11. GIC + Resin Modified Glass Ionomer Flashcards

1
Q

LOs

A
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2
Q

GIC

What are GICs and what do they exhibit ?

  • they are versatile materials that exhibit?
    (HINT - good properties they exhibit???)
A
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3
Q

GIC

  • have ability to self adhere to tooth so used in range of applications

What applications are they used for?

A
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4
Q

GIC origin - need to know??? Or delete

A
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5
Q

Why is isolation from moisture not really required for GIC compared to dental composites?

A
  • as GIC is a water based cement
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6
Q

GIC

1
Composition?

2
EGs of these components (HINT what acid or glass powder may be used?)

3
From these components, what are the 3 essential ingredients?

A

3
- polyalkenoic acid
- glass powder
- water

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7
Q

GIC composition

  • why is water an important/ main component?
A
  • as water based cement
  • water is essential for the setting of these cements
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8
Q

THE BASE: ION LEACHABLE GAS

1
What does the glass included in GIC formulation function as?

2
Why is this important?

3
What type of glass do commercially available GIC contain?

A

1
- a base

2
This allows the acid-base reaction to occur

3
Fluoro/ alumino/ silicate (FAS)

EXTRA
- the role of glass was first used by Wilson + Kent + recognised the importance of alumina: silicate ratio

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9
Q

THE BASE: ION LEACHABLE GAS

1
What does the basicity of the glass depend on?

2
What would happen if we just used silicate glasses on their own without alumina?

3
Why?

A

1
alumina : silicate ratio

2
- silicate glasses on their own lack the basicity

3
- BECAUSEs it contains sillica tetrahedra that are linked together hence carry no charge
- the inclusion of alumina into the sillica network makes it adopt a tetrahedral geometry similar to sillica to form an alumina tetrahedra

EXTRA Explanation

  • alumina is trivalent + carries a 3+ charge HENCE it does not counteract the negatively charged Oxygens as effectively as sillicone with a 4+ charge
  • hence additives such as sodium, calcium + strontium are included which makes it not only basic but also enhances the ability of these ions to be leached out - which can then take part in the acid-base reaction
  • the substitution of calcium with strontium in these glasses can be achieved using strontium oxide and strontium fluoride in places calcium oxide and calcium fluoride with the glass forming mixed
  • strontium also enhances the radioopacity of these cements
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10
Q

THE BASE: ION LEACHABLE GAS

1
Why are additives such as sodium, calcium + strontium added? Why is this useful?

2
How can the substitution of calcium with strontium in these glasses be achieved?

3
Why is strontium useful?

A

1
- alumina is trivalent + carries a 3+ charge HENCE it does not counteract the negatively charged Oxygens as effectively as sillicone with a 4+ charge

  • hence additives such as sodium, calcium + strontium are included which makes it not only basic but also enhances the ability of these ions to be leached out - which can then take part in the acid-base reaction

2
- by using strontium oxide and strontium fluoride in places calcium oxide and calcium fluoride with the glass forming mixed

3
- strontium also enhances the radioopacity of these cements
- enhances the ability of these ions to be leached out - which can then take part in acid-baser reaction

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11
Q

THE ACID: POLY(ALKENOIC ACID)

1
What acids are used in GIC formulations?

2
Examples of these acids and copolymers (IMAGE)

3
How does the nature of the polymer affect the set cement?

A

1
Polyalkenoic acids

  • these are water soluble polymers that behave as acids

3
- the nature of the polymer influences the properties of the set cement
- use of high molecular weight polymer
= usu better mechanical properties of cement
= BUT there is also an increase in viscosity so harder to mix powder phase with it
- hence a balance is needed for optimum properties

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12
Q

TARTARIC ACID

  • present in nearly all GIC formulations

1
Advantages of GIC containing tartaric acid?/ main func? (IMAGE)

2
How does Tartaric acid extend setting time / how does it work on a molecular level?

3
How do you use GIC/ mix the components in clinic? (DIAGRAM on image)

A

2
- interacts with glass particles + liberates aluminium ions which interact with polymeric acid
- hence aluminium ions aren’t immediately available for reaction with the polymeric acid so working time of cement is maintained

furthermore

  • also inhibits dissociation of polymeric acid hence delaying the onset of the initial setting

3
- have powder + liquid
- one level scoop of powder on polymer paper mixing pad
- add 2 drops of liquid (hold bottle vertically)
- (ensure good drops with no air bubbles)
- mix and use

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13
Q

GIC SETTING REACTION

1
Type of reaction

2
What is produced?

3
Approx setting time?

A
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14
Q

GIC SETTING REACTION

Stages? (IMAGE)

A

EXTRA INFO SAID IN LECTURE FOR STAGE 2 - help with understanding
- on ionisation, polymeric acid molecules adopt a more linear form which makes the carboxylic acid groups more accessible
- hence ions released on interaction of polymeric acid with glass then interact with poly acid molecules to form ionic cross links that causes the gelation
- set cement contains glass particles cores embedded in a poly acid salt matrix
- water is also present both as loose and bound
- loose water can be removed via desiccation
- bound water is chemically trapped within the matrix

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15
Q

GIC SETTING REACTION

SUMMARY OF 3 STAGES

A
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16
Q

GIC
- ratio of powder:liquid is V important

1
Usually supplied as?

2
Potential problems when hand mixing?

3
How is this hand mixing variation being overcome?

4
Why is this useful?

5

A

2
EXTRA
- EG if powder left in bottle for long time, settles at bottom and becomes more compact + dense , so if scoop, would be too much
- hence recommended to turn bottle upside down to loosen powder before dispensing

5
EXTRA
- need to secure mixing devices do not incorporate air bubbles

17
Q

GIC

1
Forms it is dispensed?

2
Other types of cements
+ what type of glass do they contain?

A
18
Q

GIC - AQUEOUS SYSTEMS

  • are aqueous systems
  • water is essential for reaction to take place

1
Water allows what to occur?

2
How does water cause acid-base reaction to occur + how does it cause F- to be released?

A
19
Q

WATER BALANCE IN GICs

  • Water is essential ingredient in setting of GICs

1
What happens if water is absent?

2
How long is the setting reactions

3
the balance of water in the first 24-48 hrs is also V important
Why?

