Article 1 (overview of biomaterials)

Question 1

Components of a pacemaker (3)

Answer 1

1) a pulse generator,
2) at least one electrode, 3) and one or two pacing leads connecting the pacemaker to the heart.

Question 2

Casing functions

Answer 2

Housing for the battery and circuits

Question 3

Where is the pacemaker implanted

Answer 3

It is usually implanted between the skin and pectoral muscle.

Question 4

The circuitry of a pacemaker converts the electrical energy

Answer 4

to small electrical signals.

Question 5

what is the Connector block of a pacemaker and

what is made of?

Answer 5

1) A connector block, is located at the top of the pacemaker It serves to attach the pacemaker to the pacemaker lead.
2) made of polyurethane

Question 6

What material was used for encasing the pulse generator? What material is used today for encasing the pulse generator and why?

Answer 6

1) ceramics and epoxy resin, with silicone rubber.
2) Titanium is used today. This allowed patients to safely use appliances such as micro- wave ovens, because titanium** helps to **shield the internal components and reduce the external electromagnetic interference.

Question 7

Location of leads (pacemaker)

Answer 7

1. One end of the lead is attached to the connector block of the pacemaker.
2. The other end is inserted through a vein and placed in the right ventricle or right atrium of the heart.

Question 8

Components of the lead of a pacemaker (4)

Answer 8

1. a connector pin (portion of the lead that is inserted into the connector block.)
2. lead body (is the insulated metal wire that carries electrical energy from the pacemaker to the heart)
3. fixation mechanism, (serves to hold the tip of the lead in place in the heart. Can be passive (

The tines become lodged in the trabeculae
(fibrous meshwork) of the heart )

or active (The helix (or screw) extends into the endocardial tissue. Allows for lead positioning anywhere in the heart’s chamber)
and
4. at least one electrode: located on the tip of the lead

Tine: a prong or sharp point, such as that on a fork or antler.

Question 9

Lead insulation materials:

Answer 9

1. Silicon rubber tubbing
2. polyurethanes

Question 10

Differences between polyurethanes (5) and silicon rubbers (2) used to make lead bodies (pacemaker)

Answer 10

1. polyurethanes
   
   • stronger
   • enables thinner leads to be used
   • greater flexibility
   • very low coefficient of friction when wet
   • Metal-ion-induced oxidation may _degrade _them.
2. silicon rubbers used to make lead bodies (pacemaker)
   
   • Not as strong as polyurethanes
   • Metal-ion-induced oxidation doesn’t affect them
   *

Question 11

Pacemaker fixation mechanism is made of:

Answer 11

1. Nickel-cobalt alloy with silver core helix or
2. platinum-iridium helix

Question 12

Composition of the electrodes that deliver the electrical energy from the pacemaker to the heart are composed of (5)

Which on is preffered and why?

Answer 12

1. platinum,
2. titanium,
3. stain- less steel,
4. silver, or
5. cobalt alloys.

• Titanium has been used because it forms a nonconducting oxide layer at the surface. This surface prevents the exchange of charge carriers across the boundary.
• Titanium also exhibits a high modulus of elasticity,
• high resistance to corrosion, and
• high durability.

Question 13

Coating of electrodes

Answer 13

1. Electrodes may be coated with iridium oxide to prevent nonconductive layers from forming.
2. The coated electrodes may reduced local inflammation.

Question 14

Why steroid-eluting leads were developed?

Answer 14

• to suppress inflammatory response of the heart wall, thus
• reducing the energy requirements of the pacemaker.

Question 15

Design/materials used for steroid-eluting leads

Answer 15

1. A silicone rubber matrix contains the steroid, and this matrix is contained in a platinum-iridium porous tip electrode.
2. The combination of platinum and iridium results in a material stronger than most steels.
3. The porous tip** electrode provides an efficient pacing and sensing surface by **promoting fibrotic tissue growth and physically stabilizing the tissue interface.

Question 16

Knee impants compossition

Answer 16

• made of metal alloys and polymeric materials.
  
  • Titanium alloys (Ti6AL4V)
  • Cobalt-chromium alloys.
  • UHMWPE
• Most of the other structures of the knee, such as the connecting ligaments, remain intact.

Question 17

Can the stem and ball be of two different materials?, (Example)

Answer 17

Yes, it is common

Examples:

1. titanium alloy femoral stem will have a Co-Cr femoral head.
2. the UHMWPE socket of the common acetabulum replacement can be implanted directly in the pelvis or be part of a modular arrangement wherein the cup is placed into a metallic shell.

Question 18

Uses of metals in medicine:

Answer 18

1. Orthopedicts,
2. maxilofacial surgery
3. cardiovascular surgery
4. dental materials

Question 19

most commonly employed metals (3)

Answer 19

1. stain- less steels,
2. commercially pure titanium and titanium alloys, and
3. cobalt-base alloys

Question 20

Polymers applications (8)

Answer 20

1. facial prostheses
2. tracheal tubes,
3. kidney and liver parts
4. heart components
5. dentures
6. hip and knee joints
7. adhesives and sealants and
8. coatings

Question 21

Ceramics applications

Answer 21

1. dentistry.
2. their use in other fields of biomedicine has not been as extensive, because of the poor fracture toughness of ceramics limits their use for load-bearing applications.

Question 22

Composites applications

Answer 22

1. dentistry as restorative materials or dental cements
2. carbon-carbon and carbon- reinforced polymer composites for bone repair and joint replacement** because of their low elastic modulus levels, these materials have **not displayed a combination of mechanical and biological properties appropriate to these applications.
3. used extensively for prosthetic limbs**, where their combination of **low density/weight and high strength make them ideal materials for such applications.

Question 23

Natural Biomaterials pros and cons: (Example)

Answer 23

1. they are similar to materials familiar to the body.
2. Natural materials do not usually offer the problems of toxicity often faced by synthetic materials.
3. Also, they may carry specific protein binding sites and other biochemical signals that may assist in tissue healing or integration.
4. problems of immunogenicity (provoke an immune response)
5. their tendency to denature or decompose at temperatures below their melting points. This severely limits their fabrication into implants of different sizes and shapes.

Question 24

Natural biomaterial Collagen

1. Properties,
2. Types,
3. uses

Answer 24

1. collagen exists mostly in fibril form, has a triple-helix structure and is the most prevalent protein in the animal world.
2. Almost 50% of the protein in cowhide is collagen. It forms a significant component of connective tissue such as bone, tendons, ligaments, and skin.
   
   • type I is found predominantly in skin, bone, and tendons;
   • type II is found in articular cartilage in joints; and
   • type III is a major constituent of _blood vessels. _
3. It has shown good promise as a s_caffold for neotissue growth_ and is commercially available as a product for wound healing. Injectable collagen is widely used for the augmentation or buildup of dermal tissue for cosmetic reasons.

Question 25

True or false:

the UHMWPE socket of the common acetabulum replacement can be __________ ____________ in the pelvis or be part of a ___________ ___________wherein the cup is placed into a ___________ ________

Answer 25

implanted directly

modular arrangement

_metallic shell _

Question 26

the oxide surface layer on titanium alloy femoral heads results in ____________ ____ to the _________ _________ ____

Answer 26

excessive wear to the UHMWPE acetabular cups.