Metals

Question 1

What are the pros of using 316L stainless steel as a biomaterial?

Answer 1

• Good corrosion and fatigue resistance in short term applications
• low cost
• easy to machine

Question 2

What are the cons of using 316L stainless steel as a biomaterial?

Answer 2

• Tend to corrode in long term applications
• high modulus which leads to the stress shielding effect
• Nickle and Chromium allergies are common

Question 3

What are the typical biomaterial applications of 316L stainless steel?

Answer 3

temporary implants such as fixations, screws and plates

Question 4

What are the pros of using Co-Cr alloys as biomaterials?

Answer 4

• Excellent corrosion resistance
• Excellent fatigue/wear resistance
• biocompatible

Question 5

What are the cons of using Co-Cr alloys as biomaterials?

Answer 5

• difficult to machine
• Expensive to process
• high modulus - stress shielding effect
• High density
• Co and Cr particles can cause allergies

Question 6

What is the stress shielding effect?

Answer 6

Reduction in the density for bone due to an implant having a higher modulus to bone and therefore bone is unloaded

Question 7

Typical biomaterial applications for Cr-Co alloys

Answer 7

• Dental replacements
• Hip replacements
• Heart Valves and Stents
• Permenent implants

Question 8

Give the crystal structure and important properties for Alpha-Titanium

Answer 8

• HCP crystal structure
• Corrosion resistant
• Biocompatible

Question 9

What does Biocompatible mean?

Answer 9

When a material is not harmful or toxic to living tissue

Question 10

Give the crystal structure and important properties for Beta-Titanium

Answer 10

• BCC crystal structure
• Ductile
• Tough

Question 11

Why would aluminium be added to titanium alloy?

Answer 11

Aluminium is added as an alpha phase stabiliser and hardener, it has a solid solution strengthening effect

Question 12

Why is vanadium added to a titanium alloy?

Answer 12

vanadium stabilises the beta phase of the alloy and therefore this has ductile properties. This increases the hot workability of the alloy

Question 13

What are the pros of using a titanium alloy as a biomaterial?

Answer 13

• Lightweight
• Greatest corrosion resistance
• Excellent biocompatibility
• Low youngs modulus

Question 14

What are the cons of using a titanium alloy as a biomaterial?

Answer 14

• lower shear strength
• low wear resistance
• expensive

Question 15

what are the typical biomaterial applications for a titanium alloy?

Answer 15

• The stem of knee prostheses
• surface for knee prosthesis
• Dental screws

Question 16

What is the most exciting property of Titanium-Nickle alloys?

Answer 16

Shape memory effect

Question 17

What is meant by the shape memory effect? Give two examples

Answer 17

If you deform a material with this quality at a low temperature, when you heat it to a certain temperature it will return to its initial shape
e.g. Stents and staples