Glass Ionomer Cements are two component systems whose base is made up of powder and liquid. The powder contains particles of calciumaluminofluorosilicate glass and the liquid is a 35-65% solution of copolymer polyalkenoic acid and water (H2O). They adhere to hard tooth tissue through mechanisms of ion-exchange which classifies them as bioactive materials. The setting of the glass-ionomer cements is called an acid-base reaction. Due to their positive characteristics they have wide applications in clinical dentistry. They are used as restorative and adhesive materials due to their adhesive bonding to hard tooth tissue, anticariogenic properties achieved through the release of fluoride, biocompatibility with hard tooth tissue and low toxicity. They are also used for cementing bridges, crowns, inlays and onlays, as well as material for fillings and bases and a fissure sealant. Due to fracture strength and lower resistance to abrasion the use of glass ionomer ements is limited in stress-bearing areas. In posterior dental regions glass ionomer cements are used as temporary fillings. The release of fluoride reduces and prevents the processes of demineralization, and increases the processes of remineralization. In contemporary literature, several ways of classifying glass ionomer cements are used. These include: the traditional classification of GICs, classification according to application and classification according to composition.