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Biomaterials (application areas (suture anchors (types (stable (synthetic)…
Biomaterials
application areas
orthopaedic implants
hip replacement surgery
structure
head
metal on metal
minimally invasive model
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ceramic on plastic
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ceramic ball and plastic liner
ceramic on ceramic
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ceramic ball and ceramic liner
reduced wear!
improved lubrication
but...
prone to fracture
more invasive
metal on plastic
cross-linked PE is more durable
ADEQUATE TOUGHNESS FOR MOST LIFESTYLES
still, may wear over time
resulting in
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ceramic on metal
durable but vulnerable to fracture
under big stress
no consensus for the BEST material
problems
wear particles
MOM horror story :ghost:
surroundings full of wear particles
''black goo''
ions were transferred into blood stream
particles formed pseudotumors
cells expressed mutagenic behaviour
BUT ALSO OTHER MATERIALS DO HAVE WEAR ISSUES
ankle and shoulder replacement
problems in total joint replacement
spinal implants
fracture fixation
bone implants
dental implants
cranio maxillofacial implants
soft tissue defects
silicone rubber
PVC
acetate copolymers
bone defects
Ti
Co-Cr
PLLA
PGA
cranial defects
3D-printed molds specifically for the patient
for bone defects many different materials are used
natural
processed human bone
inorganic mineral like HA
organic collagen
used for space-filling material for cosmetic purposes
might resorb by body
need for refilling
synthetic
ceramics
HA
CTP
glass
healing is improved by
osteoinduction
osteostimulation
osteogenesis
osteoconduction
GF
controlled drug release
solves the problem for
fluctuating drug concentration within body
accumulation thus toxic side effects
ways of doing it
plaster
tissue-inserted capsules
material requirements
controlled
stability
degradation
polymers
reservoir system
matrix system
mechanically sufficient
reliability
biocompatibility
sterile product
intelligent drug delivery
like insulin pump
periodical release
benefits
smaller dosage
fewer side effects
if biodegradable scaffold-->no need for removing
disadvantages
dosage cannot be changed
removal is diffucult
if continuous dosage--> has to be repeated periodically
regenerating damaged or lost tissue or organ
tissue engineering
methods
repair and regeneration
transplants
tissue engineering
cells are extracted from the patient, then cultured, then transferred into scallops, incubated and finally scaffold is inserted into body
scaffold provides mechanical and chemical support for cells
ECM
interconnected porous structure
scaffold strucutres
salt leaching
foaming
textile
3D printing
scaffold materials
natural polymers
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synthetic
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ceramics
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biostable materials
maintenance
improvement of functionality
to result in regeneration by growing viable new tissue
skin burns
natural polymers and hydrogels
cosmetic reconstructing implants
functions
space filler
breast implants
mechanical support
fluid carrier or storage device
function regains
cochlear implants
suture anchors
ligaments and tendons in shoulder, knee and ankle
meniscus repair
suture functions
closing wounds
types
stable
synthetic
PLA
PGA
nylon
biodegradable
silk
tapes
so that we can avoid
pressure necrosis
scar tissue formation
problems with stitch abscesses
weak tissue
still, sutures are better
misaligned wound edges
poor adhesion
staples
when aesthetics don't matter
metals
Ni-Ti
solid material types
metals
polymers
categories
bioabsorbable
intention
to provide
transient
support
capable for being
degraded
or
dissolved
AND
metabolized
classification
origin
synthetic
Polylactides
natural
prot
collagen
polysaccharides
hyaluronan
structure
polyester
polyamide
number of monomers
shape of the polymer chain
cross-linked
branched
linear
biodegradable
common synthetic bioabsorbable polymers
PGA
glycol acid polymerizes into polyglycolide
properties
high melting point
low solubility in organic solvents
degradation
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copolymerization with hydrophobic lactates--> more properites
PLA
polylactide
homopolymers
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PLLA
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copolymerixzation
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properties
good biocompatibility
enzyme and hydrolysis
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optically active
more hydrophobic than PGA
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mechanically better than PGA
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apps
sutures
implants
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Poly-e-caprolactone=PCL
properties
hydrophobic
semi-crystallized
low rate of degradation
well-mixable with other polymers
apps
degradable staples
sutures
RD
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copolymers
stereo-copolymers
mirrored strucutres
benefits
offers a chance to fine-tune the properties
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homopolymers
problematic
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heteropolymers
