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Dental Materials > Hydrocolloid impression material > Flashcards

Hydrocolloid impression material Flashcards

1
Q

What does high viscosity material give?

A

less detail

can displace soft tissues

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2
Q

What doe low viscosity material give?

A

more fine detail

tray may not contain

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3
Q

What do moist surfaces do to hydrocolloid imp materials?

A

repel material

does not give good detail

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4
Q

How are impression materials classified?

A

non elastic

elastic

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5
Q

What are non elastic imp materials?

A

imp plaster
imp compound
zinc oxide and euganol paste

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6
Q

What are elastic impression materials?

A

hydrocolloids

synthetic elastomers

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7
Q

What is a reversible hydrocolloid?

A

agar

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8
Q

What is an irreversible hydrocolloid?

A

Alginate

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9
Q

How do hydrocolloids exist?

A

both reversible and irreversible exist in sol and gel form

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10
Q

What is a sol-gel reaction?

A

cooling

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11
Q

What is a gel to sol reaction?

A

increase in temperature

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12
Q

alginate can go in what direction?

A

sol to gel only

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13
Q

agar can go in what direction?

A

sol to gel and gel to sol

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14
Q

What are synthetic elastomers?

A

polysulphides
silicone rubbers
polyethers

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15
Q

What is agar used for?

A

duplicating models

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16
Q

What does agar require?

A

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

17
Q

disadvantages of agar?

A

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

18
Q

What is the composition of alginate?

A

sodium of potassium salt of alginic acid 11-16%

cross linked gel when set

19
Q

What is the source for cross linking setting reaction?

A

calcium

20
Q

What controls working time of alginate?

A

sodium phosphate

21
Q

How does sodium phosphate control working time?

A

limits availability of calcium ions

22
Q

What are properties of alginate?

A 
low viscosity- mucostatic
aqequate working time
sets by tissues first
elastic
no less than 3-5 mm thick
23
Q

How should imps be disinfected?

A

achtochlor tablets x 10 in 1000mls

2 minutes

Dental Materials (13 decks)

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