5 Written Questions

1. a. increases
   
   although ductility of the metal ↓↓
2. 
   by comparing the <b>area</b> underneath the elastic region.
   
   ↑ the area = ↑ resilience
3. Ratio of applied force to the actual cross-sectional area; however, for convenience stress is often calculated as the ratio of applied force to the initial cross-sectional area.
4. 1. Compressive strength
   2. proportional limit
   4. ductility
5. Resistance of a material to plastic deformation typically measured under an indentation load.

5 Matching Questions

1. Shear stress
2. Units of Modulus of elasticity
3. diametral compression test
4. Why do prostheses sometimes fail under a very small force, even though the strength of the prosthetic material is relatively high?
5. fatigue failure

1. a
   Repeated stresses resulting in fractures. the fracture due to fatigue occurs at stress levels well below tensile strength.
2. b
   a test for tensile strength that is only used for materials that exhibit predominantly elastic deformation and little or no plastic deformation (brittle).
3. c Ratio of force to the original cross-sectional area parallel to the direction of the force applied to a test specimen.
4. d Flaws (could be microscopic)
5. e Giganewtons per square meter (GN/m²), or gigapascals (<b>GPa</b>)

5 Multiple Choice Questions

1. Plastic deformation occurs when the <b>elastic stress limit (proportional limit)</b> within the prosthesis is exceeded.
   1. How can resilience of two materials be compared?
   2. Plastic deformation occurs when the ______________ within the prosthesis is exceeded.
   3. What does the straight line in the strain-stress curve represent?
   4. if stress/strain value is very small the materials are said to be:
2. 1. <b>strain rate</b>
   2. the shape of the test speciment
   3. the surface finish (control flaws)
   4. the environment in which material is tested
   1. Strength depends on what factors: (4)
   2. average biting force
   3. Shear strength
   4. Stress vs. force
3. Compressive <b>stress</b> within a compression test specimen at the point of fracture.
   
   note: compressive stress -Ratio of compressive force to cross-sectional area perpendicular to the axis of applied force.
   1. Compressive stress
   2. Shear strength
   3. Compressive strength
   4. Flexural strength
4. The area bounded by the elastic region is a measure of <b>resilience</b>, and the total area under the stress-strain curve is a measure of<b> toughness</b>.
   1. The area bounded by the elastic region is a measure of ________, and the total area under the stress-strain curve is a measure of ____________.
   2. Toughness increases with increases in _____ and _________.
   3. The fracture toughness of dentin varies by a factor of 3 as a function:
   4. which of the dental restorative materials have the highest resilience?
5. Force per unit area of a material subjected to flexural loading.
   1. Flexural stress (Bending stress)
   2. Compressive stress
   3. Shear stress
   4. Flexural strength

5 True/False Questions

1. A value of 0.3 for Poisson's ratio is typical. Thus, the shear modulus is usually about ___% of the elastic modulus. → composites followed by porcelain, PMMA, amalgam and alumina.

   True        False

2. Stress → Force per unit area within a structure subjected to an external force or pressure (See Pressure).

   True        False

3. Shear stress is calculated by dividing the force by the area ________ to the force direction.
   
   a. perpendicular
   b. parallel → b. parallel
   
   brackets for braces is a good example

   True        False

4. As the interatomic spacing increases, the internal energy increases. As long as the stress is <b>not greater than the proportional limit</b>, this <u>energy</u> is known as__________. → Toughness increases with increases in strength and ductility.

   True        False

5. which of the dental restorative materials have the highest resilience? → composites followed by porcelain, PMMA, amalgam and alumina.

   True        False