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Dental Materials Y3 > Acrylics 3 - Other RT Cured Acrylics > Flashcards

Acrylics 3 - Other RT Cured Acrylics Flashcards

1
Q

By what reaction do the monomers in HC and RT cured polymers polymerise

A

Free radical, addition polymerisation

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2
Q

What is the difference found in the composition of other RT cured acrylics

A

These materials use other polymer powders instead of PMMA and a higher methacrylate monomer (Ethyl, n-butyl etc)

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3
Q

What is PEMA

A

Poly ethyl methacrylate

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4
Q

What does PEMA do in “Other” RT Cured acrylics

A

Reduces the shrinkage and exotherm - acts as a virtual filler and doesn’t take part in the free radical addition polymerisation

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5
Q

Why can PMMA only be mixed with MMA monomer

A

Otherwise it would form an incoherent gel

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6
Q

Why can’t PEMA be mixed with MMA monomer

A

Forms an incoherently mixed product

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7
Q

What monomers can PEMA be mixed with

A

Several higher molecular weight monomers (in place e of MMA)

- Can also be used without a monomer

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8
Q

What are some examples of using PEMA

A
  • Soft lining materials
  • Tissue conditioners
  • Temporary crown and bridge materials
  • Extension of impression trays and dentures
  • Hard reline material
  • Functional impression material
  • Maxillofacial prosthesis (e.g. obturators)
  • Denture lining
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9
Q

What is a soft lining material used for

A

Used to make the denture more comfortable for the patient

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10
Q

Why might the lower denture cause more pain than the top one

A

Less surface area to distribute the load

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11
Q

What are the constituents of the powder phase of RT cured soft lining materials based on PEMA as an example

A
  • PEMA powder or BMA/EMA copolymer powder
  • Benzoyl peroxide (BP) - initiator
  • Colour pigments
  • Opacifiers
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12
Q

What are the constituents of the liquid phase of RT cured soft lining materials based on PEMA as an example

A
  • Higher methacrylate monomers e.g. ethyl, butyl, hexyl methacrylates
  • Di-n-butyl phthalate or citrate plasticiser
  • Hydroquinone - inhibitor
  • DMPT - activator
  • Cross linking agent
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13
Q

Why do RT cured soft lining materials adhere well to the acrylic denture base

A
  • RT cured soft lining materials contain acrylic groups
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14
Q

What does the addition of a plasticiser do to a RT cured soft lining materials

A

This lowers the glass transition temperature

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15
Q

What kind of chemical is a plasticiser normally

A

An Aromatic ester or a di-n-butyl-phthalate

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16
Q

What is a plasticiser

A

This is an organic liquid that acts as a lubricant that seeps between polymer chains and lowers the intermolecular forces between them

17
Q

Why should RT cured soft lining materials contain little plasticisers

A

The plasticiser tends to leach out into the oral fluids with time; consequently the material hardens - obvs limiting the life of the soft lining material

18
Q

What is the biocompatibility problem with some RT cured soft lining materials

A

some plasticisers are phthalate based which is fooked

19
Q

What is being used to replace phthalate based plasticisers

A

Citrate based plasticisers

20
Q

What are temporary crowns

A

they’re used to protect the tooth after being prepared for a permanent crown

21
Q

How long can you leave temp crowns in for

A

Can take several weeks before a permanent crown is put in place

22
Q

What are the constituents of the powder of RT cured temp crowns and bridges/extension materials

A
  • PEMA powder
  • benzoyl peroxide - initiator
  • colour pigments
  • Opacifiers
23
Q

What are the constituents of the liquid of RT cured temp crowns and bridges/ extension materials

A
  • Butyl methacrylate monomer
  • Hydroquinone - inhibitor
  • DMPT - activator
24
Q

Why is the dough technique used when making PEMA RT cured temp crowns and bridges

A

The dough technique is used to reduce the overall shrinkage and exotherm of the material

25
Q

What are the advantages of using PEMA/BM compared to PMMA/MMA

A
  • Lower exotherm than PMMA/MMA
  • Much less pulpal and soft tissue irritancy from residual monomer
  • Good handling properties
  • Not brittle, a ductile material. PMMA/MMA is a brittle material
  • BM is a non-volatile monomer. MMA is a volatile monomer
26
Q

What are light (or RT) cured dimethacrylates used in

A

Composite filling materials as well as temp crown and bridge materials

27
Q

Name some general properties of HEMA (which can be used in acrylics)

A
  • Low viscosity liquid

- Hydrogel that absorbs a shit load of water.

28
Q

What are the uses of HEMA

A
  • Unsuccessful as a soft lining material

- Used in eg RMGICs and Dentine Bonding Agents

29
Q

What are cyanoacrylates used for in dentistry

A
  • Non-suture wound repair material
  • Periodontal surgery
  • Adhesive for dentine, endo cements etc

Dental Materials Y3 (9 decks)

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