Adhesion, glass-ionomers advantages

The main line of development now lies with its successor, the glass-ionomer cement, which uses a similar glass, but in which phosphoric acid is replaced by poly(acrylic acid) this cement is more resistant to acid erosion and staining and has the great advantage of adhesion to tooth material. 

The ability of glass-ionomers to form a natural adhesive bond to the surface of the tooth is one of these material s most important clinical advantages. They were originally prepared from poly(acrylic acid), a substance chosen because of its use in the zinc polycarboxylate cement, a material known to adhere to the tooth surface [123]. The advantages of adhesion by these materials were apparent right from the start, when they were used for the repair of cervical erosion lesions and as pit and fissure sealants [124,125]. 

Glass-ionomers have other advantages over composites in this appUcadon, namely that they are hydrophilic and dimensionally stable. Their hydrophilic character enables them to absorb fluid that can be left at the bottom of the fissure without jeopardizing the adhesion to enamel. The dimensional stability is important because it allows the cement to retain its marginal adaption and seal, so that there is no risk of caries developing under the fissure sealing material. Fluoride release is also potentially advantageous. 

The next adhesive repair material to become available to the dental profession was the glass-ionomer cement, which was first described by Wilson and Kent in 1972 (Wilson and Kent 1972). These materials are now used in clinical dentistry for a variety of aspects of the repair of teeth damaged by dental decay. Depending on how they are formulated, they may be used as liners and bases or as full restorations, and they may also be formulated for other clinical uses, as shown in Table 56.5. They are aesthetic in that they match the natural color of the tooth and, like the zinc polycarboxylate cement, they are able to bond directly to the surface of the tooth. They have the additional advantage of being able to release fluoride, which is generally considered beneficial, as it prevents further decay of the repaired tooth. 

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