Transcript Notes of Lesson on BIOMATERIALS AND ARTIFICIAL ORGAN

BIOMATERIALS AND ARTIFICIAL
ORGAN
BM1303
S.Sudha
Lecturer
Dept of Biomedical Engg
UNIT I
INTRODUCTION TO BIOMATERIALS
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During the last two decades, significant advances
have been made in thedevelopment of
biocompatible and biodegradable materials for
medicalapplications.
In the biomedical field, the goal is to develop and
characterize artificial materialsor, in other words,
“spare parts” for use in the human body to
MEASURE,RESTORE and IMPROVE physical
functions and enhance survival and qualityof life.
What’s a biomaterial?
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1980 - Passive and inert point of view
Any substance or drugs, of synthetic or natural origin, which
can be used for any period alone or as part of a system and that
increases or replaces any tissue,organ or function of the body

1990 – Active point of view
Non-living material used in a medical device and designed to interact
with biological systems
Classification of biomaterials
First generation: INERT
Do not trigger any reaction in the host: neither rejected
nor recognition “do not bring any good result”
Second generation: BIOACTIVE
Ensure a more stable performance in a long time or for the
period you want
Third generation: BIODEGRADABLE
It can be chemically degraded or decomposed by natural
effectors (weather, soil bacteria, plants, animals)
What is a biocompatible material?
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Synthetic or natural material used in intimate
contact with living tissue (it canbe implanted,
partially implanted or totally external).
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Biocompatible materials are intended to interface
with biological system toEVALUATE, TREAT,
AUGMENT or REPLACE any tissue, organ or
function ofthe body.
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A biocompatible device must be fabricated from
materials that will not elicit an adverse biological
response
Mechanical Properties of Metals
How do metals respond to external loads?
Stress and Strain
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Tension
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Compression
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Shear
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Torsion
Elastic deformation
Plastic Deformation
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Yield Strength
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Tensile Strength
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Ductility
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Toughness
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Hardness
Stress-Strain Behavior
Elastic deformation
 Reversible: when the stress
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is removed, the material
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returns to the dimension it
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had before the loading.
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Usually strains are small
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(except for the case ofplastics).
Plastic deformation
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Irreversible: when the stress
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is removed, the material
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does not return to its
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previous dimension.
Stress-Strain Behavior: Plastic
deformation
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Plastic deformation:
stress and strain are not
proportional the
deformation is not
reversible deformation
occurs by breaking and
rearrangement of atomic
bonds (in crystalline
materials primarily by
motion of dislocations)
Typical mechanical properties of
metals
The yield strength and tensile strength vary with prior
thermal and mechanical treatment, impurity levels,
etc. This variability is related to the behavior of
dislocations in the material. But elastic
moduli are relatively insensitive to these effects.
The yield and tensile strengths and modulus of
elasticity decrease with increasing temperature,
ductility increases with temperature.
Mechanics of Materials
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The point up to which the stress and strain are linearly
related is called the proportional limit.
The largest stress in the stress strain curve is called the
ultimate stress.
The stress at the point of rupture is called the fracture or
rupture stress.
The region of the stress-strain curve in which the material
returns to the undeformed state when applied forces are
removed is called the elastic region.
The region in which the material deforms permanently is
called the plastic region.
The point demarcating the elastic from the plastic region is
called the yield point. The stress at yield point is called the
yield stress.
Mechanics of Materials
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The permanent strain when stresses are zero is called the
plastic strain.
The off-set yield stress is a stress that would produce a
plastic strain corresponding to the specified off-set strain.
A material that can undergo large plastic deformation
before fracture is called a ductile material.
A material that exhibits little or no plastic deformation at
failure is called a brittle material.
Hardness is the resistance to indentation.
The raising of the yield point with increasing strain is
called strain hardening.
The sudden decrease in the area of cross-section after
ultimate stress is called necking.
Viscoelasticity
Definition: time-dependent material
behavior where the stress response of that
material depends on both the strain applied
and the strain rate at which it was applied!
Examples
 biological materials
 polymer plastics
 metals at high temperatures
Elastic versus viscoelastic behaviors
For a constant applied
strain
 An elastic material has
a unique material
response
 A viscoelastic material
has infinite material
responses depending on
the strain-rate
Viscoelastic Hysteresis
Viscoelastic solid

