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Dental Materials > DM3- Elastomeric Impression Materials > Flashcards

DM3- Elastomeric Impression Materials Flashcards

1
Q

What are the 4 types of elastomeric impression materials?

A
  • polysulphides
  • silicone rubbers (condensation curing)
  • silicone rubbers (Addition curing)
  • polyether
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2
Q

ISO 4823 classifies according to what?

A
  • chemical nature

- consistency

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3
Q

what is the consistency of Putty?

A
  • high dimensional stability
  • tissue displacing
  • poor dine detail capture
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4
Q

what is the consistency of light bodied material?

A
  • low dimensional stability
  • limited tissue displacing
  • fine detail capture
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5
Q

What are the two pastes in polysulphides?

A
  • base paste (white)

- catalyst past (dark brown)

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6
Q

what is base paste made up of?

A
  • polysulphide
  • prepolymer,
  • plasticiser
  • inert filler
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7
Q

what is catalyst paste made up of?

A
  • PbO2
  • sulfur
  • inert oil
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8
Q

How does a polysulphide set?

A

condensation polymererisation

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9
Q

What increases as cross linking of polysulphid occurs?

A

viscosity and elasticity

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10
Q

what are the properties of polysulfides? (6)

A
  • high tear resistance but slow incomplete elastic recovery
  • heavy bodied best dimensional stability
  • reaction continues with water loss
  • concerns
    concerning use of lead
  • impression easily read
  • bad odour and tatse
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11
Q

how are silicon rubber (condensation curing) set?

A
  • cross linking of hydroxyl terminated polydimethylsiloxane chains
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12
Q

what are the properties of silicon rubbers (condensation curing)?(8)

A
  • set time less than polysulphides
  • elasticity develops more rapidly than polysulphides
  • hydrophobic
  • tear resistance adequate
  • good elastic recovery
  • post setting dimensional changes so must pour soon
  • handle liquid components with respect
  • considered non toxic in intraoral application
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13
Q

In a silicone rubber condensation curing reaction what is the cross linking agent?

A

Alkyl silicate

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14
Q

In a silicone rubber condensation curing reaction what is the the catalyst?

A

Tin

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15
Q

what is the setting reaction of silicon rubbers (addition curing?

A

platinum catalysed addition rection

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16
Q

What are the properties of silicon rubber (additon curing) (3) ?

A
  • same as condensation silicons
  • no by products
  • hydrophobic though new formulations incorporate surface activate agents to render more hydrophilic
17
Q

how does polyether set?

A

cationic ring opening addition polymerisation

18
Q

what happens as polyether sets?

A

viscosity increases resulting in a rigid cross linked rubber

19
Q

what are the properties of polyether?

A
  • relatively rigid
  • lack of heavy body/putty limits use
  • hydrophilic which is an issue in human environments
  • allergy
  • must limit immersion to 10 mins in hypochlorite

Dental Materials (4 decks)

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