4
What happens if you have excess hydration or a lot of moisture around restoration

5
What happens if dehydration occurs or if Material not given correct amount of moisture?

6
Why may this dehydration occur?

A

1
GIC cannot set + reaction cannot occur

6
- patient is a mouth breather
- patient has dry mouth

20
Q

ADHESION BETWEEN GIC + TOOTH STRUCTURE

  • GIC can adhere to tooth tissue
  • huge clinical advantage
  • exact mechanism of adhesion is not clear
    But what are the suggested 2 theories for mechanism of adhesion?

Make more Q’s??

A

EXTRA DETAIL STATED

THEORY 1
- poly acid molecules curate?? with calcium available on the enamel + dentine surface (shown in diagram)
- the formation of the calcium polyalkenoic salts is similar to the setting reaction of GIC
- has been observed that bond strength is greater between enamel + GIC than dentine + GIC - this could be due to Ca ions in tooth

THEORY 2
- application of a fresh GIC paste, enables a good wetting of the surface of it’s tooth, due to it’s hydrophilicity
- adhesion then occurs as a result of hydrogen bonding between the free carboxylic acid groups of the cement + the bound water on the surface of the tooth
- H bonds are then replaced by ionic bonds that are formed between cations in the tooth (Ca) and anionic functional groups in the cement
- this causes a slow formation of ion exchange layer

  • 2 theories are similar except for stages that have been used to explain
  • during application of GIC - tooth us usually conditioned, this allows the removal of smear layer and partial demineralisation of the tooth surface, thereby increasing the surface area, which allows for micro mechanical attachment
  • BOTH micro mechanical attachment + true ionic bonding contribute to adhesion
21
Q

GENERAL PROPERTIES

1
what are they?

2a
- GIC have inferior aesthics compared to dental composites
Why?
2b
- how can this be overcome?

3
Why is fluoride release a useful property?

A
  • powder : liquid is important factor that determines physical properties
  • hand mixing usu ends in dry, crumbly mix
  • adding water to smooth paste + ease application of GIC adversely affects properties of cement
  • although GIC rapid initial setting, the hardening of cement takes a while
  • important during this phase, the GIC is protected from environment (early contamination of water can adversely affect properties of cement)
  • hence suggested that cements be covered with varnish or resin during first 24hr of setting
  • low solubility - only first 24 hours that protection is needed, once set has very little interaction with environmental moisture
22
Q

GIC - PROPERTIES

1
What important factor determines physical properties?

2
- hand mixing usu ends in dry, crumbly mix
What would happen if you added water to this mix?

3
- although GIC rapid initial setting, the hardening of cement takes a while
3a
- what is important to do during this hardening phase?
3b
WHY?
3c
How may we do this?

A

1
powder : liquid ratio

2
- makes smooth paste + eases application of GIC
BUT
- adversely affects properties of cement

3a
- protect the GIC from environment

3b
- early contamination of water can adversely affect properties of cement

3c
- suggested that cements be covered with varnish or resin during first 24hr of setting

23
Q

MINIMUM REQUIREMENTS OF GIC (set by ISO)

1
Luting cement

2
Restorative cement

A - setting time / min
B - compressive strength / MPa
C - opacity, C0.70

A
24
Q

GIC advantages + disadvantages summary

A
25
Q

RESIN MODIFIED GLASS IONOMER CEMENTS (RMGIC)

  • Similar to GICs

1
Set by what reaction?

2
Release fluoride?

3
Composition?

4
What is HEMA?

A
26
Q

RMGIC

Setting reaction

1
Why does setting primarily occur?

2
Rapid set is due to?

3
What happens after polymerisation occurs?

A

2
EXTRA
- shine light you’re initiating photo polymerisation reaction
- HEMA polymerises + material solidifies

27
Q

RMGIC’s PROPERTIES

1
(Similar to GIC??)(Tensile strength, shear bond strength?)
Advantages compared to GIC?

2
Disadvantage of RMGIC compared to GIC

A
28
Q

RMGICs + GICs

Clinical considerations

(Make Q’s???)

A
29
Q

Although GIC exhibit low solubility after maturation, excessive consumption of acidic or soft drinks can put conventional GIC restorations at some risk

1
Typical pH of common drinks:
- orange juice
- coffee
- Coca Cola
- apple juice
- wine

2
Do RMGICs and GIC exhibit different rates of erosion when subjected to acidic/ soft drinks/ low ph?

A

2
- RMGICs usu exhibit less erosion than GICs when subjected to low pH

30
Q

STUDY

  • Cariostatic effect of using restorative materials in conjunction with dentrifices that are fluoridated and non-fluoridated
A
  • old study
  • shows comparison
  • just by using visual examination, the scores of the cariostatic effect of using restorative materials in conjunction with dentrifices that are fluoridated and non-fluoridated
  • clear from graph that without fluoridated dentrifices, can get much more formation of caries compared to restorative materials that have been used in conjunction with fluoridated dentrifices
31
Q

What are giomers?

A
32
Q

EG of giomer material names

A
33
Q

SUMMARY

1
Use GIC for?

2
2 main advantages?

A