Brian G. Lewis

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.

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.

Glass Ionomer Cement Formulations: I. The Preparation of Novel Fluoroaluminosilicate Glasses High in Fluorine

The preparation of a large number of novel fluorine-containing aluminosilicate glasses is reported along with the properties of cements formed by their reaction to aqueous solutions of poly- (acrylic acid) (PAA).

The Influence of Polyacid Molecular Weight on Some Properties of Glass-ionomer Cements

The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained by treatment of glass-ionomer cements as thermoplastic composites. Many of the concepts of polymer science can be applied successfully in a qualitative way to these cements, including the ideas of entanglements and reptation. Molecular weight of the polyacid had a pronounced influence on setting rate, acid erosion rate, toughness, fracture toughness, and wear resistance. The chain length of the polyacid was found to be an important parameter in formulation of a cement, and the higher the molecular weight, the better the properties. However, in practice the molecular weight is limited by viscosity, and some balance has to be achieved among concentration, molecular weight, and viscosity.

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.

Characterization of glass-ionomer cements: 3. Effect of polyacid concentration on the physical properties

Abstract A study of the effect of the polyacid concentration of the liquid on the physical properties of one formulation of the glass-ionomer cement was made. All the cements were prepared at the same consistency. The required powder: liquid ratio and working time of the cement paste were constant between 28 and 38 per cent w/w polyacid concentration. At higher polyacid concentrations the powder: liquid ratio decreased and the working time increased. Setting time of the cement varied in a complex manner. Both the compressive and tensile strengths of the cement increased linearly over the range of polyacid concentrations studied and the solubility and disintegration fell non-linearly. The work suggests that it is desirable to use a high polyacid concentration.

Zinc Polycarboxylate Cements: A Chemical Study of Erosion and Its Relationship to Molecular Structure

The erosion of zinc polycarboxylate cements by water was studied by chemical techniques. In three months, the elution rate diminished. The erosion pattern of each cement was related to the type of polyacid present in the cement. Relatively large amounts of magnesium were eluted. A mechanism of hydrolysis is proposed.