Biomaterials / diploma in orthodontics in delhi

BIOCOMPATIBILITY AND
BIOMATERIALS FOR
IMPLANTS
• (Part 1)
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.comwww.indiandentalacademy.
com

• INTRODUCTION
• HISTORY
• PHYSICAL AND MECHANICAL, AND CHEMICAL REQUIREMENTS FOR IMPLANT MATERIALS
• METALS AND ALLOYS
• OTHER METALS AND ALLOYS
• OTHER MATERIALS
• FUTURE AREAS OF APPLICATION
• BIOACTIVE AND BIODEGRADABLE CERAMICS BASED ON CAL.PHOSPHATES
• SURFACE CHARACTERIZATION AND TISSUE INTERACTION
• OTHER SURFACE MODIFICATIONS
• PASSIVATION AND CHEMICAL CLEANING
• BIOCOMPATIBILITY
• STERILIZATION
• CONCLUSION
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INTRODUCTIONINTRODUCTION
• The disciplines of biomaterials and
biomechanics are complementory to the
undersatanding of device- based function
• The physical, mechanical, chemical, and
electrical properties of the basic material
components must always be fully
evaluated for any biomaterial application,
as these properties provide key inputs into
the interrelated biomechanical and
biologic analysis of function
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• Dr. John Autian regards biocompatible
as meaning that no significant harm
comes to the host.
• Another world leader in the field of
biomaterials, Dr. Jonathan Black. Has
suggested that the term “biologic
performance” is more appropriate than
biocompatibility to represent the various
interactions between the host and the
material.
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• (Weiss) Biocompatibility can be defined as “
the capacity of a material to exist in harmony
with the surrounding biologic environment ; not
having toxic or injurious effects on biologic
functions.”
Currently the most popular implant designs are
subperiosteal implants, endosteal implants and
endosteal root form or cylindrical implants.
But other implant designs such as the ramus
frame, mandibular staple bone plate, fiber
mesh are being utilized successfully as well.
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HISTORYHISTORY
• The first evidence of the use of implants
dates back to 600 A.D in the Mayan
population. A fragment of a mandible
illustrates the implantation of pieces of
shell to replicate three lower incisor teeth.
• Implant designs are tracable to early
egyptians and central / south
American cultures and have evolved into
current implant designs that are now
experiencing an explosive popularity.
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• In 1809, Maggiolo described the process of
fabricating and inserting gold roots to support teeth.
• In 1911, Greenfield described the fabrication and
insertion of an endosseous implant. The recipient site
was prepared utilising a trephine. An irridio platinum
basket, soldered with 24 carat gold, was then inserted
into prepared site.
• In 1939, Strock described a method of placing of first
cobalt chromium molybdenum alloy (Vitalium)
screw to provide anchorage for replacement of a
missing tooth. A radiograph of Vitalium screw implant
in the maxillary anterior segment eight months post
placement was taken. It demonstrated that the tissue
response after eight months was excellent, although
the implant could be rotated in its socket.
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• Venable & Stuck in 1936 Their studies
indicated that cobalt-chromium molybdenum
alloy (vitallium) was the only metal utilized
at the time that produced no electrolytic
action when buried in tissues
• In the mid 50’s, Lew introduced the use of
an endosseous implant with a central post to
circumferential extension, made of Cobalt
chromium molybdenum screw.
• In the mid 1960’s Sandhaus developed
crystalline bone screw consisting mainly of
aluminium oxide.
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In 1970, Roberts and Roberts
developed Ramus blade endosseous
implant. This ‘blade’ types of implant was
constructed of surgical grade 316
stainless steel
• By early 1970’s animal studies began on
the use of non-metallic types of
endosseous implant.
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• Vitreous carbon implants were first
placed in canines in early 1970 by
Grenoble based upon biocompatibility
and efficacy studies.
• In early 1980’s, Tatum introduced
the Omni R implant. This is a titanium
alloy root form implant with horizontal
fins, designed to be placed into a
prepared or expanded and osseous
receptor site.
• In 1980 Core-vent was introduced by
Niznick the screw vent implant was later
introduced as an endosseous screw type
implant www.indiandentalacademy.co
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• In early 80’s Calcitek corporation
began manufacturing and marketing its
synthetic poly crystalline ceramic
hydroxyapatite, hydroxyapatite –
coated cylindrical post titanium alloy
implant.
