5 Written questions
5 Matching questions
- Units of Modulus of elasticity
- ___________represents the ability of a material to sustain a large permanent deformation under a <b>tensile</b> load before it fractures.
- Elastic strain
- Plastic deformation occurs when the ______________ within the prosthesis is exceeded.
- Three types of stress in dentistry:
- a Giganewtons per square meter (GN/m²), or gigapascals (<b>GPa</b>)
- b 1. tensile stress
2. shear stress
3. compressive stress
- c Deformation that is recovered upon removal of an externally applied force or pressure.
- d Plastic deformation occurs when the <b>elastic stress limit (proportional limit)</b> within the prosthesis is exceeded.
5 Multiple choice questions
- b. dentin is tougher!
the more flexible material is the tougher it is. enamel is brittle
- Force per unit area acting on the external surface of a material.
• The <b>stress</b> at which a test specimen exhibits a specific amount of plastic strain (0.2%)
• The YS at 0.2% strain offset from the origin is 1536 MPa in this case.
maximum elastic stress (proportional limit)
5 True/False questions
Poisson's ratio → the ratio of horizontal extension to vertical compression.
Most engineering materials have values of approximately <b>0.3</b>
Shear stress → Maximum shear stress at the point of fracture of a test specimen.
Tensile strength for:
a. Dental porcelain
c. Resin-based composite
e. Alumnia ceramic → a. Dental porcelain → 50-100 MPa
b. Amalgam → 27-55 MPa
c. Resin-based composite → 30-90 MPa
d. Poly → 60 MPa
e. Alumnia ceramic → 120 MPa
the stress above which stress is no longer proportional to strain. → Force per unit area of a material subjected to flexural loading.
Strength depends on what factors: (4) →
Area or point of significantly higher stress associated with a structural discontinuity such as a crack or pore or a marked change in dimension of a structure.