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What are the three cartilage types?
- 1) Articular - Lines joins and provides bearing surface.
- 2) Elastic - Ribs
- 3) Fibro - Provides shape and stiffness (ears)
Explain how articular cartilage works.
The cartilage is filed with MPS which have negative points where water can weakly bind. This makes a hydrogel (Synovial fluid) which behaves elastically under fast loading and flows under slow loading (Thixotrophy).
What two materials are bone made out of?
- 1) Collagen for tensile loading with
- 2) discrete nano-sized Hydroxapetite for compression and crack propagation prevention.
What are the main parts of the tooth?
- 1)Enamel (95% Mineral) Hard and brittle
- 2)Dentin (Bone without cells)
- 3)Pulp (Nerves and blood supply)
What are the basic bone structures?
- Plate bones - Pelvis, skull, shoulder blade, sternum
- Long bones - Femur, tibula
- Specialize - ear
- Long bones are made up of
- i) Cancellous (Spongy) bone
- ii) Cortical (Compact) bone
What did John Curry's study show?
The amount of mineralization in bone has a large effect on its properties.
Both stiffness and strength increase with increasing mineralization, but toughness has a maximum around 67%.
What are the three types of bone samples?
- Longitudinal - Highest stiffness and toughness
- Transverse - Medium stiffness and toughness
- Radial - Lowest stiffness and toughness
**Attributes are best along osteon axis and worst across osteon axis.
What is the effect of rate on bone loading?
As the loading rate increases the bone becomes brittle and plastically deforms less before fracture.
What is Wolfs law?
The structure of a bone reflects the load placed on it. If load changes bone will remodel.
What are the two types of joints?
- Synovial - Move allot and have a cavity (knee, hip)
- Synarthrosis - No cavity and move little (Skull)
What are the two types of impact fixation?
- 1) Bone cement - Fast, bone necrosis
- 2) Porous ingrowth coating - Takes a long time, hard to remove
What are the two types of stresses we looked at in FEA?
- 1)Von-Misses - Not good for brittle material.
- 2)Strain energy density - Good for bone