Impresion Material

Question 0

What are the non elastic materials?

Answer 0

Impression wax
Impression plaster
Zn O eugenol
Impression compound

Question 1

How can we classify impression material?

Answer 1

Elastic and non elastic

Question 2

How can we classify elastic impression materials?

Answer 2

Elastomer

Hydro colloid

Question 3

What are the hydro colloids?

Answer 3

Alginate

Agar

Question 4

WHat are the elastomers?

Answer 4

Polyether
Silicone
Polysulfide

Question 5

What are the silicones?

Answer 5

Addition and condensation

Question 6

What is the purpose of an impression material?

Answer 6

To produce an accurate replica of the hard and soft tissues

Question 7

When can you use ridgid materials?

Answer 7

When there are no boney undercuts so edentulous

Question 8

When can you use elastic impression materials?

Answer 8

Can engage in undercuts

Question 9

When is impression compound used?

Answer 9

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

Question 10

Wha pt type of material is impression compound?

Answer 10

Thermoplastic

Question 11

What are the two type of impression compound?

Answer 11

Type 1: lower fusing impression material

Type 2: higher fusing tray material

Question 12

What temp is impression compound softened at?

Answer 12

55-60 degrees

Question 13

What is the molecular weight of alginate?

Answer 13

20000-200000

Question 14

What is alginate based upon?

Answer 14

A colloidal suspension of mucopilysaccahirdes in water

Alginic acid

Question 15

What states does alginate exist in in dentistry?

Answer 15

Gel and sol state

Question 16

What is the molecular structure of alginate?

Answer 16

Polymer

Question 17

What is the setting reaction for alginate?

Answer 17

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

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

Question 18

What is the constituent of alginate?

Answer 18

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

Question 19

What is the purpose of the fillers in alginate?

Answer 19

Controls consistence

Question 20

What is the purpose of the sodium alginate ?

Answer 20

Hydrogel former

Question 21

What is the purpose of calcium sulphate dihydrate?

Answer 21

Calcium ions for x linking

Question 22

What is the purpose of potassium sulphate?

Answer 22

Setting

Question 23

What is the purpose of sodium Phosohate?

Answer 23

Controls working time

Question 24

What is the purpose of sodium silicofluroide?

Answer 24

Controls pH

Question 25

What are the advantages of alginate?

Answer 25

Detail okay for dentures Short setting time Cheap

Question 26

What are the diasadvantes of alginate?

Answer 26

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

Question 27

How thick must the layer of alginate be?

Answer 27

3-5mm

Question 28

What are Polysulfide?

Answer 28

Polymer with mercaptan groups. | SH

Question 29

How does Polysulfide set?

Answer 29

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

Question 30

What are the advantages and dis of Polysulfide?

Answer 30

Highest tear stengh Good detsail Bad taste and smell

Question 31

What are polyethers?

Answer 31

Polymer with imine functional groups CH2-N-CH2

Question 32

T/F Polyether need an activator?

Answer 32

T | Aromatic sulfonate ester

Question 33

How does polyethers set?

Answer 33

Cross linking between the chains

Question 34

What are the ad and dis of Polyether?

Answer 34

AD: good detail, good dimensional stab, least hydrophobic, v low setting shrinkage Dis: stiffest, single viscosity only, swells in moisture, difficult to disinfect

Question 35

What are silicones?

Answer 35

Si-O backbone with alkyl groups

Question 36

What are condensation cured silicones?

Answer 36

Polydimethyl siloxane polymer with OH terminal groups

Question 37

What antivator is needed in condensation cured silicones?

Answer 37

Tetraethyl silicate | TES

Question 38

What are addition cure silicones?

Answer 38

Polydemetyl siloxane polymer with vinyl terminal groups C=CH2

Question 39

What is then activator needed in additions cured silicones?

Answer 39

Platinum catalyst and silanol

Question 40

Which materials have the greatest setting shrinkage?

Answer 40

They all since they are polymers

Question 41

T/F setting shrinkage is bad?

Answer 41

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

Question 42

Which material contracts or expands the most?

Answer 42

Polyether | ACS and CCS are the same

Question 43

Why do polymers shrink on setting?

Answer 43

Difference in temp between room and mouth

Question 44

Which polymer has the best storage and long term stability?

Answer 44

ACS | This is how use CCS release alcohol and polysufides release water

Question 45

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

Answer 45

T

Question 46

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

Answer 46

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

Question 47

What are the advantages and dis of condensation cured?

Answer 47

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

Question 48

What are the advantages and dis of addtion cured?

Answer 48

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

Question 49

What material do you use for primary impression of completes?

Answer 49

Impression compound in edentulous tray and wash impression with alginate for better detail When impression compound at correct temperature it has shiny surface Alginate

Question 50

What materials can you use for secondary impressions?

Answer 50

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