1.0 INTRODUCTION

Biomaterials are materials of natural or man-made origin that are used to

direct, supplement, or replace the functions of living tissues of the human body1. The

use of biomaterials such as in artificial eyes, ears, teeth, and noses were found on

Egyptian mummies2

. Over the centuries, advancements in synthetic materials,

surgical techniques, and sterilization methods have permitted the use of biomaterials

in many ways. Medical practice today utilizes a large number of devices and implants.

Biomaterials in the form of implants (sutures, bone plates, joint replacements,

ligaments, vascular grafts, heart valves, intraocular lenses, dental implants, etc.) and

medical devices (pacemakers, biosensors, artificial hearts, blood tubes, etc.) are

widely used to replace and/or restore the function of traumatized or degenerated

tissues or organs, to assist in healing, to improve function, to correct abnormalities,

and thus improve the quality of life of the patients.3

In the early days all kinds of natural materials such as wood, glue and rubber,

and tissues from living forms, and manufactured materials such as iron, gold, zinc and

glass were used as biomaterials based on trial and error. The host responses to these

materials were extremely varied. Some materials were tolerated by the body whereas

others were not. Under certain conditions (characteristiccs of the host tissues and

surgical procedure) some materials were tolerated by the body, whereas the same

materials were rejected in another situation. Over the last 30 years considerable

progress has been made in understanding the interactions between the tissues and the

materials. It has been acknowledged that there are profound differences between non-

living (avital) and living (vital) materials. Researchers have coined the words ‘

biomaterial’ and ‘biocompatibility’ to indicate the biological performance of

materials. Materials that are biocompatible are called biomaterials, and the

biocompatibility is a descriptive term, which indicates the ability of a material to

perform with an appropriate host response, in a specific application4.

1Marcel Dekker. (1992). Biological Performance of Materials: Fundamentals of Biocompatibility. 2D.F Williams and J Cunningham. (1979). Materials in Clinical Dentistry. Oxford University Press,

Oxford, UK 3 J.B Park. (1984)Biomaterials Science and Engineering. Plenum Press, New York

4D.F Williams. (1988) Consensus and definitions in biomaterials. C de Putter, K de Lange, K de Groot,

A.J.C Lee (Eds.), Advances in Biomaterials, Amsterdam, Elsevier Science. pp 11–16

1

Clinical experience clearly indicates that not all off-the-shelf materials

(commonly used engineering materials) are suitable for biomedical applications. The

various materials used in biomedical applications may be grouped into (a) metals, (b)

ceramics, (c) polymers, and (d) composites made from various combinations of (a),

(b) and (c). Researchers also classfied materials into several types such as bioinert and

bioactive, biostable and biodegradable, etc5.

A large number of polymers are widely used in various applications. This is

mainly because they are available in a wide variety of compositions, properties, and

forms (solids, fibers, fabrics, films, and gels), and can be fabricated readily into

complex shapes and structures. However, they tend to be too flexible and too weak to

meet the mechanical demands of certain applications e.g. as implants in orthopedic

surgery. Also they may absorb liquids and swell, leach undesirable products (e.g.

monomers, fillers, plasticizers, antioxidants), depending on the application and usage.

Moreover, the sterilization processes (autoclave, ethylene oxide, and 60

Co irradiation)

may affect the polymer properties.Polymer composite materials provide alternative

choice to overcome many shortcomings of homogenous materials mentioned above.

The specific advantages of polymer composites are highlighted in the following.6

The figure 1 shows the various applications of different polymer composite

biomaterials.

5 L.L Hench. (1991). Bioceramics: from concept to clinic. J. American Ceramic Society, 74, pp. 1487–

1510 6S Ramakrishna, J Mayer, E Wintermantel, and Kam W Leong. (2001). Composites Science and

Technology. 61(9), pp 1189-1224.

2

Figure 1: the various applications of different polymer composite biomaterials

The picture is taken from http://www.sciencedirect.com/science/article/pii/S0266353800002414

3

1.1 The definition of polymer

Polymers are chemical compound that are made of small molecules that are

arranged in a simple repeating structure to form a larger molecule.7 From the word it

self ―poly‖ means many and ―mer‖ means unit. Therefore, the polymers are made by

linking small molecules (mers) through primarycovalent bonding in the main

molecular chain backbone with C, N, O, Si, etc. One exampleis polyethylene, which

is made from ethylene (CH2 =CH2), where the carbon atoms shareelectrons with two

other hydrogen and carbon atoms: –CH2 -(CH2 –CH2 )n –CH2 –, in which n

indicatesthe number of repeating units. Also note (in view of the monomer structure)

that therepeating unit is –CH2 CH2 –, not –CH2 –.8

In order to make a strong solid, the repeating unit (n) should be well over

1,000. For example,the molecular weight (m.w.) of the polyethylene is over 28,000

grams per mole. This iswhy the polymers are made of giant molecules.

