Dynamic loading of dental amalgam and effects upon electrochemistry and microstructure

The stress vs. cycles (S-N) behavior for four amalgams is reported. At 10 cycles/min and for 37 degrees C air and artificial saliva environments, linear regression lines fit the data with high correlations between 10(2) and 10(4) cycles. Significance at 50% exists between the environments and with saliva decreasing failure resistance. The open circuit potential (OCP), the OCP-time transients at constant anodic currents, and the cyclic voltammetry all exhibit changes with loading. With static loading the OCP decreases, while with dynamic loading the OCP exhibits a sinusoidal pattern and a pattern with two maxima and two minima after the loading has progressed and which continues up until failure. The maximum anodic current in voltammetry increases with continual potential cycling (or load cycling), while decreases when performed without loading. The application of anodic currents to the amalgams has, however, not significantly reduced the number of cycles to failure, nor has the application of cathodic currents increased the number of cycles. Rearrangement and coalesence of voids takes place with loading and with microcracking forming preferentially between them. Crack propagation occurs predominantly within the gamma-1 matrix.