BMEN 343 Short Answer

List the implant (biomaterial) factors:

-Bulk Properties-Surface Properties-Mechanical Properties-Long term structure integrity

Name 3 ways how the host can affect the implant biologically

-calcification,-enzymatic degradation-absorption of substances form the tissues

Name 3 ways surfaces to move towards lowering their free energy

-geometric changes-bonding -dynamic rearrangement

What 4 actions are associated with acute inflammation?

-recognition-attachment-engulfment-degradation

What are the two methods of polymers synthesis?

1. Addition polymerization2. Condensation polymerization

List 3 things that would slow diffusion:

1. Close packed structure2. materials with covalent bonds3. larger diffusing atoms4. high density materials

List the three kinetic steps of addition polymerization.

1. Initiation2. Propagation3. Termination

Briefly explain the steps of solidification in solids.

1. Nuclei form2. Nuclei grow to form crystals/grain structure

List 3 methods commonly used to strengthen materials

1. Reducing grain size2. Adding impurity atoms (solid-solution strengthening)3. Adding dislocations (strain hardening, work hardening, cold-working)

What are the factors that determine crystal structures?

1. Relative sizes of ions2. Maintenance of charge neutrality

Polymer crystallinity depends on many factors. List at least 3 below.

1. Tacitity2. Degree of branching3. Mer side groups4. Regularity of Mer placement in copolymers

Describe the 2 phases of a composite material:

1. a continuous matrix component reinforced by a 2. discontinuous dispersed phase

What are the classifications of defects?

1. according to geometry2. dimensions of the defect

Rank from greatest to least the elastic modulus of average metals, polymers, and ceramics.

1. ceramics 2. metals 3. polymers

List 3 effects of increased crystallinity in a polymer

1. density increases2. stiffness/strength/toughness increases3. heat resistance increases

What are the three key compositional features for "bioactivity"?

1. less than 60 mol% S1O22. High CaO and Na2O content3. High Cao/P2O5

What factors does crystallinity depend on?

1. polymer tacticity2. degree of branching3. mer side groups4. regularity of mer placement in copolymers

What are three advantages for strengthening metal?

1. reduce grain size2. solid-solution strengthening3. strain hardening/work hardening/cold-working

What are the four categories of metallic biomaterials?

1. stainless steel2. cobalt-based alloys3. titanium alloys4. specialty metallic alloys (Ta and Mg)

In non-steady state diffusion, which 2 variables does concentration depend on?

1. time2. position

The composition of original Bioglass 45S5 is

45% SiO2, 24.5% CaO, 26.5%Na2O, and 6% P2O5

What is a biomaterial?

A biomaterial is a material that functions as a part or whole of a device that treats, assists, repairs, or replaces any tissue, organ, or function of the body.

What happens during restenosis, and how can it be avoided?

A mechanical mismatch between a stent of high modulus and a lower-modulus vessel on which it pushes outward leads to formation of thick smooth muscle in the vessel lumen (neointima) and re-blocks the vessel. Restenosis can be avoided by using a material of a more similar modulus or by making the device (stent) biodegradable.

Explain the difference between adsorption and absorption.

Adsorption is when the solvent is taken up by the material and absorption is the process of association of solvates.

List two advantages and disadvantages of biodegradable orthopedic fixation devices.

Advantages:• no second surgery to remove• can be drug-eluting• decrease stress shielding• can tune/tailor the degradation rate/profile Disadvantages:• higher cost vs metallic fixation devices• acidic degradation products can cause increased inflammation, especially in final stages of degradation

Describe the process of new bone formation around a bone implant.

After implantation, ions like Ca, Si, and Mg leach out of the implant. The ions react with ions in the body fluid to form a carbonated hydroxyapatite layer between the implant and existing bone. Osteoblasts migrate into the HCA matrix from the bone and generate new extracellular matrix to produce new bone between the implant and existing bone.

Give the electronic configuration of each element in Alumina. What are the charges of Al and O respectively? List one practical usage of this material in medicine/implants/biotech.

