Quizes (exam 1) Flashcards

1
Q

The developmental process of the biomaterials field has evolved through three distinct generations. What is true about the focus of each generation?

(a) First generation: inert equaled bioactive, use of off-shelf materials to replace soft/hard tissues; Second generation: regenerative functional tissues to provide true replacement with the use of living cells; Third generation: bioactive materials with tunable degradation rates to provide bone bonding and release drugs.
(b) First generation: inert commercially available materials that could match tissue functional properties; Second generation: materials with controlled degradation rates with the goal to eliminate the interface material-tissue; Third generation: development of biointeractive, resorbable, integrative, regenerative materials.
(c) First generation: bioactive materials to control reactions with the physiological environment; Second generation: bioinertness to minimize foreign body reactions; Third generation: regenerative tissue, true replacement with living cells.
(d) First generation: biocompatible materials with tunable degradation rates; Second generation: bioactive materials to minimize foreign-body reactions; Third generation: regenerative functional tissues.
(e) None of the above accurately describes the evolution of biomaterials science.

A

(b)First generation: inert commercially available materials that could match tissue functional properties; Second generation: materials with controlled degradation rates with the goal to eliminate the interface material-tissue; Third generation: development of biointeractive, resorbable, integrative, regenerative materials.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

First generation biomaterials

A

bioinert, off-the-shelf commercially available materials that because were inert were considered biocompatible. In this generation materials were selected for use based on their basic properties (hardness, toughness, elasticity, etc) in such a way they could match the functional properties of the tissues they were replacing.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Second generation biomaterials

A

bioactive materials, or materials that could be synthesized with tunable degradation rates with the intent of eliminating the interface with host tissues. It was believed that by eliminating the biomaterial-host interface foreign-body reactions could be prevented.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Third generation biomaterials:

A

true tissue replacement by using living cells. Use of biointeractive, resorbable, integrative and regenerative materials.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

True or false

(a) Cardiac pacing leads are designed with flexible, stable and highly conductive materials to withstand the harsh endocardial environment. Most failures with cardiovascular assist devices such as the pacemaker are observed due to failure of the leads.

A

This is correct, as mentioned most problems with these devices are due to failure of the leads. The leads are designed with flexible materials that need a combination of properties (flexibility, high resistance, conductivity) to withstand the harsh endocardial environment. A very important aspect is to ensure pacing leads make endocardial contact to properly transmit cardiac signals from the electrodes. Because severe inflammatory reactions are typically caused upon implantation of pacing leads, many designs are now available with drugs to attenuate inflammation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True or False

(b) Cardiovascular stents are tubular scaffolds typically designed with flexible polymers (ultra-high molecular weight polyethylene, UHMWPE), 316L stainless steel and CoCr alloys. These devices are typically coated with thin layers infused with drugs to eradicate inflammation.

A

False

This is incorrect, go to your slide 37 and check the materials cardiovascular stents are made of. They are not designed with UHMWPE.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

True or False
(c) Total joint implants are designed with a combination of engineering materials including commercially pure titanium (cpTi), UHMWPE, ceramics, and CoCr alloys.

A

False

This is incorrect, go to your slide 38 and check the materials hip implants are made of. They are not designed with commercially pure Ti but typically with the alloy Ti6Al4V. In the class we discussed that dental implants are typically designed with commercially pure Ti (cpTi) because this grade of titanium is softer than the alloyed form.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

True or False

Dental implants are designed with a variety of surface features typically exhibiting a porous or smooth surface. Considering cell adhesion on the surface, designs with smoother surface will facilitate bone cell adhesion and proliferation, which will provide superior mechanical stability.

A

False

This is incorrect; per our discussion rough surfaces will promote bone forming-cells adhesion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Based on the literature you read (“Overview of biomaterials and their use in medical devices”) which one of the following is not correct ?

(a) Natural materials used as biomaterials for implants are non-immunogenic.

(b) Polymeric acetabular cups may not require a metallic backing.
(c) Polymeric cushion in tibial components will reduce wear due to metal articulation.

(d)Titanium encapsulation of pacemaker provid

A

Answer (a)

All materials implanted in the body will provoke some sort of immune response regardless being natural or synthetic. Think about tissue engineered materials, for example collagen injected in the knee. Even though collagen is a natural substance, immunogenic reactions can be triggered upon material implantation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

True or false

the ideal biomaterial or synthetic material combination should have Low wear resistance to minimize wear debris generation.

A

False

Implantable materials should have high resistance to wear to minimize possible **particle generation. **

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

True or false

the ideal biomaterial or synthetic material combination should have A high modulus to maximize bone resorption.

A

Implantable materials should have modulus close to the modulus of natural tissues to prevent fracture due to excessive stresses. We will discuss this in detail later on but imagine inserting a material that is too different from the host bone in terms of mechanical properties. The material can either fracture the bone structure (if too tough) or not provide enough augmentation (if too soft).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

True or False

the ideal biomaterial or synthetic material combination should have Excellent resistance to degradation.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

True or False

The ideal biomaterial or synthetic material combination should have A biocompatible chemical composition to accept adverse tissue reaction.

A

False
A biocompatible chemical composition should always be tuned so to avoid or minimize adverse tissue reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is surface tension (γ)?