• In 1985, Straumann Company, unique
in plasma sprayed cylinders and screws
are designed to be inserted in a one-
stage operation.
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• BraneMark devoted the next 13 years
conducting animal studies, determine the
parameters under which osseo-integration
would predictably occur.
• Based on his study and others, titanium was
the material of choice.
• Many dental implants now available make use
of commercially pure or extra – low interstitial
titanium.
• Recently there has been a trend towards coated
implants, including plasma-spray, porous-www.indiandentalacademy.co
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PHYSICAL, MECHANICAL, ANDPHYSICAL, MECHANICAL, AND
CHEMICAL REQUIREMENTS FORCHEMICAL REQUIREMENTS FOR
IMPLANT MATERIALSIMPLANT MATERIALS
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Physical and MechanicalPhysical and Mechanical
PropertiesProperties
• Forces exerted on the implant
material consist of tensile,
compressive, and shear components.
• compressive strengths of implant
materials are usually greater than
their shear and tensile counterparts
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• All fatigue failures obey mechanical laws
correlating the dimensions of the material
to the mechanical properties of said
material.
• Para function (nocturnal and/or diurnal)
can be greatly detrimental to longevity
because of the mechanical properties,
such as maximum yield strength, fatigue
strength, creep deformability, ductility,
and fracture.
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• Limitations of the relevance of these
properties are mainly caused by the
variable shape and surface features of
implant designs.
• A different approach to match more
closely the implanted material and hard
tissues properties led to the
experimentation of polymeric, carbonitic,
and metallic materials of low modulus of
elasticity.
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• The higher the applied load, the higher
the mechanical stress, and the greater
the possibility for exceeding the fatigue
endurance limit of the material.
• In general, the fatigue limit of metallic
implant materials reaches approximately
50% of their ultimate tensile strength.
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• Ceramic materials are weak under shear forces
because of the combination of fracture strength
and no ductility, which can lead to brittle
fracture.
• Metals can be heated for varying periods to
influence properties, modified by the addition of
alloying elements or altered by mechanical
processing such as drawing, swaging, or
forging, followed by age or dispersion
hardening, until the strength and ductility of
the processed material are optimized for the
intended application.
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• The modifying elements in metallic
systems may be metals or nonmetals.
• A general rule is that mechanical process
hardening procedures result in an
increased strength but also invariably
correspond to a loss of ductility.
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• Most all consensus standards for metals
• [ASTM], [ISO], [ADA]) require
• a minimum of 8% ductility to minimize
brittle fractures.
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Corrosion and BiodegradationCorrosion and Biodegradation
Corrosion is defined as
‘the loss of measurable substance
within a metallic structure and the
diffusion of chemical elements in the
surrounding tissue under the effects
of the environment.’
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• Corrosion is a special concern for metallic
materials in dental implantology
• Galvanic processes depend on the
passivity of oxide layers, which are
characterized by a minimal dissolution
rate and high regenerative power for
metals such as titanium.
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• The passive layer is made of oxides or
hydroxides of the metallic elements that
have greatest affinity for oxygen.
• Williams suggested that three types of
corrosion were most relevant to dental
implants:
• stress corrosion cracking,
• galvanic corrosion, and
• fretting corrosion.
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Stress Corrosion CrackingStress Corrosion Cracking
• The combination of high magnitude of
applied mechanical stress plus
simultaneous exposure to a corrosive
environment can result in the failure of
metallic materials by cracking, where
neither condition alone would cause the
failure. (William)
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• Lemons and others hypothesized that it
may be responsible for some implant
failures in view of high concentrations of
forces in the area of the abutment-to-
implant body interface.
• Most traditional implant body designs
under three dimensional finite element
stress analysis show a concentration of
stresses at the crest of the bone support
and cervical one-third of the implant.
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• This tends to support potential SCC at the
implant interface area (i.e., a transition
zone for altered chemical and mechanical
environmental conditions).
• This has also been described in terms of
corrosion fatigue (i.e. cyclic load cycle
failures accelerated by locally aggressive
medium).
