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 dental materials. However, these alloys undergo a complex setting reaction, and problems of clinical corrosion and fractures of restored teeth have been reported. The purpose of this study was to investigate the use of DSC for study of the setting reaction and microstructural stability of a commercial product (Galloy, Southern Dental Industries, Australia). Specimens (∼20 mg) were prepared with variations in mixing times, condensation techniques, surface conditions and storage times. The DSC analyses were performed from room temperature to 225°C, using a heating rate of 10°C/min. Interpretation of the thermograms was aided by comparison to complementary X-ray diffraction (XRD) patterns of specimens subjected to the same experimental conditions. An exothermic peak was associated with absorption of liquid gallium by the starting Ag–Sn–Cu particles, and four endothermic peaks were associated with the formation of metallurgical phases during setting. The results show the great utility of DSC for study of the present gallium-based alloys and the development of improved alloy compositions.