Polycarboxylates introduction

Earlier formulations contained mainly chlorine bleach, metasiUcates, triphosphate, and nonionic surfactants. Modem manufacturers have switched to more compHcated formulations with disiUcates, phosphates or citrate, phosphonates, polycarboxylates, nonionic surfactants, oxygen bleach, bleach activator, and enzymes. The replacement of metasiUcates by disilicates lowers pH from approximately 12 to 10.5, at 1 g ADD/L water. The combined effect of decreased pH, the absence of hypochlorite, and the trend toward lower wash temperatures has paved the way for the introduction of enzymes into ADDs. Most ADD brands in Europe are part of the new generation of ADD products with enzymes. The new formulations are described in the patent hterature (55—57). 

Polyelectrolyte-based dental cements or restorative materials include zinc polycarboxylates, glass ionomers, a variety of organic polyelectrolyte adhesives as well as alginate-based impression materials. Dental cements are primarily used as luting (cementing) agents for restorations or orthodontic bands, as thermal insulators under metallic restorations, and as sealents for root canals, pits and fissures. They are also sometimes used as temporary or permanent (anterior) restorations. For further introduction to dental materials the reader is referred to standard texts [122,123]. 

Soon after the introduction of convergent dendrimer synthesis, " hemispherical, aryl-ester-coated, benzyl ether-based dendrons were reported. Attachment to a divalent core and conversion to the polycarboxylate 25 (Fig. 5) yielded dendriiners that facilitated a 200-fold increase in pyrene (26) solubility in water eompared with that of pure water without the dendrimer. Notably, use of sodium dodecyl sulfate (SDS above cmc 9 X 10 M) for pyrene encapsulation resulted in only an 100-fold enhancement. 

Another interesting example of Ag(I)-backbone organometallic polymers are those based on diallylmelamine and poly-carboxylates. Silver-vinyl bonding represents a versatile synthon for the construction of polymeric metallosupramolecular architectures. The particular structural motifs result from the introduction of different auxiliary polycarboxylates into the silver/diallylmelamine system and the diverse coordination modes and conformations of diallylmelamine (Fig. 29.3) [108]. Remarkably, apparent silver-vinyl interactions with a ri mode were commonly observed in the solid-state structures of these complexes (Ag-C = 2.311(4)-2.467(5)A). In addition, they display solid-state photoluminescence and moderate thermal stabilities at room temperature. 

One of the most significant advances in chemical analysis as applied to pharmaceuticals during the last decade is undoubtedly the introduction and development of the complexometric titration. The ability of certain amino-polycarboxylic acids to react stoichiometrically and instantaneously with certain metal ions was first recognised and described by Schwarzenbach in 1945. Later, the same author, together with co-workers, described the first metal indicator, murexide, and then, perhaps the most important of all, Eriochrome Black T (usually referred to in this country as solo-chrome black). This was followed quite shortly by the first description of the now classic use of the complexometric titration for the determination of temporary and permanent hardness in water. It was some time, however, before metal indicators capable of functioning at an acid pH were developed with the availability of such indicators a rapid increase in the application of complexometric titrations took place and there are now few metal ions that are not capable of determination by this means. In the present book reference will be found to the use of complexometric methods for determination of aluminium, bismuth, calcium, copper, iron, lead, magnesium, manganese, mercury and zinc. In addition, indirect methods are described for the determination of certain anions such as fluoride, phosphate and sulphate. 

Sometime after its introduction to the dental profession, formulations of zinc polycarboxylate were made available in which the finely divided zinc oxide is combined with a dried powder of polyacrylic acid. The mixture is activated by the addition of an appropriate amount of water, and the whole mass sets rapidly to a solid, hard mass that is indistinguishable from formulations prepared from solutions of pre-dissolved polyacrylic acid. Set cements are opaque, due to the presence in them of considerable amounts of unreacted zinc oxide powder, which acts as a reinforcing filler. 

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