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Galvanic corrosion (GG)Galvanic corrosion (GG)
• occurs when two dissimilar metallic
materials are in contact and are
within an electrolyte resulting in
current to flow between the two.
• The metallic materials with the
dissimilar potentials can have their
corrosion currents altered, thereby
resulting in a greater corrosion rate.
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Fretting corrosion (FC)Fretting corrosion (FC)
• occurs when there is a micro motion
and rubbing contact within a corrosive
environment (such as the perforation
of the passive layers and shear-
directed loading along adjacent
contacting surfaces).
• FC has been shown to occur along
implant body / abutment /
superstructure interfaces.
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Toxicity and ConsiderationToxicity and Consideration
• Toxicity is related to primary
biodegradation products (simple and
complex cations and anions), particularly
those of higher atomic weight metals.
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• Factors to be considered include
(1)the amount dissolved by biodegradation
per time unit,
(2) the amount of material removed by
metabolic activity in the same time unit,
and
(3) quantities of solid particles and ions
deposited in the tissue and any
associated transfers to the systemic
system. www.indiandentalacademy.co
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• The electrochemical behavior of
implanted materials has been
instrumental in assessing their
biocompatibility.
• Charge transfer appears to be a
significant factor specific to the
biocompatibility of metallic biomaterials.
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• Passive layers along the surfaces of
titanium, niobium, zirconium, and
tantalum increase resistance to change
transfer processes by isolating the
substrate from the electrolyte, in addition
to providing a higher resistance to ion
transfers.
• On the other hand, metals based on iron,
nickel, or cobalt is not as resistant to
transfers through the oxide like passive
surface zones.www.indiandentalacademy.co
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METALS AND ALLOYSMETALS AND ALLOYS
INTRODUCTION
• The most common metallic objects are in the
shape of nails, screws, nuts and bolts, staples,
bone plates, intramedullary pegs, wires, bands,
and joint prostheses.
• These are ordinarily used for repairing bone
injuries, or may serve as either adjuvant to
promote natural bone maturation or substitutes
for removed bony parts.
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So far three kinds of metal substrates
have been used for prosthetic purposes:
• Iron-based
• Cobalt-based
• Titanium-based
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• Several organizations have provided
guidelines for the standardization of
implant materials
• ASTM Committee F4 and ISO (ISO TC
106, ISOTR 10541) have provided the
basis for such standards.
• To date a multinational survey by ISO
indicated that titanium and its alloy are
mainly used.
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The most widely used nonmetallic implants
are
• Oxidic
• carbonitic, or
• graphitic oxide like materials.
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The major groups of implantable
materials for dentistry are:
• titanium and alloys,
• cobalt chromium alloys,
• austenitic Fe-Cr-Ni-Mo steels,
• tantalum, niobium and zirconium alloys,
• precious metals, ceramics, and
polymeric materials.
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Titanium and Titanium-6Titanium and Titanium-6
Aluminum-4 VanadiumAluminum-4 Vanadium
• Titanium oxidizes (passivates) upon
contact with room temperature air or
normal tissue fluids.
• This reactivity is favorable for dental
implant devices.
• In the absence of interfacial motion
or adverse tissue conditions, this
passivated surface condition
minimizes biocorrosion phenomena.
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• In situations where the implant would be
placed within a closely fitting receptor
site in bone, areas scratched or abraded
during placement would repassivate in
vivo.
• This characteristic is one important
property consideration related to the use
of titanium for dental implants.www.indiandentalacademy.co
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• Titanium is a highly reactive metal.
• An oxide layer 100A thick forms on the
cut surfaces of pure titanium within a
millisecond.
• Thus, any scratch or nick in the oxide
coating is essentially self-healing.
• Typically, titanium is further passivated
by placement in a bath of nitric acid to
form a thick, durable oxide coating.www.indiandentalacademy.co
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• high dielectric properties of titanium
oxide, which exceed those of most
metal oxides, - is responsible for the
positive biologic response to these
implants because they make the surface
more reactive to bio molecules via
enhanced electrostatic forces.
• Any contamination or adulteration of this
surface before placement will surely have
a negative effect on the success of the
implant.
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• The alloy of titanium most often used is
titanium-aluminium-vanadium.
