CLASSIFICATION OF BIOMATERIALS

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CLASSIFICATION OF BIOMATERIALS

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METALIC BIOMATERIALS

• Crystal structures and strong metallic bonds -
  orthopedic applications
• - the face and jaw surgery
• - cardio-vascular surgery

material joint prosthesis and bone renewal
Dental implant
Artificial heart parts, heart valve
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Metals used as Biomaterials

• Steel
• Cobalt-containing alloys
• Titanium and titanium containing alloys
• Dental amalgam (XHg)
• Gold
• Nickel- titanium alloys

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• Corrosion
• The undesired chemical reaction of metals with
  their surruondings that forms oxygen, hydroxide
  and other compounds then degradation

Corroding Metal X Biocompatible
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Ceramic Biomaterials (Bioceramics)

• The class of ceramics used for repair and
  replacement of diseased and damaged parts of the
  musculoskeletal system are referred to as
  bioceramics.
• OBJECTIVES
• To examine chemical/physical properties of
  ceramics
• To introduce the use of ceramics as biomaterials
• To explore concepts and mechanisms of bioactivity
  

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Ceramics

• (keramikos- pottery in Greek)
• Ceramics are refractory polycrystalline compounds
• Usually inorganic
• Highly inert
• Hard and brittle
• High compressive strength
• Generally good electric and thermal insulators
• Good aesthetic appearance
• Applications
• orthopaedic implants
• dental applications
• compromise of non-load bearing for bioactivity

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BIOCERAMICS

• Bioceramics
• Repair the parts of body that injured or lost
  their function, restructuring or special
  ceramics are designed to replace
• - polycrystalline structure ceramic
  (alumina),
• - bioactive glass,
• - bioactive glass-ceramics,
• - bioactive composites

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Using Areas of Bioceramics

• Glasses,
• Diagnostic devices,
• Thermometers,
• Tissue culture vessels.
• Filling materials,
• Gold-porcelain coating,
• Prosthetic parts

Health Sector
Dental
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Structure

• Ceramic Structure AmXn

ZnS
A metal, ve
CsCl
NaCl
X nonmetal, -ve
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Natures Ceramic Composites

• Natural hard tissues are ceramic-polymer
  composites
• Bones, Teeth, Shells
• Tissue organic polymer fibers mineral
  living cells
• Mineral component (Ceramic)
• Bone hydroxyapatite (HA) Ca5(PO4)3OH
• Mineralization under biological conditions
• Many elemental substitutions
• Protein directed crystallization
• Unique characteristics crystal morphology and
  solubility
• Synthetic calcium phosphates are used as
  biomaterials bioactive

Synthetic HA
Bone HA
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Types of Ceramics
nearly bioinert
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Bioactivity vs. Biocompatibility

• Biocompatibility
• Objective is to minimize inflammatory responses
  and toxic effects
• Bioactivity - Evolving concept
• The characteristic that allows the material to
  form a bond with living tissue (Hench, 1971)
• The ability of a material to stimulate healing
  and trick the tissue system into responding as if
  it were a natural tissue (Hench 2002).
• Advantages Bone tissue implant interface,
  enhanced healing response, extends implant life
• Biodegradability
• Breakdown of implant due to chemical or cellular
  actions
• If timed to rate of tissue healing transforms
  implant to scaffold for tissue regeneration
• Negates issues of stress shielding, implant
  loosening, long term stability

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Classification based on tissue attachment
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Mechanical Properties
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• BIOCERAMICS
• Bioactive ceramic, that allows the chemical bond
  formation between tissue and implant
• Bioinert ceramic, that doesnt allow the chemical
  bond formation between tissue and implant

BIOINERT BIOACTIVE
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MATERIAL TISSUE
TOXIC DEAD
Bioinert NON-TOXIC Bioactive Soluble Various thicknesses of fibrous tissue binding of tissue-implant interface, Tissue replaces Implant place
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Classification of Bioceramics According to Tissue
Responses
Implant Type Tissue response Example
Nonporous, dense and inert ceramics The formation of very fine fibrous tissue Alumina, Zirconia
Porous inert ceramics The tissue growth in pores Hydroxyapatite
Resorbable ceramics Absorption Tricalcium phosphate Bioactive glasses
Ceramic implants are non-toxic
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Bioceramics According to Structural Functions

• Oxide ceramics, inert structure, polycrystalline
  ceramics consisting of metal ions in the plane
  formed by the dissolution of oxygen ions
• Alumina (Al2O3) orthopedic
  applications
• 
  
• Zirconia (ZrO2) femoral
  prosthese

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Inert Ceramics Alumina

• History
• since early seventies more than 2.5 million
  femoral heads implanted worldwide.
• alumina-on-alumina implants have been FDA
  monitored
• over 3000 implants have been successfully
  implemented since 1987
• Smaller the grain size and porosity, higher the
  strength
• E 380 GPa (stress shielding may be a problem)
• High hardness
• Low friction
• Low wear
• Corrosion resistance
• Friction surface finish of lt0.02 um
• Wear no wear particles generated biocompatible
  

