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Dental Materials Y2 > GICs 2 > Flashcards

GICs 2 Flashcards

1
Q

Describe the powder composition of cermets

A
  • Metal (usually silver) fused to GIC powder then ground into powder together or just mixed with GIC powder (admix)
  • Titanium dioxide (5%) might be added to improve the colour
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2
Q

Describe the composition and delivery of the liquid component fo cermets

A
  • Same as conventional GIC and can be hand mixed or encapsulated
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3
Q

Describe the structure of admix

A

Silver metal and GIC powder

  • Silver = brightest on photomicrograph
  • Matrix = PAA GIC
  • Glass particles
  • Around silver and matrix = gap due to mechanical, not chemical mix
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4
Q

Describe the properties of cermets

A
  • More abrasion resistant and less brittle than conventional GICs
  • Fluoride release and bond strength are reduced
  • Radiopaque
  • Difficult to handle
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5
Q

What uses are there for Cermets

A
  • Cermet/composute laminate technique
  • Linings for amalgam restorations
  • Repair of restoratives
  • Used where aesthetics aren’t super important as they have a silver colour
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6
Q

Describe the liquid composition of Resin Modified GICs (RMGICs)

A
  • PAA + tartaric acid
  • Water compatible vinyl monomer, usually HEMA or elements of vinyl monomers will be chemically grafted into PAA as a pendant methacrylate
  • Photo-initiator system
  • Some Bis-GMA/UDMA
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7
Q

Describe the powder composition of RMGICs

A
  • Ion leachable glass
  • Photosensitiser
  • Similar to conventional GICs
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8
Q

What 2 reactions happen in the setting of RMGICs

A
  • Acid base reaction of the glass ionomer cement

- Photo-initiated polymerisation of the monomer

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9
Q

Describe the structure of the set cement

A

Interpenetrating network of the poly salt matrix entangled with poly (hydroxyethyl methacrylate)

Structure is similar to that of a conventional glass ionomer

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10
Q

What is the matrix of RMGICs made of

A

Cross linked polyacrylic acid matrix and polyhema

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11
Q

What are the advantages of RMGICs

A
  • Less soluble
  • Less brittle
  • Can be polished immediately
  • Fluoride release is similar or higher than conventional glass ionomers
  • Adhesion to tooth
  • Compressive strength
  • Longer working time an rapid set
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12
Q

What are the disadvantages of RMGICs

A
  • Addition of HEMA slows the acid base reaction
  • Depth of cure is less than composites because of the reduced light transmission of the filler
  • Polymerisation exotherm is higher than composites
  • Polymerisation shrinkage
  • Swell in water after curing as PHEMA is a hydrogel
  • Acid base reaction starts on mixing and if not photo cured quickly the properties might be affected
  • Unpolymerised HEMA will leach out resulting in increased cytotoxicity
  • Stain
  • HEMA, BisGMA and PAA can separate in the bottle
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13
Q

What can the tricure RMGIC be cured by

A

Photo cure
Room temp cure
Acid base cure

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14
Q

What chemical components allows tricure RMGICs to set at room temp

A

Ascorbic acid and potassium persulphate

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15
Q

What is the purpose of the tricure RMGIC

A

To eliminate the need for layering in deep cavities

Reduces Swelling

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16
Q

What are the uses of RMGICs

A
  • Cavity lining
  • In the GIC composite laminate technique
  • As an anterior restorative
  • Restorative for deciduous teeth
  • Luting cement
17
Q

What is a PAMC

A

Polyacid modified composite

18
Q

What are PAMCs also called

A

Compomers

19
Q

Describe the powder composition of PAMCs/compomers

A
  • BisGMA/UDMA + visible light curing system
  • Ion leachable fluoroaluminosilicate glass filler + conventional fillers
  • Acidic monomer - bifunctional monomer with pendant carboxylic groups
  • Hydrophilic monomers may bed added to aid water absorption and fluoride release
  • Moisture and light sensitive during storage
20
Q

How does the acidic monomer form

A

The composite monomer has double bonds and carboxyl groups from PAA are added to the monomers.

Therefore the acidic monomer has both C=C and carboxyl group properties and is polymerisable.

21
Q

What is the function of the acid pendant monomer/resin in PAMCs

A

Provides carboxyl groups and is hydrophilic

22
Q

What is the function of the cross linking resins in PAMCs

A

Provides harder and tougher matrix

23
Q

What is the function of fluorosilicate glass in PAMCs

A

Filler and source of fluoride, undergoes acid base reaction

24
Q

What is the function of CPQ/amines in PAMCs

A

Photoinitiator system

25
Q

What is the function of stabilisers in PAMCs

A

Extends the shelf life

26
Q

What does the base resin of GICs form

A

polymerises and forms matrix of cement

27
Q

How does the principle setting reaction of PAMCs happen

A

By photo initiation of the methacrylate groups

28
Q

What allows the acid base reaction to occur after curing of PAMCs

A

Water uptake into the mouth

29
Q

What allows fluoride release in PAMCs

A

the acid base reaction that occurs after curing

30
Q

Describe the properties of PAMC

A
  • Good handling, easy to adapt to cavity walls and do not slump
  • requires dentin bonding agent and incremental placement
  • Shrinkage similar to composite
  • Level of water uptake smiler to composite but rate of uptake is faster
  • Possible compensation for shrinkage, shrinks in volume then can expand back to near normal
  • Inferior mechanical properties compared to composites
31
Q

What are the uses of PAMCs

A
  • used in low stress situations
  • Proximal and abrasion cavities
  • Permanent restorations in primary teeth
  • Long term temporary in permanent teeth
  • More recently as a luting cement
32
Q

Describe the structural difference in Giomers compared to conventional GICs

A
  • Composite resin plus pre-reacted glass ionomer particles as filler
  • Has fluoride release and recharge of GICs with the superior properties of a composite
33
Q

What are boomers used for

A

Restoratives
Luting cement
Fissure sealants

34
Q

Name a couple disadvantages of Compomers for me b xx

A
  • Low level fluoride release post-placement

- requires bonding agent and placed incrementally

Dental Materials Y2 (13 decks)

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