Chapter 58 - Biomaterials

Question 1

pitting corrosion

Answer 1

most severe form of metallic corrosion
autocatalytic process that results from depassivation of small areas of metal with the formation of small holes or “pits”
- steel and other iron containing metals are susceptible, cobalt/chrome alloys are not susceptible

Question 2

crevice corrosion

Answer 2

a type of pitting corrosion
often occurs in metal tapers or screws
creates ionic gradients and ions accumulate in crevices causing damage

Question 3

galvanic corrosion

Answer 3

two dissimilar metals in conductive fluid create an electrochemical gradient causing implant wear

Question 4

fretting corrosion

Answer 4

morse tapers, modular implants
caused by relative micromotion between two metals
primary cause of trunnionosis

Question 5

higher modulus of elasticity indicagtes what?

Answer 5

that the material is stiffer and more resistant to elastic deformation than a material with a lower modulus

Question 6

fatigue failure

Answer 6

failure related to cyclic loading - most common mode of failure in orthopaedic applications

Question 7

anisotropic materials

Answer 7

act differently when force is applied along different axes or in different directions

Question 8

viscoelastic materials

Answer 8

exhibit a rate dependent response to loading

Question 9

creep

Answer 9

increased deformation of a material over time in response to the application of a constant force

Question 10

post irradiation oxidation of UHMWPE causes what?

Answer 10

increased modulus of elasticity
decreased toughness
increase in subsurface delamination

Question 11

crosslinking poly leads to what changes in material properties

Answer 11

increased fatigue resistance
LOWER wear rate
increased resistance to abrasive or adhesive wear
decreased ductility
decreased tensile strength
decreased resistance to fatigue crack propagtion