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Restorative > Impresion Material > Flashcards

Impresion Material Flashcards

0
Q

What are the non elastic materials?

A

Impression wax
Impression plaster
Zn O eugenol
Impression compound

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1
Q

How can we classify impression material?

A

Elastic and non elastic

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2
Q

How can we classify elastic impression materials?

A

Elastomer

Hydro colloid

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3
Q

What are the hydro colloids?

A

Alginate

Agar

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4
Q

WHat are the elastomers?

A

Polyether
Silicone
Polysulfide

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5
Q

What are the silicones?

A

Addition and condensation

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6
Q

What is the purpose of an impression material?

A

To produce an accurate replica of the hard and soft tissues

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7
Q

When can you use ridgid materials?

A

When there are no boney undercuts so edentulous

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8
Q

When can you use elastic impression materials?

A

Can engage in undercuts

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9
Q

When is impression compound used?

A

Modify stock trays and special trays and used as a foundation for a wash impression

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10
Q

Wha pt type of material is impression compound?

A

Thermoplastic

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11
Q

What are the two type of impression compound?

A

Type 1: lower fusing impression material

Type 2: higher fusing tray material

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12
Q

What temp is impression compound softened at?

A

55-60 degrees

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13
Q

What is the molecular weight of alginate?

A

20000-200000

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14
Q

What is alginate based upon?

A

A colloidal suspension of mucopilysaccahirdes in water

Alginic acid

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15
Q

What states does alginate exist in in dentistry?

A

Gel and sol state

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16
Q

What is the molecular structure of alginate?

A

Polymer

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17
Q

What is the setting reaction for alginate?

A

Sodium alginate + calcium sulphate -> sodium sulphate + calcium alginate

Calcium forms cross linking between polymer chains to form a 3d network

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18
Q

What is the constituent of alginate?

A 
Few: fillers : 52%
Soldiers: sodium alginate 18%
Can: calcium sulphate dihydrate: 14%
Pass: potassium suplphate: 10%
Simple: sodium silicofluroide: 4%
science: sodium Phosohate : 2%
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19
Q

What is the purpose of the fillers in alginate?

A

Controls consistence

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20
Q

What is the purpose of the sodium alginate ?

A

Hydrogel former

21
Q

What is the purpose of calcium sulphate dihydrate?

A

Calcium ions for x linking

22
Q

What is the purpose of potassium sulphate?

A

Setting

23
Q

What is the purpose of sodium Phosohate?

A

Controls working time

24
Q

What is the purpose of sodium silicofluroide?

A

Controls pH

25
Q

What are the advantages of alginate?

A

Detail okay for dentures
Short setting time
Cheap

26
Q

What are the diasadvantes of alginate?

A

Not good enough for crown and bridge
User dependant mixing
Moisture contamination limited shelf life
Susceptible to syneresis AND Imbibition
Muse be kept damp and model pored quickly
Low teear strength

27
Q

How thick must the layer of alginate be?

A

3-5mm

28
Q

What are Polysulfide?

A

Polymer with mercaptan groups.

SH

29
Q

How does Polysulfide set?

A

Mercaptan groups are oxidised by an accelerator and hydrogen is removed releasing water

30
Q

What are the advantages and dis of Polysulfide?

A

Highest tear stengh
Good detsail

Bad taste and smell

31
Q

What are polyethers?

A

Polymer with imine functional groups

CH2-N-CH2

32
Q

T/F Polyether need an activator?

A

T

Aromatic sulfonate ester

33
Q

How does polyethers set?

A

Cross linking between the chains

34
Q

What are the ad and dis of Polyether?

A

AD: good detail, good dimensional stab, least hydrophobic, v low setting shrinkage

Dis: stiffest, single viscosity only, swells in moisture, difficult to disinfect

35
Q

What are silicones?

A

Si-O backbone with alkyl groups

36
Q

What are condensation cured silicones?

A

Polydimethyl siloxane polymer with OH terminal groups

37
Q

What antivator is needed in condensation cured silicones?

A

Tetraethyl silicate

TES

38
Q

What are addition cure silicones?

A

Polydemetyl siloxane polymer with vinyl terminal groups

C=CH2

39
Q

What is then activator needed in additions cured silicones?

A

Platinum catalyst and silanol

40
Q

Which materials have the greatest setting shrinkage?

A

They all since they are polymers

41
Q

T/F setting shrinkage is bad?

A

Not always since gives some room for cement but you want litlle or no shrinkage

42
Q

Which material contracts or expands the most?

A

Polyether

ACS and CCS are the same

43
Q

Why do polymers shrink on setting?

A

Difference in temp between room and mouth

44
Q

Which polymer has the best storage and long term stability?

A

ACS

This is how use CCS release alcohol and polysufides release water

45
Q

T/F you ewnt your impression materials to be hydrophilic?

A

T

46
Q

T/F you want impression materials to have a low tear strength?

A

F
Low means it tears easily ie when being pulled from undercuts

High means it doesn’t tear
You want a mod high tear strength

47
Q

What are the advantages and dis of condensation cured?

A

Good details
Wide range of Viscosity
Small setting shrinkage

BUT hydrophobic, release alcohol song must be poured quick, TES hydrolysed in moisture, harder to mix than ACS

48
Q

What are the advantages and dis of addtion cured?

A

Good: detail, wide range of viscosity, very good dimensional stab, v low setting shrinkage

BUt: V hydrophobic

49
Q

What material do you use for primary impression of completes?

A

Impression compound in edentulous tray and wash impression with alginate for better detail

When impression compound at correct temperature it has shiny surface

Alginate

50
Q

What materials can you use for secondary impressions?

A

Upper and lower arch with minimal or no undercut use a CLOSE FITTING TRAY with LIGHT BODIED SILCONE or ZINc OXIDE (NB can use medium bodied as well for lower)

Upper and lower arch with flabby ridge or marked undercut then SPACED TRSY OF 1.5mm With ALGINATE or MEDIUM BODIED SILICONE

Restorative (45 decks)

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