some energy is dissipated with
dashpots (as heat)some energy is
stored in springs. Area in the
hysteresis loop is a function of
loading rate
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For viscoelastic material, energy
is dissipated regardless of whether
strains(or stresses) are small or
large
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Under repetitive loading, a
viscoelastic material will heat up
Wound healing
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All wounds heal following a a specific
sequence of phases which may overlap
The process of wound healing depends on the
type of tissue which has been damaged and the
nature of tissue disruption
The phases are:
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Inflammatory phase
Proliferative phase
Remodelling or maturation phase
The ways in which wounds heal
Three basic classifications exist:
Healing by primary intention
Two opposed surfaces of a clean, incised wound
(no significant degree of tissue loss) are held together.
Healing takes place from the internal layers outwards
 Healing by secondary Intention
If there is significant tissue loss in the formation of the
wound, healing will begin by the production of
granulation tissue wound base and walls.
 Delayed primary healing
If there is high infection risk – patient is given antibiotics
and closure is delayed for a few days e.g. bites
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Wound assessment
Signs of
infection
Odour or
exudate
Lab tests:
TcPO2
Size, depth
& location
WOUND ASSESSMENT
Wound bed:
• necrosis
Wound edge
Surrounding skin:
colour, moisture,
• granulation
The healing process
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Day 0 – 5
The healing response starts at the moment of injury –
the clotting cascade is initiated
This is a protective tissue response to stem blood loss
The inflammatory phase is characterised by heat,
swelling, redness, pain and loss of function at the
wound site
Early (haemostasis)
Late (phagocytosis)
This phase is short lived in the absence of infection or
contamination
Granulation
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Day 3 – 14
Characterised by the formation of granulation
tissue in the wound
Granulation tissue consists of a combination of
cellular elements including:
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Fibroblasts, inflammatory cells, new capillaries
embedded in a loose extra-cellular collagen matrix,
fibronectin and hyularonic acid
Moist wound healing
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Basic concept is that the presence of exudate will
provide an environment that stimulates healing
Exudate contains:
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Lysosomal enzymes, WBC’s, Lymphokines, growth factors……..
There are clinical studies which have shown that
wounds maintained in a moist environment have
lower infection rates and heal more quickly
Factors affecting healing
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Immune status
Blood glucose levels (impaired white cell function)
Hydration (slows metabolism)
Nutrition
Blood albumin levels (‘building blocks’ for repair, colloid osmotic
pressure - oedema)
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Oxygen and vascular supply
Pain (causes vasoconstriction)
Corticosteroids (depress immune function)
Host Reactions to Biomaterials
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Effect of the Implant on the Host
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Local
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Blood material interactions
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Protein adsorption
Coagulation
Fibrinolysis
Platelet adhesion, activation, release
Complement activation
Leukocyte adhesion, activation
Hemolysis
Toxicity
Modification of normal healing
 Encapsulation
 Foreign body reaction
 Pannus formation
 Infection
 Tumorgenesis
Systemic and remote
 Embolization
 Hypersensitivity
 Elevation of implant elements in the blood
 Lymphatic particle transport
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Effect of the Host on the Implant
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Physical – mechanical effects
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Abrasive wear
Fatigue
Stress corrosion, cracking
Corrosion
Degeneration and dissolution
Biological effects
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Absorption of substances from tissues
Enzymatic degradation
Calcification
Temporal Variation of Inflammatory
Response
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Activated by injury to
vascularized connective
tissue
Series of reactions
Various cells
Controlled by
endogenous and
autocoid mediators
UNIT II
