Untitled Quiz

Study Notes

Implants are used to recover physical function, specifically mechanical function, of tissues or organs.
Implants are designed to provide physical support, but they do not have other biological functions.

Implant biomaterials are subjected to complex mechanical environments in the body.
Common mechanical properties include Young's modulus, yield strength, ultimate tensile strength, fracture toughness, and elongation at break.
Young's modulus is determined by the chemical bonding of atoms and molecules and is important for predicting how a material will respond to stress.
Other mechanical properties such as yield strength, ultimate tensile strength, fracture toughness, and elongation at break are all influenced by the microstructure of the material.

Elasticity refers to a material's ability to return to its original shape after deformation.
Resilience refers to the amount of energy a material can store during elastic deformation.
Hardness is a measure of the material’s resistance to wear and friction, which is often measured using the Rockwell or Brinnell hardness tests.

It's critical to understand the reasons behind material failure to ensure safe and effective biomaterial use.
The fracture mechanism depends on the working conditions and can be influenced by fatigue, stress corrosion cracking, or a combination of both.
Fatigue occurs when a material undergoes repeated stress cycles, which can lead to progressive structural damage.
Stress Corrosion Cracking is a sudden brittle fracture of normally ductile materials when exposed to tensile stress in a corrosive environment.

Orthopedic implants must possess specific characteristics to function safely and successfully at load-bearing sites:
- No Toxicity: This is synonymous with excellent corrosion resistance.
- Suitable Mechanical Strength: The implant must be strong enough to withstand the forces experienced in the body.
- High Wear Resistance: This prevents wear particles from causing inflammation and loosening of the implant.
- Osseo-integration Ability: The implant must be able to bond with surrounding bone to prevent implant loosening.

Fatigue: A common problem for orthopedic implants. Cyclic loading during activities like walking or running can lead to fatigue.
Fretting Fatigue and Corrosion Fretting Fatigue: Occur due to the combination of cyclic stress and friction in the implant's working environment.
- Fretting Fatigue: Occurs when a foreign body is pressed against a material undergoing cyclic stress, producing oxide debris causing microscopic cracks at the contact site.
- Corrosion Fatigue: A combination of fatigue and corrosion.

Wear is an inevitable problem in joint replacements, leading to aseptic loosening.
Wear particles attract macrophages, which engulf the particles and release enzymes and metabolites that damage the implant.

Osseo-integration is the ability for an implant to bond to surrounding bone, essential for the longevity of permanent orthopedic implants.
Failure to osseo-integrate can lead to fibrous tissue formation around the implant, promoting loosening.
Factors such as surface chemistry, roughness, and topography influence osseo-integration.

The internal environment in the body is harsh for metallic materials, highlighting the need for biomaterial design that addresses mechanical and chemical challenges.