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| a non-viable material used in a medical device intended to interact with biological system |
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| biomaterial and cells to implant into body |
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| the ability of a material to perform appropriately and in concert with a certain host response in a specific application |
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| the opposite of absorption – removal of material from biomaterial surface into surrounding tissue |
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| the exchange of electrons in corrosion cell (metal s in aqueous solution) leads to sensitization and determines biomaterial’s life |
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| removal of material from device surface during sliding resulting in production of wear debris |
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| meshing of water molecules into macromolecular polymer network |
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Definition
| cross-linking and scission of long-chain molecules into lower molecular weight and the introduction of oxygen-containing groups into polymer network |
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| implant is taken out then the bone implant interface is reviewed |
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| the death or injury of a cell as a result of physical or chemical contact |
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| misreplication or mutation of the DNA or chromosome during reproduction |
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resorbtion of bone matrix
wear debris causes it which has been found to be associated with high concentrations of wear particles per gram tissue |
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Definition
a cancerous tumor when there is a critical amount of mutations and unregulated multiplication
i. Chloroform, ethylene oxide, styrene, vinyl chloride, Cr, Ni, Co
ii. We must make sure all of these ions are bound |
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| bone fragments from the patient’s own body which requires two surgical procedures, longer hospitalization, long recovery time, pain/discomfort, risk of infection and limited availability |
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| bone obtained from another surgical procedure: sterilization degrades mechanical properties, possible rejection of implant, possibility of disease transmission, limited availability |
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| what are the four device categories corresponding to location |
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Definition
i. Non-contacting: not in direct contact with the body – dialysis machine
ii. Surface contacting: electrodes, wound dressing
iii. External communicating contact: pins in skull with hole for monitoring
iv. Implant: completely in the body |
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| what are the device categories corresponding to length of use |
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Definition
v. Short term: less than 24hrs
vi. Medium term: 24hrs-30days
vii. Permanent: longer than 30days
viii. *there is no separate classification for the frequency of contact of devices so must pay attention to how much devices are re-used as a person may develop sensitization |
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| trabecular or spongy bone which forms a honeycombed structure which provides a high specific strength and resistance to impact loads. This si located at the ends of long bone |
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| outer shell around long bones and provides support and protection |
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| cylindrical structures along long axis with a hole for blood vessels |
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| surrounded by wound collagen fibers almost like fiber reinforced composite |
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| states that bone in a healthy individual will adapt to the loads under which it’s placed (if loading is increased, the bone will remodel itself over time to resist load – external cortical wall becomes thicker) |
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| a material in bone matrix which ‘glues things together’ – occurs between collagen fibrils |
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| compact tension specimens |
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Definition
| control of crack velocity so that progress of a crack through bone can be monitored |
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| list some mechanical properties of bone |
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Definition
| highly anisotropic, viscoelastic, properties depend on many factors, properties begin to degrade from 30yo, exercise increases bone density |
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| what are the three reasons the body is a hostile environment |
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Definition
i. Temperature 37*C (98.6*F)
ii. Corrosive environment
iii. Multiaxial loading |
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| what are some adverse biological reactions |
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Definition
i. Physical and chemical effects from material components
ii. Leachables (particularly polymeric)
iii. Contaminants
iv. Degradation products (wear particles) |
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| what are the three different sterilization methods |
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Definition
i. γ-irradiation: zaps bacteria, effective, but could cause damage or degrade polymeric materials
ii. Autoclaving/heat: cheap but heat could cause deformations
iii. Ethyklene oxide: questions about the safety of ethylene body |
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| what are the advantages and disadvantages of in-vitro |
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Definition
1. Advantages: sensitive (direct cell contact), cheap, quick, minimize animal experiments
2. Disadvantages: no circulation: no dynamism of cells/bad for highly soluble biomaterials, influence of mechnical loading not considered, remote (systemic reactions cannot be modelled) |
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Definition
| measure of levels of ions (organic components not considered) in bodily fluid then an artificial solution is created which simulates these levels and biomaterial is put into solution and materials surface is monitored at different time scales – what kind of apatites will form?? |
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| what has become an alternative use of simulated body fluid? what methods are used to analyze a surface? |
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Definition
creating coatings for the surface of materials
XRD, FTIR, SEM |
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| what are some quant/qualititative methods of cell cultural analysis |
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Definition
1. Qualitative assessment: extra-cellular matrix production and calcification (material has cotton wool appearance, mineral precipitates on matrix) as well as cell attachment and morpohology (flattened or balled up)
2. Quantitative assessment: cell viability (live?), proliferation (DNA synthesis – how much are they dividing), expression of phenotype (alkaline phophatase expression) |
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| what does histological response depend on? |
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Definition
| host species, defect size, site of implantation, sample orientation |
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Definition
| use of Weibull grid to determine how much bone ingrowth existed or Merz grid to determine how myuch bone coverage there is |
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| what question is biomechanical testing attempting to answer. what are some tests used? |
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Definition
how well is implant bonded?