Types of Metallic Implants
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Stainless steel
Cobalt Based Alloys
Titanium Alloys
Stainless Steels
• Fe 60-65 wt%, Cr 17-19 wt %, Ni 12-14 wt%
• Carbon content reduced to 0.03 wt% for better The
most common stainless steel: 316Lresistance to in
vivo corrosion.
• Why reduce carbon: Reduce carbide (Cr23C6)
formation at grain boundary. Carbide impairs
formation of surface oxide
• Why add chromium: corrosion resistance by formation
of surface oxide.
• Why add nickel: improve strength by increasing face
centered cubic phase (austenite)
Stainless Steels
Good stainless steel:
 Austenitic (face centered cubic)
 No ferrite (body centered cubic)
 No carbide
 No sulfide inclusions
 Grain size less then 100mm
 Uniform grain size
Cobalt Based Alloys
Common types for surgical applications:
 – ASTM F75
 – ASTM F799
 – ASTM F790
 – ASTM F 562
Cobalt Alloys: ASTM F75
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Co-Cr-Mo
Surface oxide; thus corrosion resistant
Wax models from molds of implants
Wax model coated with ceramic and wax
melted away
Alloy melted at 1400 °C and cast into ceramic
molds.
Cobalt Alloys: ASTM F75
Three caveats:
 – Carbide formation ® corrosion. Solution:
annealing at 1225 °C for one hour.
 – Large grain size ® reduced mechanical
strength
 – Casting defects ® stress concentration,
propensity to fatigue failure
Cobalt Alloys: ASTM F799,
ASTM F90
Cobalt Alloys: ASTM F799
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Modified form of F75: hot forged after casting
 Mechanical deformation induces a shear induced
transformation of FCC structure to HCP.
 Fatigue, yield and ultimate properties are twice of F75.
Cobalt Alloys ASTM F90 :
• W and Ni are added to improve machinability and fabrication
• Mechanical properties similar to F75
• Mechanical properties double F75 if cold worked
Titanium Based Alloys
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Lighter
Good mechanical properties
Good corrosion resistance due to TiO2solid
oxide layer
Ti-6% wt Al-4% wt V (ASTM F136) is widely
used
Contains impurities such as N, O, Fe, H, C
Impurities increase strength reduce ductility
Titanium Alloys: ASTM F136
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HCP structure transforms to
BCP for temperatures
greater than 882 °C.
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Addition of Al stabilizes
HCP phase by increasing
transformation temperature
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V has the inverse effect.
ceramic
Any of various hard, brittle, heat-resistant and corrosionresistant materials made by shaping and then firing a
nonmetallic mineral,such as clay, at a high temperature
 Clinical success requires:
Achievement of a stable interface with connective tissue
Functional match of the mechanical behavior of the implant
with the tissue to be replaced
 Critical Issues:
Integrity of bioceramic
Interaction with the tissue
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Hydroxyapatites (HA)
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Chemically similar to mineral component of bones
It will support bone ingrowth and osseointegration
when used in orthopaedic, dental and maxillofacial
applications
Chemical formula: Ca5(PO4)3OH
Hexagonal Bravais lattice
The chemical nature of hydroxyapatite lends itself to
substitution; common substitutions involve carbonate,
fluoride and chloride substitutions for hydroxyl
groups
Uses for HA
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Facial augmentation with hydroxyapatite has been
used for the following
corrections: Cheek, Chin, Jaw, Nose, Browbone.
Skeletal repair biomaterials
Ocular prosthesis
Hydroxyapatite from coral
The eye muscles can be attacheddirectly to this
implant, allowing it to move within the orbit-just like
the natural eye.
Calcium Phosphate Bioceramics
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There are several calcium phosphate ceramics that are
consideredbiocompatible; most are resorbable and will
dissolve when exposed tophysiological environments.
Hydroxyapatite is thermodynamically stable at physiological
pH values; actively takes part in bone bonding, forming strong
chemical bonds with surrounding bone
Mechanical properties unsuitable for load-bearing applications
such as orthopaedics
Used as a coating on materials such as titanium and titanium
alloys,where it can contribute its 'bioactive' properties, while
the metallic component bears the load
Coatings applied by plasma spraying
UNIT III
Polymeric Biomaterials
What is a polymer?
Long chain molecules that consist of a number of repeating units (mers)
Fabricated from monomers which change somehow in polymerization
Loss of H20, HCl or other molecule

