Elastomeric Impression Materials Flashcards
What are the types of elastomers
Polyether
Additional silicones
How should you select an impression material based on
material characteristics clinical performance (patient acceptance, ease of use)
What material properties should you look at
flow/viscosity surface detail (reproduction) wettability elastic recovery (%) stiffness (flexibility) tear strength mixing time working time
What is polyvinylsiloxane
additional silicone
What is the ISO standard for impression materials
that grooves/indentations of either 20um or 50um (depending on material viscosity) are replicated
What does superior elastic recovery allow
easy to remove from the patient’s mouth and elastically recover from the deformation of removal
What does high tear strength allow
The excellent tear resistance reduces the risk of tearing fine margins
What does good wettability allow
They spread easily and adapt smoothly to dentine and moist oral tissue
What are the ideal properties for impressions materials to achieve a good quality of surface interaction between material and tooth/soft tissue surfaces
viscosity
surface wetting
contact angle
What are the ideal properties for accuracy
surface reproduction (ISO) visco-elasticity/elastic recovery
What are the ideal properties for dealing with removal and undercuts
tear/tensile strength
rigidity (flexibility)
What are ISO standards designed to do
exclude unsafe and poorly performing materials from the market
What is viscosity
a measure of material’s ability to flow
What is surface wetting
must make intimate contact with teeth mucosa
What is the contact angle
determines how well material envelops the hard/soft tissue surface (to record fine detail)
What does viscosity determine
determines a material potential for making close contact with hard/soft tissue surfaces
so how well it records
What does viscosity range from
low, medium, high
Why is surface wetting important
so all surfaces are replicated
What is the ideal behavior regarding elasticity
100% elastic recovery
When is viscoelastic behavior observed
when impression material have been stretched/compressed on removal from out, fails to return to its original dimensions/shape
i.e there is permanent deformation
What is the ideal viscoelasticity
small deformation
What is tear strength
stress material will withstand before fracturing
important in the material in the undercut
What is rigidity
stress/strain
large stress needed to cause the material to change shape
ideally the impression material is flexible
If a material has low rigidity what does this allow
to ease its removal from undercut/interdental regions
Which has a lower setting time - polyethers or addition silicones
polyether
Which has a lower working time - polyethers or addition silicones
polyether
How should you make a decision as to what material you are going to use
- Know the key properties of the material
- Review product specification data
- Know typical values expected for specific properties
- Identify properties not mentioned
- Reject claims not supported with scientific and/or clinical data
