Despite many important developments in dental materials and minimally intervention techniques, in many parts of the world, most restorations tend to continue to be of a traditional form, and the material most widely used in dentistry is still amalgam. The drawbacks of amalgam as a restorative material are the presence of postoperative tooth sensitivity, susceptibility to fracture of the restored teeth, microleakage and high incidence of development of secondary caries. The reason for most of the drawbacks is due to its inability to bond adhesively to the dental substrates.
Varga et al. in 1986 first suggested the idea of applying adhesives to the walls of the cavity preparation prior to the condensation of amalgam. Current adhesive materials such as Panavia 21 and Amalgabond Plus are resins that contain bifunctional molecules that have an affinity for metal at one end and an affinity for monomers at the other end. Wilson and Kent first introduced glass ionomer cements (GIC) in 1972.It is suggested that glass ionomers could bond chemically to metal oxides like Silver and Tin oxides.Because silver and tin are the major components of amalgam, the bond between GIC and amalgam is expected to be high.
Glass ionomer has been widely advocated as a protective lining under permanent restorative materials. However, few studies have been performed on the use of glass ionomer to bond amalgam. Primarily, resins have been used for bonding amalgam.Chen et al. compared restorative glass ionomer and resin to bond amalgam, and stated both to be equally effective in bonding amalgam.The use of glass ionomers can provide advantages like decreased microleakage and postoperative sensitivity while increasing resistance to fracture of both tooth and amalgam as compared with unbonded amalgam restorations. Several different glass ionomers are presently used in restorative dentistry.