Читать книгу Manual of Laboratory Testing Methods for Dental Restorative Materials - Paromita Mazumdar - Страница 18

The behaviour of materials under the action of low but intermittent stresses shows the resistance to fatigue. This method permits measurement of a fatigue limit, with no fracture, at a given number of stress cycles. Compressive fatigue curves are generated when different materials are submitted to cyclic compressive stress. Tests are made with the test machine operation at a given loading frequency. The presence of defects in the microstructure of the restoration or specimen submitted to high or low stresses leads to the development of cracks. As clinical environment influences are critical factors due to the relatively low stress, these cracks will turn into fracture of the material [12] (as shown in Figures 1.10 and 1.11).

Figure 1.10 (a) Tooth sample, (b) crack propagation.

Figure 1.11 Assessment of resistance to fatigue by cyclic compression stress.