• The wrought alloy condition is 6 times
stronger than compact bone and thereby
affords more opportunities for designs
with thinner sections (e.g., plateaus, thin
interconnecting regions, rectangular
scaffolds, porosities).
• The modulus of elasticity of the alloy is
slightly greater than that of titanium,
being about 5.6 times that of compact
bone. www.indiandentalacademy.co
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• The emerging techniques to cast Ti and Ti
alloys remain limited for dental implant
application because of high melting
points of the elements
• and propensity for absorption of oxygen,
nitrogen, and hydrogen, which may cause
metallic embrittlement.
• Typical strengths of cast commercially
pure (CP)-Ti grade 2 and Ti-6A1-4V after
heat treatment and annealing can be in
the range of those of wrought Ti alloys
used for dental implants.
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Cobalt-Chromium-Cobalt-Chromium-
Molybdenum Based AlloyMolybdenum Based Alloy
• The cobalt-based alloys are most often
used in an as-cast or cast-and-
annealed metallurgical condition.
• This permits the fabrication of
implants as custom designs such as
subperiosteal frames.
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• The elemental composition of this alloy
includes cobalt, chromium, and
molybdenum as the major elements.
• Cobalt provides the continuous phase for
basic properties;
• secondary phases based on cobalt,
chromium, molybdenum, nickel, and
carbon provide strength (4 times that of
compact bone) and surface abrasion
resistance;
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• chromium provides corrosion resistance
through the oxide surface;
• molybdenum provides strength and bulk
corrosion resistance.
• Nickel has been identified in biocorrosion
products, and
• carbon must be precisely controlled to
maintain mechanical properties such as
ductility. www.indiandentalacademy.co
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• the cobalt alloys are the least ductile of
the alloy systems used for dental
surgical implants, and bending should be
avoided.
• When properly fabricated, implants from
this alloy group have shown excellent
biocompatibility profiles.
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Iron-Chromium-Nickel-Iron-Chromium-Nickel-
Based AlloysBased Alloys
• Is used most often in a wrought and
heat-treated metallurgical condition,
which results in a high-strength and high-
ductility alloy.
• The ramus blade, ramus frame, stabilizer
pins (old), and some mucosal insert
systems have been made from the iron-
based alloy.
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• Of the implant alloys, this alloy is most subject
to crevice and pitting biocorrosion and care
must be taken to utilize and retain the
passivated (oxide) surface condition.
• Because this alloy contains nickel as a major
element, use in patients allergic to nickel
should be avoided.
• The iron-based alloys have galvanic potentials
and corrosion characteristics that make them
subject to galvanic coupling biocorrosion if
interconnected with titanium, cobalt, zirconium,
or carbon implant biomaterials
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Other Metals and AlloysOther Metals and Alloys
• Many other metals and alloys have been
used for dental implant device
fabrication.
• Early spirals and cages included
tantalum, platinum, iridium, gold,
palladium, and alloys of these metals.
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• More recently, devices made from
zirconium, hafnium, and tungsten
have been evaluated.
• Gold, platinum, and palladium are
metals of relatively low strength, which
places limits on design.
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Other MaterialsOther Materials
 Biomedical PolymersBiomedical Polymers
 Ceramic and polymeric carbonsCeramic and polymeric carbons

• Biomedical polymers are presently being
considered the best materials for soft-
tissue implantation in the cardiovascular,
respiratory, digestive, and genitourinary
and nervous systems.
• Today some polymers are replacing
aluminium and a number of other
structural metals in certain applications in
the course of which they must endure
high temperatures and considerable
stress.
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The molecular structure of polymers
can belong to four different classes:
• Linear chains
• Branched chains
• Lattice three-dimensional chains
• Star-like chains
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COLLAGENCOLLAGEN
• Among natural biopolymers,
collagen deserves special attention.
• Its fundamental building block is
believed to be the triple-helical,
dipolar tropo-collagen unit.
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RESORBABLE POLYMERSRESORBABLE POLYMERS
• Polyactide (PLA) polyglycolide (PGA)
coprolactone and their relative
copolymers are promising implant
materials.
• They are presently used as bioabsorbable
fibers widely employed as suture materials
for avoiding any post operative adhesion
or in growth of injured defective tissue.
