that would adversely affect the IM surface
How is the reproduction of surface detail tested
An IM is poured on top of 3 notches of varying width and depth
Then a load is applied which presses down evenly on the material such that it flows into the notches
If the IM flows into the notch, it shows that that level of detail can be recorded
What is tear strength
Stress that causes fracturing, especially for material in undercut regions
What is the ideal rigidity of an elastomer
Low rigidity (high flexibility) This means a small stress would cause a significant change in the shape for it to be removed