Polymer properties are more complex than for simpler materials
Types of polymers
Biological polymers
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DNA, cellulose, starch, proteins, rubber, etc
 Often reconstituted to form usable polymer
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Mainly collected from animals
Synthetic polymers
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Fabricated from petroleum products (generally)
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May be also a modified biological polymer
 Most plastics and similar materials
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Classification
Polymers
Thermoplastics
examples
Thermosets
examples
Elastomers or
Rubbers
examples
Classes of Polymers (I)
• Thermoplastic polymers:
– Long chains with very limited or no cross-linking
– They behave in a plastic, ductile manner (above Tg)
– Melt when heated and are thus easily remolded and
recycled
• Thermoset polymers:
– Highly cross-linked, 3D network structures
– Generally brittle (at most temperatures)
– Decompose when heated and can’t easily be reshaped
or recycled
Classes of Polymers (II)
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Elastomers and rubbers
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Large amounts of elastic deformation
Some (light) cross-linking
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elastomer
Typically, about 1 in 100 molecules are crosslinked on average
Average number of cross-links around 1 in 30 thermoset
yields a more rigid and brittle material (closer to
a thermoset)
Crosslinks allows material to return to
original shape without plastic deformation
Definitions
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Oligomer- molecules with n<10 (less than ten monomers)
Degree of polymerization, P= number of monomer residues
per chain
Functionality: number of bonding sites per monomer.A
monomer must possess at least two bonding sites
Homopolymer
A-A-A-A-A-A-A-A
Copolymer
Random : A-B-A-A-A-B-B-A-B-B-B-A-B-B
Alternating : A-B-A-B-A-B-A-B-A-B
Block : A-A-A-A-A-B-B-B-B-B-B
Graft A’s with B’s on branches
Linear polymer- no branches
Branched polymer - multiple branches
Crosslinked polymer- links between branches
Polymer Basics
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Polymerization process:
Initiation: I → 2R• (the active center which
acts as a chain carrier is created)
Propagation: RM1• + M → RM2• (growth of
macromolecular chain)
Termination: kinetic chain is brought to halt
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Synthesis Reactions:
Addition polymerization
Condensation polymerization
Source: Askeland & Phule p 677
PE (Polyethylene) PP (Polypropylene)
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Used in high density form
astubing for drains and
catheters
Ultra high molecular weight
form used as acetabul
component in artificial hips
and other prosthetic joints
Has good toughness and
wear resistance
Resistant to lipid absorption
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High rigidity
Good chemical resistance
Good tensile strength
Excellent stress cracking
resistance
Used for sutures and hernia
repair
PTFE (Polytetrafluoroethylene)
PVC(Polyvinylchloride)
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Aka Teflon
Very hydrophobic
Good lubricity
Low wear resistance
Used for catheters and
vascular grafts (GoreTex)
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Made flexible and soft
bythe addition of
plasticizers
Not suitable for long
term use because
plasticizers can be
extracted by thebody
Used as tubing for
blood transfusions,
feeding anddialysis, and
blood storagebags
Elastomers - Entropy
If you stretch it far enough the chains will
line up straight enough to crystallize
Elastomer vs. Thermoplastic
Elastomers
• Some amorphous polymer exhibit elastomeric behavior, yet
have no chemical crosslinks
– Usually block copolymers possessing both rubbery
regions and stiff regions in the chain
– Physical interactions between stiff chain regions act a
Styrene butadiene styrene (SBS)
physical “crosslinks”
– Rubbery regions allow large
deformations
– Thermoplastic in nature; can be
melted since there are no chemical
crosslinks
Thermosets
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Disadvantage
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Advantages in engineering design applications
1.
2.
3.
4.
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Thermosets are difficult to re-form
High thermal stability and insulating properties
High rigidity and dimensional stability
Resistance to creep and deformation under load
Light-weight
Crosslinking of thermosets
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10-50% of the ‘mers’ in a chain are crosslinked
Heat treatment, vulcanization processes link existing
chains
Two part chemistries (resin and curing agent) are mixed
and react at room temp or elevated temperatures –
multi-functional end groups
Polymers as Biomaterials
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Hydrogels
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Piezoelectric materials
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swellable materials, usually acrylic copolymers, e.g. poly(2hydroxyethyl methacrylate): PHEMA
More in lecture 10
materials that generate transient electrical charges on their
surfaces upon mechanical deformation, e.g. polyvinylidene
fluoride, collagen
Resorbable materials
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Resorbed with time, e.g. polyglycolic and polylactic acid
