The transmission and attentuated total reflectance spectra of a dental cement formed from an aluminosilicate glass and aqueous polyacrylic acid (ASPA) are reported. Interpretation of spectra show that a siliceous hydrogel is formed together with the polyacrylate salts of calcium and aluminum. In the fully hardened cement a minor proportion of -COOH remains unconverted to -COO-groups for steric reasons. Chemical studies on the formation of the glass-ionomer cement, ASPA, show that the setting mechanism can be described as an acid-base interaction between an aluminosilicate body and polyacrylic acid.

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A three-month study of the chemistry of the water erosion of two forms of ASPA cement has been made. The effect of varying cement consistency and cure time was investigated. The results are discussed in terms of the known chemistry and structure of the cement. The erosion behavior is compared to that of silicate, silicophosphate, and zinc polycarboxylate dental cements. The state of absorbed water and the mechanism of erosion is discussed.

WVater-soluble ions in dental cements of different ages were studied. The cement is formed by the reaction between aqueous polyacrylic acid and an aluminosilicate glass.Electrical conductance measurements were made on cements up to three months after formation. Calcium polyacrylate is formed before aluminum polyacrylate. Calcium ions are fully combined within three hours, whereas aluminum ions continue to react for at least 48 hours.Wilson and Kent' have developed a dental cement using the reaction of an aluminosilicate glass and aqueous polyacrylic acid (PAA). Previous papers in this series have reported the initial attack on the glass by PAA2 and an infrared spectrometric study' of the cement reaction. The study of the reaction by chemical and electrical conductance methods is reported in this paper. All the techniques used in this series were developed previously by Wilson and Kent for investigation of the dental silicate cements.4-7Previous studies in this series showed that rapid attack of the powdered glass occurred which resulted in the release of metal cations.2 Considerably more calcium was liberated than other metal ions. The infrared spectrometric studies' showed that there is rapid production of calcium polyacrylate followed by a slower formation of aluminum polyacrylate. Other features of the cement were the presence of silica gel and free COOH groups.In this study, the water-soluble ions were extracted from cements of various ages. Thus, information unobtainable by infrared This work was carried out on behalf of the National Research Development Corporation.

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