Elastomeric impression materials are crosslinked polymers that can be ________ when set and rapidly recover to their original dimensions when _____ is released
stretched ; stress
Which material?
High tear strength and elasticity
Hydrophobic
Elevated humidity and temperature accelerate the reaction
Stored at temperatures of 62 to 74°F and used within one year
polysulfide
which material?
Working time: 4-7 minutes
Setting time: 7-10 minutes
Requires a custom tray
Greatest potential distortion on removal
By-product of the reaction: water (effect on the dimensional stability)
No multiple casts
polysulfide
which material?
Hydrophobic
Great potential for distortion on removal (less than polysulfide)
Working time: 2.5-4 minutes
Setting time: 6-8 minutes
Stock tray
CONDENSATION SILICONE
Which material?
By-product of the reaction: ethyl alcohol (contraction during setting)
Pour up the impression immediately
No multiple casts
condensation silicone
which material?
Greatest dimensional stability - no production of by-products!
Release hydrogen gas - wait 1 hour to pour up the gypsum
No affect on the dimensional stability - bubbles in the stone cast (< 1 h)
Hydrophobic
ADDITION SILICONE
which material?
Sulfur contamination from natural latex gloves inhibits the setting
Working time: 2-4 minutes
Setting time: 4-6.5 minutes
Multiple casts
Pour up gypsum for up to 7 to 14 days
ADDITION SILICONE
which material?
The most HYDROPHILIC of all elastomeric impression materials
Great dimensional stability - no production of by-products
The stiffest of elastomers
Working time: 2.5-3 minutes
Setting time: 6 minutes
Pour up gypsum immediately or for up to 7 days
POLYETHER
do not exceed ____ minutes when disinfecting
30
Hydrophobic materials
Prevent voids
Thin layer on the impression
surfactant
which property has a tear strength of 2500-7000
polysulfide
which property has a tear strength of 1800-4800
polyether
which property has a tear strength of 1500-4300
addition silicone
which property has a tear strength of 2300-2600
condensation silicone
at 24 hours, which property has a percent contraction of 0.14-0.17
addition silicone
at 24 hours, which property has a percent contraction of 0.19-0.24
polyether
at 24 hours, which property has a percent contraction of 0.40-0.45
polysulfide
at 24 hours, which property has a percent contraction of 0.38-0.60
condensation silicone
which material is most stiff?
polyether
which material is least stiff
polysulfide
which material is most hard
polyether
which material is least hard
polysulfide
which material has the least distortion on removal
addition silicone
which material has the most distortion on removal
polysulfide
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