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With the formation of the glassionomers one wanted to combine the major qualities of the silicate cement, the composite resins and the polycarboxylate cement. The greatest advantages are bonding to tooth structure, the release of fluorides and thereby an inhibition of secondary caries, and a thermal coefficient similar to tooth structure. The glassionomers are more compatible to the pulp than the old silicates. The bonding to tooth structure is increased through pretreatment where polyacrylic acid is most recommendable. Today there are two major types of glassionomers: the water-based which contain freeze-dried acid in the glass powder, and the original, determined by the addition of an aqueous solution of polyacrylic acid to the glass powder. Certain types are delivered in premeasured capsules for mechanical blend, which decreases the sensitive handling of the material. The use of glassionomers serves a number of purposes and will properly be more widespread in the future, especially the concern of lining in combination with composite resins, the metal-reinforced to crown-buildup and the luting types, when the considerations about earlier hypersensitivity after luting of castings is clarified. The restorative types shows better promising results than composite resins in Class V restoration.