elastomeric impressions

what are elastomeric impression materials

derived from industrial applications

offers solutions to hydrocolloid impressions

(poor tear resistance and poor dimensional stability)

what are the 4 types

polysulfides

condensation curing silicone rubber

addition curing silicone rubber

polyether

describe putty material

high dimensional stability

tissue displacing

fine detail capture

describe light bodied material

low dimensional stability

limited tissue displacement

fine detail capture

What are polysulfides?

white baste paste -SH group

brown catalyst paste

what are polysulfides set by

condensation polymerisation

what does cross linking do

increases viscosity and elasticity

what are the properties of polysulphides

gradual increase in viscosity and elasticity

takes 10 mins to set

high tear resistance but slow elastic recovery

best dimensional stability

bad taste

what makes up a silicone rubber condensation curing

paste - liquid silicone prepolymer and inert filler

paste2/liquid- akyl silicitate and tin compound

what are the properties of silicone rubbers condensation curing

set time less than polysliphides

elasticity is more rapid

hydrophobic

tear resistant but not as good as polysulphides

good elastic recovery

what makes up an addition curing silicone rubber

paste - filler, liquid silicone prepolymer, methyl groups replaced with vinyl and a catalyst

paste2 - filler, liquid silicone prepolymer, methyl groups replaced with hydrogen

what are the properties of silicone rubber addition curing

no by products

hydrophobic

What are polyethers

2 pastes;

base paste and catalyst

how do polyethers set

by cationic ring opening

as it sets, viscosity increases resulting in a rigid rubber

what are the stages of addition polymerisation

1. activation

2. initiation

3. propagation

4. termination

what are the properties of polyethers

similar tear resistance to silicones

rigid

lack of heavy body/putty limits the use

hydrophillic - issue in humid environments