The elastomeric polymers were first developed for making synthetic rubbers

for militarypurpose. A good understanding and synthesis of various polymers were

accelerated sinceWorld War II. Figure 1 shows some history of some commercially

important polymers:

Figure 2: history of some commercially important polymers

(taken from 1984, wiley)

7http://www.merriam-webster.com/dictionary/polymer 8 Polymeric implant materials

4

1.2 Polymerization

Polymerization is a process in which relatively small molecules,

called monomers, combine chemically to produce a very large chainlike or

network molecule called a polymer.9

Polymerization can occur when the unit of

copolymers joined together, or when there is free radical to initiate the process and

also when there is cross-linkage between the monomers. By controlling the reaction

temperature, pressure, and time in the presence of catalyst(s), the degree to which

repeating units are put together intochains can be manipulated. There are two types of

polymerization, which are condensation (or step reaction polymerization) and

addition (or free radical polymerization).

In condensation polymerization, each step of the process is accompanied by

formation of a molecule of some simple compound often water.The chemical reaction

for condensation process is shown in figure 2:

Figure 3: chemical reaction for condensation

(taken from 1984, wiley)

In addition polymerization, monomers react to form a polymer without the

formation of by-products. Addition polymerizations usually are carried out in the

presence of catalysts, which in certain cases exert control over structural details that

have important effects on the properties of the polymer. The chemical reaction for

condensation process is shown in figure 3:

Figure 4: chemical reaction for addition

(taken from 1984, wiley)

The breaking of a double bond can be made with an initiator. This is usually a

free radical such as benzoyl peroxide. The initiation can be activated by heat,

ultraviolet light, and other chemicals. The free radicals (initiators) can react with

monomers and also another monomer. The process can continue on and this process is

called propagation. The propagation process can be terminated by combining two free

radicals, by transfer or by disproportionate processes, respectively.

9http://www.britannica.com/EBchecked/topic/468745/polymerization

5

1.3 Types of polymer

There are many types of polymers including synthetic and natural polymers.

Natural polymers are proteins such as silk, collagen, and keratin, carbohydrates such

as cellulose, starch, glycogen and DNA. Other natural polymers are rubber

(hydrocarbon base) and silicones (alternating silicon and oxygen)10

. Two types of

polymer:

Homopolymers - consist of chains with identical bonding linkages to each monomer

unit. This usually implies that the polymer is made from all identical monomer

molecules.

These may be represented as: - [A-A-A-A-A-A]-

Copolymers - consist of chains with two or more linkages usually implying two or

more different types of monomer units. These may be represented as:

- [A-B-A-B-A-B]-

Polymers are further classified by the reaction mode of polymerization, these include:

Addition Polymers - the monomer molecules bond to each other without the loss of

any other atoms. Alkene monomers are the biggest groups of polymers in this class.

Table 1 shows some example of the addition polymers:

Monomers name Chemical formula

Acrylonitrile CH2=CH–CN

Ethylene CH2=CH2

Methyacrylate CH2=CH–COOCH3

Propylene CH2=CHCH3

Vinyl chloride CH2=CHCl Table 1: example of the addition polymers

(taken from 1984, wiley)

Condensation Polymers - usually two different monomer combine with the loss of a

small molecule, usually water. Polyesters and polyamides (nylon) are in this class of

polymers. Polyurethane Foam in graphic. Figure 4 shows some example of the

condensation polymers:

10Painter, Paul C.; Coleman, Michael M. (1997). Fundamentals of polymer science : an introductory text. Lancaster, Pa.: Technomic Pub. Co. p. 1.

6

Figure 5: example of the condensation polymers

(taken from 1984, wiley)

1.4 Structure of polymers

1.4.1 Addition Polymers

Figure 6: Structure of polyethylene (addition polymer type)

The picture is taken from (C. Ophardt, 2003)

Polymers are long chain giant organic molecules are assembled from many

smaller molecules called monomers. Polymers consist of many repeating monomer

units in long chains. A polymer is analogous to a necklace made from many small

beads (monomers).

7

Many monomers are alkenes which react by addition to their unsaturated

double bonds. The formation of polyethylene from ethylene (ethene) may be

illustrated in the figure 5.

The electrons in the double bond are used to bond two monomer molecules

together. This is represented by the red arrows moving from one molecule to the

space between two molecules where a new bond is to form.

Note that in the complete polymer, all of the double bonds have been turned

into single bonds. No atoms have been lost and you can see that the monomers have

just been joined in the process of addition. A simple representation is -[A-A-A-A-A]-.

