Bioceramics1

Bioceramics1 - This file is to be used strictly for...

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This file is to be used strictly for personal reading and non-commercial teaching purposes. Not for circulation. The file contains images from recent journal papers. Bioceramics Inorganic compounds that contain metallic and non-metallic elements with ionic or covalent interatomic bonding, generally formed at high temperatures Greek word keramos, science and art of making solid materials by action of heat on earthy raw materials Inert Bioactive High wear resistance Aesthetic for dental applications Similar to natural material bone hydroxyapatite Brittle Low tensile strength Categories Classified as inert, surface reactive and bioresorbable depending on chemical reactivity in physiological environment Inert bioceramics like alumina have low reactivity peak in the order of 250 years High reactivity seen in surface reactive group like bioglass peaking in the order of 100 days Highly resorbable is tricalcium phosphate peaks by 10 days Ceramic-tissue interactions Type I: Dense inert non-porous materials Fixed by cementing or press fitting into defect : Morphological fixation Type 2: Inert but porous Fixed by bone ingrowth into pores: Biological fixation Type 3: Dense, non-porous, surface reactive Attach directly by chemical bonding with bone: Bioactive fixation Type 4: Dense porous or non-porous resorbable Degrades to be slowly replaced by tissue Alumina based ceramics Alumina is aluminium oxide Al2O3 Very hard Mohs hardness 9 Used to fabricate hip joint sockets and dental root implants Inert Dense high purity greater than 99.5% Al2O3 Pressing and sintering fine powders at temperature between 1600 to 1700 °C
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Magnesium oxide MgO < 0.5% added to limit grain growth For desired mechanical properties require an average grain size of < 4 microns An increase of grain size from 4 to 7 microns decreases mechanical properties by 20% Hip joint replacement Ball and socket often fabricated of alumina High wear resistance, low friction Wear can be 10 fold lower than cobalt chromium on polymer Good biocompatibility Excellent corrosion resistance Another possibility of using alumina for the ball but UHMWPE for the socket But tensile strength and fracture toughness remain low for ceramics as compared to metals Zirconia based ceramics Zirconia has higher fracture toughness than alumina Used as zirconia femoral heads Low friction and low amount of polyethylene debris formation
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This note was uploaded on 10/01/2009 for the course CS BCB/Co taught by Professor Olivereulenstein during the Fall '06 term at Iowa State.

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Bioceramics1 - This file is to be used strictly for...

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