More in lecture 11
Fluorinated Polymers
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PTFE
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Fluorocarbons
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Plain or expanded (Gore-Tex)
Vascular grafts, sutures, middle ear prostheses
High affinity for oxygen
Blood substitutes
Vinylidene Fluoride (PVDF)
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Piezoelectric
Actuators, nerve guidance
PTFE unsuccessful in
joint replacements
Polymethyl methacrylate
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PMMA
A hydrophobic linear chain polymer that is transparent,
amorphous and glassy at room temperature (also known as
plexiglass or lucite)
Good light transmittance, toughness, and stability
A good material for intraocular lenses and hard contact lenses
Also used as a bone cement
Polyethylene
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PE
High density form (HDPE)
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High molecular weight form (UHMWPE)
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Used for tubing in catheters and drains
Contact surface in artificial hips, knees
Good toughness, resistance to fat and oils, and low
cost
Polyethylene Glycol
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PEG
Short chain neutral hydrophilic polymer
Shown to repel cells due to surface energy
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Used for coatings – non-thrombogenic
Wound healing: polymerization on the wound
Microencapsulation and drug delivery
Biological Polymers
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Many cellular and extracellular materials are
polymers
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Polysaccharides (made from monosaccharides)
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Proteins (made from amino acids)
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Collagen
Actin
Fibrin
Nucleic Acids (made from nucleotides)
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Cellulose
Alginate
DNA
RNA
More in lecture 12
Silicones
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Silicone polymers
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e.g. Polydimethylsinoxane (PDMS)
No carbon backbone – silicone and oxygen instead
Elastomers (with crosslinks)
Silicones as biomaterials
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Very low Tg
Excellent flexibility and stability
Used in catheters, pacemaker leads,
vascular grafts, and breast and
facial implants
High oxygen permeability - membrane
oxygenators
Common clinical applications and types of polyCommon clinical
applications and types of polymers
used in medicine
application
Polymers In Specific Applications
properties and design
requirements
polymers used
stability and corrosion resistance,
plasticity
•strength and fatigue resistance,
coating activity
•good adhesion/integration with
tissue
•low allergenicity
PMMA-based
resins for
fillings/prosthesis
polyamides
poly(Zn acrylates)
gel or film forming ability,
hydrophilicity
•oxygen permeability
polyacrylamide gels
PHEMA and
copolymers
strength and resistance to
mechanical restraints and fatigue
•good integration with bones and
muscles
PE, PMMA
PL, PG, PLG
dental
•
ophthalmic
•
orthopedic
•
cardiovascular
•
fatigue resistance, lubricity,
65 Teflon,
silicones,
UNIT IV
Soft Tissue Implants
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Attempts have been made to replace or augment most
of the soft tissues in the body
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Most soft tissue implants are constructed from
synthetic polymers
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Connective tissues: skin, ligament, tendon, cartilage
Vascular tissue: blood vessels, heart valves
Organs: heart, pancreas, kidney
Other: eye, ear, breast
Possible to choose and control the physical and mechanical
properties
Flexibility in manufacturing
"Soft tissue implants" can also be designed for soft
tissue repair
Sutures
 Used to repair incisions and lacerations
Important characteristics for sutures::
 Tensile strength
 Flexibility
 Non-irritating
Tissue Adhesives
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Used for repair of fragile, non-suturable tissues
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Examples: Liver, kidney, lung
The bond strength for adhesive closed tissues
is not as strong after 14 days as for suture
closed tissues
Percutaneous Implants
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Refers to implants that cross the skin barrier
 In contact with both the outside environment and the
biological environment
Used for connection of the vascular system to external
"organs"
 Dialysis
 Artifical heart
 Cardiac bypass
Also used for long term delivery of medication or nutrition
(IV)
Main Problems:
 Attachment of skin (dermis) to implant difficult to maintain
through ingrowth due to rapid turnover of cells
 Implant can be extruded or invaginated due to growth of
skin around the implant
 Openings can also allow for the entrance of bacteria, which
may lead to infection
Artifical Skin
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Is actually a percutaneous implant -- contacts both
external and biological environments
No current materials available for permanent skin
replacement
Design ideas:
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Graft should be flexible enough to conform to wound bed
and move with body
Should not be so fluid-permeable as to allow the underlying