Polyethylene is used in plastic bags, bottles, toys, and electrical insulation11

Figure 7: Structure of other addition polymer type (PVC, Polypropylene, Polystryrene)

The picture is taken from (C. Ophardt, 2003)

PVC (polyvinyl chloride): which is found in plastic wrap, simulated leather, water

pipes, and garden hoses, is formed from vinyl chloride (H2C=CHCl). The reaction is

shown in the graphic on the left. Notice how every other carbon must have a chlorine

attached.

Polypropylene: The reaction to make polypropylene (H2C=CHCH3) is illustrated in

the middle reaction of the graphic.Notice that the polymer bonds are always through

the carbons of the double bond. Carbon #3 already has saturated bonds and cannot

participate in any new bonds. A methyl group is on every other carbon.

Polystyrene: The reaction is the same for polystrene where everyother carbon has a

benzene ring attached.

11Roiter, Y.; Minko, S. (2005). "AFM Single Molecule Experiments at the Solid-

Liquid Interface: In Situ Conformation of Adsorbed Flexible Polyelectrolyte Chains".

Journal of the American Chemical Society127 (45)

8

1.4.2 Condensation Polymers

Figure 8: Structure of polyester (condensation polymer type)

The picture is taken from (C. Ophardt, 2003)

Polyesters such as PET (polyethylene terephthalate) are condensation

polymers. The formation of a polyester follows the same procedure as in the synthesis

of a simple ester12

. The only difference is that both the alcohol and the acid monomer

units each have two functional groups - one on each end of the molecule. In this

polymer, every other repeating unit is identical.

PET is made from ethylene glycol and terephthalic acid by splitting out water

molecules (-H from alcohol and -OH from acid as shown in red on the figure). The

units are joined to make the ester group shown in green. A simple representation is -

[A-B-A-B-A-B]-.

Depending upon the processing a variety of products are possible. If cross

linked it is made into clear plastic soft drink bottles. It can also be made into textile

fibers known as Dacron and accounts for 50% of all fibers used to make clothing.

Blended with cotton, Dacron is made into no-iron clothes13

.

12Painter, Paul C.; Coleman, Michael M. (1997). Fundamentals of polymer science : an introductory text. Lancaster, Pa.: Technomic Pub. Co. p. 1. 13Roiter, Y.; Minko, S. (2005). "AFM Single Molecule Experiments at the Solid-Liquid Interface: In Situ Conformation of Adsorbed Flexible Polyelectrolyte Chains". Journal of the American Chemical Society127 (45)

9

This same polymer with the trade name of mylar when made as "tape" is

magnetically coated for use in tape recorders and videotape machines14

.

Figure 9: Structure of polyamide (condensation polymer type)

The picture is taken from (C. Ophardt, 2003)

Polyamides such as nylon are also condensation polymers. The formation of a

polyamide follows the same procedure as in the synthesis of a simple amide. Again,

the only difference is that both the amine and the acid monomer units each have two

functional groups - one on each end of the molecule. In this polymer, every other

repeating unit is identical.

Nylon is made from 1,6-diaminohexane and adipic acid by splitting out water

molecules (-H from the amine and -OH from acid as shown in red on the figure

above). The units are joined to make the ester group shown in green. A simple

representation is -[A-B-A-B-A-B]-.

Nylon 66, discovered in 1931 by Wallace Cruthers at DuPont was the first completely

synthetic fiber produced. It was introduced to women in nylon stockings in 1939 to

immediate success. During World War II, nylon production went into making

parachutes and other items needed by the military.

Nylon is very similar to the protein polyamides in silk and wool, but is stronger. more

durable, more chemically inert, and cheaper to produce than the natural fibers.

14Allcock, Harry R.; Lampe, Frederick W.; Mark, James E. (2003). Contemporary Polymer Chemistry (3 ed.). Pearson Education. p. 21.

10

Figure 10: Structure of polyurethane (condensation polymer type)

The picture is taken from (C. Ophardt, 2003)

Polyurethanes are made from a dialcohol and diisocyanate monomers. The

isocyanate compounds contain the functional group (O=C=N-). A rearrangement

reaction leads to the formation of the urethane linkage. Technically polyurethane is

not a condensation polymer since no molecules are lost, but the functional group does

rearrange.

Hydrogen moves from the alcohol to the nitrogen, while the oxygen links to

the carbon. The urethane functional groups are similar to the amide group [1]. In

some applications the urethane polymer chains are further reacted to make cross-

links. Think of a chain link fence to get the idea of cross-linking chains together.

Polyurethane can be drawn into fibers used in upholstery. Soft polyurethane

foam can be used as padding in furniture and mattresses, while rigid foam is used as

insulation in buildings.

