Glass Ionomer Cements Flashcards
Why is the SiO2 to Al2O3 ratio important in the GIC powder composition?
The ratio governs reactivity
Which components in the GIC powder composition are important for radiopacity? (3)
- Sr2+
- Ba2+
- La3+ (lanthanum)
Which components in the GIC powder composition boost fluoride release? (3)
- Na3AlF6
- AlF3
- NaF
Which components in the GIC powder composition provides phosphate release? (2)
- P2O5 (Phosphorus pentoxide)
- AlPO4 (Aluminium phosphate)
At what temperature is the ion leachable glass melted at?
1150 – 1450°C
Describe the process of acquiring the cement version of the ion leachable glass (4)
- Melted at high temperature
- Rapid cool
- Grind into a powder
- Acid wash to control reactivity
What is the liquid composition of GIC?
- 50% Polyacryclic acid (PAA)
- 10% Tartaric acid
- 40% Water
What are the 3 stages of the GIC setting reaction?
- Dissolution phase
- Gelation phase
- Final Maturation
What occurs during the dissolution phase of the GIC setting reaction?
H+ ions from the PAA attack the glass liberating Ca2+ and Al3+
What other ions are released/formed during the dissolution phase of the GIC setting reaction? (3)
- Na+ released
- F- released
- Released silicon forms Si(OH)4
What happens to the liberated Ca2+ and Al3+ during the dissolution stage of GIC setting?
Ca2+ and Al3+ will be in the form of complexes with F- or tartaric acid
What is the benefit of tartaric acid in GIC?
They “hold” the cement forming ions (increasing working time) until the acid is partially neutralised
How does the GIC set in phase 2 occur?
- Polymer chain entanglement
- Cross-linking of the chains by: Ca2+ & Al3+
What do Ca2+ & Al3+ form in the gelation stage of GIC setting? (2)
- Hydrated Calcium
- Aluminium polyacrylates
How long can the final maturation stage of GIC setting take?
Can take 24 hours
What occurs during the final maturation stage of GIC setting?
- Ratio of bound to unbound water increases
- Strength increases
What occurs during early water exposure to GIC?
- Result in dissolution of reactive components
- Poor cement properties
What occurs during dehydration to GIC?
- Loss of water critical for the continuation of the setting reaction
- Poor cement properties
Explain the fluoride release from GIC
- Initial high level release from exposed glass particles
- Long term lower level release from deeper areas of the matrix
What can GIC release for caries inhibition? (3)
- F-
- Sr2+
- Ca2+
Comment on the biocompatibility of GIC
- Bioactive
- Low irritant despite low pH
What are some advantages of GIC? (7)
- 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
What are some disadvantages of GIC? (2)
What affect does age have on these?
- Weaker than composites and amalgam but strength increases with age
- Poor wear resistance at the early stage, improves with age
What are some uses of GIC? (6)
- Restorations for anterior teeth
- Tunnel restorations
- Luting
- Cavity lining
- Repair of erosion lesions
- Fissure sealant
