Resin Modified Glass Ionomer Flashcards
What are the different types of resin modified glass ionomer
Self cured
Light cured
Why was RMGIC developed
To overcome the shortcomings of conventional GIC and combine the advantages of it such as bonding to tooth and fluoride release with the advantages of composite such as light curing, improved physical properties and better aesthetics
What powders can be found in RMGIC
Fluro-alumino-silicate glass Barium glass Vacuum dried polyacrylic acid Potassium persulphate Ascorbic acid Pigments
Why is barium glass used in RMGIC
Provides radiopacity
Why is potassium persulphate used in RMGIC
Redox catalyst to provide resin cure in the dark
What liquids are used in RMGIC
HEMA
Polyacrylic acid with pendant methacrylate groups
Tartaric acid
Water - allows reaction between poly acid and glass
Photo-initiators - enables light curing
What are the different types of setting reactions in RMGIC
Dual curing
Tri curing
Describe dual curing
The acid base reaction begins in the same way as conventional GIC
On light activation a free radical methacrylate reaction occurs resulting in a resin matrix being formed
Light activation is complete (20s)
Acid base reaction continues within the resin matrix for several hours
How should RMGIC be placed and why
In increments as it is quite opaque, so light doesn’t penetrate deeply into the material
What is the outcome of the redox reaction within the setting reaction
It produced free methacrylate radicals which allows the RMGIC to set in the dark
Describe tri curing
Acid base reaction begins in the same way as conventional GIC
The redox reaction begins
On light activation a free radical methacrylate reaction occurs resulting in a resin matrix being formed
Light activation is complete (20s)
The redox reaction continues for about 5 minutes after initial mixing
Acid base reaction continues within the resin matrix for several hours
Final hardening of the acid/base phase with aluminium polyacrylate formation can take days
Describe the advantageous properties of RMGIC
Good bond to enamel and dentine
Superior bond strength than conventional GIC
Better physical properties due to the resin matrix
Lower solubility
Flouride release
Better translucency and aesthetics
Better handling
Describe the disadvantageous properties of RMGIC
Polymerisation contraction
Exothermic setting reaction
Swelling due to uptake of water - HEMA is extremely hydrophilic
Monomer leaching - HEMA is toxic to the pulp it must be polymerised completely
Reduced strength if not light cured
Benzoyl iodides and bromides can be released which are cytotoxic
How does light curing affect the acid base reaction
Light curing slows down the acid base reaction
How is RMGIC’s flouride release compared to conventional GIC
Flouride release is no better