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2.0 INTRODUCTION TO BIOACTIVE MATERIAL

2.1 Tissue attachment of biomaterials

The mechanism of tissue attachment of an implant is directly related to the

tissue response at the implant interface. No material implanted in living tissues is

inert. All materials elicit a response from the host tissue. According to the different

types of implant-tissue attachment, biomaterials are classified into four types of tissue

attachments. Table 2 shows the types of tissue attachment of biomaterials:

Type of implant Type of attachment Example

Nearly inert Mechanical interlock

(morphological fixation)

Metals, Alumina, Zirconia,

Polyethylene(PE)

Porous lngrowth of tissues into

pores (biological fixation)

Hydroxyapatite (HA), HA

coated porous metals

Bioactive Interfacial bonding with tissues

(bioactive fixation)

Bioactive glasses, HA,

Bioactive glass-ceramics

Resorbable Replacement with

tissues

Tricalcium phosphate,

Polylactic acid (PLA)

Table 2: types of tissue attachment of biomaterials

The info is obtained from: Wanpeng Cao and Larry L. Hench. (1995). Bioactive

materials. Ceramics International 22 (1996) 493-507, Elsevier Science Limited and

Techna S.r.1.

12

2.2 Bioactive material

―A bioactive material is one that elicits a specific biological response at the

interface of the material which results in the formation of a bond between the tissues

and the material‖. This definition was given by Hench, who initiated this subject of

research with his colleagues in the early 1970s.15

The surface chemistry of implants

needs to be optimized to meet the requirements of aged, diseased and damaged

tissues. Biocompatibility, or tissue tolerance, is not enough. A general theory of

biomaterials was expressed by Hench and Ethridge in 1982 as:16

a) An ideal implant material performs as if it were equivalent to the host tissue.

b) Axiom 1. The tissue at the interface should be equivalent to the normal host

tissue.

c) Axiom 2. The response of the material to physical stimuli should be like that

of the tissue it replaces.

These axioms are interdependent. A stable interfacial bond between tissue and

implant must be achieved in order to obtain an equivalent physical response, and

controlled physical stimuli is necessary for a stable interface to be produced. This

general theory requires that a biomaterial have both biochemical compatibility and

biomechanical compatibility. So, besides bioactivity, a match in physical and

mechanical properties is also essential for an implant to replace bone.

They discovered that certain compositions of glasses in the system SiO2, CaO,

Na2O and P2O5 were able to form a bond with bone once they are implanted. In fact,

when these glasses were put in contact with biological fluids, a layer of

hydroxyapatite (HA) analogue to the mineral phase of bones was deposited on their

surface. Collagen molecules were incorporated into this layer, and a biological bond

15Hench LL, Splinter, RJ, Allen WC, Greenlee TK. Bonding mechanisms at the interface of ceramic

prosthetic materials. J. Biomed. Mater. Res. Symp.1971; 2 (Part I): 117–141 16Hench, L. L. &Ethridge, E. C., Biomaterials: An Interfacial Approach. Academic Press, New

York,1982.

13

could be formed. Later work by Wilson and Nolletti showed that a bond with soft

tissue could be achieved too, if the speed of apatite formation was high enough.17

The use of synthetic materials as a way to replace damaged tissues has been

studied and practiced for a long time. The initial goal was focused on finding an ideal

biomaterial that would promote minimum response from the body. This initial idea of

"bioinertness" was progressively realized not to be enough for many applications.

Moreover, it was observed that even the most "inert" material would provoke some

type of reaction from the body, expressed by the formation of a thin non-adherent

fibrous capsule that would prevent higher levels of interaction between tissue and

biomaterial18

. Nevertheless, fixation of the implant in place is desired in many

applications and then adhesion in the biomaterial-tissue system needs to be achieved.

Several ways to promote adhesion were then investigated, such as use of plates, pins

and screws (mechanical interlock) growth of tissue through a porous biomaterial

(biological fixation) fixation due to a cementation or polymerization reaction and use

of biodegradable pins or sutures19

.

Another way to promote fixation was demonstrated in the late sixties. In this

case, coupling between tissue and material was promoted by an integration process.

This integration process is based on the processing of a group of reactions on the

material surface that will lead to the formation of a dynamic high-strength interphase.

In this interphase, both inorganic and organic species are combined through physical-

chemical and biochemical interactions. Materials that promote this type of interaction

with living tissues by forming chemical linkages are called bioactive materials.

Bioactive glasses and hydroxyapatite are examples of this type of material20

.

In the early 1970s bioceramics began to be used in certain implant

applications, which depended on the fact that a smooth oxide ceramic surface,

17Wilson J, Nolletti D. In Handbook of Bioactive Ceramics. Yamamuro T, Hench LL, Wilson J

Editors. CRC Press, Boca Raton, FL. 1990: 283. 18Hench, L. L. and Wilson, J. (1993). An Introduction to Bioce-ramics, World Scientific. 19Hench, L. L. and West, J. K. (1996). Life Chem. Report. 13, pp187. 20Oréfice, Rodrigo L., Hench, Larry L., & Brennan, Anthony B.. (2000). In vitro bioactivity of

polymer matrices reinforced with a bioactive glass phase. Journal of the Brazilian Chemical

Society, 11(1), 78-85. Retrieved January 11, 2014, from

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-

50532000000100014&lng=en&tlng=en. 10.1590/S0103-50532000000100014.

