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Yr 3 Restorative - biomaterials and CSL > GIC's > Flashcards

GIC's Flashcards

1
Q

What’s in a GIC filler?

A

SiO2
CaF2
Al2O3

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2
Q

What are fillers for GICs?

A

Glass of silica and alumina in a calcium fluoride flux

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3
Q

What is a flux?

A

A material with a lower melting temperature is mixed with the other components = melts and binds together all other components = then ground down = even mix

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4
Q

What are the minor components of GICs?

A

Sodium aluminium fluorides

Calcium or aluminium phosphates

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5
Q

What are the function of the minor components?

A

Fluxes

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6
Q

Why is tartatic acid in a GIC?

A

Chelates calcium = snap set (initially retards setting reaction after 90 seconds = accelerated setting)

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7
Q

What are the polyacids in a GIC?

A

Polyacrylic acid or co-polymer of acrylic and itaconic acids or acrylic and maleic acids

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8
Q

Whats the function of polyacids in a GIC?

A

Form a matrix in which filler particles are embedded

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9
Q

What is the function of water?

A

Setting reaction is aqueous ( has to procede in the presence of water)

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10
Q

Setting of a GIC occurs via?

A

Polymer cross linking

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11
Q

What are the stages of setting of a GIC?

A
  1. Dissolution = addition of water removes protons from molecule = carboxyl groups, ions attack glass particle = dissolution of outside layer = frees Al, ca & Na ions to interact & an aqueous silica gel
  2. Gellation = formation of calcium bridges
  3. Hardening = Calcium bridges replaced by aluminium = trivalent (occurs over hours)
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12
Q

Are GIC filler particles coated with Silane?

A

NO (would stop the GICs behaviour)

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13
Q

What is silane and what is it used with?

A

Silane makes composites hydrophobic filler and hydrophobic matrix compatible with each other

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14
Q

What properties would you typically asociate with a GIC?

A
  • Fluoride release from the restoration (although ultimately still not a conclusive body of evidence that this release decreases secondary caries)
  • Negligible shrinkage or expansion on setting (if any = minimal so no issues like cuspal flexure)
  • No limit to depth of cure by particle size and shade (NOT light cured)
  • More moisture tolerant (but excessive fluids still compromise the bind and mechanical properties)
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15
Q

Which bonding do GICs form to the tooth structure?

A
  1. Hydrogen bonding to collagen
  2. Ionic bonding to hydroxyapatite (Ca)
    n. b. there may also be an intermediate layer of polyacrylate and free Ca, PO4 ions
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16
Q

What is the bond strength of GICs?

A

2-7 MPa

17
Q

Where does bond failure in GICs occur?

A

Within the glass ionomer (not in the resin)

18
Q

Which GIC do we use in BDH?

A
  • “nano” glass ionomer = restorative, especially abrasion lesions, deciduous teeth, cavity liner and blocking out undercuts
  • luting cements = permanent, suitable for ortho = fluoride release
19
Q

Variations of GICs: Diamond products =

A

Polyposphonic & Polyacrylic acid

-> claims faster reaction with immediate saliva resistance

20
Q

Whats in a compomer?

A
  • Fluoride glass fillers like those in a GIC
  • Resin monomers like those in a composite
  • Special resins with acid groups (-COOH) to aid the reaction with fillers
21
Q

What changes in compomers between brands?

A

Whats in a compomer

22
Q

What is the main resin of Compomers?

A

UDMA = resin monomers = provides H+ ions

23
Q

What are the filler particles in compomers?

A

Fluoride glass = silica, alumina, CaF

24
Q

What does containing hydrophilic monomers allow for?

A

Allows the release and migration of fluoride ions

25
Q

What is the initiator in a compomer?

A

Camphiquinone (Blue light = releases radicals)

26
Q

What is the principal setting mechanism for compomers?

A

Mainly polymerisation (blue light) but also cross linking of polymers (GIC) over several days

27
Q

How do compomers typically compare with GICs in terms of flioride release?

A 
Traditionally = less fluoride release by compomers and cant be recharged by toothpastes etc.
Modern = less fluoride release by compomers but can be recharged
28
Q

Do compomers exhibit setting shrinkage?

A

Yes = polymerisation (blue light)

29
Q

Do compomers have a limited depth of cure?

A

Yes (blue light initiator)

30
Q

What is the main mechanism of adhesion for compomers?

A

Requires a bonding agent/ adhesive (its own adhesion is insufficient)

31
Q

What other properties are associated with compomers?

A
  • Generally inferior mechanical properties to composites
  • Nit used for heavy load-bearing applications
  • Can exhibit excessive expansion due to water absorption
32
Q

What are Resin modified GIC’s like?

A

More of a GIC than a composite

33
Q

What are the components of a resin modified GIC?

A
  • Contains polyacids of GIC
  • Glass filler
  • Resin = must be water soluble (GIC setting is aqueous reaction and to allow ion movement)
    n. b. quite a variable composition between brands
34
Q

Tell me more about the resin component of resin modified GIC’s:

A 
Often Haema (water soluble)
= needs camphiquinone to provide free radicals for setting reaction, polyacid molecules may have pendant methacryloxy groups for further polymerisation linkages
35
Q

How do GIC’s and resin modified GICs (RMGIC) compare?

A

Curing: both light cured
Compressive, tensile and bond strength: smaller in GICs
Working time: better in resin modified (like resin)
Adhesion: in both (better than compomer) although variation from material to material = follow instructions
Fluoride release: similar
Setting shrinkage: resin modified only
Depth of cure: an issue in resin modified only
Resistance to acid attack and dessication: more so in resin modified

36
Q

Are resin modified GICs light cured?

A

YES!!

37
Q

When are resin modified GICs used?

A

Similar applications to GICs

Yr 3 Restorative - biomaterials and CSL (16 decks)

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