Polysalt matrix

Table 8. The influence of the amount and type of polysalt matrix on the rate of salt uptake by thermally regenerable plum pudding resins...

The glass-ionomer cement is an acid-base cement based on weak polymeric acids and powdered glasses that are basic in character [1], Their setting takes place within water and resnlts in a complex polysalt matrix, formed by chemical reaction of the acidic polymer solntion with the basic glass. The structure also contains a snbstantial amount of nnreacted glass that acts as reinforcing filler [2], In terms of materials classification, this makes them composites, but convention in dentistry is to consider them distinct from composites, and to classify them as cements. 

Formation of at least part of the polysalt matrix from the acid-base components has been shown to reduce the efficiency of the polymerization process [19]. hi a study in which the application of the dental cure lamp was delayed for 20 min following mixing of the cement, the degree of conversion was found to be substantially reduced and the overall rate of polymerization to be lower than in systems that were irradiated immediately after mixing [ 19]. It is worth noting that conversion of HEMA to polymer is never particularly efficient in these systems, and that the maximum reported conversion in this study was only about 60%, and this was for a specific material, namely Fuji II EC (Fig. 7.2). 

Not all cement is based on CS or CA, . A group of cements known as glass ionomer cements (GICs) is used as cements in dentistry. The reaction involves an ion-leachable alumina-silicate glass and an aqueous solution of polyalkenoic acid. The resulting cement consists of glass particles in a polysalt matrix. This is a specialty topic with far-reaching applications. 

F. 8. Rate of salt uptake from 0.02 N salt solution by thermally r nerable plum pudding resins containing the same De-Acidite G and Zeo-K.arb 226 plums, and 30% matrix by weight, as a function of the nature of matrix. Particle size 14-52 mesh, BSS, base resin to acid resin ratio 2 5. (1) ethyl cellulose (2) polysalt (3) crosslinked poly (vinyl alcohol) (4) normal De-Acidite G and Zeo-I b 226 mixed bed... 

A flocculation process. This serves to harvest the bacterial cells, i.e. remove cells from the growth medium, and ultimately to form the support matrix. This stage in the process is achieved by the sequential addition of cationic and anionic polyelectrolytes. The two polyelectrolytes used are capable of forming a polysalt complex and it is believed that this complex structure, in which the bacterial cells are embedded, gives rise to the product s robust physical characteristics whilst allowing the desired enzyme performance. 

Glass + Polyelectrolyte = Polysalt hydrogel + Silica gel (base) (acid) (matrix) (coating)... 

---