Creep and rupture of dental amalgam under bending stress

The bending creep of six different dental amalgams was continuously measured up to 30 days under different static loads. All six amalgams induced creep rupture within 30 days under 9 kgf of static load and some of them did under the lower static load. The high copper amalgams resisted for a longer period of time compared to the low copper amalgams. The admixed high copper amalgam had the highest creep value at rupture under the same load, which indicates that this amalgam is more flexible under continuous loading than the other amalgams. The rupture time was approximately proportional to the reciprocal of the creep rates and the rupture time drastically increased as the creep rate decreased. This result basically explains and supports the previously reported correlation between the compressive creep during a specific period of time and the marginal fracture of amalgam restorations.