5 Written questions
5 Matching questions
- average biting force
- in most cases fracture occurs because of the _____ stress component.
- 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.
- Elastic modulus
- Compressive stress
- a 756 N
- b b. tensile
- c Ratio of compressive force to cross-sectional area prependicular to the axis of applied force.
- d strength
- e Relative stiffness of a material; ratio of elastic stress to elastic strain
5 Multiple choice questions
- Relative inability of material to deform plastically
Tension would develop on the occlusal half where as compression would develop in the gingival half.
however, the <b>elastic modulus</b> is always a constant. never changes! it describes material's <b>relative</b> stiffness.
- 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 ratio of horizontal extension to vertical compression.
Most engineering materials have values of approximately <b>0.3</b>
5 True/False questions
Shear strength → Maximum shear stress at the point of fracture of a test specimen.
the stress above which stress is no longer proportional to strain. → Proportional limit
Strength depends on what factors: (4) → 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
Three types of stress in dentistry: →
a test for tensile strength that is only used for materials that exhibit predominantly elastic deformation and little or no plastic deformation (brittle).
When a metal had been stressed beyond its proportional limit, the hardness and strength of the metal ________ at the area of deformation.
b. decreases → Proportional limit