Materials - Nonaqueous Elastomeric Impression Materials

Front 1

component forming the main structure of the set material

Back 1

base

Front 2

component of the rxn that speeds up the setting rxn and is similar to the catalyst

Back 2

accelerator

Front 3

component that initates the setting rxn but does not become part of the final product

Back 3

catalyst

Front 4

lightly cross-linked material having elastic behavior after setting

Back 4

elastomer

Front 5

single-component material that is viscous enough to serve as a tray material yet serves as a syringe material after shear-thinning

Back 5

monophase (single phase)

Front 6

time-dependent pseudoplastic behavior of materials characterized by the gradual decrease of viscosity under a constant applied shear rate

Back 6

thixotropic

Front 7

time from start of mixing until just before elastic properties have developed

Back 7

working time

Front 8

time from start of mixing until material can resist permanent deformation

Back 8

setting time

Front 9

characteristic behavior of a material that behaves intermediate to an elastic solid (spring) and a viscous fluid (dashpot)

Back 9

viscoelastic behavior

Front 10

ADA spec 19 divides elastomeric impression materials into 3 types based on what?

Back 10

selected elastic properties and dimsional change of the material

Front 11

4 types of elastomers based on chemical composition

Back 11

polysulfide, condensation silicone, addition silicone, polyether

Front 12

definition of elastomeric impression materials

Back 12

cross-linked polymeric two-paste materials that set by irreversible chemical reactions

Front 13

elastomers are used to obtain highly accurate impressions for what type of restorations?

Back 13

indirectly-fabricated

Front 14

why do elastomers require tray adhesive?

Back 14

to keep polymerization shrinkage in proper direction (toward tray)

Front 15

what is the purpose of the fast strain rate (rapid removal) property of most elastomeric impression materials

Back 15

reduces distortion and increases tear resistance

Front 16

polysulfide setting rxn

Back 16

[polymer + filler] + [lead dioxide] --> set material + H2O

Front 17

function of lead dioxide in polysulfide setting rxn

Back 17

brown reactor/accelerator paste; oxidizing agent

Front 18

what does the base polymer contain in polysulfide?

Back 18

linear polyfunctional mercaptan or polysulfide (characteristic odor)
lithopone or TiO2 filler

Front 19

what is the plasticizer in polysulfide?

Back 19

dibutyl phthalate

Front 20

what are the retarders in polysulfide?

Back 20

oleic/stearic acid retarders

Front 21

what is cross-linked in the polysulfide setting rxn?

Back 21

SH groups in the base polymer and lead dioxide

Front 22

color of lead dioxide

Back 22

brown

Front 23

what type of reaction is the polysulfide setting rxn?

Back 23

exothermic condensation polymerization rxn

Front 24

vulcanization

Back 24

formation of disulfide bonds (cross-linking)

Front 25

nature of polymer in polysulfide

Back 25

hydrophobic

Front 26

speed of setting of polysulfide

Back 26

slow setting: leave in mouth for 10 min

Front 27

which material has the highest tear resistance of all impression materials?

Back 27

polysulfide - so don't remove rapidly

Front 28

which material has the slowest elastic strain recovery and most permanent deformation after compressive strain?

Back 28

polysulfide

Front 29

for polysulfide, how long should you wait to pour and why?

Back 29

should be w/in 30 min but best if immediately to reduce shrinkage by water loss

Front 30

which materials require custom tray?

Back 30

polysulfide and polyether

Front 31

which is the material that does not specify to use for edentulous ridges?

Back 31

condensation silicone

Front 32

what is added to the paste in silicone impression materials for condensation silicones?

Back 32

reinforcing agents (silica)

Front 33

setting rxn for condensation silicone

Back 33

polymer + cross-linking agent --> set material + ethanol

Front 34

what is the polymer for condensation silicone?

Back 34

alpha - omega hydroxy-terminated polydimethyl siloxane

Front 35

what does the polymer react with in condensation silicone?

Back 35

tri or tetra functional alkyl silicates

Front 36

cross-linking occurs bw what in condensation silicone?

Back 36

silicone polymers and silicates

Front 37

by product of condensation silicone

Back 37

ethanol

Front 38

what happens to the set condensation silicone material?

Back 38

it will shrink and change dimension and release volatile by-product

Front 39

compensation for polymerization shrinkage in condensation silicone products

Back 39

putty-wash

Front 40

amount of shrinkage for condensation silicone

Back 40

.03-0.06%

Front 41

when should you pour for condensation silicone rxns?

Back 41

w/in 30 min, but after ethanol has evaporated

Front 42

what are the implications of condensation silicone materials, since it is so very hydrophobic?

Back 42

need dry field for impression and difficult to pour cast w/o getting bubbles in stone

Front 43

does condensation silicone have high or low tear strength?

Back 43

low

Front 44

why is condensation silicone not used as commonly as addition silicones?

Back 44

poor dimensional stability

Front 45

setting reaction for addition silicone?

Back 45

polymer + Pt salt w/ pre-polymer --> set material

Front 46

what is the base of addition silicone?

Back 46

polymethyl hydrogen siloxane

Front 47

what is the catalyst for addition silicone?

Back 47

divinyl polydimethyl siloxane

Front 48

shrinkage on curing for addition silicone

Back 48

0.05-0.16%

Front 49

best dimensional stability

Back 49

addition silicone

Front 50

what do some manufacturers add to addition silicone to make it more hydrophilic?

Back 50

surfactant

Front 51

when do you pour the cast for addition silicone?

Back 51

wait to permit the release of H2 gas

Front 52

base for polyether

Back 52

polyether pre-polymer, colloidal silica filler, glycolether or phthalate plasticizer

Front 53

accelerator for polyether

Back 53

sulfonate ester initiator, imine catalyst

Front 54

which material has a high modulus of elasticity?

Back 54

polyether

Front 55

shrinkage on curing of polyether

Back 55

0.15%

Front 56

which material should you use on pts who gag?

Back 56

polyether

Front 57

does polyether have high or low tear strength?

Back 57

low

Front 58

least hydrophobic elastomer

Back 58

polyether

Front 59

where should you definitely not use polyether?

Back 59

full arch impressions or for impression of sub-gingival region