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Dental Materials Y2 > Glass Ionomer Cements > Flashcards

Glass Ionomer Cements Flashcards

(44 cards)

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1
Q

What is the main component of GIC powder

A

Ionomer (ion leachable) glass

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2
Q

What are the 3 major basic components of GIC powder

A

SiO2
Al2O3
CaF2/SrF2

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3
Q

What governs the speed of reactivity of GICs

A

SiO2 : Al2O3 ratio

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4
Q

What ions can be used to add radiopacity

A

Sr2+
Ba2+
La3+

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5
Q

What can be used to boost fluoride release in GICs

A

Na3AlF6
AlF3
NaF

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6
Q

What can be used to provide phosphates in the GICs powder

A

P2O5

AlPO4

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7
Q

What temperatures do the GICs melt at to allow them to form

A

1150-1450C

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8
Q

After melting how is the GIC obtained

A
  • Rapidly cooled in ice water
  • Grind into a powder
  • Acid wash to control reactivity
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9
Q

What is the major component of the liquid component of GICs

A

Polyacrylic acid (PAA) - aqueous solution - usually about 50% conc.

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10
Q

What other acids can be used in the liquid component of GICs alongside PAA or in the place of PAA

A

Copolymers - itaconic acid

Polycarboxylic acids - Polymaleic acid

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11
Q

What other acids are usually in the liquid component of GICs

A

Tartaric acid - 10%

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12
Q

How are the acids in the liquid component of GICs converted into powder

A

Acids are freeze dried and the usually mixed with the GIC powder

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13
Q

What is the main difference between Acrylic acid and the Itaconic and Maleic carboxylic acids

A

The number of Carboxyl groups for each C=C bond in the acid, Acrylic acid has one and Itaconic and Maleic have 2 per double bond

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14
Q

What kind of reaction allows the setting of GICs

A

Acid base chemical reaction

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15
Q

What is the first stage of the acid base setting reaction for GICs and describe it

A

Dissolution stage - H+ ions from polyacid attack the glass, liberating Ca2+, Na+ and Al3+

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16
Q

Where are the protons lost from in the polyacrylic acid molecule that are used to attack the glass

A

Lost from the COOH group when they are dissociated and put into solution

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17
Q

What form are the Ca2+ and Al3+ ions released in, in the dissolution stage

A

Released in the form of complexes with F- or tartaric acid

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18
Q

What form is silicon released in

19
Q

How does tartaric acid increase working time for GICs

Study These Flashcards
A

They hold the cement forming ions until the acid is partially neutralised then the insane released and give a sharp set

20
Q

What is the second stage of the GIC setting reaction

Study These Flashcards
A

Gelation and Hardening stage

21
Q

How does the setting in the gelation and hardening stage occur

Study These Flashcards
A

Occurs by polymer chain entanglement and cross linking of the chains by: Ca2+ (initial set) and Al3+ (final set)

22
Q

Describe the features of Calcium polyacrylates

Study These Flashcards
A

As Ca2+ is a mobile ion its gives weak bonding and a water soluble polyacrylate

23
Q

Describe the features of Aluminium polyacrylates

Study These Flashcards
A

As Al3+ is a less mobile ion it gives a strong bond and insoluble polyacrylate

24
Q

How does Gelation occur

Study These Flashcards
A

Calcium ions link 2 carboxyl groups between 2 PAA molecules via an ionic bond - gives gel like consistency

25
Describe how hardening happens
Aluminimum ions are trivalent so can cross link 3 carboxyl groups and that eventually leads to the hardening of the cement
26
What is the 3rd stage of the GIC setting reaction
Final Maturation - Ratio of bound to unbound water increases - Strength increases and this can take 24 hours
27
AY BAWS CAN I HABE DE NOTE PLZ
The cement needs to be protected immediately after placement
28
What can be found in the structure of a GIC
- Cross linked polyacrylic acid matrix - Unreacted glass that acts as a filler - The border between the glass and matrix = silica gel--
29
What can early water exposure cause to GICs
Early water exposure will result in dissolution of the reactive components (cross linking ions)
30
What can dehydration of GICs cause
Leads to loss of water that is critical for the continuation of the setting reaction
31
What is done before the GICs are placed to prepare the tooth surface
Tooth surface is conditioned before GIC placement with PAA solution of 10-30% to remove smear layer and make surface chemically active
32
What bond forms between the GICs and tooth
Chelation of Ca2+ from hydroxyapatite with the COO- from the PAA = strong ionic bond
33
What other bonds can occur
Hydrogen bonding with amino groups e.g. in collagen
34
Describe the levels of fluoride release from GICs
Initially is high from the exposed glass particles | Decreases over time but happens for a long time from the unreacted glass
35
What does fluoride do in the oral cavity
Inhibits deminerlisation | Uptakes by dentin and enamel to become more acid resistant
36
What other ion exchanges from GICs helps to inhibit caries
Sr2+ and Ca2+
37
How are GICs low irritant despite their low pH
H+ movement is restricted as the high molecular weight polymeric anion
38
What are some of the advantages of used GICs
- Chemical bond to tooth (as opposed to mechanical) - Long term fluoride release and uptake - No shrinkage, No exotherm and no free monomers - Self healing and can be repaired, uptake of Ca2+ and PO4,3- from saliva onto the surface - Potential to remineralise - Thermal expansion coefficient similar to tooth - Aesthetics
39
What are the some of the disadvantages of using GICs
- Weaker than composites and amalgam but strength increases with age - Poor wear resistance at the early stage, improves with age
40
What are the uses of GICs
- Restoration of anterior teeth - Tunnel restorations - Cavity lining, base under amalgam and composites - Repair of erosion lesions and fissure sealants - With composites in the sandwich technique - Luting/cementing and repair materials for crown and bridge prostheses
41
Describe the delivery of Powder and liquid GICs
- Read instructions - Shake the bottle, scoop the powder, remove the excess - Dispense the liquid drops, no squeezing the liquid bottle - 2 increments of powder - Mix quickly, typically 20 secs
42
Describe the delivery of encapsulated GICs
- Read instructions - Shake the capsule - Activate the capsule by pushing the plunger inside the capsule - Spin (mixing) it in the amalgamator, typically 10-15secs - Dispense via the delivery gun
43
How are high viscosity GICs different to conventional GICS
- Designed for Atraumatic restorative treatment - Improved compressive strengths - High molecular weight acids - boost compressive strengthes - Higher fluoride release - Finer particle size powder accelerates initial setting reaction
44
What cause the higher viscosity
Higher powder to liquid ratio

Dental Materials Y2 (13 decks)

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