5 Written Questions
5 Matching Questions
- Compressive stress
- Tensile strength for:
a. Dental porcelain
c. Resin-based composite
e. Alumnia ceramic
- When a metal had been stressed beyond its proportional limit, the hardness and strength of the metal ________ at the area of deformation.
- a 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
- b Relative ability of a material to deform physically under a <b>tensile</b> stress before it fractures
- c a. increases
although ductility of the metal ↓↓
- d Force per unit area acting on the external surface of a material.
- e Ratio of compressive force to cross-sectional area prependicular to the axis of applied force.
5 Multiple Choice Questions
- Ultimate strength
- Resistance of a material to plastic deformation typically measured under an indentation load.
- Relative inability of material to deform plastically
- a. low impact
5 True/False Questions
Shear stress is calculated by dividing the force by the area ________ to the force direction.
b. parallel → b. parallel
brackets for braces is a good example
From mechanical property point of view, why isn't it a good idea to burnish amalgam, composites, ceramics and nonresin luting agents? → because they have <b>low</b> or <b>zero</b> percent elongation.
Units of Modulus of elasticity → Giganewtons per square meter (GN/m²), or gigapascals (<b>GPa</b>)
How does polshing of brittle material help their strength? →
by comparing the <b>area</b> underneath the elastic region.
↑ the area = ↑ resilience
Stress vs. force →
Stress = Force / area
stress units - MPa