poly(lactide-co-glycolide) PLGA
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Poly(lactose-co-caprolactone) PLCL
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material properties
D,L-lactide
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Glycolide
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L-lactide
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TMC
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two methods
hydrolysis
compound takes up a water molecule and thus breaks apart
''addition of water''
consequences
MW decreases
polymer mass loss
degradation intro monomers
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enzymatic degradation
enzymes cut the polymer into oligomers/monomers
BOTH produce low MW products that are water-soluble and metabolized through body's metabolism
inside the implant
three stages:
2
water breaks the material even more
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3
metabolic elimination
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1
water molecules cut the polymer chains of the material
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erosion
bulk
water penetrates entire polymer bulk causing hydrolysis throughout the entire polymer matrix
water diffusion is faster than hydrolysis
surface
water penetration slightly faster than degradation
polymer volume is reduced layer by layer
MW reamins constant
as the material only ''shrinks'' but is not affected by its sturcutre
autocatalytic degradation
products are acidic
speed up the process
inside degrades quicker
outside:degradation products dissolve into surroundings
time
depends on
material properties
hydrophobicity/hydrophilicity
polymer structure
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MW
manufacturing process
process parameters
sterilization method
implantation site
inside/outside bone
thickness of the covering soft tissue
individual differences!
metabolism
local vasculature
usage of bioabsorbable apps
advantages
no need for sec surgery
degradation products are natural metabolites of the body
no toxicity?
new properties not present in metals
easier reoperations
no growth disturbance (children)
no permanent implants
no long term complications
apps
soft tissue reconstruction
sutures
still, non-absorbable synthetic like PE and PP are being used
scaffolds
vascular stents
CONTROLLED DRUG RELEASE
legislation
stricter requirements in terms of biocompatibility
degradation products need to be assessed
properties
strength?
weak compared to metals
natural and modified-natural bioabsorbable polymers
modified natural
polymers derived from renewable surces
plants
animals
micro-organisms
can also be insoluble, like sulphate polysaccharides present in micro-organisms
natural
proteins
disadvantages
often antigenic
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not available in large quantities
batch per batch variation
origin might be dead
advantages
used proteins
collagen
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albumin
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fibrin
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elastin
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polysaccharides
hydrogel preparation
hydrogels :<3:
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production of bio-active polymers
cell-signaling
non-toxic degradation
polyesters
polyhydroxyalkanoates
produced by microbes
enzymatic degradation
Polyhydroxybutyrate
biocompatible
apps
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chemically known for the body's metabolism
biodegradation is based on N and O atoms
advantages
good biocompatibility
increased
cell adhesion
migration
proliferation
biodegradability
via enzyme
non-toxicity
water binding
protein materials interact with the adjacent cells
disadvantages
mechanically weak
difficult chemistry-->difficult to mold
cross-linking chemicals may be toxic
batch-to-batch variations
degradation rate is difficult to predict
apps
hemostasis
sponges
fibers
fleece-like products
dermatology
injectable collagen
RD
wound dressing
artificial skin
cardiovascular apps
blood vessels
heart valves
neurosurgery
guided growth of nerve cells
opthalmology
cornea cover
biostable
synthetic
examples
Polyolefins
PE
aesophagus
subtypes of different densities
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properties
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PP
properties
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apps
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PVC
structure
hard
brittle
can be modified
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properties
possible extraction of plasticizers
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apps
dialysis devices
PET
structure
amorphous
apps
vascular prostheses
stents
polyurethane
strucutre
urethane bond
can be modified
apps
vascular protheses
Teflon
structure
polutetrafluoroethylene
crystalline
dense
properties
not soluble
difficult to process
good hemocompatibility
apps
coating in vascular prostheses
membrane material
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PMMA
structure
hard
rigid
amorphous
light transparency
high index of refraction
properties
good biocompatibility
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polysiloxane
=silicones
structure
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properties
