Zinc polyacrylate cement

Nicholson, J. W., Brookman, P. J., Lacy, O. M., Sayers, G. S. Wilson, A. D. (1988a). A study of the nature and formation of zinc polyacrylate cement using Fourier transform infrared spectroscopy. Journal of Biomedical Materials Research, 22, 623-31. 

Certain oxides of divalent metals, those of ZnO, CuO, SnO, HgO, and PbO, form cements that are hydrolytically stable in addition MgO, CaO, BaO and SrO form cements that are softened when exposed to water. Compressive strengths of these materials range from 26 to 83 MPa, the strongest being the copper(II) and zinc polyacrylate cements (Table 5.1). Crisp, Prosser Wilson (1976) found that for divalent oxides the rate of reaction increased in the order... 

Lawrence, L. G., Beagrie, G. S. Smith, D. C. (1975). Zinc polyacrylate cements as alloplastic bone implant. Journal of the Canadian Dental Association, 41, 456-61. 

Peters, W. J., Jackson, R. W. Smith, D. C. (1974). Studies of the stability and toxicity of zinc polyacrylate cements (PA2). Journal of Biomedical Materials Research, 8, 53-60. 

X-ray diffraction shows that both the cement matrix and the salt are amorphous (Wilson, 1982 Smith, 1971 Steinke et al., 1988). On the basis of chemical analysis, Wilson (1982) assigned the following empirical formula to the zinc polyacrylate salt ... 

He compared the infrared spectra of cements with that of zinc polyacrylate salt and found differences. Inspection of his data shows that, unlike the cements, the salt was purely ionic, so that it seems here that cement formation is associated with the formation of coordination complexes. There are no ligand field stabilization effects with the Zn ion because it has a completed d shell (Cotton Wilkinson, 1966). For this reason the... 

Abramovich, A., Kaluza, J. J., Macchi, R. L. Ribas, L. (1977). Enamel surface treated with zinc polyacrylate dentine cements. Journal of Dental Research, 56, 471-3. 

Beagrie, G. S., Main, J. H. P. Smith, D. C. (1972). Inflammatory reaction evoked by zinc polyacrylate and zinc eugenate cements a comparison. British Dental Journal, 132, 351-7. 

Powers, J. M., Johnson, Z. G. Craig, R. G. (1974). Physical and mechanical properties of zinc polyacrylate dental cements. Journal of the American Dental Association, 88, 380-3. 

Glass ionomer cements have now largely replaced zinc phosphate cements [14]. They are based on ground glasses made with similar components to the above, which are mixed with polycarbox-ylic acids such as polyacrylic acid, immediately prior to use. Superior adhesion to both dentine and tooth enamel are claimed. The aluminosilicate glass formulations may sometimes include a phosphate component. 

Zinc polycarboxylate was the first of the adhesive dental restorative materials to be described. It was invented by Smith (1968) who reported that it was fabricated from aqueous polyacrylic acid and deactivated zinc oxide, and that it had excellent adhesion to both dentin and enamel. It was also found to have other desirable properties. For example, it set rapidly with minimal shrinkage, it was bland toward the soft tissues of the mouth, and it was almost completely insoluble in saliva (Smith 1968). Zinc polycarboxylate cement can thus be considered a major development in the field of adhesive dentistry. Typical properties of zinc polycarboxylate cement are shown in Table 56.4. 

In 1968 Smith (4) replaced phosphoric acid by poly(acrylic acid) to give the zinc polycarboxylate cements, and in 1971 Wilson and Kent (5) reported a cement formed by the reaction between an ion-leachable glass and an aqueous solution of poly(acrylic acid). They termed this material the glass-ionomer or ASPA cement. (ASPA is the acronym of Alumino Silicate PolyAcrylic Acid). The cement-forming mechanism may be represented as a reaction between two pol3nners to form a third which acts as a cementing matrix ... 

Silvey, R. G. Myers, G. E. (1976). Clinical studies of dental cements. VI. A study of zinc phosphate EBA-reinforced zinc oxide eugenol and polyacrylic acid cements as luting agents in fixed prostheses. Journal of Dental Research, 56, 1215-18. 

A notable apphcation of polyacrylic acid is for cements in dentistry. These are made by mixing an aqueous solution of the polymer with zinc oxide when the zinc salt precipitates as a highly cross-linked gel that rapidly sets to a hard mass under oral conditions. In a variation of this reaction, the zinc oxide is replaced with a tooth-colored glass powder that releases Al and Ca ions. These cements, called ASPA (aluminosihcate polyacryhc acid) or glass ionomer, set very rapidly, bond well to tooth enamel, and are compatible with hving tissue. 

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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