A preliminary study of the interaction of glass-ionomer dental cements with amino acids

Objectives: The aim of the study was to determine how the presence of low concentrations of the amino acids glycine and alanine affected the interaction of restorative glass-ionomer cements with water. Methods: For each material (Fuji IX and Ketac Molar, both handmixed), sets of six cylindrical specimens of 4 mm diameter×6 mm height were prepared and weighed; then stored individually in one of: deionized water, 0.1% by mass glycine, 0.5% glycine, 0.1% alanine (Sigma Aldrich) and 0.5% alanine. After 1 week, the specimens were re-weighed and the pH of each solution determined. The solutions were then bulked and analyzed for ion content (Na, Ca, Al, Si and P) using ICP-OES. In a separate series of experiments, disks (12 mm diameter×1 mm thick) were prepared, and exposed to similar solutions for periods of a week, after which Vickerʹs hardness was determined. Differences were analysed by one-way ANOVA, followed by Neumann–Keuls post-hoc analysis (P<0.05). Results: All specimens increased in weight, and altered pH of the storage solution to similar values. Both cements released less aluminum, but generally more sodium, calcium and silicon in the presence of amino acids. Little or no phosphorus was found to be released under any conditions. Surface hardness of Fuji IX was not influenced by the presence of amino acids, but for Ketac Molar it was generally lower in the presence of amino acids. Significance: These results show that the interaction of glass-ionomer cements with water is influenced by the presence of low concentrations of amino acids, and that this may alter surface hardness.