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Flashcards in elastomeric impression materials Deck (28):
1

what are main problems re. hydrocolloid materials?

poor tear resistance
poor dimensional stabilty

2

what are the 4 types of elastomeric impression materials?

polysulphides
silicone rubber (condensation curing)
silicone rubber (addition curing)
polyether

3

what material is preffered re implant work?

polether

4

how are elastomeric materials classified?

according to chemical nature
according to consistency

5

type 0?

very high consistency- putty

6

type 1? h

high consistency- heavy body

7

type 2?

medium consistency- medium bodied

8

type 3?

low consistency- light body

9

properties of putty?

high dimensional stability
tissue displacement
poor fine detail capture

10

properties of light body?

low dimensional stability
limited tissue displacement
fine detail capture

11

what are benefits of polysuphides?

very easy to read

12

disadvantages of polysulphides?

unpleasant for patient re. smell and taste

13

what is base paste of polysuphides?

terminal and pendant thiol -SH groups
polysulphide prepolymer
plasticiser ( di-n-butyl phthalate)
inert filler (chalk/Ti)2)

14

what is the catylst paste of polysulphides?

pbo2 ( lead dioxide)
sulphur
inert oil

15

what is the setting re. polysulphides?

condensation polymerisation

16

as cross linking occurs what increase?

viscosity and elastcity

17

what is setting reaction re silicone rubbers- condensation curing

cross linkin of hydroxyl terminated polydimethylsiloxane chains

18

what is the by product of the setting reaction of silicone rubbers- condensation curing?

ethyl alcohol

19

what is the cross linking agent re. condensation curing silicone rubber>

alkyl silicate

20

what is the catalyst re. condensation curing silicone rubber?

tin compound

21

what is the compostion of silicone rubbers - condensation curing?

paste- hydroxyl terminated polydimethylsilxane chains+ inert fillers (silica)
paste 2/liquid- alkyl silicate+ tin compound

22

what are the properties of silicone rubber- condensation curing?

set times less than polysulphides
elasticity develops more rapidly
tear resistance adequate
good elastic recovery
post setting dimensional changes

23

what are the by products re. addition curing and silicone rubber?

none
? hydrogen gas

24

what is the setting reaction re addition curing and silicone rubbers?

platinum catalysed addition reaction

25

what are the two pastes re. polyether?

base paste- imine terminated prepolymer+ inert filler
catalyst- aromatic suphonic acid ester+ oils and fillers

26

what is the setting reaction re. polyether?

by catatonic ring opening addition polymerisation
no by products

27

what are the stages of setting re polyether?

activation
initiation
propagation
termination

28

what are properties re. polyethers?

good tear resistance and elastic properties
relatively rigid
lacks of heavy body limits use
hydrophilic
must limit immersion in hypochlorite