14

especially AlzOs, elicited very little tissue reaction and provided good wear

characteristics for a bearing surface. In 1969, the concept of a bioactive material was

discovered. Since then, the field of ceramics has expanded enormously to include

many new compositions of glasses, glass-ceramics and ceramics.

A bioactive material creates an environment compatible with osteogenesis

(bone growth), with the mineralizing interface developing as a natural bonding

junction between living and non-living materials. This concept has now been

expanded to include a large number of bioactive materials with a wide range of rates

of bonding and thickness of interfacial bonding layers. They include bioactive glasses

such as Bioglass, bioactive glass-ceramics such as Ceravital, A/W glass-ceramics and

machineable glass-ceramics, dense calcium phosphate ceramics such as synthetic

hydroxyapatite (HA), bioactive composites such as PE-HA mixtures, and a series of

bioactive coating materials. For the various bioactive materials, the mechanism of

bonding, the time dependence of bonding, the strength of the bonding, and the

thickness of bonding zone are different. The rate of development of the interfacial

bond can be referred to as the level of bioactivity.21

2.3 Definition of bioactive polymeric materials

Bioactive polymer are synthetic or artificial polymers substituted with specific

chemical functional groups carried by the macromolecular chain that are designed to

develop specific interactions with living systems. When a polymeric material is

exposed to a biological environment, there is a natural tendency to induce different

reactions such as blood coagulation, complement activation and cell interactions.

Polymer scientists have synthesized a large number of polymers and have evaluate

their behavior when they are in contact with biomolecules, viruses, bacteria, body

fluids, cells and whole organisms.

Bioactive polymers are used to repair, restore or replace damaged or diseased

tissue or to interface with the physiological environment. They are basically three

main types of polymers used in a biological environment.

i) Polymer used as biomaterials, such as in organ replacement and bone surgery.

21Wanpeng Cao and Larry L. Hench. (1995). Bioactive materials. Ceramics International 22 (1996)

493-507, Elsevier Science Limited and Techna S.r.1.

15

ii) Polymers serve as matrices in devices that permit control release of anactive

substance over along period of time.

iii) Soluble polymers are synthetic polymers that themselves display

biologicalactivities.

3.0 FEATURES OF BIOACTIVE POLYMERS

Some of important properties should be required for bioactive polymers are as follows

i) Biocompatibility

Acceptance of an artificial important by the surrounding tissue and by the body as a

whole.

ii) Physical, Chemical & Mechanical Properties

These must be capable with the proposed and for example, in the design of heart, the

flexing characteristics of the polymer have often been overlooked.

.

iii) Polymer Purity

Industrial reins are highly variable in nature from manufacture to manufacturer. A

variety of other materials incidental to the polymer process suchas residual initiators,

initiator fragments, solvents, plasticizers, trapped freeradicals, inhibitors, lubricants,

heat sand light stabilizers, fillers, parting agents, anti oxidants, degradation products,

curing agents, residual monomers and allow molecular weight oligomers may be

present. There may be variations in the molecular weight and in the mol. Wt.

distribution, as well linkages and branching.

iv) Ease of fabrication

The desired device should be capable of fabrication without damages in properties,

surface characteristics, crystallinity, surface oxidation, or contamination by

processing aids such as oils, solvents or like that.

16

v) Stability

Bioactive polymers should not be adversely affected by the normal physiological

environment. No biodegradation that could compromise function over the short or

long term should occur, and no process should release toxic to the environment.

vi) Tolerability

Bioactive polymers should not exhibit toxic or irritant qualities, or elicit adverse

physiological responses locally or systemically. Toxicity can also be affected by the

rate of release of the substance and the biological processing and removal of the

substance.

vii) Sterilizability

The physical, chemical, mechanical and biochemical characteristics of the device or

material must not undergo any change during sterilization. This is often not as easy as

it may seem. Light, heat, radiation, or chemical treatment may beused during this

process.

viii) Foreign body reaction

The polymer should cause only minimal, if any, foreign body interaction,

inflammation, encapsulation or cell change response in the surrounding tissue. Italso

should not cause tissue or other reaction remote from the site of implantation and

should be free of response.

