Like composite resins, these materials are tooth-colored. Ionomers are made from a combination of various materials, including ground glass and acrylic resins. Ionomers are typically used for fillings near the gum line or tooth root, where biting pressure is not a factor. They are more fragile than dental amalgam, however. A small amount of fluoride is released by these compounds in order to facilitate strengthened enamel in the affected area.