tissue to become dehydrated but should not retain so much
moisture that edema (fluid accumulation) develops under
the graft
Artificial Skin - Possibilities
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Polymeric or collagen-based membrane
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Fabrics and sponges designed to promote tissue ingrowth
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Some are too brittle and toxic for use in burn victims
Flexibility, moisture flux rate, and porosity can be controlled
Have not been successful
Immersion of patients in fluid bath or silicone fluid to prevent
early fluid loss, minimize breakdown of remaining skin, and
reduce pain
Culturing cells in vitro and using these to create a living skin
graft
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Does not require removal of significant portions of skin
Soft Tissue Augmentation
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Generally used for reconstructive or cosmetic
enhancement
Functions include one or more of the following
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Space filler
Mechanical support
Fluid carrier or storer
Common applications for soft tissue augmentation
are:
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Maxillofacial implants
Eye and ear implants
Fluid transfer implants
Breast implants
Maxillofacial implants
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Designed to replace or enhance hard or soft tissue in the jaw and
face
Intraoral prosthetics (implanted) are used to reconstruct areas that
are missing or defective due to surgical intervention, trauma, or
congenital condition
Must meet all biocompatibility requirements
Metals such as tantalum, titanium, and Co-Cr alloys can be used to
replace bony defects
Polymers are generally used for soft tissue augmentation
 Gums, chin, cheeks, lips, etc.
Injectable silicone had been examined for use in correcting facial
deformities; however, it has been found to cause severe tissue
reactions in some patients and can migrate
Extraoral prosthetics (external attachment) should:
 Match the patients skin in color and texture
 Be chemically and mechanically stable
 Not creep, change colors, or irritate skin
 Be easily fabricated
Fluid Transfer Implants
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May be designed as permanent implants to treat
chronic problems
Hydrocephalus
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Ear Infections
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Build up of cerebrospinal fluid in the brain
Can result in brain damage if pressure becomes too high
Treated by draining the fluid to the vascular system or
abdominal cavity
Uses a permanent shunt from the ventricles of the brain,
under the skin, to the receiving tissue
Tubing is made of silicone rubber made radiopaque to allow
for observation with x-rays
"Tubes" in the ears are drainage tubes designed to remove
fluid from the middle ear
Constructed from teflon or other inert materials
Not permanent implants (removed after several years)
Orthopaedic Soft Tissue
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Replacement of cartilage, ligaments, and tendons
Difficult to obtain fixation with bone
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In many cases autographs are used - may be patellar tendon for
ACL reconstruction
Allographs - cryo-preserved, fresh-frozen, or freeze dried
specimens taken from cadavers
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Screws or pins involve stress concentrations and the possibility of
corrosion
Strength of anchorage depends on thickness of cortical bone at
attachment site
Often attached to treated bony insertion sites which can be used as bone
grafts (See Figure 6)
Preservation and cold sterilization procedures may adversely affect
properties of implants
Available from tissue banks
Artificial Orthopaedic Soft Tissues
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Ligament Augmentation Devices (LAD's)
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Artificial materials used to take some of the stress normally applied to a
ligament while healing occurs
May or may not be resorbable
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Contradictory results exist in the literature as to the effectiveness of
LAD's
Ligament scaffolds
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Gore-Tex: non-resorbable
PDS: resorbable plastic
Made of polyester or other polymers
Used to induce tissue ingrowth
May be implanted alone or with a section of tissue (fat pat, fascia lata,
piece of tendon) to increase rate of ingrowth
Region of fixation for artifical ligaments or reconstructions
with LAD's for the ACL deviates from normal more than for
reconstructions with patellar tendon alone
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Fibrous tissue instead of normal transition from ligament to bone
Total Hip Replacement
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A prosthetic hip that is implanted in a similar
fashion as is done in people. It replaces the painful
arthritic joint.
The modular prosthetic hip replacement system
used today has three components – the femoral
stem, the femoral head, and the acetabulum. Each
component has multiple sizes which allow for a
custom fit.
The components are made of cobalt chrome
stainless steel and ultra high molecular weight
polyethylene. Cementless and cemented prosthesis
systems are available.
Common Causes of Hip Pain and
Loss of Hip Mobility
Osteoarthritis