stable
unreactive
hydrophobic
long-term use
apps
stents
breast implants
joint implants
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usage
in the body
stability
applications
implants
outside the body
applications
pharma packing
hospital supplies
basis of the structure
strong C-C-bond
degradation sensitive atoms
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O
N
stability affecting parameters
intramolecular bonds
functional groups
electronegativity
stereochemistry
bonding
flexibility
crystallinity
crystal structure
conformation/orientation
copolymer composition
impurities
intention
stay unchanged the whole life
pros
variety in composition
variation in properties
variation in available forms
fabrication easy
all shapes and sizes
reasonable costs
biodegradation
cons
lower strength
not in load bearing applications
''perfect material'' (implanted)
no pathogen transfer
immunologically inert
doesn't cause chronic inflammation
no antigens
non-toxic
biocompatible
biosimilarity to surroundigs
bioabsorptable/biodegradable
induces
neovascularisation
angiogenesis
composites
definition
materials made from two or more constituent materials with significantly different physical or chemical properties
which remain separate
and distinct on a macroscopic level within the finished structure
create a material with better properties
than the individual components alone
synergistic behaviour
parts
matrix phase
''rautaputki''
reinforcing phase
''sementti''
''teräsbetoni''
types
particulate
laminate
fibre reinforced
classification
according to structure
fiber-reinforced composites
particle reinforced composites
partially crystalline materials
sandwich structure
coating
with bioactive material
aims in coating biomaterials
modifications of hemocompatibility of the material :red_circle:
enhancing bioactiveness
cell adhesion
cell growth
controlling cell adhesion
increasing wear and corrosion resistance :large_orange_diamond:
modification of transfer properties :truck:
modification of electric properties :zap:
protecting underlying material/surrounding tissue :green_heart:
decreasing the growth of fibrous capsule :no_entry:
according to used materials
metal matrix composites
matrix
Co-Cr
Ti
Ti-alloys
stainless steel
filler
boron
carbides
carbon/aluminum oxides
advantages
good cross-sectional mech properties
high compressive and shearing strength
resterilation as a possibnility (instruments)
disadvantages
structurally very far from biological tissue
interference with imaging
corrosion
wear
stress shielding
bone gets osteopenia as it weakens around the implant because implant takes the most load and bone tissue gets lighter weight
coating
ceramics
pyrolytic carbon
used in cardiac valve prostheses
good hemocompatibility
ceramic matrix composites
used in
craniofascial applications
hip prostheses
bone filling materials
dental surgery
controlled drug delivery
materials
inert
Al2O3
porous
hydroxyapatite
as in bone
bioactive
bioactive glass
resorbable
tricalcium phosphate
advantages
the freedom of choice, based on surface chemistry
inert
bioactive
similar to bone
good wear resistance
disadvantages
brittleness
difficult to handle
processing
polymer matrix composites
types
stable polymers
apps
parts of prostheses
vascular prostheses
bone cements
bioabsorbable polymers
polylactide
polyglycolide
natural
like
collagen
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polyhydroxybutyrate
starch-polymer blends
used in
hydrogels
collagen-polymer films
collagen-liposome for controlled drug delivery
apps
controlled drug delivery
fracture fixation
temporary support
matrix polymer must be reinforced to achieve adequate mechanical properties
advantages
suitable for many apps
easy to process and mold
price is low
light
wide range of properties
disadvantages
strength and stiffness is not compared to metals and ceramics
according to properties
fully absorbable
partially absorbable
non-bioabsorbable
properties
depend on
shape of the heterogenities
orientation of the filler phase
volume fraction occupied
interaction between constituent materials
adhesion
exist in the body
bone
loose connective tissue
advantages
material properties can be tailored
additional functionality as there is more materials
bioactivity
enhances bone formation
accelerates bone ingrowth
prevents fibrous capsule formation
coating with bioactive materials (like calcium phosphate)
enhances bone formation not fibrinous capsule
prevents unwanted protein layer agglomeration on the surface
mechanical properties
tailoring suitable density and mass vs. mechanical and chemical properties
like reinforcing polymer matrix composites
desired degradation profile
controlled drug release
drug
PLGA+antibiotics
Mirena contraceptive device
PE body
coated with polysiloxane film releasing levonorgestrel
GF
collagen
cells can also be inserted
enhances tissue healing
collagen gel with chondrocytes
improvement of stregth
single material is seldom perfect as itself
disadvantages
increased risk of poor biocompatibility
more materials
degradation products can react in an undesired way
degradation products can form new, unwanted compounds
manufacturing is more difficult
design
polymer-ceramic composite
HA
collagen
bioabsorbable polymers and bioceramics/bioactive glass
nanocomposites
=composite material with
reinforcement/filler in nanoscale
is considered a nanocomposite
polymer nano-composites