Al: 1s(2)2s(2)2p(6)3s(2)3p(1) - has a 3+ chargeO: 1s(2)2s(2)2p(4) - has a 2- charge Hip replacement head is a good example.

Briefly describe what qualifies a material as amorphous?

An amorphous material is a solid in which short-range order might be present but long-range order is not present.

How does annealing increase the ductility of a cold-worked metal?

Annealing allows for recrystallization by adding heat. Atoms gain enough energy to rearrange themselves back into their close-packed structures, which better allow dislocation movement and thereby increase ductility.

How does glass behave below it's transition temp?

As a solid

What type of stereoisomerism would be the most difficult to crystallize and why?

Atactic: Side groups are less ordered so neighboring chains cannot easily form crystalline structures.

What is the electron configuration for Barium cation? (Ba2+)

Ba: 1s22s22p63s23p64s24p64d105s25p66s2Ba2+: 1s22s22p63s23p64s24p64d105s25p6

What is a lamella?

Basic unit of crystalline structure.

Name and describe the two elements of biocompatibility.

Biosafety - appropriate systemic and local host response, and the absence of cytotoxicity, mutagenesis, and/or carcinogenesisBiofunctionality - the ability of the material to perform the specific task for which it is intended to

Name and describe the two termination processes of addition polymerization.

Coupling - coupling together of two growing chains to form a longer polymer chainDisproportionation - hydrogen atom is transferred from one growing chain to another

Define biocompatibility. What are the two elements?

Def:= A material which neither directly nor indirectly through release of mater constituents is (1) carcinogenic, (2) produces local/systemic adverse effects, nor (3) produces developmental/reproductive adverse effects. two elements: (1) biosafety and (2) biofunctionality

Define physisorption

Def:= Physical aDsorption with long range and weak van der Waals attraction between adsorbate and substrate

What is Wolff's Law? List at least one device where Wolff's Law is applicable and how.

Def:= bone adapts to modified mechanical loading environments - more stress = osteogenic processes, less stress = osteoclastic processes. Wolff's Law is applicable for any orthopedic implant at a load bearing joint. Example: total knee replacements, hip replacements, ankle replacements. The implant can/will likely modify the mechanical loading environment, leading to stress shielding and asceptic loosening or other bone morphologies that otherwise impair joint function.

Briefly explain why external surgical methods are rarely used for long bone repair.

External surgical methods are not used often because this method has a high risk of infection. Presence of infection can lead to many serious complications for the patient.

How are collagen and gelatin related and what is a use for each?

Gelatin is an irreversibly denatured form of collagen Gelatin: cosmetics and food products Collagen: cosmetics, some forms of breast implants

List 4 polymorphic forms of carbon

Graphite, Fullerenes, Nanotubes, Diamond

List the stacking sequences for FCC, HCP and an FCC crystal with a twin boundary

HCP: ABABABABFCC: ABCABCABC FCC w/ Twin Boundary: ABCABABC

How does alloying increase the strength of a metal?

Impurity atoms disrupt the uniform crystal structure of a metal, which impedes the movement of dislocations (which decreases plastic deformation)

What would decreasing temperatures in thermoplastics cause?

Increasing E, Increasing TS, Decreasing %EL

What is carburizing?

Increasing the surface concentration of carbon with diffusion

Why is molybdenum added to cobalt based alloys?

Mo increases strength by producing fine grains

There are 3 properties that characterize polymers. Name at least 2 of them.

Molecular weightCrystallinityThermal Transitions

Describe what stress-shielding is.

Osteopenia as a result of removal of normal stress from the bone by an implant

Briefly describe what "osteopenia" is.

Osteopenia is a reduction in bone mass due to the decrease of normal stress on the bone. This decrease of normal stress is a result of the implant carrying too much of the load.

What elements determine grades of cp-Ti (commercially pure Titanium) ?

Oxygen, Iron and Nitrogen

Explain why PEEK is used to replace metal orthopedic components.

PEEK has an elastic modulus and density that resembles bone's to reduce stress shielding.

Define creep.

Progressive strain (deformation) over time at constant stress (load), usually at high temperatures.

