Metals

Question 1

Why might a metal orthopedic be designed with holes in the fixture? What are some pros and cons?

Answer 1

Holes can be used for weight reduction, and tissue fixation/integration, but also loss in mechanical strength (stress concentrations)

Question 2

Why might a metal orthopedic be designed with a tapered shaft?

Answer 2

The tapered shaft plays a role in customization.

Question 3

Why is are metallic implants easier to evaluate post implantation?

Answer 3

They can be easily seen in x rays etc.

Question 4

Ranks the unit crystal packing from least to most compact: body/face centered

Answer 4

Body centered is less compact than face centered.

Question 5

How many atoms exist in a unit of a body centered arrangement?

Answer 5

2 atoms

Question 6

How many atoms exist in a unit of a face centered arrangement?

Answer 6

4 atoms

Question 7

Stainless steel primarily consists of the following three metals:

Answer 7

Fe(iron), Cr(Chromium), and Ni(Nickel)

Question 8

Steel is usually used in orthopedics for the following pieces:

Answer 8

Screws, nails, plates

Question 9

Stainless steel can corrode in vivo in areas of :

Answer 9

Low oxygen content

Question 10

Cobalt alloys mainly consist of these three metals:

Answer 10

Cobalt, chromium, and Mo

Question 11

For cobalt alloys, work hardening can be avoided due to the process of :

Answer 11

the lost wax method

Question 12

Cobalt alloys: Pro and Con

Answer 12

Pro: good corrosion resistance. Con: difficult to fabricate and shape

Question 13

Cobalt alloys: usually used in:

Answer 13

dental applications and orthopedics

Question 14

Titanium: Consists of the following metals:

Answer 14

Titanium, Oxygen, Aluminum, and V

Question 15

Titanium: Pros and Cons

Answer 15

Pros: Light weight and high strength. Cons: Hard to fabricate due to sensitivity at high temperatures due to extreme oxidation

Question 16

Titanium: You can avoid reactivity and corrosion/oxidation by adding this metal:

Answer 16

Aluminum

Question 17

Galvanic Battery: Oxide layer forms on the (anode/cathode)

Answer 17

anode

Question 18

Galvanic Battery: Electrons flow from

Answer 18

anode to cathode.

Question 19

Pitting Corrosion:

Answer 19

Local imperfections in oxide layer cause anionic and cathodic areas.

Question 20

Fretting Corrosion:

Answer 20

Passive layer removed due to mechanical forces

Question 21

Environmental Stress/Stress Corrosion

Answer 21

Active radicals/oxidation causing cracking at stress concentration fronts

Question 22

Galvanic Corrosion

Answer 22

The presence of two different metals in the same material cause one to become more anodic and the other more cathodic.

Question 23

What is a pretty good rule to prevent corrosion when selecting materials for a device?

Answer 23

You should try not to use 2 different metals in the same area. This prevents galvanic corrosion.

Question 24

Crevice Corrosion

Answer 24

Breakage at the stress concentration points.

Question 25

In what ways can corrosion with the aid of biological molecules create a positive feedback loop?

Answer 25

When biological molecules consume metals, it can change the pH and lead to decreased oxygen transport that can both break down the oxide layer.