Elastomeric Impression materials

Question 1

what are the problems with hydrocolloid materials?

Answer 1

poor tear resistance

poor dimensional stability

Question 2

what are the 4 types of elastomeric impression materials?

Answer 2

polysulphides
silicone rubbers - condensation curing/addition curing
polyether

Question 3

what is the committee that classifies impression materials by chemical nature and consistency?

Answer 3

ISO 4823

Question 4

what does consistency dictate?

Answer 4

clinical application

Question 5

putty has more inert fillers which make it?

Answer 5

more dimensionally accurate = does not flow very well because of viscosity = does not capture fine detail

Question 6

clinical properties of putty?

Answer 6

high dimensional stability
tissue displacing
poor fine detail capture

Question 7

properties of light bodied materials?

Answer 7

low dimensional stability
limited tissue displacement
fine detail capture

Question 8

combine viscosities to maximise?

Answer 8

clinical application

Question 9

polysulphides come as?

Answer 9

2 pastes

Question 10

what is the polysulphides baste paste?

Answer 10

baste paste is white
terminal and pendant thiol SH groups - bad smell
-polysulphide prepolymer
-plasticiser
-inert filler

Question 11

what is in the catalyst paste on polysulphides?

Answer 11

dark brown
lead dioxide
sulphur
inert oil

Question 12

how do polysulphides set?

Answer 12

by condensation polymerisation

Question 13

as cross linking occurs in polysulphides what happens?

Answer 13

increased viscosity and elasticity

Question 14

after mixing, what happens to polysulphides?

Answer 14

gradual increase in viscosity
slow development of elasticity
set time is 10 mins

Question 15

polysulphides have a high what? and slow?

Answer 15

high tear resistance

slow incomplete elastic recovery

Question 16

what have the best dimensional stability?

Answer 16

heavily bodied materials

Question 17

reactions of polysulphides continue with?

Answer 17

water loss

Question 18

concerns of use of what constituent in polysulphides?

Answer 18

lead

Question 19

polysulphide has a bad?

Answer 19

odour and taste

Question 20

are polysulphide impressions easy to read?

Answer 20

yes

Question 21

condensation cured silicone rubbers come as?

Answer 21

2 pastes or a paste and a liquid

Question 22

what types of condensation cured silicone rubbers can you get?

Answer 22

putty, heavy/regular/light bodied

Question 23

what is the setting reaction of condensation cured silicone rubber?

Answer 23

cross linking of hydroxyl terminated polydimethylsiloxane chains

Question 24

what is the catalyst in condensation cured silicone rubbers setting reaction? what is the cross linking agent?

Answer 24

catalyst - tin compound

cross linking agent - alkyl silicate

Question 25

what is a by product of condensation cured silicone rubbers setting reaction? what can it cause?

Answer 25

C2H5OH - an alcohol | can potentially make it dimensionally unstable

Question 26

what does cross linking in the condensation cure setting reaction cause?

Answer 26

increases materials viscosity and elastic properties

Question 27

paste one of silicone rubber (condensation) is?

Answer 27

hydroxyl terminated polydimethylsiloxane chains - liquid silicone prepolymer inert fillers - e.g silica

Question 28

paste 2 of silicone rubber (condensation) is?

Answer 28

alkyl silicate | tin compound e.g dibutly tin dilaurate

Question 29

silicone rubber (C) set time is?

Answer 29

less than polysulphides

Question 30

silicone rubber (C)'s elasticity develops?

Answer 30

more rapidly than polysulphides

Question 31

is silicone rubber (C) hydrophobic or hydrophillic?

Answer 31

hydrophobic

Question 32

what is the wear resistance of silicone rubber C like? | elastic recovery is?

Answer 32

adequate | good elastic recovery

Question 33

silicone rubbers C have post setting dimensional changes so must pour soon, with loss of?

Answer 33

loss of volatile by product

Question 34

silicone rubber addition curing paste 1?

Answer 34

filler liquid silicone prepolymer - white some methyl groups replaced with vinyl groups catalyst e.g chlorplatinic acid

Question 35

paste 2 of silicone rubber addition curing?

Answer 35

filler liquid silicone prepolymer polydmethylsiloxane prepolymer with some methyl groups replaced with hydrogen

Question 36

silicone rubber addition cured is available in what forms?

Answer 36

automax form | viscosities of - putty, regular and light

Question 37

what is the setting reaction of addition cured silicone rubber?

Answer 37

platinum catalysed addition reaction no by products hydrogen gas possibly involved b/c platinum catalyst with moisture

Question 38

properties of silicone rubber addition cured?

Answer 38

as for condensation silicones no by products hydrophobic - but some new formulas have surface active agents to make it more hydrophillic

Question 39

polyether - 2 pastes. what is the base paste?

Answer 39

comes in large tube imine terminated polymer inert filler

Question 40

polyether catalyst?

Answer 40

smaller tube reaction initiator - aromatic sulphonic acid ester paste forming oils and fillers

Question 41

polyether also available in what units?

Answer 41

automix

Question 42

how do polyethers set?

Answer 42

by cationic ring opening addition polymerisation | no by products

Question 43

as setting of polyethers increases what happens?

Answer 43

viscosity increases = rigid cross linked rubber

Question 44

polyethers have similar tear reistance and elastic properites to?

Answer 44

silicones

Question 45

polyethers rigidity makes it?

Answer 45

hard to remove difficult to remove die without fracture good for implant work

Question 46

use limited because polyethers do not come as?

Answer 46

heavy bodied or puttys

Question 47

are polyethers hydrophobic or hydrophillic?

Answer 47

hydrophillic

Question 48

what can polyethers cause?

Answer 48

an allergy

Question 49

limit emersion of polyethers to?

Answer 49

10 mins in hypochlorite