Use of DSC for study of the complex setting reaction and microstructural stability of a gallium-based dental alloy

Gallium-based alloys have been introduced as mercury-free restorative denta l materials. However, these alloys undergo a complex setting reaction, and problems of clinical corrosion and fractures of restored teeth have been re ported. The purpose of this study was to investigate the use of DSC for stu dy of the setting reaction and microstructural stability of a commercial pr oduct (Galloy, Southern Dental Industries, Australia). Specimens (similar t o 20 mg) were prepared with variations in mixing times, condensation techni ques, surface conditions and storage times. The DSC analyses were performed from room temperature to 225 degreesC, using a heating rate of 10 degreesC /min. Interpretation of the thermograms was aided by comparison to compleme ntary X-ray diffraction (XRD) patterns of specimens subjected to the same e xperimental conditions. An exothermic peak was associated with absorption o f liquid gallium by the starting Ag-Sn-Cu particles, and four endothermic p eaks were associated with the formation of metallurgical phases during sett ing. The results show the great utility of DSC for study of the present gal lium-based alloys and the development of improved alloy compositions. (C) 2 001 Elsevier Science B.V. All rights reserved.