Hydrocolloid impression material Flashcards Preview

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Flashcards in Hydrocolloid impression material Deck (23):
1

What does high viscosity material give?

less detail
can displace soft tissues

2

What doe low viscosity material give?

more fine detail
tray may not contain

3

What do moist surfaces do to hydrocolloid imp materials?

repel material
does not give good detail

4

How are impression materials classified?

non elastic
elastic

5

What are non elastic imp materials?

imp plaster
imp compound
zinc oxide and euganol paste

6

What are elastic impression materials?

hydrocolloids
synthetic elastomers

7

What is a reversible hydrocolloid?

agar

8

What is an irreversible hydrocolloid?

Alginate

9

How do hydrocolloids exist?

both reversible and irreversible exist in sol and gel form

10

What is a sol-gel reaction?

cooling

11

What is a gel to sol reaction?

increase in temperature

12

alginate can go in what direction?

sol to gel only

13

agar can go in what direction?

sol to gel and gel to sol

14

What are synthetic elastomers?

polysulphides
silicone rubbers
polyethers

15

What is agar used for?

duplicating models

16

What does agar require?

water bath conditioning:
100 degrees- gel to sol
65 degrees- holding temperature
45 degrees- clinical usage

17

disadvantages of agar?

cross infection
requires specialist equipment
low tear strength
dimensionally unstable due to water content

18

What is the composition of alginate?

sodium of potassium salt of alginic acid 11-16%
cross linked gel when set

19

What is the source for cross linking setting reaction?

calcium

20

What controls working time of alginate?

sodium phosphate

21

How does sodium phosphate control working time?

limits availability of calcium ions

22

What are properties of alginate?

low viscosity- mucostatic
aqequate working time
sets by tissues first
elastic
no less than 3-5 mm thick

23

How should imps be disinfected?

achtochlor tablets x 10 in 1000mls
2 minutes