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Biosci 3110: BME > Biomaterials > Flashcards

Biomaterials Flashcards

1
Q

Define prosthetic

A

an artificial device that replaces a missing body part, which may be lost through trauma, disease, or congenital conditions

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2
Q

Define implant

A

a medical device placed inside the body to replace/support a missing biological structure

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3
Q

Define Biomaterial

A

a material intended to interface with biological systems to evaluate, treat, augment, or replace any tissue, organ, or function of the body

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4
Q

Define Biological Material

A

a material such as bone, skin, or artery produced by a biological system

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5
Q

Define Osseointegration

A

the formation of a direct interface between an implant and bone without intervening soft tissue

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6
Q

Define Osteoinduction

A

undifferentiated and pluripotent cells are stimulated to develop into the bone-forming cell lineage

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7
Q

Define Osteoconduction

A

the process by which bone is directed to conform to a material’s surface

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8
Q

What is the role of osteoblasts and osteocytes?

A

involved in the formation/mineralization of bone

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9
Q

What is the role of osteoclasts only?

A

involved in the resorption of bone tissue

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10
Q

Define biocompatible (FDA)

A

produces no harm to the host

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11
Q

Define biocompatible (Ours)

A

the ability of a material to perform with an appropriate host response in a specific situation

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12
Q

Define Biomedical material

A

the broadest category for materials used in or on the surface of the human body

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13
Q

Define thrombogenicity

A

the tendency of a material to interact with the blood to produce a clot

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14
Q

Define carcinogenicity

A

A substance that is able to cause cancer usually be damaging the genome or disrupting metabolic processes

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15
Q

Define mutagenicity

A

the ability to cause genetic damage

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16
Q

Define stress shielding

A

the interface between bond and an implant with a high modulus begins to deteriorate

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17
Q

Define fatigue failure

A

micro-defect creates nucleation point that will fracture under repeated loading/unloading

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18
Q

Define aseptic loosening

A

the failure of the bond between an implant and bone in the absence of infection usually caused by wear debris

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19
Q

Define fretting fatigue

A

occurs when a foreign body is statically pressed against the surface of the specimen upon which a cyclic stress is being applied

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20
Q

Define tension

A

pull

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21
Q

Define compression

A

push

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22
Q

Define shear stress

A

scissors, slide

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23
Q

Define extensometer

A

used to measure the change in dimensions of a test sample along the axis of loading

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24
Q

Define proportional limit

A

highest stress where stress is linearly proportional to strain

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25
Q

Define yield stress

A

stress which causes the onset of permanent deformation (also called yield strength or elastic limit)

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26
Q

Define ultimate strength

A

the area under the stress strain curve up to the failure point

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27
Q

Define strain hardening

A

an increase in stress levels after the yield stress is reached

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28
Q

Define viscoelastic material

A

show a time-dependent deformation component due to viscous flow within the material

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29
Q

Define Class I Biomedical Device

A

low to moderate risk to the patient and/or user (elastic bandages, stethoscopes, surgical tools)

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30
Q

Define Class II Biomedical Device

A

pose a moderate to high risk to the patient and/or user (infusion pumps, surgical drapes, acupuncture needles)

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31
Q

Define Class III Biomedical Device

A

have a high risk to the patient and/or user (pacemaker, vascular stents, implants)

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32
Q

Define tough

A

a material that is both strong and ductile (withstand both high stresses and high strains)

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33
Q

Define generation III alloy

A

Designed to act as temporary structures that can degrade over time allowing native tissue to integrate with the implant and eventually replace it

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34
Q

Ionic bond

A

a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions

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35
Q

Metallic bond

A

a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons and positively charged metal ions

Tightly packed cations surrounded by an electron cloud

Allows for good charge transfer that makes metals good conductors of heat and electricity

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36
Q

Covalent bond

A

a type of chemical bond that involves the sharing of electron pairs between atoms

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37
Q

Sigma bond

A

the strongest covalent bonds, due to head-on overlapping of orbitals on two different atoms

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38
Q

Pi bond

A

where two lobes of an orbital on one atom overlap two lobes of an orbital on another atom

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39
Q

Hydrogen bond

A

a partially electrostatic attraction between a H atom bound to a more electronegative atom such as FON and another similar atom

40
Q

Properties of polymers (modulus, toughness, plastic deformation)

A

Low modulus
Higher toughness than ceramics
Large plastic deformation

41
Q

Composition of polymers

A

Long molecules built from monomers (ex: DNA/protein)

Crosslinked polymers common in implants → toughen material and make it insoluble

42
Q

High Density Polyethylene

A

POLYMER

Plastic liner of hip implant
Can be crosslinked or not
Non-toxic, super insoluble

