elastomeric IM

Question 1

what are the 2 types of elastomers?

Answer 1

polyether

addition silicone

Question 2

what material properties are important?

Answer 2

flow/viscosity
surface detail
wettability
elastic recovery
stiffness
tear strength
mixing time
working time

Question 3

what is the ISO standard for impression materials?

Answer 3

grooves/indentations of either 20um or 50um are replicated

Question 4

what are the ideal properties?

Answer 4

quality of surface interaction between material and teeth/soft tissue
-viscosity
-surface wetting
accuracy
-surface reproduction
-visco-elasticity
dealing w/ removal/undercuts
-tear/tensile strength
-rigidity

Question 5

how should standards be used?

Answer 5

as a minimum

exclude unsafe and poorly performing materials from the market

Question 6

what is viscosity?

Answer 6

measure of material’s ability to flow
determines a material’s potential for making close contact with hard/soft tissue surfaces
-so how well it records surface detail

Question 7

what is wettability?

Answer 7

IM must make close contact with teeth/surfaces
so all of surface is replicated
the better wetting, less bubbles/voids

Question 8

what is viscoelastic behaviour?

Answer 8

IM after stretching/compression on removal, fails to return to original dimensions/shape
permanent deformation

Question 9

what is tear strength?

Answer 9

stress material will withstand before fracture

Question 10

which has shorter setting and working time?

Answer 10

polyethers less than addition silicones