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BDS 2: Dental Materials > Glass Ionomer Cements > Flashcards

Glass Ionomer Cements Flashcards

1
Q

Why is the SiO2 to Al2O3 ratio important in the GIC powder composition?

A

The ratio governs reactivity

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2
Q

Which components in the GIC powder composition are important for radiopacity? (3)

A
  • Sr2+
  • Ba2+
  • La3+ (lanthanum)
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3
Q

Which components in the GIC powder composition boost fluoride release? (3)

A
  • Na3AlF6
  • AlF3
  • NaF
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4
Q

Which components in the GIC powder composition provides phosphate release? (2)

A
  • P2O5 (Phosphorus pentoxide)

- AlPO4 (Aluminium phosphate)

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5
Q

At what temperature is the ion leachable glass melted at?

A

1150 – 1450°C

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6
Q

Describe the process of acquiring the cement version of the ion leachable glass (4)

A
  • Melted at high temperature
  • Rapid cool
  • Grind into a powder
  • Acid wash to control reactivity
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7
Q

What is the liquid composition of GIC?

A
  • 50% Polyacryclic acid (PAA)
  • 10% Tartaric acid
  • 40% Water
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8
Q

What are the 3 stages of the GIC setting reaction?

A
  1. Dissolution phase
  2. Gelation phase
  3. Final Maturation
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9
Q

What occurs during the dissolution phase of the GIC setting reaction?

A

H+ ions from the PAA attack the glass liberating Ca2+ and Al3+

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10
Q

What other ions are released/formed during the dissolution phase of the GIC setting reaction? (3)

A
  • Na+ released
  • F- released
  • Released silicon forms Si(OH)4
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11
Q

What happens to the liberated Ca2+ and Al3+ during the dissolution stage of GIC setting?

A

Ca2+ and Al3+ will be in the form of complexes with F- or tartaric acid

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12
Q

What is the benefit of tartaric acid in GIC?

A

They “hold” the cement forming ions (increasing working time) until the acid is partially neutralised

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13
Q

How does the GIC set in phase 2 occur?

A
  • Polymer chain entanglement

- Cross-linking of the chains by: Ca2+ & Al3+

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14
Q

What do Ca2+ & Al3+ form in the gelation stage of GIC setting? (2)

A
  • Hydrated Calcium

- Aluminium polyacrylates

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15
Q

How long can the final maturation stage of GIC setting take?

A

Can take 24 hours

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16
Q

What occurs during the final maturation stage of GIC setting?

A
  • Ratio of bound to unbound water increases

- Strength increases

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17
Q

What occurs during early water exposure to GIC?

A
  • Result in dissolution of reactive components

- Poor cement properties

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18
Q

What occurs during dehydration to GIC?

A
  • Loss of water critical for the continuation of the setting reaction
  • Poor cement properties
19
Q

Explain the fluoride release from GIC

A
  • Initial high level release from exposed glass particles

- Long term lower level release from deeper areas of the matrix

20
Q

What can GIC release for caries inhibition? (3)

A
  • F-
  • Sr2+
  • Ca2+
21
Q

Comment on the biocompatibility of GIC

A
  • Bioactive

- Low irritant despite low pH

22
Q

What are some advantages of GIC? (7)

A
  • Chemical bond to tooth
  • Long-term fluoride release and uptake
  • No shrinkage
  • Self healing and can be repaired
  • Potential to re-mineralize
  • Thermal expansion coefficient similar to tooth
  • Aesthetics
23
Q

What are some disadvantages of GIC? (2)

What affect does age have on these?

A
  • Weaker than composites and amalgam but strength increases with age
  • Poor wear resistance at the early stage, improves with age
24
Q

What are some uses of GIC? (6)

A
  • Restorations for anterior teeth
  • Tunnel restorations
  • Luting
  • Cavity lining
  • Repair of erosion lesions
  • Fissure sealant
25
Q

What are the 2 powder compositions methods of cermets? (2)

A
  • Metal (usually silver) fused to GIC powder then ground

- Metal powder mixed with GIC powder (Admix)

26
Q

What are the delivery systems of cermets? (2)

A
  • Hand mixed

- Encapsulated

27
Q

List 2 advantages and 2 disadvantages of cermets (4)

A
  • More abrasion resistant and less brittle than conventional GICs
  • They are radiopaque
  • Difficult to handle
  • Fluoride release and bond strength are reduced compared to GICs
28
Q

What are some of the uses for cermets?

A
  • Cermet/composite laminate technique
  • Linings for amalgam restorations
  • Repair of restoratives
29
Q

What is the liquid composition for Resin Modified Glass Ionomer Cements (RMGIC)? (5)

A
  • PAA
  • Tartaric acid
  • Hydroxyethyl Methacrylate (HEMA)
  • Bis-GMA
  • Photo-initiator system
30
Q

What is the powder composition for RMGIC? (2)

A
  • Ion-leachable glass

- Photosensitiser

31
Q

Comment on the dual setting of RMGIC

A
  • Acid-base reaction of the glass ionomer cement

- Photo-initiated polymerisation of the monomer

32
Q

What are some advantages of RMGIC? (7)

A
  • Less soluble
  • Less brittle
  • Can be polished immediately
  • Fluoride release is similar/higher than GIC
  • Adheres to tooth
  • High strength
  • Longer working time with a rapid set
33
Q

What are some disadvantages of RMGIC? (6)

A
  • Addition of HEMA slows the acid base reaction
  • Depth of cure is less than composite because less light transmission due to glass
  • Polymerisation exotherm is higher than composites
  • Polymeristaion shrinkage
  • Swell in water
  • Stain
34
Q

What are the uses for RMGIC? (5)

A
  • Cavity lining
  • In the GIC-composite laminate technique
  • As an anterior restorative
  • Restorative for deciduous teeth
  • Luting cement
35
Q

What is the powder composition of Polyacid Modified Composites (PAMC)? (4)

A
  • BisGMA (plus light cure)
  • Ion-leachable fluoroaluminosilicate glass
  • Acidic monomer
  • Hydrophilic monomers
36
Q

How is PAMC set?

A

The principle setting reaction is by photo initiation of the methacrylate groups

37
Q

How is fluoride released by PAMC?

A

After curing, water uptake in the mouth allows the acid/base reaction to occur
Results in fluoride release over an extended period
but at a lower level compared to conventional GIC and RMGIC

38
Q

What releases more fluoride PAMC or (RM)GIC?

A

PAMC releases fluoride at a lower level compared to conventional GIC and RMGIC

39
Q

Comment on the handling properties of PAMC

A

Good handling properties

40
Q

What are some of the uses of PAMC? (4)

A
  • Proximal and abrasion cavities
  • Permanent restorations in primary teeth
  • Long-term temporary in permanent teeth
  • More recently as a luting cement
41
Q

What type of bonding agent is required with PAMC?

A

Require dentine bonding agent

42
Q

Compare PAMC to Composites (2)

Shrinkage?
Mechanical properties?

A
  • Shrinkage similar to composites

- Inferior mechanical properties compared to composites

43
Q

How is PAMC placed in a restoration?

A

Require incremental placement

BDS 2: Dental Materials (13 decks)

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