43
Q

Poly(ether ether ketone) or PEEK

A

POLYMER

spinal implants

44
Q

Poly(methyl methacrylate) or PMMA

A

POLYMER

bone cement

45
Q

Poly(hydroxyethyl methacrylate) or pHEMA

A

POLYMER

soft contact lenses

46
Q

poly(lactic-co-glycolid acid) or PGLA

A

POLYMER

polylactic resorbable orthopedics

47
Q

Properties of ceramics (modulus, toughness, plastic deformation, insulator/conductor)

A

Hard (high modulus)
Brittle (less tough than polymers) with little plastic deformation
Insulators

48
Q

Composition of ceramics

A

Composed of metallic and non-metallic elements, can be crystalline or amorphous

49
Q

Define glass

A

CERAMIC

Amorphous solid with slow transition to liquid after glass transition temperature, undefined composition

50
Q

What is the composition of window glass?

A

CERAMIC

Mostly silicon-oxygen linkages (70% SiO2) with (14%) sodium oxide and (9%) calcium oxide (soda/lime) (form basic hydroxides in water)

51
Q

What is the code for bioactive glass?

A

45S5

52
Q

What is the composition of bioactive glass?

A

CREAMIC

Composed of (25%) calcium oxide, (25%) sodium oxide, (6%) phosphorus pentoxide, and (45%) silicon dioxide (compounds naturally present in bone)

53
Q

What if bioactive glass has too much silica, sodium oxide, or phosphorous pentoxide?

A

bioinert like window glass

unstable

prevent glass formation or causes crystals

54
Q

Example of bioactive glass uses and why it was a good replacement

A

CERAMIC

Used in ear implants to avoid the formation of scar tissue (metal/polymer) that moved the implants out of position, leading to damaging vibrations

55
Q

Define bioactive bonding

A

Direct bond to bone, release ok ions

56
Q

Describe the melt process of making glass

A

Heat raw materials together → yields dense solid materials with low porosity

57
Q

Alumina/Zirconia

-used in and properties

A

ceramic acetabular cups of hip implants

hard with good compression strength

58
Q

What does hydroxyapatite contain at minimum?

A

CERAMIC

Contains (at minimum) calcium, hydroxyl groups, and ortho phosphate (Ca to Phos of 1.67)

59
Q

What happens if you switch the OH- from HA to F or Cl?

A

Can switch OH- with F- (more hydrophobic) or Cl- (hydrophilic)

60
Q

What happens if you switch the phosphate from HA to carbonate or silicate?

A

Can switch phosphate with carbonate or silicate to match bone more closely

61
Q

A layer of HA forms on top of bioactive glass. Why?

A

Surface layer forms on bioglass due to the reaction between calcium (bioglass) and soluble phosphates

62
Q

Porous forms of HA used in…

A

Porous forms used in cancellous bones, orthopedic surgeries, and dental surgeries

63
Q

Micropores in HA would…

A

allow cells that remodel, resorb, and form bonds → increases rate of dissolution

64
Q

Formation of HA through solid state reactions

A

can prepare HA, but require high temps and are lengthy and require careful stoichiometric control, yield highly crystalline HA

65
Q

Formation of HA through sintering

A

heat above 900*C for several hours, increases mechanical properties, similar tensile strength to bone, fracture toughness much lower than bone

66
Q

Formation of HA through wet chemical processes

A

smaller crystals, more homogenous products, make more like bone, low temp

67
Q

beta tricalcium phosphate

components, uses, properties, solubility

A

Bioresorbable
Ratio of Ca to PO4 → has low Ca
Denser are less resorbable
Many calcium salts are not soluble (calcium chloride and nitrate will dissolve)

68
Q

Properties of metals (modulus, tough, plastic deformation, atoms, oxidation)

A

High modulus / Very tough
Can undergo plastic deformation
Tightly packed atoms with sea of electrons
Usually 0 oxidation

69
Q

Oxide layer formation in metals

A

can react with water and oxygen to form oxide layers (may protect the metal underneath)
Can be sloughed off to release metal ions → Fretting fatigue and other wear

70
Q

Production of metals

A

Wrought or forged alloys have superior mechanical properties compared to cast ones

71
Q

Special Stainless Steel (name, composition, additives, generation)

A

GENERATION 1

Iron with higher Cr/Ni for protective oxide layer
Carbide layer reacts with Cr to use it up and cause oxidation → only short term implants
Oxygen can reform oxide layer if damage occurs, but O2 levels are low in body
Molybdenum for chloride resistance

