Glass carbomer bioactivity

Glass-ionomers not only release ions, but are capable of taking them up. Studies have shown that cements exposed to natural saliva take up calcium and phosphate ions, and develop a surface of significantly increased hardness [121]. Also, when used as pit and fissure sealants, they interact with saliva to form a substance with increased content of calcium and phosphate that is considerably more resistant to cutting with a dental drill than the original material. Under these circumstances, the cement had become transformed into a material with enamel-like optical and mechanical properties [122]. This observation is the basis of the development of glass-ionomer type materials with even further enhanced bioactivity, the so-called glass carbomers, which are discussed in Chapter 8. 

In recent years, a new type of glass-ionomer material has become available that overcomes this problem of the weakening effect of additional fillers designed to enhance the bioactivity of the cement. Known as the glass carbomer , it overcomes the problem of slow setting by specifying the need to cure with the aid of heat from dental cure lamps. 

The components of the enhanced bioactivity conventional glass-ionomer (glass carbomer) are as follows ... 

Enhanced bioactivity conventional glass-ionomers (glass carbomers) are intended for use in the same range of applications as conventional glass-ionomers, ie, liners and bases, full restorations of various types, and pit-and-fissure sealants. Because of their similarity to conventional glass-ionomers, it is considered that these materials wiU prove useful in the restoration of primary dentition [15],... 

There have been pubhcations on the effectiveness of glass carbomer as a pit-and-fissure sealant. In one [16], the study compared glass carbomer with a resin-based sealant in 48 teeth in 24 patients. After 6 months, both materials showed 100% retention and after 12 months, they both showed 75% retention. This showed that in terms of one important requirement of fissure sealants, namely retention, the glass carbomer performed quite well. However, further work is necessary to establish whether the enhanced bioactivity confers any further or longer term benefits by way of caries inhibition. 

The materials are described by the manufacturer as bioactive , but there has been no published information about how this bioactivity is achieved, nor whether it is notably better than that of established resin-modified glass-ionomers. For example, there is no indication about whether the materials contain an additive to promote bioactivity, such as hydroxyapatite, like the glass carbomers. It may be that they are bioactive in just the same way that any member of glass-ionomer family is bioactive, namely because of the ionic composition of the glass and the ability to exchange fluoride. 

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