4.0 MATERIALS USED AS BIOACTIVE POLYMERS

The following materials using as bioactive polymers.

i) Polyetherurhaneurea (PEUU)

ii) Silicons

iii) TFE polymers

iv) PVC

v) Polyolefins

vi) Polycarbonate

vii) PMMA

17

viii) Polyesters

ix) Cellulose

x) Polyvinyl alcohol

xi) Epoxy resins

5.0 ADVANTAGES & DISADVANTAGES

The major advantages and few disadvantages of bioactive polymers are as follows

Advantages

1. The bioactive polymers must be capable of good response from bodysurrounding body

tissue.

2. They will not cause of inflammation.

3. They will not produce infection.

4. They will not responsible for thrombogenesis.

5. No adverse immunological response or neoplasm induction or promotion.

6. The artificial heart and valve, kidney, lung saves the life of the patient byimproving the

function of organ.

Disadvantages

1. Sometimes growth of bacteria takes place on the surface of implant.

2. Implant will be cause of cancer due to foreign body reaction.

3. Bioprosthetic valve fail due to calcification (Calcium from the bloodstream form

deposits on the implant).

4. Bioprosthetic valves are also susceptible to mechanical fatigue. Artificial heart, kidney,

lung is more expensive and also involves great risk of life

18

6.0 THE USE OF BIOACTIVE POLYMERIC MATERIALS IN

BIOMEDICAL ENGINEERING

The uses of bioactive polymeric material in Biomedical Field

- Hip and Joint Prosthesis

- Finger Joint Prosthesis

- Bone Cement for Joint Prosthesis Fixation.

- Soft Lens and Rigid Lens

6.1 Hip and joint prosthesis

Hip joint replacement is surgery to replace all or part of the hip joint with a man-made

(artificial) joint. The artificial joint is called a prosthesis. Total hip replacement is

most commonly used to treat joint failure caused by osteoarthritis. Other indications

include rheumatoid arthritis, avascular necrosis, traumatic arthritis,protrusioacetabuli,

certain hip fractures, benign and malignant bone tumors, arthritis associated with

Paget's disease, ankylosing spondylitis and juvenile rheumatoid arthritis. The aims of

the procedure are pain relief and improvement in hip function. Hip replacement is

usually considered only after other therapies, such as physical therapy and pain

medications, have failed.

Material used in hip and joint prosthesis

1. Metal-on-Metal

One option for total hip replacement is a metal-on-metal prosthesis. This implant

consists of a metal socket, a metal ball that goes into the socket and a metal stem that

goes into the thigh bone. The metal-on-metal prosthesis reduces your risk of

dislocation following surgery. Also, your new hip will have a low wear rate, which

increases its longevity. However, when the ball and socket rub together during

movement, some pieces of metal may come off and damage nearby bone and other

tissue. This can be painful and possibly lead to implant failure22

.

19

Figure 11: example of metal-on-metal

2. Metal-on-Polyethylene

The most common type of hip replacement implant is the metal-on-polyethylene

prosthesis, which consists of a ball and stem made of metal and a socket made of

polyethylene, a type of plastic. Highly cross-linked polyethylene is a newer type of

plastic that produces less wear at the hip joint compared to traditional polyethylene.

However, highly cross-linked polyethylene does not have the same fracture-resistant

properties as traditional implants. Also, the particles coming off of the cross-linked

polyethylene may be more biologically active. These bioactive particles can lead to

inflammation and possible bone changes, potentially resulting loosening or failure of

the new hip.

3. Ceramic-on-Polyethylene

For younger patients, a ceramic-on-polyethylene prosthesis may be a preferred choice

because of its durability. This type of prosthesis includes a ball made of ceramic

material and a polyethylene socket. The main benefit of this type of prosthesis is

reduction in joint wear compared to a metal-on-polyethylene prosthesis. The ceramic

material remains better lubricated than other prosthetic materials. This type of hip

prosthesis is more costly than others23

.

20

Figure 12: example of Ceramic-on-Polyethylene

1. Ceramic-on-Ceramic

Another prosthetic option is the ceramic-on-ceramic hip implant. Your hip

replacement will include a ceramic ball and a socket with ceramic lining. Because all

material is ceramic, this type of prosthetic has the lowest wear rate out of any device.

Also, fewer particles are released from the prosthesis during movement and the

particles are not as biologically active as those from other types of implants. A

potential drawback of this implant is a risk for fracture of the ceramic head and

socket. Squeaking is another issue with a ceramic-on-ceramic prosthetic. This can be

a nuisance and increase your chance of a revision surgery24

.

21

Figure 13: ceramic on ceramic hip implant

6.2 Finger joint implant

Patients suffering from finger joint pain or dysfunction due to arthritis and traumatic

injury may require arthroplasty and joint replacement. This intervention is indicated

for the finger joints when medical management has failed to relieve the pain or when

the digit deformity is interfering with hand function and activities of daily living

(ADL). Surgical procedures can greatly improve function and relieve pain, allowing

patients to maintain independence and improve their quality of life.

