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Biomaterials > Test 1 > Flashcards

Test 1 Flashcards

1
Q

Two important aspects of identifying a biomaterial to be used in the human body are functional performance and _____________ .

A

Biocompatibillity

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2
Q

________ are widely used as biomaterials for their strength and toughness

A

metals

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3
Q

give 3 examples of metals used throughout the human body

A
  1. stainless steel 316L 2. titanium 3. cobalt alloys
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4
Q

what is the most common type of medical grade stainless steel? Name 3 elements in this type of stainless steel

A

stainless steel 316L iron, chromium, nickel

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5
Q

state 3 physical properties of metals that make them attractive for their use as a metallic biomaterial?

A

Ductile, high melting point, luster, malleable

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6
Q

what element increases the formation of carbon dioxide (Cr23C6) in 316L stainless steel?

A

chromium

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7
Q

name the overall classification of materials that could potential used as biomaterials

A

metals, ceramics, composites, polymers

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8
Q

give 3 examples of materials that can be used as dental metals

A

Amalgam, gold and gold alloy, nitinol

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9
Q

which of these metallic biomaterials has the best corrosion resistance; which of these metallic biomaterials cobalt alloys, stainless steel or pure titanium?

A

pure titanium

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10
Q

why is pure gold not useable in dental applications? What is added to it to make it a better dental biomaterial

A

pure gold is too soft add platinum

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11
Q

why is it advisable to reduce carbon content in medical grade stainless steel material

A

reduce carbide formation at grain boundary carbide impairs formation of surface oxide

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12
Q

what is the main advantage of using a titanium alloy in bone as opposed to any other metal

A

permits bone growth at the interface

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13
Q

what is purpose of adding tungsten of nickel to cobalt based alloys

A

improve machinability and fabrication

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14
Q

state 3 reasons why amalgam is preferred as a dental biomaterial?

A

stable strong inexpensive and endurbale

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15
Q

metalls are widely used as biomaterials due to their ______ & ___________

A

strength and toughness

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16
Q

list four metallic implants materials and explain the composition properties and potential applications for one of them

A

Cobalt chromium alloys- Co:58-69%, Cr: 27-30%, Mo: 5-7% titanium based alloys- Ti: 89%, Al: 6%, V: 4% 316L stainless steel- 60-65% iron, 17-19% chromium, 12-14% nickel nitinol- Nickel and titanium aplication: bone plates, stents and orthodontic wires

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17
Q

what is biocompatibility

A

does not elicit a negative response with the body

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18
Q

What is nitinol

A

an alloy of Nickel and titanium also is a shape memory alloy

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19
Q

name 3 types of medical devices

A

drug delivery cardiovascular devices orthopedic

20
Q

state 2 ways in which atoms of metals mix to form alloys

A

substitution and intersticial

21
Q

describe shape memory alloys

A

have the ability to return to a predetermined shape when heated

22
Q

what is the outer layer that protects a metal from corrosion

A

surface oxides

23
Q

although several types of stainless steel are available for implant use, in practice the most common is grade 2, _________ stainless steel. This stainless steel alloy is composed predominantly ____, which makes up approximately 60-65%, plus addition of ____, makes up 17-20% of the alloy. Additionally, approximately 12-14% of the alloy is comprised of _____. In order to reduce the possibility of in vivo corrosion only trace amounts less than 0.03% of ____ are found in the alloy.

A

316L iron chromium nickel carbon

24
Q

Co-Cr-Mo alloys, ASTM F75 or ASTM F799 are mostly made up of Cobalt comprising _______%. also in the compound is approx _______% of chromium and roughly ____% of molybdenum

A

Co:58-69% Cr: 27-30% Mo: 5-7%

25
Q

define unit cell as it relates to metallic crystal structure

A

smallest repetive volume which contains the complete lattice pattern of a crystal and metals are crystalline solids

26
Q

state and describe 3 tpyes of imperfections/ defects in the metallic crystal structure

A

vacancy atoms- empty spaces where an atom is missing interstitial-extra atoms are positioned between atomic sites dislocations- line defects, slip between crystal planes result when dislocations move

27
Q

state and describe 2 metal fabrication methods

A

Forming- forging, rolling, drawing, extrusion casting- mold is filled with a metal joining- powder metallurgy, welding

28
Q

In an electrochemical redox reaction, loss of electrons is _______ and a gain of electron is ______,

A

loss of electron is OXIDATION gain of electrons is REDUCTION

29
Q

describe the mechanism of metallic corrosion

A

corroded state is preferred since lowest energy state metal atoms ionize go into solution and combine with oxygen metal flakes off

30
Q

define galvanic corrosion

A

two different metals/ alloys that are in close proximity in an electrolytic environment

31
Q

what is corrosion

A

gradual wearing away process

32
Q

what are the 2 primary factors that drive metallic corrosion

A
  1. thermodynamic driving forces (reduction/oxidation)
  2. kinetic barriers
33
Q

what substance is oxidized and which substance is reduced in the formation of rust?

4Fe+2 + O2 + 8H2O → 2Fe2O3H2O + 8H+

A

Oxidized: Fe

reduced: oxygen

34
Q

what is the main function of the oxide layer on the surface of a metal

A

to prevent corrosion and rusting

35
Q

state and describe 3 types of corrosion

A

galvanic- 2 different metals/ alloys that are in close proximity in an electrolytic environment

crevice- found in the crevices or deep, narrow flaws

uniform attack- general corrosion that is evenly distributed over entire corrosion region

36
Q

name and describe 2 basic reactions associated with corrosion

A

Ionization: formation of metallic cations under acidic or reducing conditions

oxidation: reaction of metal with oxygen

37
Q

how does galvanic corrosion occur

A

metals/ alloys in close proximity with electrolytic environment

38
Q

which is the reducing agent and which is the oxidizing agent in the reaction below?

Cu + 2Ag+ → Cu+2 + 2 Ag

A

oxidation: Cu to Cu2+
reduction: 2Ag+ to 2 Ag

39
Q

In the galvanic series which (gold, magnesium, and titanium) is considered the most active metals in seawater?

A

magnesium

40
Q

which type of corrosion occurs when 2 different metals/alloys are in close proximity in an electrolytic environment?

A. Pitting corrosion

B. Crevice corrosion

C. galvanic corrosion

D. Intergranular corrosion

A

C. galvanic corrosion

41
Q

what is fretting corrosion

A

wear process due to relative motions in highly loaded devices exaggerated by corrosive environment

42
Q

what can one do to prevent corrosion

A

use appropiate metals

minimize pits and crevices

avoid implantation of dissimilar metals

43
Q

describe uniform attack corrosion

A

general corrosion that is evenly distributed over entire corrosion region

44
Q

explain deposit corrosion mechanism

A

foreign substances with moisture which come from the environment adhearing to a surface of a metal cause the deposit corrosion because of the lack of oxygen under the deposit.

45
Q

what is the difference between galvanic and fretting corrosion

A

galvanic corrosion is when 2 different metals/ alloys are in close proximity with electrolytic environment

fretting corrosion is the wear process due to relative motion in highly loaded devices exaggerated by corrosive environment

46
Q

describe the possible effects of corrosion of medical devices

A

biocompatibility

mechanical integrity

aesthetics

47
Q

what are some of the advantages and disadvantages of the use of magnesium for implant material applications

A

Advantages:

  • biodegradable
  • lightweight
  • biocompatibility

disadvantages:

  • low corrosion resistance
  • fast hydrogen evolution
  • degradation occurs before end of healing

Biomaterials (4 decks)

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