Biomaterials Exam 1 - Details

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1) Chapter 1 View

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64 questions

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Inorganic, non-metallic compounds; high melting point, chemical resistance, brittle, high strength, high modulus, wear resistance

Ceramics and name 3 properties

Crystalline, Glass, and Glass-ceramic

Main types of Ceramics

BCC, FCC, Hexagnal

Most common crystalline structures

Inert, non-allergic, long life time, temp. resistance, non-carcinogenic Alumina, Zirconia, Calcium Phosphates (HAP)

Desired properties of Implantable Bio-ceramics (name 3) and examples

Wear resistance, long life time, mostly used in dental implants

Alumina properties

Relatively flexible, tough, low modulus, strong (stress shielding)

Zirconia properties

Good mechanical properties, osteoinductive

HAP (Hydroxyapatite) properties

Measuring crystallinity of a material, crystalline peaks and amorphous humps

XRD is used for?

Slurry of ceramic material, to stabilize fractures, injected with low exothermic reaction during hardening and sets at the appropriate time

Bone Cements (what, why, how?)

To material surfaces coming together and staying intact

Cohesion is?

Implantable solid particles that can be resorbed and stabilize a fracture example: JAX or Osteoset

Bone Void Fillers are?

Material can uptake payload, material can hold on to payload as directed/needed, payload is delivered properly. Drugs to be delivered are antibiotics, anti-inflammatories, hormones, etc.

Drug Delivery basics

Form apatite layer and is good as a bone filler

Bioactive Glass can?

Semi-crystalline, devitrification (resistant to thermal shock, increased toughness)

Glass-Ceramics properties

Hard, shiny, malleable, fusible, and ductile material with good electrical and thermal properties. Crystalline solid with an electron cloud. -grain boundaries and dislocations: created in processing and determine properties -Alloying controls properties

Metals and its properties

1. Get metal (found in ore): ore separation (smelting, chemical, water flow) 2.Prepare raw material: casting (forging, CAD, investment, powdering processing 3. Surface Treatment: adding porosity (plasma spray) 4. Packaging: polishing, cleaning, sterilize, etc.

Process of Obtaining Metal

Abrasion- harder surface dents softer Adhesion- soft surface smears on harder Fatigue- repeated alternate loading (cyclic)

Mechanisms of wear

Is oxidation; Galvanic- two metals with different inertness Passivation-layer that forms to protect metal from corroding Pitting- localized corrosion, picks at passivating layer Crevice- two surfaces meet Cracking promotes corrosion (failure)

Corrosion

Wear + corrosion cracks + corrosion

Fretting

Wear resistance, patient comfort, longevity, corrosive resistant, carry the load (cyclic and monotonic)

Implant Requirements

Pros: ductile, tough cons: can have nickel allergies, limited wear resistance, limited strength

Stainless Steel pros and cons

Pros: strength, ductility, toughness, corrosion resistance cons: not very wear resistance, can have nickel allergies

Cobalt-chromium alloys pros and cons

Pros: passivating layer, ductile, strong cons: higher chance of stress shielding

Titanium alloys pros and cons

Workable and moldable, great for crowns or cusps, super biocompatible

Gold

A group of repeated mer units forming a long chain. unique materials, very large molecules cause chain entanglement and influence properties

Polymers

Cross-linked polymers that cannot be melted

Thermoset

Meltable plastics, can recyclable

Thermoplastic

Stretch, but return

Elastomers

Unsaturated-double or triple bond between carbons saturated- all bonds are single

Hydrocarbon molecules

Initiation: R-active initiator w/ loose electron Propagation: bonds with electron (longer chains) Termination-I: active ends of two chains come together Termination-II: single activator ends line

Polymerization

Monomers come together w/ water or hydrochloric acid

Condensation Polymerization

Polyolefins - made w/ alkene monomers polyesters, amindes, urethanes - made with whose function groups natural - polysaccharides, proteins, DNA, rubber, cellulose

Polymer families

1. random 2. alternating 3. block 4. graft

Types of copolymers

1. linear 2. branched 3. cross-linked 4. network

The polymer arrangements

Different conformations through rotation of valance bonds Isotactic, Syndiotactic, Atactic

Tacticity and types

Glass transition temperature, when above polymer becomes hard like glass when below they are more elastic and flow

Glass Transition

Fillers Plasticizers (make flexible and ductile) Stabilizers (protect against UV or oxidation) Colorants and Flame retardants

Types of Polymer processing

1.Compression molding 2.Injection molding 3.Extrusion (good for rods) 4.Blow molding (good for hollows)

Fabrication of Polymers

Tough, long lasting, semi-crystalline, won't melt in body temperature wear occurs from repetitive motion, particles released cause macrophage activity

UHMWPE

Semi-crystalline, high tensile strength, forms well, chemically stable

PEEK

Breakdown or removal of a material in a body Polymers will decrease molecular weight, strength, and mass

Degradation

Hydrophilic - water breaks down polymer all at once with diffusion

Bulk degradation

Hydrophobic- polymer breaks down faster than water diffusion, like peeling an onion

Surface Erosion

Hydrolysis - cleavage of molecules, most common way Enzymatic - catalyzed by enzymes

Mechanisms of Degradation

With 1:1 ratio: lower modulus, bulk degrades (acidic) decreased ratio: higher modulus, short degrade time, FDA approved

PLGA

Polymers that change in presence of a stimulus Ex: pH, temperature, etc. Types of changes: phase, shape, degrade, etc.

Smart Polymers

Material made with two or more other materials Can be same material different forms, Can be different materials

Composites

A hierarchical Composite (multiple composite organizations are different scales

Bone as a composite

1. Fiber 2. Particle 3. Laminar (layers) 4. Flake 5. Filled (porous filled with matrix)

Composite Organization

Concentration, size, shape, orientation, distribution

Considerations

Material in parallel w/ load axis, so strains are equal

Isostrain

Material are perpendicular with load axis, so stresses are equal

Isostress

Materials come apart, no more adhesion between layers, try to keep layers perpendicular to cracks

Delamination

Tortuosity, reinforced sections stop failing

Crack Deflection

Crack would need to use a long of energy to continue (unfavorable)

Reinforcement cracking

Fiber spans crack, fiber pullouts also happen (helps prevent continuation of crack)

Fiber Bridging

Dental composites: better looks, mechanical properties, particle organization, crack deflection

Alumina- Glass

Self-nuetralizing

PPHOS-PLGA

Hip implant: state of the art Cobalt-chrome core surrounded by PEEK shell and a titanium mesh. no stress shielding, mesh promotes bone growth for better fixation and load transfer

EPOCH

Fill bone defects: types: autografts, allografts, bone scaffolds

Bone Grafts

Taken from one site of patient to use at enough pros: biocompatible, osteoinductive. cons: limited supply, donor-site morbidity

Autografts

Taken from donor pros: no limit, no morbidity cons: sterilize (may change mechanics), less osteoinductive, disease transmission

Allografts

A material used as bone graft pros: good strength, tough, degradable, osteo inductive, and biocompatible cons: PLGA has limited osteoinductiveness, Calcium Phosphate can be brittle and difficult to form

Bone scaffolds

Increases stiffness, strength, creep resistance allows thinner sections can replace metals PEEK- OPTIMA carbon compounds: x-ray and MRI compatible,

Carbon fiber composites

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