The goals of implant arthroplasty of the finger joints are pain relief, correction of

deformity, and improvement in the function and appearance of the hand. Many

prosthetic implants have been designed for the replacement of MCP and PIP joints.

The most popular finger implant is the Swanson prosthesis, a single piece of silicone

that acts as a flexible space. Several silicone finger joint prostheses designs have

Ontario Health Technology Assessment Series

Patients suffering from finger joint pain or dysfunction due to arthritis and traumatic

injury may require arthroplasty and joint replacement. This intervention is indicated

for the finger joints when medical management has failed to relieve the pain or when

the digit deformity is interfering with hand function and activities of daily living

22

(ADL). Surgical procedures can greatly improve function and relieve pain, allowing

patients to maintain independence and improve their quality of life.

For patients with metacarpophalangeal (MCP) deformities, surgical options include

synovectomy, intrinsic release/transfer, extensor tendon relocation, arthrodesis, and

implant arthroplasty. Relatively few surgical options exist for the painful arthritic

interphalangeal (PIP) joints. Currently, patients with arthritis of the PIP joints have 2

surgical options—arthrodesis or implant arthroplasty25

.Arthrodesis provides excellent

pain relief and stability. However, it sacrifices finger function in exchange for these

benefits.

The goals of implant arthroplasty of the finger joints are pain relief, correction of

deformity, and improvement in the function and appearance of the hand. Many

prosthetic implants have been designed for the replacement of MCP and PIP joints.

The most popular finger implant is the Swanson prosthesis, a single piece of silicone

that acts as a flexible space26

. Several silicone finger joint prostheses designs have

tried to improve upon the Swanson prosthesis.

Material use in Finger Implant

Figure 14: Artificial joint

The artificial joints as shown in figure 14 are available for the finger. These silicone

implants are used by hand surgeons primarily to replace the MCP joint, which are

commonly referred to as your knuckles. The implant, or ―prosthesis‖ (prosthesis

meaning artificial body part), acts as a spacer to fill the gap created when the arthritic

surfaces of the MCP joint are removed.

23

Figure 15

To perform a joint replacement of the MCP joint, the surgeon first makes an incision

in the back of the hand over the joints or between the first and middle finger and

between the ring and little finger as shown in figure 15.

Each joint that needs to be replaced is then opened so that the surgeon can see the

joint surfaces. The cartilage is removed from both joint surfaces to leave two surfaces

of bone as shown in figure 16.

Figure 16: arthtitic joint surfaces removed

Next, a small cutting tool called a burr is used to make holes in the bones of the finger

joint as shown in figure 17.

24

Figure 17: initial opening made in metacarpal

The artificial finger joint has a stem on each side that is inserted into the canals

created in the bone of the finger and the metacarpal joint as shown in figure 18.

Figure 18: artificial joint inserted

The surgeon then completes the operation by using the tendons and ligaments around

the joint to form a tight sack to hold the implant in place. The skin is sutured together

and a splint is applied. Patient will probably be in a splint, brace, or cast for six

weeks27

.[DepuuSynthes Joint Reconstruction]

25

6.3 Cemented Fixation

Most knee replacements done today are cemented into place. Cemented fixation has a

generally excellent track record and may last more than 20 years. The longevity and

performance of a knee replacement depends on several factors, including activity

level, weight, and general health.

Cemented fixation relies on a stable interface between the prosthesis and the cement

as well as a solid mechanical bond between the cement and the bone. Metal alloy

components rarely break, but they can occasionally come loose from the bone. Two

processes, one mechanical and one biological, can contribute to loosening.

During natural movement, the knee is subject to considerable loads and stresses,

which the prostheses must transfer to the underlying bone. Because the hard

subchondral bone of the shinbone (tibia) is removed during a knee replacement, loads

are absorbed by the softer cancellous bone and the peripheral cortical bone that

remains. If loads are heavier than the underlying bone can bear over a long period, the

prosthesis will begin to sink into or loosen from its attachment to the bone.

Additionally, if the load applied to the knee during walking is uneven, one side of the

implant may lift off the bone as the other side is pressed into it, resulting in uneven

wear of the polyethylene liner between the metal components. This wear creates

debris particles of polyethylene that can trigger a biologic response and further

contribute to loosening of the implant and sometimes to bone loss around the implant.

