Stephen Crisp

Reactions in Glass Ionomer Cements I. Decomposition of the Powder

The initial stages of the reaction between the glass ionomer cement powder and polyacrylic acid solutions (aluminosilicate polyacrylate cement) are described. Polyacrylic acid rapidly decomposes the ion-leachable powder, possibly aided by some metal comPlex-forming function. The amount of fluoride extracted, which is related to its molecular condition in the glass, is of considerable importance.

Reactions in Glass Ionomer Cements: II. An Infrared Spectroscopic Study

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.

Characterization of glass-ionomer cements

Abstract An investigation has been made of the relationship between the powder:liquid ratio and the properties of glass-ionomer cements. Four types of this cement were studied. An increase in the powder:liquid ratio led to increases in stiffness of mix, setting rate, compressive strength, superficial hardness and resistance to aqueous attack. It is concluded that the highest powder:liquid ratio compatible with convenient mixing and adequate working should be used.

Reactions in Glass Ionomer Cements: III. The Precipitation Reaction:

Water-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.

Characterization of glass-ionomer cements: 6. A study of erosion and water absorption in both neutral and acidic media

Abstract The erosion and water absorption of several glass-ionomer cements, a zinc polycarboxylate cement and a dental silicate cement were compared both in neutral and acid solution. The glass-ionomer cements showed the greatest initial water uptake, but this trend did not continue. Both soluble and insoluble erosion products are formed and the proportion of each depends both on the nature of the cement and the test media. The glass-ionomer cements are least affected by acid solutions.

Glass Ionomer Cements: Chemistry of Erosion

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.

Characterization of glass-ionomer cements. 1. Long term hardness and compressive strength.

Abstract A study of the long term hardness and compressive strength of three variants of glass-ionomer cement is reported. It was found that hardness was between the values for a dental silicate cement and a zinc polycarboxylate cement and was substantially at its maximum at 24 hours. Cements stored in water increased their compressive strength with age and after 1 year appeared to be attaining ultimate strength. Samples stored in paraffin were stronger than the water-stored ones, and the compressive strength was continuing to increase at 1 year.

Properties of improved glass-ionomer cement formulations.

Abstract The properties of variants of the ASPA cement are described. Improved manipulative and hardening properties are obtained by the incorporation of chelating co-monomers to the polyelectrolyte liquid and by replacing polyacrylic acid by alternative polyalkenoic acids.

Reactions in Glass-Ionomer Cements: IV. Effect of Chelating Comonomers on Setting Behavior

The effect of the addition of chelating comonomers, to the polyacid liquids, on the setting characteristics of the glass-ionomer cement system is described. Certain acid chelating agents significantly improve the setting behavior of the system.

Glass-ionomer Cement Formulations. II. The Synthesis of Novel Polycarboxylic Acids

The synthesis of many polycarboxylic acids is reported. An account is given of their stability in aqueous solution and the properties of cements formed by their reaction with ion-leachable glasses. A copolymer of acrylic and itaconic acids was found to combine several favorable characteristics.