Fluoride-containing composite resins

J. Arends, J. Ruben, A.G. Dijkman, The effect of fluoride release from a fluoride-containing composite resin on secondary caries An in vitro study, Quintessence Int. 21 (1990) 671-674. 

Unlike glass-ionomers or compomers, composite resins are not inherently fluoride-releasing and they do not generally contain any fluoride compounds. However, they can be formulated with such compounds [281], for example NaF, YbFs or ion-leachable glass [201]. Organic fluorides can be used, too, such as methacryloyl fluoride-methyl methacrylate (MF-MMA) or tetrabutyl ammonium tetrafluoroborate. These latter substances impart the property of slow release of fluoride to the surrounding tissue without the creation of voids within the material. 

Polyacid-modified composite resins were developed in an attempt to make a composite resin with the sort of ion-release capability of glass-ionomer cements, especially of fluoride [38]. They are similar to conventional composites in that they are mainly based on the hydrophobic monomers bis-GMA or urethane dimethaaylate, and their setting is typically initiated by light. In addition, they contain inert fillers of appropriate particle size. 

One of the properties of glass-ionomer cements that polyacid-modified composite resins are designed to possess is the ability to release fluoride. The reactive glass filler is an ionomer-type glass, and as such contains fluoride. This becomes available for release following its incorporation into the polysalt phase as a result of the moisture driven acid-base reaction with the acid-functional monomer component [1]. 

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. 

Some measurements of this property have been made in a range of electrically conducting polymers. These include epoxy resin/polyaniline-dodecylbenzene sulfonic acid blends [38], polystyrene-black polyphenylene oxide copolymers [38], semiconductor-based polypyrroles [33], titanocene polyesters [40], boron-containing polyvinyl alcohol [41], copper-filled epoxy resin [42], polyethylidene dioxy thiophene-polystyrene sulfonate, polyvinyl chloride, polyethylene oxide [43], polycarbonate/acrylonitrile-butadiene-styrene composites [44], polyethylene oxide complexes with sodium lanthanum tetra-fluoride [45], chlorine-substituted polyaniline [46], polyvinyl pyrolidine-polyvinyl alcohol coupled with potassium bromate tetrafluoromethane sulfonamide [47], doped polystyrene block polyethylene [38, 39], polypyrrole [48], polyaniline-polyamide composites [49], and polydimethyl siloxane-polypyrrole composites [50]. 

Nafion-115, Nafion-112, and Nafion-212 which have thickness of 175 pm, 125 pm, 50 pm, and 50 pm, respectively. These thiimer composite PEMs contain significantly less amounts of the expensive Nafion resin than the thicker neat Nafion membranes. Thus, another advantage of Nafion/PTFE composite PEMs is the fact that they are inexpensive. Besides porous PTFE films, porous films such as polyethylene (PE) [21, 22] and electro-sptm polymer nanofiber films such as those of poly(vinyhdene fluoride) (PVdF) [23, 24], poly(vinyhdene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) [25], and poly(vinyl alcohol) (PVA) [26-31] have also been used as supporting films for impregnating Nafion ionomer solutions to prepare Nafion/fiber composite PEMs for PEMFC and DMFC applications. 

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