Glass ionomers or “giomers” are resin composites used in restorative dentistry to save the teeth from decay and damage. These materials release fluoride and resemble our natural tooth color. A number of applications in the field of dentistry have been identified for which these materials can be effectively used. After their introduction in 1972, many types of glass ionomers have been produced which can be used for different purposes. Giomers are actually a combination of the original glass ionomers and composite materials. They are also known as resin-modified glass ionomers which can be used for filling and bonding.
There are five types of glass ionomers which have been classified according to their physical and chemical properties. These types are, conventional glass ionomer cements, resin-modified glass ionomers, hybrid ionomers, tri-cure glass ionomers, and metal-reinforced glass ionomer cements. Dentists prefer hybrid and resin-modified glass ionomers over traditional ionomers because they set faster and have high viscosity. A number of other factors can be considered when making a choice among different types of giomers available out there. In some types of ionomers finer glass particles are used which make them better suited to a number of applications. A high powder-to-liquid ratio is another desirable property in glass ionomers.
Resin-modified and hybrid glass ionomers are light-cured systems in which the acid-base reaction is supported by resin polymerization for faster setting. They are also known as dual-cured glass ionomer cements because of this reason. These giomers are popular for their strength and translucency. Light-activated hybrid glass ionomers are superior to the conventional ones because of their setting properties. It has also been found that hybrid materials are more radiopaque than other types of glass ionomers. Many of the resin-modified glass ionomers save time and are ideal for patients who are intolerant of treatments that take a long time to complete.
Another benefit of hybrid and resin-modified glass ionomers is that they are available in a number of esthetic shades. Furthermore, they are prepared according to the triple curing technology which includes self-curing, light curing and glass ionomer curing. Some giomers are selected based on their excellent mechanical properties, while others are chosen due to their good physical properties. Tri-cure glass ionomers are the strongest of all giomers because they are prepared by incorporating a third polymerization reaction in addition to the acid-base and photo-initiation reactions. They can be used in cases where opaque structures are involved.
Metal-reinforced glass ionomers are prepared by adding silver-amalgam alloy powder to the conventional giomers to increase radiopacity and physical strength. These materials have very low esthetic value and therefore are not widely used in dental procedures. The final color of all these types of glass ionomers depends on the polishing technique used by the dentist. Some of them tend to discolor after a period of time; however, all of them have incomparable physical strength and high retention rate. Some disadvantages of glass ionomers include abrasion, sensitivity to water during setting stage, and less esthetic appeal than traditional resin composites.