Chemical classification
GICs are commonly classified into five principal types:
* Conventional Glass Ionomer Cements
* Resin Modified Glass Ionomer Cements (Conventional with addition of HEMA)
* Hybrid Ionomer Cements (Also known as Dual-cured Glass Ionomer Cements)
* Tri-cure Glass Ionomer Cements
* Metal-reinforced Glass Ionomer Cements
Conventional glass ionomer cements
Conventional GlCs were first introduced in 1972 by Wilson and Kent. They are derived from aqueous polyalkenoic acid such as polyacrylic acid and a glass component that is usually a fluoroaluminosilicate. When the powder and liquid are mixed together, an acid-base reaction occurs.
Resin Modified Glass Ionomer Cements
Resin Modified Glass Ionomer Cements are conventional glass ionomer cements with addition of HEMA.
Hybrid Ionomer Cements or Resin-modified Glass Ionomers or Dual-Cured GIC
These combine an acid-base reaction of the traditional glass ionomer with a self-cure amine-peroxide polymerization reaction. These light-cured systems have been developed by adding polymerizable functional methacrylate groups with a photo-initiator to the formulation. Such materials undergo both an acid-base ionomer reaction as well as curing by photo-initiation and self cure of methacrylate carbon double bonds or in other words their acid-base reactions are supplemented by a second resin polymerization initiated (usually) by a light-curing process. For this reason they’re also called Dual-Cured GIC. Developed in 1992 the resin-modified glass ionomer cements in their simplest form are glass ionomer cements that contain a small quantity of a water-soluble, polymerizable resin component. More complex materials have been developed by modifying the polyalkenoic acid with side chains that could polymerize by light-curing mechanisms in the presence of photo initiators, but they remain glass ionomer cements by their ability to set by means of the acid-base reaction.
Modern resin modified glass ionomer cements include Advance, GC Fuji PLUS [1] and Vitremer Luting. Most recent development in this field are the paste-paste resin modified GIC luting cement such as GC FujiCEM [2].
Tri-cure Glass Ionomer Cements
Some systems have also incorporated a chemical curing tertiary amine-peroxide reaction to polymerize the methacrylate double bonds along with the photo-initiation and acid-base ionic reaction. These materials are known as tri-cure glass ionomer cements. The chemical cure component of tri-cure cements has been shown to have a significant effect on their overall strength. Photo-initiated cements cannot be used in cases involving opaque structures such as metal substrates. The resin-modified glass ionomer cements generally have a much lower release of fluoride than the conventional glass ionomer materials.
Metal Reinforced Glass Ionomer Cements or Cermets
Metal-reinforced glass ionomer cements were first introduced in 1977. The addition of silver-amalgam alloy powder to conventional materials increased the physical strength of the cement and provided radiopacity. Subsequently, silver particles were sintered onto the glass, and a number of products then appeared where the amalgam alloy content had been fixed at a level claimed to produce optimum mechanical properties for a glass cermet cement. Nowadays these materials are considered as old-fashioned as the conventional glass ionomer cements have comparable physical properties and far better aesthetics.
The clinical performance of cements is considered to be inferior to other restorative materials, so much so that their use is now discouraged.
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