Test 1

Question 1

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

Answer 1

Biocompatibillity

Question 2

________ are widely used as biomaterials for their strength and toughness

Answer 2

metals

Question 3

give 3 examples of metals used throughout the human body

Answer 3

1. stainless steel 316L 2. titanium 3. cobalt alloys

Question 4

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

Answer 4

stainless steel 316L iron, chromium, nickel

Question 5

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

Answer 5

Ductile, high melting point, luster, malleable

Question 6

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

Answer 6

chromium

Question 7

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

Answer 7

metals, ceramics, composites, polymers

Question 8

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

Answer 8

Amalgam, gold and gold alloy, nitinol

Question 9

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

Answer 9

pure titanium

Question 10

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

Answer 10

pure gold is too soft add platinum

Question 11

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

Answer 11

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

Question 12

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

Answer 12

permits bone growth at the interface

Question 13

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

Answer 13

improve machinability and fabrication

Question 14

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

Answer 14

stable strong inexpensive and endurbale

Question 15

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

Answer 15

strength and toughness

Question 16

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

Answer 16

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

Question 17

what is biocompatibility

Answer 17

does not elicit a negative response with the body

Question 18

What is nitinol

Answer 18

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

Question 19

name 3 types of medical devices

Answer 19

drug delivery cardiovascular devices orthopedic

Question 20

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

Answer 20

substitution and intersticial

Question 21

describe shape memory alloys

Answer 21

have the ability to return to a predetermined shape when heated

Question 22

what is the outer layer that protects a metal from corrosion

Answer 22

surface oxides

Question 23

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.

Answer 23

316L iron chromium nickel carbon

Question 24

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

Answer 24

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

Question 25

define unit cell as it relates to metallic crystal structure

Answer 25

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

Question 26

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

Answer 26

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

Question 27

state and describe 2 metal fabrication methods

Answer 27

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

Question 28

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

Answer 28

loss of electron is OXIDATION gain of electrons is REDUCTION

Question 29

describe the mechanism of metallic corrosion

Answer 29

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

Question 30

define galvanic corrosion

Answer 30

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

Question 31

what is corrosion

Answer 31

gradual wearing away process

Question 32

what are the 2 primary factors that drive metallic corrosion

Answer 32

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

Question 33

what substance is oxidized and which substance is reduced in the formation of rust? 4Fe⁺² + O₂ + 8H₂O → 2Fe₂O₃H₂O + 8H⁺

Answer 33

Oxidized: Fe reduced: oxygen

Question 34

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

Answer 34

to prevent corrosion and rusting

Question 35

state and describe 3 types of corrosion

Answer 35

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

Question 36

name and describe 2 basic reactions associated with corrosion

Answer 36

Ionization: formation of metallic cations under acidic or reducing conditions oxidation: reaction of metal with oxygen

Question 37

how does galvanic corrosion occur

Answer 37

metals/ alloys in close proximity with electrolytic environment

Question 38

which is the reducing agent and which is the oxidizing agent in the reaction below? Cu + 2Ag⁺ → Cu⁺² + 2 Ag

Answer 38

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

Question 39

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

Answer 39

magnesium

Question 40

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

Answer 40

C. galvanic corrosion

Question 41

what is fretting corrosion

Answer 41

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

Question 42

what can one do to prevent corrosion

Answer 42

use appropiate metals minimize pits and crevices avoid implantation of dissimilar metals

Question 43

describe uniform attack corrosion

Answer 43

general corrosion that is evenly distributed over entire corrosion region

Question 44

explain deposit corrosion mechanism

Answer 44

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.

Question 45

what is the difference between galvanic and fretting corrosion

Answer 45

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

Question 46

describe the possible effects of corrosion of medical devices

Answer 46

biocompatibility mechanical integrity aesthetics

Question 47

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

Answer 47

_Advantages:_ * biodegradable * lightweight * biocompatibility _disadvantages:_ * low corrosion resistance * fast hydrogen evolution * degradation occurs before end of healing