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Inert Ceramics Aluminum Oxides (Alumina Al2O3)

• Applications
• orthopaedics
• femoral head
• bone screws and plates
• porous coatings for femoral stems
• porous spacers (specifically in revision surgery)
• knee prosthesis
• dental crowns and bridges

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Alumina

• Bioinertness
• Results in biocompatibility low immune response
  
• Disadvantage
• Minimal bone ingrowth
• Non-adherent fibrous membrane
• Interfacial failure and loss of implant can occur
  

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Inert Ceramics Zirconia, ZrO2

• zirconium named from the Arabic, zargun gold
  color
• Fabrication
• Obtained from the mineral zircon
• Addition of MgO, CaO, CeO, or Y2O3 stabilize
  tetragonal crystal structure (e.g. 97 molZrO2
  and 3 molY2O3)
• Usually hot-pressed or hot isostatically pressed
• Applications
• orthopaedics femoral head, artificial knee, bone
  screws and plates, favored over UHMWPE due to
  superior wear resistance
• dental crowns and bridges

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• Glass and glass-ceramics
• Silica(SiO2) based ceramics (Includes
  Lithium-Aluminum or Magnesium-Aluminum crystals )
• Bioglass
• Instead of some silica groups, calcium,
  phosphorus or sodium is present (SiO2, Na2O, CaO,
  P2O5)

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Bioactive Ceramics Glass Ceramics

• Glass
• an inorganic melt cooled to solid form without
  crystallization
• an amorphous solid
• Possesses short range atomic order ? Brittle!
• Glass-ceramic is a polycrystalline solid prepared
  by controlled crystallization of glass
• Glass ceramics were the first biomaterials to
  display bioactivity (bone system)
• Capable of direct chemical bonding with the host
  tissue
• Stimulatory effects on bone-building cells

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Bioactive Ceramics Glass Ceramics

• Composition includes SiO2, CaO and Na2O
• Bioactivity depends on the relative amounts of
  SiO2, CaO and Na2O
• Cannot be used for load bearing applications
• Ideal as bone cement filler and coating due to
  its biological activity

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Bioactive Ceramics Glass ceramics
A Bonding within 30 days B Nonbonding,
reactivity too low C Nonbonding, reactivity too
high D Bonding
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Bioactive Ceramics Glass Ceramics

• Bioactive capable of direct chemical bonding
  with the host biological tissue
• Glass
• an inorganic melt cooled to solid form without
  crystallization
• an amorphous solid
• possesses short range atomic order ? BRITTLE!
• Glass-ceramic is a polycrystalline solid prepared
  by controlled crystallization of glass ? LESS
  BRITTLE

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• Calcium-phosphate ceramics their structure is
  the form of multiple oxides of calcium and
  phosphate atoms
• Hydroxyapatite Ca5(PO4)3OH,
• Tricalcium phosphate, Ca3(PO4)2
• Oktacalcium phosphate CaH(PO4)3.2OH

In medicine and dentistry
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Biodegradable Ceramics Calcium (Ortho) Phosphate

• Structure resembles bone mineral thus used for
  bone replacement
• Coating of metal implants to promote bone
  ingrowth
• Different forms exist depending on Ca/P ratio,
  presence of water, impurities and temperature
• 7 different forms of PO4 based calcium phosphates
  exist - depend on Ca/P ratio, presence of water,
  pH, impurities and temperature

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Calcium Phosphate

• Powders
• Scaffolds
• Coatings for implants metals, heart valves to
  inhibit clotting
• Self-Setting bone cement

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Calcium Phosphates

• Uses
• repair material for bone damaged trauma or
  disease
• void filling after resection of bone tumors
• repair and fusion of vertebrae
• repair of herniated disks
• repair of maxillofacial and dental defects
• ocular implants
• drug-delivery
• coatings for metal implants, heart valves to
  inhibit clotting

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Advantage of Bioceramics

• The resistance to
• Microorganisms,
• Temparature,
• Solvents
• pH changes
• High pressures is the advantage in health and
  dental aplications

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Bioceramics are used repair or renewal of a hard
connective tissue in the skeleton

• The elderly, the bones are very brittle
• slow-moving cracks,
• uncertainties to durability
• in different strokes and pressures

The most important reasons for limiting the use
of bioceramics,
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Interaction of bioceramics with tissues

• All materials placed on live tissue, takes
  response from tissue
• TISSUE - IMPLANT

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Why Use Bioceramics?
General Options Toxic/ Imunogenic/ Disease transmission? Mechanical Properties? Bioactive? Degradable?
Autograft
Allograft
Metals
Ceramics
Polymers
Composites

• Advantages to Bioceramics
• Biological compatibility and activity
• Less stress shielding
• No disease transmission
• Unlimited material supply

• Disadvantage of Bioceramics
• Brittleness not for load bearing applications