Current Biomaterials

Question 1

Four types of biomaterial the body responds to

Answer 1

• Biotoxic
• Bioinert
• Bioactive
• Bioresorbable

Question 2

Biotoxic - material and reaction

Answer 2

Materials: cadmium, vanadium, carbon steels, carbides
Reaction: atrophy, pathological change or rejection of living tissue

Question 3

Bioinert - material and reaction

Answer 3

Material: tantalum, titanium, aluminium oxide and zirconium oxide
Reaction: Coexistence of material without noticeable change, separation from material by layer of fibrous tissue

Question 4

Bioactive - material and reaction

Answer 4

Material: high density hydroxyapapatite, calcium phosphates, some bioglasses
Reaction: formation of biochemical bonds with surface of material and free growth

Question 5

Bioresorbable - material and reaction

Answer 5

Material: tricalcium phosphate, porous hydroxyapapatite, some bioglasses

Question 6

Physical properties of metals
- properties of bone implants

Answer 6

Metals:
- positive ions surrounded by sea of free electrons
- can conduct heat and electricity
- non directional bonds - plastically deformable
Bone implants:
- strong to support loads of bone
- ductile to avoid catastrophic failure - failure won’t happen as quickly as brittle fracture
- material can be replaced during failure process
- malleable to be machines easily

Question 7

Polymers characteristics

Answer 7

• cheap
• lightweight
• easy to shape
• flexible and tough
• resistant to chemical attack
• low stiffness and strength - E = 1GPa
• high coefficient of thermal expansion
• degrade when exposed to uv light and oxygen

Question 8

Homopolymer
Copolymer

Answer 8

Homo: Consists of one type of monomer unit
Co: Made up of more than one type of monomer unit

Question 9

Thermoplastic vs thermoset

Answer 9

• thermoplastic can be heated, cooled and reshaped without changing chemical structures - melt at high T
  -amorphous and semicrystalline
• thermoset is irreversibly cured
  
  • amorphous

Question 10

Amorphous vs crystaline polymers

Answer 10

Amorphous have random orientation of polymer chains whereas crystaline polymers form highly ordered crystal structures within amorphous matrix

Question 11

Ceramics
- definition, characteristics

Answer 11

• Ceramics are solid inorganic compounds with various combinations of ionic or covalent bonding
• more complex crystal structures than metals
• highly inert
• hard and brittle
• high compressive strength
• good insulators
  Light

Question 12

Physical properties of ceramics

Answer 12

• high melting points
• chemically stable at high temperatures
• high elastic modulus
• high hardness
• brittle
• sensitive to microcracks
• high compressive strength