Читать книгу Manual of Laboratory Testing Methods for Dental Restorative Materials - Paromita Mazumdar - Страница 33

1 Tensile strength, diametral compression test, compressive strength, flexural strength, resistance to fatigue, hardness, elastic modulus, fracture toughness are the various mechanical properties that are measured in the field of dental material sciences.

2 Universal Testing Machine (UTM) is used for most of the tests with the only difference being that the sample preparations differ for each test. Hardness testing depends upon the material to be tested.

3 The samples are prepared as per ISO standards to get optimum results. Also, the area which is subjected to the force differs due to the size of the stick/blade.

4 Axial forces in a straight line and in opposite directions result in tension in the body of a material, and the resistance of the material to this load is called tensile strength. Nominal value of tensile strength is determined by the equation of load and cross‐sectional area (Kgf/cm2).

5 The diametral tensile strength (DTS) test is useful for materials where information regarding stretching or elongation resistance is required and the failure has to occur along the center of the specimen.

6 Compressive strength is used to test materials which are subjected to occlusally directed forces in the oral cavity.

7 Flexural forces are the forces that generate repeated flexing, bending and twisting of the materials.

8 Resistance to fatigue is the measurement of a fatigue limit, with no fracture, at a given number stress cycles.

9 Hardness of a material gives an indication of the resistance to penetration when indented by a hard asperity.

10 Types of hardness: macro hardness and micro hardness.

11 Macro hardness has force application greater than 50 N, and micro hardness has force application less than 10 N. Macro hardness test is done using Vickers, Rockwell and Brinell hardness tester, whereas micro hardness test is done using Vickers and Knoop hardness tester.