Setting of dental polyelectrolyte cements--viscosity studies of model systems

In order to gain information on the setting of dental cements, the influence of Ca2+, Mg2+, Zn2+, and Al3+ ions on the viscosity of concentrated solutions of partly neutralized poly(carboxylic acids) has been measured. The increase in viscosity with increasing cation concentration was semi-quantitatively interpreted in terms of chain growth and branching due to intermolecular bridging of the carboxylate groups by the metal ions. The concentration of cation required to produce gelation was considerably greater than expected and may be due to the wastage of cations by the formation of intramolecular links. The incorporation of tartrate ion into the polyacid solution retarded the reaction between Al3+ and the polyacid and may explain some features of the setting of glass ionomer cements.