BR Biomaterials

Question 1

What is biocompatibility?

Answer 1

The biocompatibility of a material must consider both the hosts response to a material and the physiological effect of the environment on the material.

Question 2

What is stress?

Answer 2

The ratio of applied force to cross-sectional area.

Question 3

Is strain?

Answer 3

Strain is defined as ratio of change in length to the original length of material specimen.

Question 4

What is the ductility of a material?

Answer 4

Ductility is a measure of the degree of plastic deformation sustained at a fracture.
It can be expressed as either percent elongation or percent area reduction.

Question 5

What is a materials hardness?

Answer 5

The measure of a materials resistance to localized plastic deformation. It relates directly to the wear of a material.

Question 6

What is fatigue failure?

Answer 6

Delayed failure resulting from fluctuating or cyclic stresses.

Question 7

What is viscoelasticity?

Answer 7

Describes viscous and elastic properties typical of polymers and biological materials.

Question 8

What is creep of a substance?

Answer 8

A permanent deformation that occurs over time as a result of an applied constant stress.

Question 9

What are the three categories of materials used as biomaterials?

Answer 9

Ceramic
Metal
Polymers

Question 10

What type of hypersensitivity is seen with metal implants?

Answer 10

Type IV
A delayed response of hypersensitivity
“ACID”

Question 11

What metal sensitivity is most common for humans?

Answer 11

Nickel!
15% of the population exhibits an allergic response to the metal.

Stainless steel contains 13-15.5% nickel.

Question 12

What is stress shielding?

Answer 12

Phenomenon in which bone mass is decreased over an extended period of time as a result of the presence of a rigid device.
When a rigid device that has a higher stiffness than bone, such as a metal implant, is placed adjacent to bone , the applied stress gets transfered to the metal and as a result shields the bone from stress leading to atrophy.

Question 13

How can you reduce stress shielding?

Answer 13

Less rigid or flexible fracture fixation devices.

Polymers and composits or very thin metal plates.

Question 14

What are two types of commonly used absorbable polymers?

Answer 14

PGA and PLA

Polyglycolic acid and polylactic acid

Question 15

What forces do ceramics resist well?

Answer 15

Ceramics resist compressive forces much better than tension forces.

Question 16

What are the applications of hydroxyapatite?

Answer 16

Hydroxyapitite can be used for porous or solid implants.

It can be used as a coating on implants or filler in gaps.

Question 17

How is biological fixation achieved?

Answer 17

Osteointegration!
Procces in which bone attaches to a material or device.
Can be enhanced by textured/porous surfgaces or coating with a material that serves osteoinduction (hydroxyapatite/glass ceramics)