1. Introduction to DMS Flashcards
Mechanical properties of materials (3)
Forces
Stress
Strain
Types of forces (3)
Compressive
Tensile
Shear
What do forces cause when applied
Change in material shape (stretch/compress, deform, fracture)
Stress calculation
Stress (Pa/Nm2) = force (F) / unit area (A)
YM and rigidity relationship
Greater value of elastic modulus/YM, greater the rigidity (stiffness)
YM calculation
YM (MPa) = stress / strain
Typical biting forces
500-700N (50-70kg)
Definition of tensile force (2)
Grinding/chewing involves the tooth sliding along the surface of the other
Frictional forces are experienced - this is tensile force
(Abrasion involves the tooth grinding/sliding along the opposing tooth surface. The tooth is abraded (loss of material surface layers –> roughened surface))
Why does material need to adhere to enamel
If not, it will be removed by masticatory (shear) forces
Gradual increases in biting forces can cause
Fractures
Reason for most fatigues (2)
Most fatigues are not due to the application of a single load (force)
When repeated loads are applied, small flaws (cracks) in the material grow (propagate), allowing fracture when only a relatively small force is applied
Chemical properties of materials (3)
Setting time
Setting mechanism
Corrosive potential
Physical properties of materials (5)
Viscosity Thermal conductivity Thermal expansion Density Radiodensity
Definition of ideal material properties
Perfect or maximum characteristics of a material
Material failure mechanisms (9)
Fracture Hardness Abrasion Abrasion resistance Fatigue Creep Deformation De-bond Impact