A
    • Surface tension is the opposing force to atmospheric pressure.
    • Force acting at interfaces.
    • Force acting on boundaries.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Cite 4 events (with examples) occurring at surfaces?

A
  1. Hydration (water molecules approach the surface),
  2. adsorption (proteins, bacteria, cells),
  3. degradation (corrosion, wear, scratching, cracks),
  4. electrical properties (double layer, cations/anions movement to/from surface).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In terms of composition, why are surfaces different from the bulk given they are made of the same materials?

A

Because surfaces interact with the biological environment leading to deposition of proteins, water and other molecules, bacteria, cells etc. Thus the alloy composition is different on the top layers.

17
Q

How would you determine how hydrophilic or hydrophobic a surface is?

A
  • By measuring the contact angle (Ө) between the surface and solution of interest.
  • Small contact angles indicate that the surface has affinity for the medium (droplet spreads out trying to maximize interaction with the surface, configuration of lowest free energy).
  • Large contact angles indicate hydrophobic surfaces (droplet balls up in an attempt to minimize interaction with the surface, configuration of minimum surface energy).
  • Contact angles are measured using microscopy techniques or an equipment called Goniometer.
18
Q

Cooling metal rapidly by immersing the material in salt water, water, oil, molten salt, air or gas.

(a) Hardening
(b) Annealing
(c) Quenching
(d) Normalizing

A

(c) Quenching

The above question is nothing but the definition for quenching which involves rapid cooling of metal.

19
Q

Co-Cr alloys are shaped into implant through:

(a) Conventional machining methods
(b) Investment casting
(c) Powder metallurgy
(d) Both (b) & (c)

A

(d) Both (b) & (c)

CoCr alloy cannot be fabricated to complex implant designs by conventional machining technologies. It can be fabricated either by investment casting (or) powder metallurgy

20
Q

Metals and alloys may not possess all the desired properties in the finished stock form. Therefore, what method is extensively used to control metal properties?

(a) Metal rolling
(b) Powder production
(c) Metal forging
(d) Heat treatment

A

(d) Heat treatment

There are six points which explain the need for heat treatments. These points state that fracture, fatigue, hardness, toughness, residual stress and homogeneity of micro-grains of a material can be controlled and fine-tuned by heat treatment techniques.

21
Q

What methods are used in surface hardening?

(a) Quenching,Annealing
(b) Strengthening, Normalizing
(c) Heating followed by cooling,Thermo-chemical treatment
(d) (a)and( c)

A

(c)Heating followed by cooling,Thermo-chemical treatment

two different methods for obtaining surface hardening are provided namely (i) Heating followed by cooling and (ii) Thermo-chemical treatment.

22
Q

Which one of the following is not correct?

(a) Stress-strain curve of ceramics only has a linear elastic region.
(b) Biocompatibility is the ability of a material to stimulate healing and trick the tissue system into responding as if it were a natural tissue.
(c) Bioactivity is the characteristic that allows the material to form a bond with living tissue.
(b) further explains bioactivity which explains the ability of the biological interaction to stimulate healing and trick the immune system.of the implant due to chemical or cellular interaction.

A

(b) Biocompatibility is the ability of a material to stimulate healing and trick the tissue system into responding as if it were a natural tissue.

This is not correct because biocompatibility is the ability of a material to avoid toxicity and immune response

(a) Stress-strain curve of ceramics only has a linear elastic region.

This is correct because ceramics does not have a plastic deformation phase.

(c) Bioactivity is the characteristic that allows the material to form a bond with living tissue.

This is correct. This is the definition of Bioactivity which explains the ability of materials to interact and chemically bond with physiological environment. Choice (b) further explains bioactivity which explains the ability of the biological interaction to stimulate healing and trick the immune system. Biomaterials and Medical Devices BMEN 4360 Fall 2014

3

(d) Biodegradability is the breakdown of the implant due to chemical or cellular interaction.

This is correct. This is the definition of Biodegradabilitiy which is the ability of the material to degrade when it interacts with the chemicals and cells in the biological environment.

Answer: (b)

Go to your Slide 9 in “Week 5” presentation. Definitions for different terminologies such as Bioactivity, Biocompaitbility and Biodegradability are provided.

23
Q

Choose the best match that represents the implant -tissue in different classes of ceramics: (i) No biological (or) chemical bond; (ii) Degrades gradually and replaced by tissue; (iii) Attached by chemical bonds; (iv) Biological fixation.

(a) Type I – (i); Type II – (ii); Type III – (iii); Type IV – (iv)
(b) Type I – (iv); Type II – (ii); Type III –(iii); Type IV – (i)
(c) Type I – (iv); Type II – (i); Type III – (iii); Type IV – (ii)
(d) Type I – (i); Type II – (iv); Type III – (iii); Type IV – (ii)

A

Answer: (d)

Type I is the inert ceramic where there is no chemical or biological bond connecting the implant and the tissue.

Type II is the porous ceramics where osteoblast cells grasp the pores and a biological fixation is established.

Type III is the Bioactive glass (or) the surface reactive ceramics. Hydroxy apatite is an example of bioactive ceramic which interacts with the tissue and forms a chemical bond such as carbonated-HA.

Type IV is the bioresorbable ceramic which degrades invivo due to phagocytic and acidic reactions. The resorbed ceramic material is replaced by a tissue.