5 Written Questions
5 Matching Questions
 The __________ of a material is defined as the average level of stress at which a material exhibits a certain amount of initial plastic deformation or at which fracture occurs in test specimens of the same shape and size.
 How does polshing of brittle material help their strength?
 Name three properties that are related to heardness:
 Strain
 Three types of stress in dentistry:
 a
Change in length per unit initial length.
Units are in %  b strength
 c 1. Compressive strength
2. proportional limit
4. ductility  d flaws on the surface are associated with higher stresses than are flaws of the same size in interior regions. Thus surface finishing of brittle materials such as ceramics, amalgams, and composites is extremely important in areas subjected to tensile stress.
 e 1. tensile stress
2. shear stress
3. compressive stress
5 Multiple Choice Questions
 Relative inability of material to deform plastically
 b. dentin is tougher!
the more flexible material is the tougher it is. enamel is brittle  Deformation that is recovered upon removal of an externally applied force or pressure.
line below which the material will NEVER fail under an
infinite amount of cycles: IDEAL!!!! 1. the stress intesntiy at these flaws increases with the length of the flaw, specially when it is oriented prependicular to the direction of tensile stress
2. flaws on the surface are associated with higher stresses than are flaws of the same size in interior regions.
5 True/False Questions

which tooth structure has the hgiher <b>propotional limit</b> and <b>modulus of elasticity</b>?
a. enamel
b. dentin → Proportional limit 
True stress → Ratio of applied force to the actual crosssectional area; however, for convenience stress is often calculated as the ratio of applied force to the initial crosssectional area.

For brittle materials that exhibit only elastic deformation and can sustain no plastic deformation, stresses at or slightly above the ________________ result in fracture. → ↑ elastic modulus
↓ resilience/springiness 
Three common methods for measurement of ductility: → Compressive <b>stress</b> within a compression test specimen at the point of fracture.
note: compressive stress Ratio of compressive force to crosssectional area perpendicular to the axis of applied force. 
Materials with a high elastic modulus have:
a. high strength values.
b. low strength values. → b. dentin is tougher!
the more flexible material is the tougher it is. enamel is brittle