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• other polymeric substances are
polyglycolide, poly hydroxybutyric
acid and polyester amides.
• The only polymers fit for contact with
blood proved to be Mylar and Silastic,
which after 17 months did not appear to
have been affected significantly by the
action of the physiological environment.
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CERAMIC AND POLYMERICCERAMIC AND POLYMERIC
CARBONS:CARBONS:
• It is represented by polymeric
carbons with either ceramic or
fibrous structure, used in a variety of
biomedical applications.
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VITREOUS CARBONVITREOUS CARBON
• It is now possible to manufacture dental
implants and heart valves based on
vitreous carbons.
• These materials for example carbon
reinforced with carbon fibers, can be
manufactured in the shape of rigid forms
for the substitution of the facial mandible
bone.
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Properties:
• It is prepared by controlled thermal degradation
of some organic polymers, for example phenol-
formaldehyde.
• One of the major differences between the
physical properties of vitreous carbon and those
of graphite is the extremely low permeability of
vitreous carbon to gases.
• It is much stable than a variety of other
carbons or graphites.
• It is very inert www.indiandentalacademy.co
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CARBON-COATED IMPLANTSCARBON-COATED IMPLANTS
• In order to eliminate the use of PMMA
cement to achieve prosthesis fixation,
systems of direct biological coupling have
been examined over the past few years.
• some metal prostheses made of Ti-6A1-
4V were studied and provided with a
porous surface a combination that has
the advantage of enabling bone in growth
on the carbon surface in association with
bone tissue expansion within the porosity
of the substrate.www.indiandentalacademy.co
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PYROLYTIC CARBONSPYROLYTIC CARBONS
• High resistance, pyrolytic carbons
are prepared by decomposition of
hydrocarbon gases.
• Characterized by high compatibility
with blood and exhibiting a close and
extremely adhesive epithelium/coal
interface was also prepared
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GRAPHITEGRAPHITE
• Graphite is the stablest phase of solid-
state carbon.
• Graphite occurs in two distinct phases a
dihexagonal dipyramidal one and a
ditrigonal disphenoidal one.
• The latter is metastable as compared
with the hexagonal phase.
• As far as its use as a biomaterial is
concerned, graphite, or heparin-coated
graphite, has revealed a highly
thromboresistant surface.www.indiandentalacademy.co
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BIOLOGICAL GLASSESBIOLOGICAL GLASSES
• Most of the vitreous systems reveal in
their composition the presence of
phosphates, and all of them contain
either silica or silicates.
• The function of silica is to give rise to a
low-solubility molecular matrix whose
network of silicate chains acts as a
container for those elements in ionic form
whose role is to stimulate the biochemical
environment surrounding the bioactive
glass. www.indiandentalacademy.co
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LOADED BIOLOGICALLOADED BIOLOGICAL
GLASSGLASS
• In order to improve their quality and
preserve their elastic properties in time,
biological glass compositions can be
loaded with inert materials
• refractory oxides and nitrides in the form
of grains or whiskers, or metal whiskers,
or Pt powders able to induce
crystallization from bioactive glasses to
bioactive glass-ceramics, or nets of either
metallic or polymeric fiber.
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CERAMICSCERAMICS
• In the field of material science the term
‘ceramic’ includes all non-metallic
inorganic materials.
• A number of new ceramics have emerged
which have given remarkable
performance in terms of hardness,
thermal resistance, corrosion resistance,
and electrical properties.
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There follows a list of assets and defects,
as well as specific characteristics of
advanced ceramics:
1.Resistance to heat, wear, corrosion
2.Unsurpassed properties of electric insulation
3.Good magnetic permeability
4.Particular optical properties
5.Great hardness
6.High dielectric constant
7.High mechanical strength at high temperatures
8.High melting point
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ZIRCONIUM OXIDEZIRCONIUM OXIDE
• The zirconium oxide is not suitable for use as
the only material from which a body is
manufactured because, in the transition from
tetragonal to monoclinic during cooling,
tensions are generated inside the ceramic body
by the different contraction relationships
between the granules, which can cause
fractures.
