Quizes (exam 1) Flashcards
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.
(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.
First generation biomaterials
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.
Second generation biomaterials
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.
Third generation biomaterials:
true tissue replacement by using living cells. Use of biointeractive, resorbable, integrative and regenerative materials.
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.
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.
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.
False
This is incorrect, go to your slide 37 and check the materials cardiovascular stents are made of. They are not designed with UHMWPE.
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.
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.
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.
False
This is incorrect; per our discussion rough surfaces will promote bone forming-cells adhesion.
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
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.
True or false
the ideal biomaterial or synthetic material combination should have Low wear resistance to minimize wear debris generation.
False
Implantable materials should have high resistance to wear to minimize possible **particle generation. **
True or false
the ideal biomaterial or synthetic material combination should have A high modulus to maximize bone resorption.
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).
True or False
the ideal biomaterial or synthetic material combination should have Excellent resistance to degradation.
True
True or False
The ideal biomaterial or synthetic material combination should have A biocompatible chemical composition to accept adverse tissue reaction.
False
A biocompatible chemical composition should always be tuned so to avoid or minimize adverse tissue reaction.
What is surface tension (γ)?
- Surface tension is the opposing force to atmospheric pressure.
- Force acting at interfaces.
- Force acting on boundaries.
Cite 4 events (with examples) occurring at surfaces?
- Hydration (water molecules approach the surface),
- adsorption (proteins, bacteria, cells),
- degradation (corrosion, wear, scratching, cracks),
- electrical properties (double layer, cations/anions movement to/from surface).