Conventional glass-ionomer cement types

Resin-modified glass-ionomer cements have been used in Class V cavities, again with much of this use being in primary dentition [94]. For this type of repair, there do not appear to be any advantages of resin-modified over conventional glass-ionomers cements. Both types of material have proved effective in this application [57,102]. 

The clinical technique known as Atraumatic Restorative Treatment (ART) has been developed since the mid-1980s in response to dental clinical needs in Third World countries. It is an important application of adhesive dental materials, specifically conventional glass-ionomer cements, and would not be possible without this type of adhesive material (Frencken et al. 2004). ART involves the removal of carious tooth tissue with hand instruments rather than conventional dental drills. These hand-held instruments are formed as spoon-shaped excavators, and come in graded sizes. 

In addition, compomers contain extra monomers from conventional composites, and these contain acidic functional groups. The most widely used monomer of this type is so-called TCB, which is a di-ester of 2-hydroxyethyl methacrylate with butane tetracarboxylic acid [271]. This acid-functional monomer is a very minor component and compomers also contain some reactive glass powder of the type used in glass-ionomer cements [266]. 

De Moor R, Verbeeck R, Martens L. [Evaluation of long-term release of fluoride by type II glass ionomer cements with a conventional hardening reaction]. Rev Beige Med Dent 1996 51(3) 22-35. 

The term polyacid-modifled composite resin was originally proposed for these materials by McLean et al. in 1994 [6], and was felt to be a more accurate description than the term compomer under which they had been first marketed. The latter word was coined as a hybrid of the terms composite and glass-ionomer , but lacked any indication that the materials in question more closely resembled conventional composite resins than glass-ionomer cements. In particular, they are formulated without any water present, and are substantially hydrophobic, albeit less so than conventional composite resins. Also, despite early claims, they show no inherent adhesion to the tooth surface, and have to be used in association with bonding agents of the type used with conventional composites [1,6]. 

One of the key features of polyacid-modified composite resins is their lack of adhesion to tooth tissnes [5]. This is a feature that they share with conventional dental composite resins, and the contrasts with the behaviour of the glass-ionomer cement. It is further evidence that these materials are essentially composite resins, and have very little of the anticipated hybrid character of composites and glass-ionomers. Bonding therefore reqnires the type of bespoke bonding agents used for conventional composite resins, together with the appropriate preparation of the freshly cut tooth surface [6]. 

Resin-modified glass-ionomer cements have been used for both Class II and Class III restorations in primary teeth [97,98]. Their lower brittleness compared with conventional glass-ionomers make them appropriate for these applications, though composite resin again appears preferred for these types of cavity in permanent teeth [94], Various clinical studies have shown resin-modified glass-ionomers to perform well in these restorations [99,100], and in addition they have been shown to have useful caries inhibition properties as a result of their fluoride release [101]. 

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