• The most common zirconium oxide is often
contaminated, particularly the oxides of the
lanthanide elements, which are present as
minerals and which diminish the mechanical
properties of the ceramics that will be obtained.www.indiandentalacademy.co
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ALUMINAALUMINA
• It was a ceramic material widely used for
porcelains
• The methods used for the production of
A1203 powders are:
the Bayer process
pyrogenic process
kaolinite clay process
chemical method
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TITANIATITANIA
With respect to Titania, at present no
prosthesis in bulk form has been
experimented with.
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SILICON NITRIDESILICON NITRIDE
• For some time silicon nitride (Si3N4) has
been in the forefront of the development
of high-strength high-temperature
materials able to replace metal alloys in a
great number of applications.
• As a covalent substance, however,
silicon nitride presents a very small
concentration of vacancies and cannot be
sintered to high densities by heat
application alone.
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CALCIUM ALUMINATECALCIUM ALUMINATE
• Used in a variety of prosthetic forms, for
example to build bridges able to ensure
locking to bone, and for mastoid cavities,
long-bone prostheses, and tracheal or
dental implantations.
• Its biocompatibility has proved
acceptable, and so has its great capacity
for growth into the porous mass of both
soft and hard tissue has been
ascertained. www.indiandentalacademy.co
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• Application of calcium aluminates will be
possible when there is no need for
particular qualities of mechanical
strength, such as when the purpose is to
either fill hollows or remedy skeleton
malformation.
• The biocompatibility of a material such as
this is clearly high and wettability is also
reasonably good. It is therefore possible
for other substances to filter through its
pores. www.indiandentalacademy.co
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BIOLOGICAL RESPONSESBIOLOGICAL RESPONSES
OF CALCIUM ALUMINATEOF CALCIUM ALUMINATE
• In invitro tests it appeared that
unfortunately its biodegradability by the
tissues into which it was inserted was
excessive so much so as to compromise
the stability of the prosthesis introduced
• On account of its poor characteristic
calcium aluminates was abandoned both
as bulk and as a coating material.
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COMPOSITESCOMPOSITES
• A composite material is an association of
intimately linked substances.
• It is made up of a matrix, which builds
the main body of the composite and
constitutes a homogeneous phase of this,
and of one, or more than one, added
substances, which form inclusions
connected to the matrix.
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• With respect to the ceramic sector
various kinds of composites can be
distinguished.
1. The CERMET ones, consisting of an
association of a ceramic matrix with
metallic threads, plates, or grains.
2. The CERFIB ones, ceramic matrix and
load-bearing component consist of
vitreous fibers in this case the fibers may
be short or long and may be arranged
either orderly or randomly.
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PHOSPHATE CERAMICSPHOSPHATE CERAMICS
• Phosphatic substances, notably calcium salts,
are particularly interesting as materials for
surgical grafts.
• These materials provide the appropriate surface
for cell bonding.
• The behaviour in vivo of calcium phosphate
implants depends on a variety of factors,
among which the Ca/P relationship, the
crystallographic structure, and the amount of
porosity appear particularly important.www.indiandentalacademy.co
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APATITESAPATITES
• Apatite, or more precisely calcium
hydroxyapatite {Ca10 (PO4) 6 (OH) 2},
is the main constituent of hard tissues
such as bone, dentin, and enamel.
• In reality we classify apatite as a
whole family of substances who’s Ca2-
can be replaced by other alkaline-earth
ions, for example Sr2+ or Ba2+ to obtain
strontium hydroxyapatite (SrHA) and
barium hydroxyapatite (BaHA)
respectively. www.indiandentalacademy.co
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BIOACTIVE AND BIODEGRADABLEBIOACTIVE AND BIODEGRADABLE
CERAMICS BASED ON CALCIUMCERAMICS BASED ON CALCIUM
PHOSPHATESPHOSPHATES

Bone Augmentation andBone Augmentation and
ReplacementReplacement
• The calcium phosphate (Ca.PO4) ceramics used
in dental reconstructive surgery include a wide
range of implant types and thereby a wide
range of clinical applications.
