DMS-Elastomers Flashcards
What is the contact angle?
This is how closely the IM envelopes the tooth surface.
A small contact angle- means there is no space between the globules meaning the IM contacts the target surface allowing full replication.
A large contact angle- means there are spaces between the globules of the IM. This results in some of the tooth surfaces not being replicated.
How do you measure the surface reproduction of an impression
You use the international standard measure which creates grooves in the impression material of 20/50/70um.
You see which grooves the impression material can fill.
The smaller the groove that is filled, the more accurate the IM
Different depth holes and see how much of the IM material fills them.
List the ideal properties for an impression material ?
Surface interaction
- be able to flow well
- Surface wetting
- small contact angle
Accuracy
- Good surface reproduction
- viscoelastic recovery
Removal of undercuts
- high fin length
- large tear strength
- low rigidity
Dimensional stability
- Low setting shrinkage
- Similar thermal expansion and contraction
Name and describe how we test the ability of the impression mateiral to deal with undercuts?
Shark fin test
which shows the flow under pressure by:
Forcing the IM down into a slot of specific depth.
The IM that flows further under pressur eis better at recording the deeper undercuts.
