Lernmaterialien für DMS an der University of Glasgow

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TESTE DEIN WISSEN

What are 2 disadvantages of alginate?

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Poor tear strength
Must be provided ASAP
- Syneresis and inhibition with moisture

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TESTE DEIN WISSEN

What are 5 disadvantages of GI?

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TESTE DEIN WISSEN

Brittle and poor wear resistance
Moisture susceptible when first placed
- Most importantly during hardening phase
- Must be water and dessication free
- Consequences
  - Aluminum ions may leach out and therefore reducing mechanical properties
  - Saliva contamination causes excess water absorption
- Overall, results in weak material
Lower compressive strength than composite (by 50%)
Poorer aesthetics
Poor handling characteristics

Lösung ausblenden

TESTE DEIN WISSEN

What is the composition of GI?

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Acid
- Polyacrylic and tartaric acid
Base
- Quartz
- Alumina
- Aluminium phosphate
- Aluminium fluroide
- Sodium fluoride
- Calcium fluoride
Lithium and strotinum salts can be added to increase radiopacity but do not take part in reaction

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TESTE DEIN WISSEN

How does bonding take place in GI?

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Carboxyl groups in cement bond to enamel
Hydrogen ion bonding and metallic ion bridging with collagen in enamel

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TESTE DEIN WISSEN

What are the 7 ideal properties of denture bases/acrylics?

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Dimensionally stable
Biocompatible
Easy/cheap to manufacture and reproduce
High
- Youngs Modulus
- Proportional limit (elastic limit)
- Softening temp
- Transverse, fatigue and impact strength
- Thermal conductivity
- Hardness and resistance abrasion

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TESTE DEIN WISSEN

What are 4 elastomer impression materials?

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TESTE DEIN WISSEN

Polysulphides
Polyether
- Impregnum
Curing Silicone
- Addition (Aquasil Ultra)
- Non-Addition (Verone)

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TESTE DEIN WISSEN

What are 4 faults that occur during production of heat-cured acrylic and why do they occur?

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TESTE DEIN WISSEN

Under-curing
- Too much monomer (irritant) and decrease in mechanical properties
Over-curing
- Contraction porosity/polymerisation shrinkage
  - Monomer shrinks by 20%
  - Too much monomer, insufficient pressure, insufficient excess material
- Gaseous porosity
  - Monomer boiling in bulkier parts of denture creating voids
- Granularity
  - Not enough monomer
- Crazing
  - Internal stresses due to fast cooling rate

Lösung ausblenden

TESTE DEIN WISSEN

What are 3 advantages of elastomeric impressions?

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TESTE DEIN WISSEN

Higher tear strength/resistance
Greater elastic recovery
Lower visco-elasticity
Lower rigidity
Greater reproduction of surface detail

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TESTE DEIN WISSEN

What are the constituents of PMMA?

IPPPCo MHCo

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TESTE DEIN WISSEN

Powder
- Benzoyl peroxide (initator)
- PMMA particles (pre-polymerised beads)
- Plasticiser (quicker dissolving in monomer liquid)
- Co-polymer (improves mechanical properties)
- Pigments (colour)
Liquid
- Methymethacrylate monomer (polymerises)
- Hydroquinone (inhibitor by reacting with free radicals and therefore increasing shelf life)
- Co-polymer (improves mechanical properties)

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TESTE DEIN WISSEN

What are 4 non-elastic impression materials?

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TESTE DEIN WISSEN

Impression compound
Impression waxes
Impression plasters
ZOE

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TESTE DEIN WISSEN

What are 2 advantages of alginate?

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TESTE DEIN WISSEN

Relatively easy to use
Operator compatible
- Can decide on working and setting time
Quite accurate
- Relatively fine detail recorded
Cheap
Non-irritant and non-toxic

Lösung ausblenden

TESTE DEIN WISSEN

What is the setting reaction of alginate?

Lösung anzeigen

TESTE DEIN WISSEN

2Na_nAlg + nCaSO₄ ----> nNa₂SO₄+ Ca_nAlg

Sodium alginate to calcium alginate
Cross-linking with calcium allows alginate to set
Intermediate reaction between sodium to calcium delays setting

Lösung ausblenden

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What are 2 disadvantages of alginate?

Poor tear strength
Must be provided ASAP
- Syneresis and inhibition with moisture

What are 5 disadvantages of GI?

Brittle and poor wear resistance
Moisture susceptible when first placed
- Most importantly during hardening phase
- Must be water and dessication free
- Consequences
  - Aluminum ions may leach out and therefore reducing mechanical properties
  - Saliva contamination causes excess water absorption
- Overall, results in weak material
Lower compressive strength than composite (by 50%)
Poorer aesthetics
Poor handling characteristics

What is the composition of GI?

Acid
- Polyacrylic and tartaric acid
Base
- Quartz
- Alumina
- Aluminium phosphate
- Aluminium fluroide
- Sodium fluoride
- Calcium fluoride
Lithium and strotinum salts can be added to increase radiopacity but do not take part in reaction

How does bonding take place in GI?

Carboxyl groups in cement bond to enamel
Hydrogen ion bonding and metallic ion bridging with collagen in enamel

What are the 7 ideal properties of denture bases/acrylics?

Dimensionally stable
Biocompatible
Easy/cheap to manufacture and reproduce
High
- Youngs Modulus
- Proportional limit (elastic limit)
- Softening temp
- Transverse, fatigue and impact strength
- Thermal conductivity
- Hardness and resistance abrasion

Mehr Karteikarten anzeigen

What are 4 elastomer impression materials?

Polysulphides
Polyether
- Impregnum
Curing Silicone
- Addition (Aquasil Ultra)
- Non-Addition (Verone)

What are 4 faults that occur during production of heat-cured acrylic and why do they occur?

Under-curing
- Too much monomer (irritant) and decrease in mechanical properties
Over-curing
- Contraction porosity/polymerisation shrinkage
  - Monomer shrinks by 20%
  - Too much monomer, insufficient pressure, insufficient excess material
- Gaseous porosity
  - Monomer boiling in bulkier parts of denture creating voids
- Granularity
  - Not enough monomer
- Crazing
  - Internal stresses due to fast cooling rate

What are 3 advantages of elastomeric impressions?

Higher tear strength/resistance
Greater elastic recovery
Lower visco-elasticity
Lower rigidity
Greater reproduction of surface detail

What are the constituents of PMMA?

IPPPCo MHCo

Powder
- Benzoyl peroxide (initator)
- PMMA particles (pre-polymerised beads)
- Plasticiser (quicker dissolving in monomer liquid)
- Co-polymer (improves mechanical properties)
- Pigments (colour)
Liquid
- Methymethacrylate monomer (polymerises)
- Hydroquinone (inhibitor by reacting with free radicals and therefore increasing shelf life)
- Co-polymer (improves mechanical properties)

What are 4 non-elastic impression materials?

Impression compound
Impression waxes
Impression plasters
ZOE

What are 2 advantages of alginate?

Relatively easy to use
Operator compatible
- Can decide on working and setting time
Quite accurate
- Relatively fine detail recorded
Cheap
Non-irritant and non-toxic

What is the setting reaction of alginate?

2Na_nAlg + nCaSO₄ ----> nNa₂SO₄+ Ca_nAlg

Sodium alginate to calcium alginate
Cross-linking with calcium allows alginate to set
Intermediate reaction between sodium to calcium delays setting

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Lernmaterialien für DMS an der University of Glasgow

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