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CHEE 340 Biomaterials

CHEE 340 Biomaterials. Metallic and Ceramic. Metallic Biomaterials. Advantages: Strong, relatively bioinert , electrically conductive Disadvantages: Corrosion, stress shielding, osteolysis Properties necessary for use:

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CHEE 340 Biomaterials

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  1. CHEE 340 Biomaterials Metallic and Ceramic

  2. Metallic Biomaterials Advantages: Strong, relatively bioinert, electrically conductive Disadvantages: Corrosion, stress shielding, osteolysis Properties necessary for use: Applications: teeth implants, artificial heart valves, spine correction: pins/screws/plates/fixation wires

  3. Metallic Biomaterials Properties of metal crystal lattice structures: • Comprised of multiple repeating __________ • High Tm • Most stable crystal form is _________ • Substitutions of different elements in crystal structure change mechanical properties, called __________ How does grain size affect strength? Small grain size __________strength

  4. Metallic Biomaterials Methods of metal product manufacture: 1. ___________: raw metal cut to desired shape and size 2. _____________: pour hot metal into molds 3. _________: heat till plastic deformation state then hammer/press/roll 4. ________________________: sinter a compacted powder bed then forge What properties do these processes affect:

  5. Metallic Biomaterials Describe the 3 groups of metal biomaterials: 1. _____________: lowest biocompability, cheap, high strength, low wear and abrasion, high corrosion 2: ___________: high strength, lower corrosion than stainless steel, more biocompatible 3. ____________________: best biocompatibility, expensive, low E, good corrosion properties, harder to work

  6. Metallic Biomaterials Corrosion is a redox reaction: M Mn+ + ne- (oxidation) __________________: electrochemical process between two metals where the more active anodic metal dissolves more quickly when immersed in an electrolyte solution ____________: Treatment of a metal surface to produce a metal oxide layer to protect against corrosion Mechanisms of corrosion:

  7. Metallic Biomaterials Ways to improve corrosion resistance: Proteins in the body can influence corrosion by: • Binding to metal ions which then move away from the surface and _______________ • Can interact with charges at surface and affect _________________ • Protein adsorption can limit O2 diffusion to surface and enhance ________________ Two types of wear: _________ and __________

  8. Ceramic Biomaterials Describe the properties of ceramics: • Composed of ___________________, but also partly metallic • Crystalline material made up of _________________of unequal charges leading to complex crystal structures • Often ___________ found substituting ions in crystal lattice Orthopaedic applications: Hip prosthetics, temporary bone space fillers, metal coatings

  9. Ceramic Biomaterials Hench classifications of tissue response to ceramics: Type 1: ____________ -dense, nonporous -can have bone ingrowth if have surface irregularities or morphological fixation Type 2: ____________________ -pores allow ingrowth termed biological fixation Type 3: ________________________ -dense, nonporous -adhere through chemically bonding with bone Type 4: ____________ -dense, porous or nonporous -slowly replaced by bone

  10. Ceramic Biomaterials Types of bioceramics: Alumina and zircona, Bioglass, Hydroxyapatite (HA), Tricalcium phosphate (TCP) Describe liquid-phase sintering: -compress fine-grained particulates mixed with an in water _______ into a mold -T varied to evaporate water then fire (900-1400°C) to burn out binding agent to increase ______________________and ________ -different ceramic phases made by altering: ____________ and __________ Describe solid- state sintering: -compact powder into any liquid phase then fire at very high T (50% > than Tm) -creates very ________, _____________, ________ material

  11. Ceramic Biomaterials Alumina is a type 1 bioinert ceramic that is biocompatible with low immune response. However, it has minimal bone ingrowth, non-adherent fibrous membrane, and interfacial failure. These factors lead to implant movement therefore we need to minimize this by:

  12. Ceramic Biomaterials Bioactive glass preparation: • Melt then quench glass to form ___________ material • Working below Tm, heat to 500-700°C to form ____________ • Still below Tm, increase T to 600-900°C to promote _____________ Surface reactivity due to:

  13. Ceramic Biomaterials Mechanism of hydroxyapatite formation on bioglass

  14. Ceramic Biomaterials Describe the nature of bone: Consists of inorganic mineral deposited on a framework of organic support material (osteoid) that is 95% collagen and gives ___________ properties. Main mineral constituents of bone and teeth: ______________________ Bone is a calcium-deficient carbonate hydroxyapatite , Ca5(PO4)3OH, with traces of other minerals. What is the importance of calcium phosphate as a biomaterial?

  15. Ceramic Biomaterials Mechanisms of biodegradation: Factors influencing dissolution:

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