a. Tensile, push-out (hard to do must make sure you are pushing at the perfect angle otherwise data varies much), pull-out |
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| describe the three elements of biomaterial/host interaction |
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Definition
a. The material’s response to a living system and host response to the presence of a material
b. Biomaterial degradation
c. Host response |
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Definition
a. The material’s response to a living system and host response to the presence of a material
absorption, leaching, corrosion, wear, polymer hydrolysis, polymer oxidation |
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Definition
| cytotoxicity, haemocompatibility, sensitization, irritation, carcinogenicity |
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Definition
| covered with cartilage to provide a low friction surface for joint movement |
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Definition
| continuous with the periosteum, a fibrous sheath, which covers the external surface of the bone |
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Definition
| the internal tissue in bones |
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Definition
| collagen-mineral composite is formed into densely packed concentric lamellar structures parallel to bone axis |
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Definition
| small channels that reduce density |
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| at the ultrastructure level, what is the composition of bone? |
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Definition
i. At the ultrastructure level, bone contains both a mineral component (similar to hydroxyapatite Ca10(PO4)6(OH)2)and organic component (collagen)
similar to a composite system |
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| what are bone mechanical properties affected by |
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Definition
| age, location, mineral content, hydration, temperature, sex |
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| describe three of the main mechanical features of bone |
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Definition
i. Anisotropic therefore modulus varies by a factor of 2 or more
ii. Visoclastic: speed of test effects results
iii. Fracture toughness: difficult to get repeated value for ‘identical’ samples therefore compact tension specimen tests are carried out |
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| what are the two forms of bone tissue? |
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Definition
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| what equation and what system represents bone? |
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Definition
1. Eb=EhVh+EcVc
2. Hydroxyapatite-polyethylene composites (HAPEX) 40%HA, 60%PE acts as a bone anlog with an inorganic bioactive phase in an organic biointert matrix |
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| what are the constituents of bone matrix |
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Definition
| collagen fibers, bone mineral crystals, ground substance |
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| what ratio effects how bones behave |
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Definition
| Ca:P (relevant in hydroxyapatite) |
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Definition
bone production
i. Plump cells elongated on one axis and they synthesize collagen, deposite calcium, and mineral homeostasis. Attmpts to make as much surface contact as possible |
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Definition
resorption of bone
i. Aggressive cells that eat away bone but also signal new bone growth. They exist as multinuclei cells and lie in lacunae on bone surface |
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Definition
bone maintanence
i. Spidery shape (plump bodies with long ‘legs’) an occur in small holes called lacunae. They also supply oxygen, nutrints and minerals to bone |
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| what are the three main components of bone |
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Definition
| bone matrix, bone cells, bone marrow |
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Definition
| states that bone in a healthy individual will adapt to the laods under which it’s placed (if loading is increased, the bone will remodel itself over time to resist load – external cortical wall becomes thicker) |
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| name some types of bone fracture (13) |
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Definition
i. Open-bone through skin
ii. Closed-complete fracture inside skin
iii. Compression
iv. Stress: muscle forces fracture
v. Avulsion: bone unattached, broken off often due to contraction of muscle
vi. Impacted: lim compression but bones inside each other
vii. Comminuted: multiple fractures
viii. Linear: along axis
ix. Transverse: perpendicular to axis
x. Oblique: at angle other than 0 or 90
xi. Spiral: at least some of the bone has been twisted
xii. Complete
xiii. Incomplete: sometimes referred to as greenstick |
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| how can you improve bone bonding |
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Definition
i. Reduce wear debris, materials based on natural system, composites, bioactive ceramics and glasses
ii. Bone is a mineral reservoir and inorganic phase contains many ions such as carbonate, sodium, magnesium, and silicon |
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| what are the ideal characteristics of bioceramics |
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Definition
| bioinert, bioactive, resorbable, production of wear debris due to ceramic is low |
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Definition
| highly bioactive and able to induce bone formation, contains much silica glass |
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| significance of calcium phosphates |
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Definition
used to improve bone bonding
ideal because Ca/P ratios relate well to HA. Want ones that take more time to dissolve usually Ca:P ratio of 1.67 and higher |
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Definition
| has enhanced mechanical properties over calcium phosphates and bioglasses. Used clinically in spinal spplicaitons but he problem is it will heterogeneously nucleate upon casting therefore huge grain sizes |
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Definition
| normally contain calcium ions, some silicate and phosphate ions (ceramics, glasses, glass ceramics) |
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Definition
a bioceramic
high density high purity with very small grain size, low corrosion reactivity, good biocompatibility, excellent corrosion resistance, low friction, high wear resistance, and high strength |
