Mgunen.bioceramic.ppt

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bioceramic

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Mgunen.bioceramic.ppt

  1. 1. 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 bioceramics  To introduce the use of ceramics as biomaterials  To mention the current and future status in bioceramics
  2. 2. Bioceramics Advantages High Compression Strength Disadvantages High Modulus Wear & Corrosion Resistance Low Strength In Tension Bioactive/inert Low Fracture Toughness Can Be Highly Polished Difficult To Fabricate
  3. 3. Types of Bioceramics
  4. 4. Mechanical Properties
  5. 5. Biocompatibility & Bioinertness Biocompatibility: Objective is to minimize inflammatory responses and toxic effects Bioinertness: Results in biocompatibility – low immune response Advantage: Making material more biocompatible Disadvantages: Minimal bone ingrowth, Non-adherent fibrous membrane, Interfacial failure and loss of implant can occur
  6. 6. Bioactivity & Biodegradability Bioactivity: Having a capacity to interact with a living tissue or system. Advantages: Bone tissue – implant interface, enhanced healing response, extends implant life Biodegradability: The capacity of a natural environment to chemically break down an object.
  7. 7. Inert Ceramics: Aluminum Oxide (Alumina – Al2O3) History:  Since 1975, alumina ceramic has proven its bioinertness  Since early seventies more than 2.5 million femoral heads implanted  worldwide Over 3000 implants have been successfully implemented since 1987
  8. 8. Inert Ceramics: Aluminum Oxide (Alumina – Al2O3) 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 <0.02 um Wear: no wear particles generated – biocompatible
  9. 9. Inert Ceramics: Aluminum Oxide (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
  10. 10. Inert Ceramics: Zirconium Dioxide (Zirconia - ZrO2)  Obtained from mineral zircon  Usually hot-pressed  Bright future because of its high mechanical strength and fracture toughness
  11. 11. Inert Ceramics: Zirconium Dioxide (Zirconia - ZrO2) Applications - Orthopaedics: femoral head bone screws and plates Artificial knee - Dental: crowns and bridges
  12. 12. Bioactive Ceramics: Glass Ceramics Glass:  an inorganic melt cooled to solid form without crystallization  an amorphous solid  Possesses short range atomic order  Brittle!
  13. 13. Bioactive Ceramics: Bioglass  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
  14. 14. Bioactive Ceramics: Bioglass SiO2 B C A D CaO A: Bonding within 30 days Na2O B: Nonbonding, reactivity too low C: Nonbonding, reactivity too high D: Bonding
  15. 15. Bioactive Ceramics: Hydroxyapatite (HA) Formula: Ca10(PO4)6(OH)2  Similar composition to bone  High biocompability Good osteoconductive properties 
  16. 16. Bioactive Ceramics: Hydroxyapatite (HA) Applications - Femoral knee - Femoral hip - Tibial components - Acetabular cup
  17. 17. Biodegradable Ceramic: Calcium (Ortho) Phosphate  Structure resembles bone mineral; thus used for bone replacement  7 different forms of PO4 - depend on Ca/P ratio, presence of water, pH, impurities and temperature
  18. 18. Biodegradable Ceramic: Calcium (Ortho) Phosphate Usage Areas:       repair material for bone damaged trauma or disease void filling after resection of bone tumors repair of herniated disks repair of maxillofacial and dental defects ocular implants coatings for metal implants
  19. 19. Why Use Bioceramics? General Options Toxic/ Imunogenic/ Disease transmission? Mechanical Properties? Bioactive? Degradable? Autograft Allograft Metals Ceramics Excellent Moderate Low Polymers Composites Advantages to Bioceramics: Disadvantage of Bioceramics: • Biological compatibility and activity • Brittleness – not for load bearing applications • Less stress shielding • No disease transmission • Unlimited material supply
  20. 20. Current Status And Trends √ Calcium phosphates for bone grafting and tissue engineering √ Calcium phosphates as fillers in composites √ Chemically and physically modified hydroxyapatite
  21. 21. Current Status And Trends Animal testing, clinical trials, a new material takes around 15 to 20 years to hit the market  Trend is towards resorbable materials which eliminate the need for a secondary procedure and mouldable materials 
  22. 22. Bioceramics in Future Other trends include engineering the materials for specific tasks. Ongoing research involves the chemistry, composition, micro and nanostructures of the materials to improve their biocompatibility.
  23. 23. Bioceramics in Future  Improvement of the mechanical performance of existing bioactive ceramics. • Enhanced bioactivity in terms of gene activation. • Development of improved biomimetic composites. • Treatment works of cancer.

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