GICs 2 Flashcards
Describe the powder composition of cermets
- Metal (usually silver) fused to GIC powder then ground into powder together or just mixed with GIC powder (admix)
- Titanium dioxide (5%) might be added to improve the colour
Describe the composition and delivery of the liquid component fo cermets
- Same as conventional GIC and can be hand mixed or encapsulated
Describe the structure of admix
Silver metal and GIC powder
- Silver = brightest on photomicrograph
- Matrix = PAA GIC
- Glass particles
- Around silver and matrix = gap due to mechanical, not chemical mix
Describe the properties of cermets
- More abrasion resistant and less brittle than conventional GICs
- Fluoride release and bond strength are reduced
- Radiopaque
- Difficult to handle
What uses are there for Cermets
- Cermet/composute laminate technique
- Linings for amalgam restorations
- Repair of restoratives
- Used where aesthetics aren’t super important as they have a silver colour
Describe the liquid composition of Resin Modified GICs (RMGICs)
- PAA + tartaric acid
- Water compatible vinyl monomer, usually HEMA or elements of vinyl monomers will be chemically grafted into PAA as a pendant methacrylate
- Photo-initiator system
- Some Bis-GMA/UDMA
Describe the powder composition of RMGICs
- Ion leachable glass
- Photosensitiser
- Similar to conventional GICs
What 2 reactions happen in the setting of RMGICs
- Acid base reaction of the glass ionomer cement
- Photo-initiated polymerisation of the monomer
Describe the structure of the set cement
Interpenetrating network of the poly salt matrix entangled with poly (hydroxyethyl methacrylate)
Structure is similar to that of a conventional glass ionomer
What is the matrix of RMGICs made of
Cross linked polyacrylic acid matrix and polyhema
What are the advantages of RMGICs
- Less soluble
- Less brittle
- Can be polished immediately
- Fluoride release is similar or higher than conventional glass ionomers
- Adhesion to tooth
- Compressive strength
- Longer working time an rapid set
What are the disadvantages of RMGICs
- Addition of HEMA slows the acid base reaction
- Depth of cure is less than composites because of the reduced light transmission of the filler
- Polymerisation exotherm is higher than composites
- Polymerisation shrinkage
- Swell in water after curing as PHEMA is a hydrogel
- Acid base reaction starts on mixing and if not photo cured quickly the properties might be affected
- Unpolymerised HEMA will leach out resulting in increased cytotoxicity
- Stain
- HEMA, BisGMA and PAA can separate in the bottle
What can the tricure RMGIC be cured by
Photo cure
Room temp cure
Acid base cure
What chemical components allows tricure RMGICs to set at room temp
Ascorbic acid and potassium persulphate
What is the purpose of the tricure RMGIC
To eliminate the need for layering in deep cavities
Reduces Swelling
What are the uses of RMGICs
- Cavity lining
- In the GIC composite laminate technique
- As an anterior restorative
- Restorative for deciduous teeth
- Luting cement
What is a PAMC
Polyacid modified composite
What are PAMCs also called
Compomers
Describe the powder composition of PAMCs/compomers
- BisGMA/UDMA + visible light curing system
- Ion leachable fluoroaluminosilicate glass filler + conventional fillers
- Acidic monomer - bifunctional monomer with pendant carboxylic groups
- Hydrophilic monomers may bed added to aid water absorption and fluoride release
- Moisture and light sensitive during storage
How does the acidic monomer form
The composite monomer has double bonds and carboxyl groups from PAA are added to the monomers.
Therefore the acidic monomer has both C=C and carboxyl group properties and is polymerisable.
What is the function of the acid pendant monomer/resin in PAMCs
Provides carboxyl groups and is hydrophilic
What is the function of the cross linking resins in PAMCs
Provides harder and tougher matrix
What is the function of fluorosilicate glass in PAMCs
Filler and source of fluoride, undergoes acid base reaction
What is the function of CPQ/amines in PAMCs
Photoinitiator system
What is the function of stabilisers in PAMCs
Extends the shelf life
What does the base resin of GICs form
polymerises and forms matrix of cement
How does the principle setting reaction of PAMCs happen
By photo initiation of the methacrylate groups
What allows the acid base reaction to occur after curing of PAMCs
Water uptake into the mouth
What allows fluoride release in PAMCs
the acid base reaction that occurs after curing
Describe the properties of PAMC
- Good handling, easy to adapt to cavity walls and do not slump
- requires dentin bonding agent and incremental placement
- Shrinkage similar to composite
- Level of water uptake smiler to composite but rate of uptake is faster
- Possible compensation for shrinkage, shrinks in volume then can expand back to near normal
- Inferior mechanical properties compared to composites
What are the uses of PAMCs
- used in low stress situations
- Proximal and abrasion cavities
- Permanent restorations in primary teeth
- Long term temporary in permanent teeth
- More recently as a luting cement
Describe the structural difference in Giomers compared to conventional GICs
- Composite resin plus pre-reacted glass ionomer particles as filler
- Has fluoride release and recharge of GICs with the superior properties of a composite
What are boomers used for
Restoratives
Luting cement
Fissure sealants
Name a couple disadvantages of Compomers for me b xx
- Low level fluoride release post-placement
- requires bonding agent and placed incrementally