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| significance of inert bioceramics |
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Definition
| undergo little or no chemical change during long-term exposure to the physiological environment, a very thin fibrous membrane around the implant forms |
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| difference between ceramics and metals in terms of wear debris |
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Definition
| i. In ceramics wear debris simply falls off where as in metals there is plastic deformation resulting in a constant wearing away of materials |
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| what are the advantages of and problems with metal biomaterials |
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Definition
a. Ideally a material with minimum grain size, minimum porosity, and uniform grain size distribution
b. Problems with metals: stiffness, corrosion (galvanic, crevice, intergranular, pitting, fretting, fatigue, film breakdown, stress corrosioln), wear, sensitization, fatigue |
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| what are future adapations of use of metal materials |
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Definition
| reduce implant cross section, use composites, use higher strength/lower stiffness alloys, develop new processing routes |
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Term
| what are variables of interest in plasma spraying |
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Definition
| type of gas, flame T, flame size, substrate nozzle separation, nozzle diameter, time particles are in flame, shape and size of particles, powder feed rate, number of passes. These all influence crystallinity and phase purity and influence the ability of bone to bond with the coating and the lkelihood of coating resorbtion |
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| what are the advantages of plasma spraying |
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Definition
| direct bond is formed between biological tissues and implant, wear debris is less likely to be able to migrate, implants have high success rate |
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Term
| what are the disadvantages of plasma spraying |
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Definition
| major load bearing can not take place immediately, potentially reproducibility problems, substrates hve to be metallic, mechanical instability due to spalling of the coating from metallic substrate (interfacial issues) |
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Term
| plasma sprayed HA coatings |
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Definition
on femoral stem of hip prostheses are successful for young patients (old patients use bone cement)
1. Can be done in different atmospheres: air, vacuum (most popular – coating is 50-150microns thick), low-pressure
2. Often the coatings contain small quantities of other Ca-P phases which like to be avoided but hard to control due to high temperature situation |
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Term
| what are the three main categories of response and what are they effected by |
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Definition
destruction, dilution, or isolation (fibrous capsule where size depends on motion)
iii. Affected by surface charge, texture, hydrophobicity, degradation, corrosion properties |
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Term
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Definition
| cells that exhibit phagocytosis and also mediate the activity of many other cells |
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Term
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Definition
| activated macrophages, more aggressive, can even eat into bone |
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Term
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Definition
| immune system creates antibodies to reject foreign agents – this often leads to unwanted allergic respons |
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| hypersensitivity (name some elements leading to it) |
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Definition
| Ni, Co, Cr sensitivity affect the host immune system |
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Definition
also known as thrombosis is the natural blood clotting process that occurs after damage to blood carrying vessels
1. in dynamic blood flow situations, a local thrombus may result in emboli at remote sites (VERY bad)
2. often a pre-implantation coating of the material with ‘neutral’ proteins prevents activation of the coagulation process |
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Definition
the death of blood cells resulting in the release of their contents often brought about by motion at the material/blood interface or chemical nature of material
1. blood flow velocity and shear stress must be taken into heavy consideration |
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Term
| what are types of response (5) |
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Definition
| cytotoxicity, mutagenicity, carcinogensis, haemolysis, coagulation |
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| name some uses of bone grafts and what type is most common |
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Definition
spinal fusion, revision joints, fracture repair, defect filling
allotropic |
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Term
| what effects the wear rate at joints? |
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Definition
| load, area, distance, and speed |
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Term
| what do peaks in stress loading curves for joints refer to |
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Definition
| because of the stress put on muscles, tendons, and ligaments |
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Term
| what is the purpose of synovial fluid |
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Definition
| viscoelastic response which restricts amount of physical activity. Too much loading too fast the joint actually gets stiffer. Synovial capsule DRASTICALLY reduces coefficient of friction. |
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Term
| describe the 6 stages in the polymerization process (all is exothermic) |
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Definition
i. Initiation: constant temperature, speed depends on T, solubility, concentration
ii. Propagation: rapid addition of monomer molecules to form polymer chains. Highly viscous
iii. Termination: elimination of active free radicals, temperature begins to drop as heat is dissipated to surroundings, high viscosity preventing chain ends meeting, concentration of monomer is depleted.
