Resin Modified Glass Ionomer Cements
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what is the chemical composition of the powder of RMGIC?
• fluro-alumino-silicate glass • barium glass • vacuum dried polyacrylic acid • potassium persulphate • ascorbic acid • pigments
what is the purpose of potassium persulphate in RMGIC?
redox catalyst to provide resin cure in the dark
what is the chemical makeup of the liquid aspect of RMGIC?
• HEMA • polyacrylic acid with pendant methacrylate groups • tartaric acid • water • photo-initiators
what is HEMA?
water miscible resin
what is the purpose of tartaric acid found in RMGIC?
speeds up the setting reaction
what photoinitiator tends to be found in RMGIC?
camphorquinone
what is different about the setting reaction of RMGI compared to GI?
• on mixing the acid base reaction begins in the same way as GIC • the redox reaction begins • on light activation a free radical methacrylate reaction occurs resulting in a resin matrix being formed • the redox reaction continues for about 5 mins after mixing • acid base reaction continues within the resin matrix for several hours
what are some good properties of RMGI/
• good bond to enamel and dentine • better physical properties (compared to GI because of resin matrix) • lower solubility • fluoride release • better translucency and aesthetics • better handling
some negative properties of RMGIC compared to GIC?
• polymerisation contraction • exothermic setting reaction • swelling due to uptake of water (HEMA is v hydrophilic) • monomer leaching • reduced strength if not light cured
overall, what makes RMGIC superior to GIC?
• better aesthetics • easier to use • stronger
what are advantages of using RMGIC over composite?
• easier to use - fluoride release