=filler is a polymer
classification
nanoplatelets
nanospheres
nanofibers
nanotubes
carbon nanotubes
nanoclay
parallel sheets of tetrahedral silicate
used as a filler in nanocomposites
bionanocomposites
like tissue-engineered bone:
top layer
collagen I
middle layer
collagen+HA nanoparticles 60/40
bottom layer
collagen+HA nanoparticles 70/30
generally successful, yet MRI scan revealed some issues although scaffold itself was integrated well
ceramics
ceramics and glass
hemocompatibility
without causing adverse reactions like
hemolysis
inflammation
thrombosis
ceramics
definition
inorganic, solid material that is non-metallic
hard, brittle, heat- and corrosion-resistant material made of
metallic elements + C, N, P
poor conductors
crystalline structure
prepared from powdered material
fabricated into products through the usage of heat
structure
varies
simple
complex
microstructure
entirely glassy
entirely crystalline
atoms are arranged in periodic pattern
long-range order
combination of crystalline+glassy
glass surrounds crystals
interatomic bonds
amorphous
lack of order
=glasses
ionic/covalent bonds
hard, brittle nature
high compression strength
similar properties based on chemistry with bone
main classes
oxides
nitrites
carbides
usage
face and cranial repair
hip prostheses
bone fillers
drug delivery
AESTHETICS
classification due tissue response
nearly inert
materials
Al2O3
stregth is based on
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properties
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for load-bearing apps
processing
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carbon
allotropic forms
fibers can be used as reinforcement in polymers and ceramics
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pyrolytic carbon
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mechanical interlock
provides structural support
still, poor tenacity
resist corrosion and wear
non-adherent fibrous capsule when implanted
attaching via
bone growth into surface irregularities
cementing into the tissue
press-fitting to the defect
porous
ingrowth with tissue pores
loosening of the implant won't happen
hydroxyapathite
can be
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anchors the implant
pore size
over 100 um
pores interconnected
used to coat metals
resorbable
replacement with tissues
designed to dissolve at the same rate as the surrounding tissue grows
eventually they are replaced
material requirements
must be dissolved by the body's enzymes
metabolites can't be
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degradation rate must be adjusted to the surrounding tissue
bioactive glass
bioactive
interfacial bonding with tissues
responds to tissue
undergo chemical and biological bonding in the interface
prevents motion bc bonds
mimics the interface when tissue is healing
controlled rate of chemical reactivity
at the surface!!!
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bioactive glass
bonds bone AND stimulates
bone growth
bonding to hard and soft tissues, I value >8
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bonding only to the hard bone
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bioactivity index describes the rate of development of interfacial bonding
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Index=100/t50, in which t50= 50% of surface is bonded to tissue
materials
Ca-P-ceramics
in aqueous solutions
Ca-P turn into hydroxyapathite
through
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most used
HA
most commonly used, synthetic Ca-P-ceramic
chemically similar than inorganic component of bone
stable compared to others
bonds to bone
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properties depend on porosity
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usage
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TCP
tricalcium phosphate
resorbable
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properties
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bioactive glass
properties
amorphous
bioactive, bioceramic
antibacterial properties
weak mechanical properties
inorganic
different compositions
parameters that can be controlled
chemical properties
rate and degree to bond tissue
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rate of resorption
osteoconductivity
congruent dissolution
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types
SiO2-based
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process
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manufacturing process
high T-->small volume of liquid
T decreases--> atomic structure will gradually change
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usage
replacing small bones of middle ear
bone grafts
as coatings
toothpaste for dentinal hypersensitivity
scaffolds for tissue engineering
advantages
biocompatibility
nearly inert
bioactive
similarity to ceramics
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good durability
good wear resistance
mechanical properties
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thermal and electrical insulation
aestehtical
lightly colored
can be polished
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disadvantages
brittleness
low fracture tolerance
no molding possibility
low tensile strength
fibers are an exception
poor fatigue resistance
ceramics crack easily
flaw sensitivity
difficult to fabricate