iv. Dough time: time from initial mixing until the point when the cement no longer adheres to a gloved hand
v. Working time: the time during which the cement can be moulded into shape
vi. Setting time: the midpoint between RT and maximum exotherm |
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Term
| describe a thin film low temperature coating method |
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Definition
| kukobo's simulated body fluid |
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Term
| describe some biodegradable biomaterials |
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Definition
| i. Temporary scaffold, artifical support for weakened tissue, temporary barrier, drug dlivery device, multifunctional implant, bone plates, screws |
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Definition
aka bone cement
i. This si a thermoplastic polymer used to fix joint prostheses for hip and knee joints. Ther is no chemical reaction, it acts like a grout (space filling material) this material sets after about 12mintues |
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Term
| describe the constituents of bone cement, its advantages, and disadvantages |
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Definition
PMMA powder + monomer methyl methacrylate liquid (typically 2:1 powder to liquid ratio by weight.
iii. Advantage: flexibility of procedure
iv. Disadvantage: major exothermic reaction causing local bone death, systemic reacitons to residual monomer/reduction in blood pressure, brittlenesss, aseptic loosening (wear debris), stress shielding |
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Term
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Definition
| low density for plastic bags; high density for plastic containers; ultrahigh molecular weight (UHMWPE) which is mainly used in biomedical load bearing applications |
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Term
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Definition
| High rigidity, good chemical resistance, good tensile strength, stress cracking resistance is superior to PE |
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Term
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Definition
same structure as PE
Stable thermally and chemically, hydrophobic therefore great lubricity Difficult to process, poor wear resistance>can not be used for acetabular cups – makes tons of wear debris/much better for vascular components |
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Definition
tough elastomers
Good fatigue resistance, used for implantable devises because they are stable to hydrolysis |
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Definition
often used with carbon fiber
Good T stability, stiff/strong |
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Term
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Definition
Addition of sidegroup to PMMA causing material to become hydrophilic, amorphous, semicrystallilne, hydrogen bonded
Can be used as soft contact lenses, drug delivery time release as water goes in and drug comes out, wound dressing. |
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Definition
Mainly used in tubing in biomedical applications
Requires the addition of plasticizers which can be problematic as these are leached ofut of the polymer by the body leading to embrittlement |
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Term
| austenitic stainless steels |
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Definition
| Bone interacts with its surface oxide, little carbon to minimize possibility of in-vivo corrosion (no carbides) |
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Term
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Definition
Oxide layer provides corrosion resistance and contributes to biological performance, best in terms of modulus
Suffrers from low fatigue life, requires oxygen to increase strength and fatigue life |
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Definition
Wear debris is greatly reduced, hardness lubricity, and abrasion resistance all improved
Oxidized zirconium metal |
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Definition
| an implant takes the load so according to Wolff's law, the normally healthy bone loses mass and becomes weaker. therefore it is not ideal to have a very strong/stiff implant |
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Term
| steps taken in the design of medical devices |
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Definition
determine specs
conduct risk analysis of device and components
determine pivotal test and trials
determine how device fits into health care picture
estimate market potential and process costs
check literature, patents, knwon failures |
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| name some cup/hip materials combinations |
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Definition
PE cup + stainless steel
PE cup + Al2O3 |
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