The microscopic debris particles are absorbed by cells around the joint and initiate an

inflammatory response from the body, which tries to remove them. This inflammatory

response can also cause cells to remove bits of bone around the implant, a condition

called osteolysis. As wear continues, so does the bone loss. The bone weakens, and

the loosening of the implant from bone increases. Despite these recognized failure

mechanisms, the bond between cement and bone is generally very durable and

reliable. Cemented fixation has been used successfully in all patient groups for whom

total knee replacement is appropriate, including young and active patients with

advanced degenerative joint disease28

. [Chu KT, Oshida Y, Hancock EB, Kowolik

MJ, Barco T, Zunt SL]

26

Material use in cemented fixation

Bone cement (PMMA)

Figure 19: example of PMMA

Polymethyl methacrylate has been used as self-polymerising bone cement in

orthopaedics since the 1960s. Acrylic bone cement is the only material currently used

to fill the irregular space between prosthesis and bone during total hip replacements

(THR). Its main function is to transfer body weight and service loads from the metal

prosthesis to the bone and/or increase the load carrying capacity of the prosthesis-

bone cement-bone system. However, the cement is not without its drawbacks. The

main one is the role that it has been postulated to play in the aseptic loosening and,

hence, clinical life of the arthroplasty. In turn, this role is directly related to the

mechanical properties of the cement, especially the resistance to fracture of the

cement in the mantle at the cement-prosthesis interface or the cement-bone interface.

It has been observed that mixing procedures play a significant role in governing the

quality of the bone cement produced. A high degree of porosity is found to be present

in cement that is inadequately mixed. These pores act as stress raisers and initiating

sites for cracks, rendering the cement susceptible to early fatigue failure28

.[ Dr.

Nicholas Dunne]

27

6.4 Contact Lenses

Figure 20: Example of soft lens

1. Soft lens

In 1998, silicone hydrogels became available. Lenses are mainly silicone acrylates.

These lenses were made from silicone and methacrylic acid polymers. The silicone

provides increased oxygen permeability, while the methacrylic acid is present for

wettability and optical clarity. Because silicone allows more oxygen permeability than

water, the oxygen permeability of silicone hydrogels is not tied to the water content of

the lens. Lenses have now been developed with so much oxygen permeability that

they are approved for overnight wear (extended wear). Lenses approved for daily

wear are also available in silicone hydrogel materials.

Disadvantages of silicone hydrogels are that they are slightly stiffer and the lens

surface can be hydrophobic, and thus, less "wettable." These factors can influence the

comfort of the lens. New manufacturing techniques and changes to multipurpose

solutions have minimized these effects. A surface modification processes called

plasma coating alters the hydrophobic nature of the lens surface. Another technique

incorporates internal rewetting agents to make the lens surface hydrophilic. A third

process uses longer backbone polymer chains that results in less cross linking and

increased wetting without surface alterations or additive agents.

Another material used is fluorosilicone acrylates. These would normally be the

material of first choice in a new RGP fit. These are fluorinated monomers combined

with silicone acrylates. The #uorine helps to improve wettability while maintaining

high oxygen transmission. These materials show less protein deposition but can be

prone to lipid deposits29

. [Santos, L, Rodrigues, D, Lira, M, Oliveira, R, Real

Oliveira, ME, Vilar, EY &Azeredo, J]

28

2. Rigid lenses

Figure 21: example of rigid lenses

Glass lenses were never comfortable enough to gain widespread popularity. The first

lenses to do so were lenses made from polymethyl methacrylate (PMMA or

Perspex/Plexiglas). PMMA lenses are commonly referred to as "hard" lenses. A

disadvantage of these lenses is that they do not allow oxygen to pass through to the

cornea, which can cause a number of adverse clinical events.

Starting in the late 1970s, improved rigid materials which were oxygen-permeable

were developed. Lenses made from these materials are called rigid gas permeable or

'RGP' lenses.

A rigid lens is able to replace the natural shape of the cornea with a new refracting

surface. This means that a spherical rigid contact lens can correct for astigmatism.

Rigid lenses can also be made as a front-toric, back-toric, or bitoric. This is different

from a spherical lens in that one or both surfaces of the lens deliver a toric correction.

Rigid lenses can also correct for corneal irregularities, such as keratoconus. In most

cases, patients with keratoconus see better through rigid contact lenses than through

glasses. Rigid lenses are more chemically inert, allowing them to be worn in more

challenging environments than soft lenses30

. [Hollingsworth JG, Efron N (June

2004).]

29

7.0 CONCLUSION

Based on the reading from the other research that been done by a lots of

people, we can conclude that bioactive polymeric material have a lot of application in

biomedical field. However, this type of material still have some disadvantages on its

uses. So far, based on all the material being study, all the material have its own

disadvantages when come to biomedical field. The researcher all over the world only

have an option to lower the disadvantages and its bad effect to human body.

The application that we discussed in this report was some of the common

application of bioactive polymeric material in biomedical field. There was also a lot

of other application for this kind of material.

We also have discussed about what are the meaning of bioactive polymeric

material and its structure also. Based on this we can compare between the normal

polymeric material and bioactive polymeric material.

30

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33