Conventional glass-ionomer cement

Resin-modified glass-ionomers, like their conventional counterparts, are capable of releasing fluoride [224,264,265], and in greater amounts under acid conditions than neutral ones [265], Release rates and release profiles have been shown to be comparable with those from conventional glass-ionomer cements [264,265], Other ions have also been shown to be released by these materials and, as for fluoride, these ions show a greater release under low pH conditions [265], However, the level of phosphorus released has been shown to be much lower from resin-modified glass-ionomers than from conventional ones [263], This suggests that there is little or no possibility of association of fluoride as monofluorophosphate, but rather that almost all of the fluoride is released either as the free fluoride ion or as alumino-fluoride complex ions. 

A.D. Wilson, R.G. Hill, C.P. Warrens, B.G. Lewis, The influence of polymer molecular weight on some properties of glass-ionomer cements, J. Dent. Res. 68 (1989) 89-94. M.A. Farced, A. Stamboulis, Nanoclay addition to conventional glass-ionomer cements influence on properties, Eur. J. Dent. 8 (2014) 456-463. 

M.A. Fareed, A. Stamboulis, Nanoclay addition to a conventional glass ionomer cements influence on physical properties, Eur. J. Dent. 8 (2014) 456-463. 

Table 7.1 Effect of OT aiiic compounds on the working and settii times of a water-activated conventional glass-ionomer cement...

In this section, three aspects of the interaction of resin-modified glass-ionomers with water are dealt with, namely water uptake, fluoride release and other ion release and its associated buffering effect. Like conventional glass-ionomer cements, resin-modified glass-ionomers are deployed in an essentially wet environment and their behaviour in terms of each of these features differs more or less from that of conventional glass-ionomers, due to the presence of the polyHEMA phase. These are considered in turn. 

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]. 

M.F. Costa Cabral, R.L. de Menezes Martinho, M.V. Guedes-Neto, M.A.B. Rebelo, D.G. Pontes, F. Cohen-Cameiro, Do conventional glass ionomer cements release more fluoride than resin-modified glass ionomer cements Restor. Dent. Endod. 40 (2015) 209-215. 

Studies have been made of the inclusion of two possible substances to enhance the bioactivity of conventional glass-ionomer cements, hydroxyapatite [7] and bioglass powder [8]. Both were found to reduce the speed of the setting reaction of the cement, with the reduction being greater with larger proportions of additive. In all cases, the set cements were consistently weaker than those with no additive (Table 8.1). This result has also been found with completely inert powders, such as borax [9]. 

Table 8.1 Effect on mechanical properties and setting behaviour of hydroxyapatite incorporated into a conventional glass-ionomer cement [7]...

Enhanced bioactivity conventional glass-ionomer cement... 

Table 8.2 Weight percentage composition of glasses in various commercial conventional glass-ionomer cements... 

From the and T MAS-NMR spectra, it was apparent that the adjunct filler was substantially hydroxyapatite rather than fluorapatite. The diminution in the P peak due to orthophosphate was taken to indicate that this apatite filler was undergoing a reaction with the polymeric acid, and contributing to setting. This reaction has not been observed previously when synthetic hydroxyapatite was included in a conventional glass-ionomer cement [7], though reaction of poly(acryUc acid) with other calcium phosphate minerals has been observed previously [25]. 

Table 8.3 Knoop hardncss values for glass carbomer and conventional glass-ionomer cement [27]...

Yesilyurt, C. et al. (2008) Bond strengths of two conventional glass-ionomer cements to irradiated and... 

Typical properties of conventional glass-ionomer cements... 

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. 

Clinical studies have shown that ART is an effective treatment in a variety of countries of the world (Frencken et al. 2004). Modern conventional glass-ionomer cements for use with this technique have been formulated with optimized particle size and size-distribution glass powders, and they are found to perform very well in patients. Long survival times are being recorded, with almost no problems of debonding in clinical service. 

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