• Micro structural and chemical properties of
these particulates were controlled to provide
forms that would either dissolve or remain
intact for structural purposes after
implantation. www.indiandentalacademy.co
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• The laboratory and clinical results for
these particulates were most promising
and led to implant expansions, including
larger implant shapes (such as rods,
cones, blocks, H-bars) for structural
support under relatively high magnitude
loading conditions
• Mixtures of particulates with collagen and
subsequently with drugs and active
organic compounds such as Bone
Morphogenic Protein (BMP) increased the
range of applications.www.indiandentalacademy.co
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Endosteal andEndosteal and
Subperiosteal ImplantsSubperiosteal Implants
• The first series of structural forms for dental
implants included rods and cones for filling
tooth root extraction sites (ridge retainers)
and, in some cases, load-bearing endosteal
implants.
• Limitations in mechanical property
characteristics soon resulted in internal
reinforcement of the Ca*PO4 ceramic
implants through mechanical (central
metallic rods) or physiochemical (coating
over another substrate) techniques.www.indiandentalacademy.co
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• The coatings of metallic surfaces using
flame or plasma spraying (or other
techniques) increased rapidly for the
Ca*PO4 ceramics.
• The coatings have been applied to a wide
range of endosteal and subperiosteal
dental implant designs with an overall
intent of improving implant surface
biocompatibility profiles and implant
longevities.
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The recognized advantagesThe recognized advantages
associated with the Ca*PO4associated with the Ca*PO4
ceramic biomaterials are:ceramic biomaterials are:
• Chemical compositions of high purity and of
substances that are similar to constituents of
normal biological tissue (calcium, phosphorus,
oxygen, and hydrogen).
• Excellent biocompatibility profiles within a
variety of tissues when used as intended.
• Opportunities to provide attachments between
selected Ca*PO4 ceramics and hard and soft
tissues.
• Minimal thermal and electrical conductivity
plus capabilities to provide a physical and
chemical barrier to ion transport (e.g.,
metallic ions) www.indiandentalacademy.co
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disadvantages associated withdisadvantages associated with
these types of biomaterials are:these types of biomaterials are:
• Variations in chemical and structural
characteristics for some currently
available implant products.
• Relatively low mechanical tensile and
shear strengths under condition of
fatigue loading
• Relatively low attachment strengths for
some coating-to-substrate interfaces
• Variable solubilities depending on the
product and the clinical application.www.indiandentalacademy.co
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Ca.PO4 Ceramic PropertiesCa.PO4 Ceramic Properties
Chemical AnalysisChemical Analysis
Forms, Microstructures, andForms, Microstructures, and
Mechanical PropertiesMechanical Properties
Density Conductivity and SolubilityDensity Conductivity and Solubility
www.indiandentalacademy.comwww.indiandentalacademy.com

Chemical AnalysisChemical Analysis
 TheThe crystalline monolytic hydroxylapatitecrystalline monolytic hydroxylapatite
(HA) [fired ceramic Ca10 (PO4) 6(OH) 2] of(HA) [fired ceramic Ca10 (PO4) 6(OH) 2] of
high density and purity (< 50 ppm impurities)high density and purity (< 50 ppm impurities)
has provided one standard for comparisonhas provided one standard for comparison
related to implant applications.related to implant applications.
 TheThe crystalline tricalcium phosphatecrystalline tricalcium phosphate [[ββ
Ca3 (PO4) 2] (TCP) ceramic has also providedCa3 (PO4) 2] (TCP) ceramic has also provided
a high-purity (< 50 ppm impurities) biomateriala high-purity (< 50 ppm impurities) biomaterial
for comparison with other products.for comparison with other products.www.indiandentalacademy.comwww.indiandentalacademy.com

These two compositions have been usedThese two compositions have been used
most extensively asmost extensively as
 - Particulates for bone augmentation and- Particulates for bone augmentation and
replacementreplacement
 - Carriers for organic products, and- Carriers for organic products, and
 - As coatings for endosteal and subperiosteal- As coatings for endosteal and subperiosteal
implants.implants.

 One of the more important aspects ofOne of the more important aspects of
the Ca.PO4 ceramics relates to thethe Ca.PO4 ceramics relates to the
possible reactions with waterpossible reactions with water ..
 For example, hydration can convert TCP toFor example, hydration can convert TCP to
HA;HA;
 also, phase transitions among the variousalso, phase transitions among the various
structural forms can exist with any exposure tostructural forms can exist with any exposure to
water.water.

