Biomaterials In The Human Body And Tissue Engineering Flashcards
Anatomical structure of tooth
Enamel - hard outer coating which is wear resistant
Dentine - core structure that is tough and resilient
Pulp - nutrition, sensory and repair system (odontoblasts make dentin)
Cementum - anchorage site for periodontal ligament
Periodontal ligament - load absorbing and distributing membrane
Material selection for modern dentures
- Polymethylmethacrylate
- Perspex, plexiglass
- tough, shatter resistant polymer variant of glass
- cheap and chemically resistant
- Metal coated with ceramic
- mitigates problems with toughness of ceramic and plasticity of metal
Material selection of modern tooth fillings
- composite resin
- matrix (normally photocurable polymer), filler, coupling agent
- glass ionomer
- matrix of polyacrylate, filler of glass particles
Metal corrosion and factors in body that lead to it
- continued oxidation of metal to metal oxides,
hydroxides or other compounds - known as redox reaction
- tissue fluid contains: water, oxygen, proteins, ions, chloride and hydroxide
Redox reactions
- oil rig
- anode oxidation - loss of electrons
- cathode reduction - gain of electrons
In corrosion:
M -> M+ + e- (oxidation of metal to form metallic cations)
02 + 2H2O + 4e- -> 4OH- (reduction of oxygen)
Mechanism of corrosion
- materials have tendency to reach lowest free energy
- alloys, hydroxides, sulphides have negative free energy of formation and are thermodynamically favoured over pure metal
- metal atoms ionise and combine with oxygen
- propensity of metal to oxidise is given by electrochemical series
Objective of tissue engineering
- repair, regenerate or replace damaged or diseased tissues to their original state and function
- generate natural tissues in sufficient quantity and of desired shape that are structurally and functionally equal or better than the tissue
Tissue engineering procedure
- human stem cells taken from patient
- cells are proliferated and differentiated
- cells are attached to a scaffold
- extracellular matrix is laid down to give a biocomposite
- tissue is implanted
Cell sources for tissue engineering
- mature cells from patient - nullipotent
- adult, mesenchymal stem cells from patients bone marrow - multipotent
- umbilical cord blood stem cells - hematopoietic multipotent
- embryonic stem cells - pluripotent
- induced pluripotent stem cells
Nullipotent vs multipotent vs pluripotent
Nullipotent - can only differentiate into its own cell type
Multipotent - can differentiate into a limited number of cells of closely related lineage
Pluripotent -can differentiate into 3 germ layer cells, endoderm (gastrointestinal, stomach lining and lungs), mesoderm (muscle, bone, blood), ectoderm (epidermal tissues and nervous tissues)
Advantages and disadvantages of adult cells for tissue engineering
+ : easily obtained from patient, no need for immuno suppression
- : only used for autologous tissue transplants, poor growth, difficult to get enough cells, tendency to turn into unwanted cell types
Functions of the skin
- sensor system
- thermal control system
- protection
- maintains shape and enables movement
Layers of the skin
- epidermis: surface layer, tough, stiff, physical barrier
- keratinocytes: stem cells that generate epidermal cells and keratin
- dermis: collagen fibres and fibroblasts that help bind epidermis, blood vessels, hair roots, sebaceous glands, nerves
- hypodermis: looser connective tissue, insulating and cushioning, larger blood vessels, fatty tissue
Layers of the skin
- epidermis: surface layer, tough, stiff, physical barrier
- keratinocytes: stem cells that generate epidermal cells and keratin
- dermis: collagen fibres and fibroblasts that help bind epidermis, blood vessels, hair roots, sebaceous glands, nerves
- hypodermis: looser connective tissue, insulating and cushioning, larger blood vessels, fatty tissue
Degrees of burns
1st: only epidermis
2nd: epidermis and part of dermis
3rd: epidermis and dermis destroyed
4th: damage to underlying tissue and nerve endings destroyed