Usually occurs after age
50 and often in an
individual with a family
history of arthritis. In this
form of the disease, the
articular cartilage
cushioning the bones of
the hip wears away. The
bones then rub against
each other, causing hip
pain and stiffness.
Operation
Removing the Femoral Head
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Once the hip joint is
entered, the femoral
head is dislocated from
the acetabulum.
Then the femoral head
is removed by cutting
through the femoral
neck with a power
saw.
Reaming the Acetabulum
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After the femoral head is
removed, the cartilage is
removed from the
acetabulum using a
power drill and a special
reamer.
The reamer forms the
bone in a hemispherical
shape to exactly fit the
metal shell of the
acetabular component.
Inserting the Acetabular Component


A trial component, which is
an exact duplicate of your
hip prosthesis, is used to
ensure that the joint will be
the right size and fit for the
client.
Once the right size and shape
is determined for the
acetabulum, the acetabular
component is inserted into
place.
Preparing the Femoral Canal
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To begin replacing the
femoral head, special rasps
are used to shape and scrape
out femur to the exact shape
of the metal stem of the
femoral component.
Once again, a trial
component is used to ensure
the correct size and shape.
The surgeon will also test
the movement of the hip
joint.
Inserting Femoral Stem

Once the size and
shape of the canal
exactly fit the
femoral component,
the stem is inserted
into the femoral
canal.
Attaching the Femoral Head

