Conventional Bioactive Glasses

An alternative route to the production of bioactive glasses is to use low temperature processing methods including Sol-Gel Technology. Materials can be prepared from colloidal powders and simple molecular alkox-ide precursors. The glass phase originally forms as a gel that can subsequently be dried by supercritical methods or conventional heating to moderate temperatures of... 

Fig. 12.14 Mechanical parameters calculated by nano-indenta-tion tests for a conventional sol—gel glass and two different bioactive star gels with analogous Ca/Si molar ratio.

The alternative tooth-coloured material, the glass-ionomer cement, has also been widely studied, especially in terms of its bioactivity. This arises from its ability to exchange ions with its surroundings when placed in the mouth. Typical conventional glass-ionomers have been shown to release sodium, silicon and phosphorus under neutral conditions, and also calcium and aluminium under acidic conditions [48]. The non-metals are assumed to be released as sihcate, Si03 ", and phosphate, PO/, respectively. In addition, they release fluoride [49], a process that is capable of continuing for several years [50]. 

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]. 

Enhanced bioactivity conventional glass-ionomer cement... 

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

One study has compared two physical properties of the enhanced bioactivity conventional glass-ionomer with those of a well-established brand of conventional glass-ionomer, Fuji IX (GC Corporation, Leuven, Belgium) [27]. Properties studied were Knoop Hardness, tested 20min after setting, and microshear bond strength on both sound and caries-affected dentine. The latter test was carried out after storing the specimens in water at 37 C for 24h. 

Clinical uses of enhanced bioactivity conventional glass-ionomers... 

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],... 

Biocompatibility and bioactivity are outstanding properties on their own. Several glass ceramics have been developed which show high biocompatibility or bioactivity but which are not machinable with conventional metal-working tools [1.47]. 

Bioactive mesoporous particles have also been found to have hemostatic (blood clotting) properties and have emerged as a potential rapid clotting agent for large wounds such as battlefield injimes [4]. More conventional wound healing materials tend to be in the form of fiber mats or textiles and glasses can now also be made in that form. 

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