The mitochondria is also known by its scientific name as what?

The powerhouse of the cell.

Describe the properties of a material at its Tg.

The properties change continuously from those of a solid to those of a liquid.

Why is soda glass transparent?

There is no long range symmetry and very little short range. This does not reflex light

Compare and contrast thermoset and thermoplastic properties.

Thermoplastics are linear and branched polymers that can be reprocessed. Thermosets are crosslinked polymers that cannot be reprocessed.

What is the structural difference between thermoplastic and thermoset polymers?

Thermoset polymers are highly cross-linked

Why is alloying a common practice in material production?

To improve mechanical strength and corrosion resistance of the material.

Explain theoretical density

Total mass of atoms in the unit cell divided by the total volume of the unit cell

Explain the difference between a vacancy and a self-interstitial.

Vacancies are vacant atomic sites in a structure, while self-interstitials are extra atoms positioned between atomic sites.

List 6 possible directions from the family of directions, <121>.

[121], [211], [112], [1-21], [-211], [11-2]

What is a metal?

an element which readily loses electrons to form positive ions in a sea of electrons

The word to describe something that is stronger in compression than in tension is

anisotropic

What are the wt% of Bioglasses

ans: 45 wt% SiO2, 24.5 wt% CaO, 24.5 wt% Na2O, and 6 wt% P2O5

Describe the differences between absorption and adsorption

ans: Adsorption is the process of association of solvates to a material's surface. While absorption is when the solvent is taken up by the material.

Why does PEEK have a low percent crystallinity?

ans: It is a chain with bulky benzene rings, making it difficult to crystallize.

IN the space below list the steps for the processing of ceramics

ans: compounding, forming, drying, and firing & sintering.

List the steps of annealing.

ans: recovery, recrystallization, and grain growth

What is/are the purposes of the matrix phase of composites?

ans: transfer stress to dispersed phase and protect dispersed phase from the environment

The two major types of bone tissue are

cancellous and cortical.

How are the strength and ductility changed after cold-working and annealing?

cold-working: increase strength and decrease ductility annealing: decrease strength and increase ductility

What are two advantages of replacing metal implants with biodegradable polymers?

decreases stress shielding and no second surgery to remove the metal implant

Define stress shielding and give an example of when this could occur.

def: Osteopenia (reduced bone mass) as a result of removal of normal stress from the bone by an implant

What are three ways to process ceramics?

drying, sintering, and compounding

The difference between absorption and adsorption is

in absorption, solvent is taken up by the material and adsorption is attachment to the surface.

How does sphereulite size effect a polymer?

it increases the yield but decreases the elasticity

Draw a stress strain curve comparing a small spherulite semi-crystalline polymer (A) to a larger spherulite semi-crystalline polymer (B)

n the graph: B>A for the entirety of the sketch. A has a dip and return and B is just a hill.

Explain what happens regarding exudation after an injury.

the blood and blood proteins escape from vasculature and go to the injury/implant

Describe the type of test used to mechanically test ceramics

• 3 point bend test to rod with circular or rectangular cross-sectional areao apply force in centero place holders at each end L-length apart o force applied up (on bottom face) for tension and force applied down (on top face) for compression

WHat are the Hume-Rothery Rules?

• change in radius is less than 15%• vacancy is the same• same crystalline structure• electronegativity is within a +- 0.3

List the four properties that valence electrons determine

• chemical• electrical• thermal• optical

list the types of tissues.

• epithelial• connective• muscular• nerve

list host response to an implant.

• injury• acute inflammation• chronic inflammation• granulation tissue• foregin body eaction• fibrosis and encapsulation

List the five factors that influence degradation

• location in the body• water• proteins• inflammatory cells• mechanical stress

what are the types of ceramics?

• nonporous nearly inert• porous inert• nonporous bioactive• resorbable materials

List the three ways dislocations are formed or introduced

• solidification• plastic deformation• thermal stresses

what are the types of point defects?

• vacancy atoms• interstital atoms• substitutional atoms

List the three types of point defects

• vacancy atoms• interstitial atoms• substitutional atoms