The metal ball that
replaces the femoral
head is attached to
the femoral stem.
The Completed Hip Replacement
•
•
Client now has a new
weight bearing surface to
replace the affected hip.
Before the incision is
closed, an x-ray is made to
ensure new prosthesis is in
the correct position.
Treatment by Kinesiologist
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-Early Postoperative ExercisesRegular exercises to restore your normal hip motion
and strength and a gradual return to everyday
activties.
Exercise 20 to 30 minutes a day divided into 3
sections.
Increase circulation to the legs and feet to prevent
blood clots
Strengthen muscles
Improve hip movement
UNIT V
Artificial heart valve

An artificial heart valve is a device implanted
in the heart of a patient with heart valvular
disease. When one of the four heart valves
malfunctions, the medical choice may be to
replace the natural valve with an artificial
valve. This requires open-heart surgery.
Types of heart valve prostheses

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There are two main types of artificial heart valves: the
mechanical and the biological valves.
Mechanical heart valves

Percutaneous implantation
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Sternotomy/Thoracotomy implantation
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Stent framed
Not framed
Ball and cage
Tilting disk
Bi-leaflet
Tri-leaflet
Biological heart valves
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Allograft/isograft
Xenograft
Types of mechanical heart valves
Design challenges of heart valve
prostheses

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A replaceable model of Cardiac
Biological Valve Prosthesis.
Thrombogenesis /
haemocompatibility

Mechanisms:
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Forward and backward flow
shear
Static leakage shear
Presence of foreign material (i.e.
intrinsic coagulation cascade)
Cellular maceration
Valve-tissue interaction
Wear
Blockage
Getting stuck
Dynamic responsiveness
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Failure safety
Valve orifice to anatomical orifice
ratio
Trans-valvular pressure gradient
Minimal leakages
Replaceable Models of Biological
Valves
Artificial limb

An artificial limb is a type of prosthesis that
replaces a missing extremity, such as arms or
legs. The type of artificial limb used is
determined largely by the extent of an
amputation or loss and location of the missing
extremity. Artificial limbs may be needed for a
variety of reasons, including disease,
accidents, and congenital defects.
Lower Limb Prosthesis

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Components of the
Prosthesis
Socket- Forms the
connection between the
residual limb and the
prosthesis.
Sleeve- Provides suction
suspension for prosthesis.
Shank (pylon)- Transfers
weight from socket to the
foot-ankle.
Foot-ankle- Absorbs shock
and impact and provides
stability.
Dental implant

A dental implant is an artificial tooth root
replacement and is used in prosthetic dentistry
to support restorations that resemble a tooth or
group of teeth. There are several types of
dental implants. The major classifications are
divided into osseointegrated implant and the
fibrointegrated implant. Earlier implants, such
as the subperiosteal implant and the blade
implant were usually fibrointegrated
WHAT IS A DENTAL IMPLANT?
 Dental implant is an artificial titanium fixture
(similar to those used in orthopedics)
which is placed surgically into the jaw bone to
substitute for a missing tooth and its root(s).
Surgical Procedure
STEP 1: INITIAL SURGERY
STEP 2: OSSEOINTEGRATION PERIOD
STEP 3: ABUTMENT CONNECTION
STEP 4: FINAL PROSTHETIC RESTORATION
Success Rates
lower jaw, front – 90 – 95%
lower jaw, back – 85 – 90%
upper jaw, front – 85 – 95%
upper jaw, back – 65 – 85%
First Implant Design by Branemark
All the implant designs are obtained by the
modification of existing designs.
John Brunski
Comparison of Implant Systems
Astra Tech.
ITI
Bicon
Perfectly elastic large displacement non-linear
contact finite element analysis for different
insertion depths.
Perfectly Elastic Finite Element Results
Contact Pressure (P) psi
500000
450000
Interference depth: 0.002 in
400000
Interference depth: 0.004 in
350000
Interference depth: 0.006 in
300000
250000
200000
150000
100000
50000
0
0.47
0.49
0.51
0.53
0.55
Vertical Position
0.57
0.59
 Contact pressure increases linearly with insertion depth.
Elastic-plastic large displacement non-linear
contact finite element analysis for different
insertion depths
Bilinear Isotropic Hardening Model
Stress
(MPA)
% Strain
Contact Pressure Distribution for Different
Insertion Depths
Elastic-Plastic Finite Element Results
300000
Contact Pressure (P) psi
Interference depth: 0.004 in
Interference depth: 0.006 in
250000
Interference depth: 0.008 in
200000
Interference depth: 0.010 in
150000
100000
50000
0
0.45
0.47
0.49
0.51
0.53
0.55
Vertical Position
0.57
0.59
 Contact pressure increases non-linearly with larger
insertion depths.
FUTURE WORK
 Comparison of different implant designs in
terms of stress distribution in the bone due to
occlusal loads.
 Modeling non-homogenous bone material
properties by incorporating with CT scan data.
 Comparison of different implant-abutment
interfaces