توافق أحيائي

• Biomaterials


  Synthetic material used to replace or restore function to a body tissue and is continuously or intermittently in contact with body fluids
• Types of biomaterials by origin


  • Synthetically (Artificially) based
  • Naturally (Biologically) derived

  
• Synthetically (Artificially) based biomaterials


  • Metals
  • Polymers
  • Ceramics
  • Composites
• Naturally (Biologically) derived biomaterials


  • Protein
  • Polysaccharide
  • Gum

  
• Metal biomaterials (Biometal)


  • High mechanical properties (high strength, tough, strong, fatigue & wear resistance)
  • Ductility
  • Easy to sterilize
  • Shape memory
• Metal biomaterials (Biometal)


  • Poor compatibility
  • Stiffness & high modulus
  • High weight (dense)
  • May corrode
  • Difficult to fabricate
  • Metal ion sensitivity & toxicity
  • Metallic looking
• Polymer biomaterials (Biopolymer)


  • Toughness (Resilient)
  • Surface modification
  • Low weight
  • Easy to process (fabricate)
  • Tailorable physical & mechanical properties
• Polymer biomaterials (Biopolymer)


  • Degradability over time
  • Deformability over time
  • Low mechanical strength
  • Absorb water & protein etc
  • Difficult to sterilize
  • Surface contamination
  • Wear & breakdown
• Ceramic biomaterials (Bioceramic)


  • Good biocompatibility
  • Chemical inertness/bio active
  • High compressive strength
  • Wear & corrosion resistance
  • Can be highly polished
• Ceramic biomaterials (Bioceramic)


  • High weight
  • Brittleness
  • High modulus (mismatched with bone)
  • Low tensile strength
  • Not easy (difficult) to process
  • Not tough
  • Low fracture toughness
• Composite biomaterials (Biocomposite)


  • Strong
  • Tailor made
• Composite biomaterials (Biocomposite)


  • Difficult to prepare
• Bioinert biomaterials


  Achieve suitable combination of physical properties with a minimal toxic response in the host, producing thin fibrous capsules surrounding the implant
• Bioactive biomaterials


  Interact with the surrounding bone and in some cases, even soft tissue through an ion-exchange reaction that forms a biologically active carbonate apatite layer
• Bioresorbable biomaterials


  Start to dissolve (resorbed) and slowly replaced by advancing tissue (such as bone)
• Applications of biomaterials


  • Orthopedic (bone)
  • Cardiovascular (heart)
  • Ophthalmology (eye)
  • Oral implants & orthodontic (tooth)
  • Ear
  • Lung (Respiratory)
  • Urinary (kidney and Bladder)
  • Integumentary and Wound healing
  • Nervous
  • Endocrine
  • Drug delivery system
  • Joint replacement
  • Facial implants
  • Vascular graft
  • Reconstructive surgery
• Biocompatibility


  The totality of the interfacial reactions between biomaterials (biomedical device) and tissues of patient body (host) without having any risk of injury, toxicity, or rejection by the immune system and undesirable or inappropriate local or systemic effects
• The human body's immune system is designed to protect it from external attacks including gems (viruses, parasites, bacteria and fungi)
• When an object is incorporated into the body without any immune responses it is said to be biocompatible
• Biocompatibility testing is critical for all classes of medical devices
• Biocompatibility is a very complex matter because there are a very large number of mechanisms by which biomaterials may interact with human tissues, and these interactions may be viewed either in a negative (undesirable) or positive (advantageous) way
• The term "biocompatibility" has to include not only "biological compatibility" but also a functional evaluation of the entire implantable system
• Teflon is biologically compatible but not functionally compatible when used for replacing the temporomandibular joint, as it resulted in large fragmentation and caused huge foreign body giant cell responses that progressively eroded adjacent structures
• Biocompatibility


  1. Mechanisms by which biomaterials may interact with human tissues

  2. Interactions may be viewed as negative (undesirable) or positive (advantageous)
• Biocompatibility


  Includes biological compatibility and functional evaluation of the entire implantable system
• Biologically compatible materials that did not pass the functional check


  • Teflon used for replacing the temporomandibular joint resulted in large fragmentation and caused huge foreign body giant cell responses that progressively eroded adjacent structures
• Highly tumorigenic polymeric plates exhibited lower carcinogenicity after damage, while their fragmentation resulted in almost complete loss of carcinogenicity
• Reactions induced by metals were studied early in the XIX century since metals were exploited at that time
• Corrosion


  The sum of (electro) chemical phenomena that commonly take place in the presence of water and oxygen
• After surgical implantation, all metallic devices are exposed to the attack of the body's structures that act as a defense system, and some metals are oxidized, releasing ions that can be toxic both locally and systemically
• Components of Biocompatibility


  • Beneficial tissue response and the clinically relevant performance
  • Cytotoxicity (systemic and local)
  • Genotoxicity
  • Mutagenicity
  • Carcinogenicity
  • Immunogenicity
• Cytotoxicity


  Ability of chemical means to destroy/damage of living cells (biological system)
• Local toxicity


  Adverse reactions emerging at the application site
• Systemic toxicity


  Adverse reactions appear in an area distant from the application site
• Necrosis


  Cell death
• Apoptosis


  Programmed cell death
• Immunogenicity


  The ability of a foreign substance, such as an antigen, to provoke an immune response
• Allergic reaction


  Can be produced if the organism was previously sensitized to this substance and the concentrations of it vary between subjects
• Genotoxicity


  Toxic (damaging) to DNA
• Genotoxic substances are not necessarily carcinogenic