72
Q

Oxidation levels of Cr

A

Cr has three oxidation states: 0, +3, and +6 (dangerous)

73
Q

CoCrMo (generation, uses, properties, additives) (crystal structure in separate question)

A

GENERATION 1

Femoral stem of hip implant, knee implants, load bearing
Strong/high modulus, heat/corrosion resistant, expensive, Co/Cr toxic, stress shielding, bend > fracture

Can add tungsten to co-cr alloys, but it reduces corrosion resistance

74
Q

CoCrMo two crystal structures

A

Two crystal structures → barrier of motion for deformation

Face centered cubic and Hexagonal close packed

75
Q

Nitinol (composition, uses)

A

Alloys of 49% Ni and 51% Ti can form stents to be inserted at RT but expand at body temperature

76
Q

Titanium (generation, properties- special, toxicity, oxide, use, modulus, $)

A

GENERATION 2

can osseointegrate, nontoxic, stable oxide layer, load bearing, closest modulus to bone, less expensive

77
Q

Titanium osseointegrate (what/how/use)

A

Osseointegrate - direct bonds with bone, prevents loosening/vibrations
Not good for temporary
Titanate with O- + Ca from blood + PO4 → bone-apatite (osteocytes remodel)

78
Q

Describe the alpha grade of titanium and what can be added to stabilize it

A

𝞪 - commercially pure titanium, low strength

Aluminum, gallium, tin stabilizes

79
Q

Describe the beta grade of titanium and what can be added to stabilize it

A

𝜷 - lower modulus, enhanced ductility, low wear resistance

Molybdenum, tantalum, vanadium, niobium, tungsten, chromium, iron, cobalt, nickel, copper, or manganese stabilize

80
Q

Describe the alpha/beta grade of titanium

A

𝞪-𝜷 - high tensile/fatigue strength, low ductility, cannot biodegrade

81
Q

Use of alpha, beta, and alpha/beta alloys of titanium?

A

alpha and beta → not used in structural, coatings

alpha/beta → structural implants such as femoral stems of hip implants and knee implants

82
Q

How are the grades of titanium determined?

A

Based on O2 content (small differences) and can also be classified based on crystal structure

83
Q

Generation of magnesium alloys and why

A

Gen 3 → Biodegrade and resorb over time

84
Q

Two general drawbacks of magnesium

A

generate hydrogen gas

low solubility with additives

85
Q

Describe the hydrogen gas production of magnesium and what can modify it

A

0 oxidation (metal), forms Mg(OH)2 and H2 gas → M(OH)2 will produce MgCl2 (very soluble)

Rate can be controlled with different elements (Ca, Zn)

Adding zinc reduces the rate of hydrogen gas production

86
Q

What additives can be added to magnesium alloys? What effects can they have?

A

Low solubility with additives

Such as those that increase corrosion resistance (Mn, Cu, Al, Ca, Zr, Gd)

Amorphous magnesium glass can be created that improves corrosion, hydrogen production, strength, and elasticity, but have lower ductility (more like glass)

87
Q

Shapes for tensile or compression testing, correlation between

A

Test tensile strength with dogbone, test compression with cylinder/rectangle
Ceramics are good at compression but bad at tensile (does not correlate)

88
Q

Hooke’s Law

A

strain is proportional to stress as long as it is below elastic limit (yield stress)

Revert to original dimension when unloaded

89
Q

Poisson’s ratio

A

the ratio of transverse contraction strain to longitudinal extension strain

Volume remains steady, which causes transverse deformation that increases length and decreases diameter

90
Q

Two shear testing equations

A

Shear stress = force * cross sectional area II to applied force
Shear stress = shear modulus * shear strain

91
Q

Two types of bending testing

A

Bending testing → Three (strength) or four point (material properties)

92
Q

…….. introduced aseptic techniques in the 1860s

A

Lister introduced aseptic techniques in the 1860s

93
Q

……. invented bioactive glass at the University of Florida

A

Larry L Hench invented bioactive glass at the University of Florida

94
Q

Three ear bones

A

The malleus, incus, and stapes are the three ear bones

95
Q

……….. was the first to do hip replacements, made of ………….

A

Sir John Chamley was the first to do hip replacements, his were made of stainless steel

96
Q

Two major types of joints

A

Static (skull, wrists, teeth)

Mobile (hips, knees, ankles, shoulders, elbows)

97
Q

Two types of mobile joints

A

Congruent
Ball-shaped head fits closely into a cup-like socket

Incongruent
Consist of two incongruent hard surfaces that create highly concentrated (heterogeneous) stresses usually compensated by thick cartilage and synovial fluid

Biosci 3110: BME (6 decks)

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