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Prosthetics > Introduction into Dental Polymers > Flashcards

Introduction into Dental Polymers Flashcards

1
Q

What is a polymer?

A

Long, chain molecules consisting of many distinct repeating smaller units called monomers

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2
Q

What reaction occurs to form polymers from monomers?

A

Polymerization

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3
Q

In what 2 states do monomers exist?

A
  1. Liquids

2. Gasses

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4
Q

In what 3 states do polymers exist?

A
  1. Crystalline solids
  2. Amorphous solids
  3. Fibres
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5
Q

Name 2 types of polymers

A
  1. Naturally occuring polymers

2. Synthetic polymers

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6
Q

Name 4 examples of naturally occuring polymers

A

1 . Cellulose

  1. DNA proteins
  2. Latex
  3. Sillk
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7
Q

Name 3 examples of synthetic polymers

A
  1. PVC
  2. Nylon
  3. Polystyrene
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8
Q

What is plastic?

A

A material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and can be moulded into solid objects

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9
Q

Name the 4 most produced plastics in the world

A
  1. Polyeythlene (PE)
  2. Polypropylene (PP)
  3. Polyvinyl chloride (PVC)
  4. Polyethylene terephthalate (PET)
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10
Q

What are thermoplastics?

A

Plastics that do not undergo chemical change in their composition when heated and can be moulded again and again

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11
Q

What are thermosets?

A

Thermosets can melt and take shape once; after they have solidified they stay solid as the thermosetting process is an irreversible chemical reaction

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12
Q

Name 2 types of polymerization

A
  1. Condensation

2. Addition

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13
Q

What is the difference between condensation and addition polymerization?

A

A small molecule is produced as a by-product during condensation polymerization but no by-product is produced during addition polymerization

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14
Q

When does addition polymerization occur?

A

Vinyl compounds as they are reactive organic compounds with carbon-carbon double bonds

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15
Q

What are the 4 stages of addition polymerization?

A
  1. Activation
  2. Initiation
  3. Propagation
  4. Termination
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16
Q

Name 3 ways activation is achieved during addition polymerization

A
  1. Light
  2. Heat
  3. Chemicals
17
Q

What is the most common compound responsible for activation in dental applications?

A

Benzoyl peroxide

18
Q

What does the activation of benzoyl peroxide result in?

A

Production of free radicals - A very reactive chemical species with an unpaired electron

19
Q

Describe initiation during additional polymerization

A

Activated free radicals react with a monomer unit to initiate polymerization reaction

20
Q

Describe the propagation stage of addition polymerization

A

The reactive monomer-free radical complex produced in initiation react with each other to build a chain

FR-M* + M = FR-M-M* + M etc.

21
Q

What are 2 ways termination of an addition polymerization reaction can occur?

A
  1. Monomers completely used up

2. Free radicals completely consumed

22
Q

Describe the physical changes on polymerization

A
  • Liquid at first
  • Molecular weight increases as reaction progresses
  • Chain entanglement occurs and viscosity increases as becomes amorphous solid
  • Cross linking between chains if cross-linking agent is present
23
Q

What is an example of a cross-linking agent?

A

Ethylene glycol dimethacrylate

24
Q

Name 3 properties of synthetic polymers

A
  1. Glass Transition Temperature (Tg)
  2. Plasticiser
  3. Fillers
25
Q

What is glass transition temperature?

A

Temperature at which polymer softens which is specific to each polymer - Above Tg polymer acts as a rubber / Below Tg acts as a solid

26
Q

What is a plasticiser?

A

Reduces the force of attraction between polymer chains and they become more flexible

27
Q

What is the function of fillers?

A

Particles which give increased mechanical strength, colour or bulk

28
Q

Name 4 methods of shaping dental polymers

A
  1. Compression moulding
  2. Injection moulding
  3. Pourable resin technique
  4. Thermoforming
29
Q

Describe compression moulding

A
  • Powder and liquid is mixed and begins to set
  • Product is placed into mould
  • Two halves of the mould reassembled and shape the polymer
  • Product allowed to set
30
Q

Describe injection moulding

A
  • Mould is created from wax which is then boiled away
  • Sprue added to allow channel into mould
  • Polymer injected under pressure to take the shape of wax
  • Once taken shape polymerization must take place in hot water bath
  • Denture retrieved from mould, sprue cut off and processed
31
Q

Describe pourable resin technique

A
  • Powder and liquid monomer mixed and poured into the mould
32
Q

Describe thermoforming in shaping dental polymers

A
  • Model produced in gypsum and blank acetate placed on top of the model
  • Under pressure and heat, acetate sucked down through vacuum over the model to take its shape
  • Trimmed and fitted onto model
33
Q

Name 4 uses of dental polymers

A
  1. Dentures
  2. Glass ionomers
  3. Composite
  4. Impressions
34
Q

What is biocompatibility?

A

Safe in the mouth, for the dental team and the environment

Prosthetics (16 decks)

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