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Ceramic and Glass Biomaterials

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					Ceramic Biomaterials
Lecture outline


•   Structure of Ceramics
•   Structure properties relationship
•   Types of ceramic biomaterials
•   Uses of ceramic biomatrials
What are ceramics?


Ceramics are an earthy materials

composed of metallic and non
 metallic elements mainly
 metallic oxides.
• (e.g., Al2O3, NaCl, SiC, SiO2)
 Atomic Bonds
• Ionic
  • Large differences in electronegativity
  • Non directional strong bonds


• Covalent
  • Small differences in electronegativity
  • Strong, directional bonds
Structure of ceramics




                                 Partially crystalline
 Crystalline   Non crystalline
               Amorphous         Glass-ceramic

 Al3O2          Glass            Consists of two-phases
 Zr O                            crystals in a glass matrix.
    Properties of Ceramics

•   High melting temperature (ionic-covalent)
•   Low thermal conductivity
•   Good thermal insulators
•   Low thermal expansion coefficients
•   Low density
•   High melting point,
•   Chemically inert or unreactive– oxides do
    not oxidize further
   Mechanical Properties

• High strength, compressive strength usually ten
  times > tensile

• Very high elastic modulus (stiffness greater than
  metals)

• Very high hardness & low fracture strength can
  make it difficult to make ceramic components

• Brittle

• High wear resistant
    Mechanical behaviour of ceramics compared to
                      metals
   Metals usually                   Necked region
    undergo plastic
    deformation
   Ceramics exhibit
    brittle fracture                 Brittle behaviour
Ceramics as Biomaterials

• Advantages
  • Inert in body (or bioactive in body); chemically
    inert in many environments

  • High wear resistance (orthopedic & dental
    applications) no wear particles generated –
    biocompatible

  • High modulus (stiffness) & compressive
    strength

  • Esthetic for dental applications
Ceramics as Biomaterials


• Disadvantages
  • Brittle (low fracture resistance, flaw tolerance)

  • Low tensile strength (fibers are exception)

  • Poor fatigue resistance (relates to flaw
    tolerance)
     Applications

• Orthopedics:
   • bone plates and screws
   • total & partial hip components (femoral head)
   • coatings (of metal prostheses) for controlled implant/tissue interfacial
     response
   • space filling of diseased bone


• Dentistry
   • dental restorations (crown and bridge)
   • implant applications
      (implants, implant coatings, ridge maintenance)
   • orthodontics (brackets)

• Other
   • inner ear implants (cochlear implants)
   • ocular implants
   • heart valves
 Types of BioCeramics

 Bioceramic are classified according to the
 tissue response to a material
    (Biocompatibility) into:

• Bioinert

• Bioactive

• Biodegradable
Types of Bioceramics




                       13
Bio inert Ceramics:

• Bio Inert Ceramics: are materials that
  retain their structure in the body after
  implantation and do not cause any
  undesirable reaction

• Alumina Al2O3
• Zirconia ZrO2
• Pyroltic Carbon
                      a – Alumina   b – Zirconia
       Alumina & Zirconia Applications

• Orthopedics – femoral head, bone screws and
  plates
   • Alumina at a bone interface: bone will grow right up to
     it, but will not grow in
   • Ceramic-polymer contact used in hip and knee
     replacements
   • Ceramic-ceramics contact also used
   • Problem with stiffness of alumina…
• Dental restorations – crowns, bridges, brackets
Bio inert Ceramics:

 Advantages
  High hardness:
  • Low friction
  • Low wear
  • Corrosion resistance
  • Biocompatible:
     - no wear particles generated – biocompatible
     - no tissue reaction occurs
   Disadvantage:
     • Minimal bone ingrowth
     • Interfacial failure and loss of implant can occur
Bioactive Ceramics: Glass Ceramics


 • Bioactive Ceramics: are materials
   that form bonds with the living
   tissues and perform specific
   biological response at the interface

 • Bioglass SiO2, CaO and Na2O


 • Calcium Phosphate
Bioactive Ceramics: Glass Ceramics

 • Glass:
   • an inorganic melt cooled to solid form
     without crystallization

   • an amorphous solid

   • Possesses short range atomic order 
     Brittle!


                                      18
• Glass-ceramic is a polycrystalline solid
  prepared by controlled crystallization of
  glass
• Capable of direct chemical bonding
   with the host tissue
• Stimulatory effects on bone-building
  cells
Bioactive Ceramics: Glass Ceramics



   • Composition includes SiO2, CaO and
     Na2O

   • Cannot be used for load bearing
     applications

   • Ideal as bone cement filler and coating
     due to its biological activity

                                       20
Calcium Phosphate


• Structure resembles bone mineral; thus
  used for bone replacement




                                     21
Calcium Phosphates


• Uses
  • repair material for bone damaged
    trauma or disease
  • void filling after resection of bone
    tumors
  • repair of maxillofacial and dental
    defects
  • ocular implants
  • coatings for metal implants, heart
    valves to inhibit clotting
                                           22
Biodegradable Ceramics


• Biodegradable Ceramics: materials
  that degrade in the body and slowly
  replaced by natural tissues. The
  chemical byproduct of the degrading
  materials are absorbed and released
  by the body.
• Calcium phosphate
• Tricalcium Phosphate
Questions


• Compare the structures of glass,
  glass ceramics and ceramics.

• Mention the properties of ceramics
  as biomaterials
References


• Biomaterials Science. An
  introduction to materials in dentistry.
  Ratner B,D, Hoffman A, Schoen F,
  Lemons J, E . First Edition,.1996

• Biomaterials :An introduction Park j,
  Lakes R.S. Third Edition,2007

				
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