 Steam or water autoclavingSteam or water autoclaving couldcould
significantly change the basic structure andsignificantly change the basic structure and
properties of Ca.PO4 (or any bioactive surface)properties of Ca.PO4 (or any bioactive surface)
and thereby provide an unknown biomaterialand thereby provide an unknown biomaterial
condition at the time of implantation.condition at the time of implantation.
 This is to be avoided through the use ofThis is to be avoided through the use of
presterilized or clean, dry, heat-sterilizationpresterilized or clean, dry, heat-sterilization
conditions.conditions.

Forms, Microstructures, andForms, Microstructures, and
Mechanical PropertiesMechanical Properties
• Particulate HA, provided in a nonporous
(<5% porosity) form as angular or
spherically shaped particles, is an
example of a crystalline, high-purity HA
biomaterial.
• These particles can have relatively
high compressive strengths (>500
MPa), with tensile strengths in the
range of 50 to 70 MPa.www.indiandentalacademy.co
m

• The macro- (i > 50 µm), or micro- (i <
50 µm) porous particulates have an
increased surface area per unit volume.
• This provides more surface area for
dissolution under static conditions and a
significant reduction in compressive and
tensile strengths.
• The porous materials also provide
additional regions for tissue in growth
and integration (mechanical stabilization)
and thereby a minimization of interfacial
motion and dynamic (wear-associated)
interfacial breakdown.www.indiandentalacademy.co
m

• The coatings of Ca.PO4 ceramics onto
metallic (cobalt- and Ti-based)
biomaterials have become a routine
application for dental implants.
• These coatings, for the most part, are
applied by flame or plasma spraying;
have average thicknesses between 20
and 100 µm;
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Density Conductivity andDensity Conductivity and
SolubilitySolubility
• Bioactive ceramics are especially interesting
for implant dentistry because the inorganic
portion of the recipient bone is more likely to
grow next to a more chemically similar
material.
• Under the bioactive (bioreactive)
categorization are included calcium
phosphate materials such as TCP, HA,
calcium carbonate (corals), and calcium
sulfate-type compounds and ceramics.
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• Dissolution characteristics of
bioactive ceramics have been
determined for both particulates and
coatings.
• , the larger the particle size, the
longer the material will remain at an
augmentation site.
• The crystallinity of HA also affects
the resorption rate of the material. The
highly crystalline structure is more
resistant to alteration and resorption
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• The purity of the HA bone substitutes
may also affect the resorption rate.
• The resorption of the bone substitute
may be cell or solution mediated.
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• Cell-mediated resorption requires
processes associated with living cells to
resorb the material, similar to the
modeling / remodeling process of living
bone, which demonstrates the coupled
resorption / formation process.
• A solution mediated resorption permits
the dissolution of the material by a
chemical process.
• Impurities or other compounds in
bioactive ceramics, such as calcium
carbonate, permit more rapid solution
mediated resorption, which then
increases the porosity of the bone
substitute.
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• The pH in the region in which the bone
substitutes are placed also affects the
rate of resorption.
• As the pH decreases the components of
living bone, primarily the calcium
phosphates, resorb by a solution-
mediated process.
• The CaPO4 coatings are
nonconductors of heat and
electricity. www.indiandentalacademy.co
m

Current Status andCurrent Status and
Developing TrendsDeveloping Trends
• The CaPO4 ceramics have proved to be
one of the more successful high
technology-based biomaterials that have
evolved within the past decades.
• Their advantageous properties strongly
support the expanding clinical applications
and the enhancement of the
biocompatibility profiles for surgical
implant uses.
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FUTURE AREAS OFFUTURE AREAS OF
APPLICATIONAPPLICATION
• Synthetic substances for tissue
replacement have evolved from selected
industrial grade materials such as metals,
ceramics, polymers, and composites.
• Knowledge of tissue properties and
computer-assisted modeling and analyses
also support the present developments.
• and control of all aspects of
manufacturing, packaging, delivering,
placing, and restoring enhance the
opportunities for optimal application and,
it is hoped, device treatment longevities.
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• Devices that function through bone or
soft tissue interfaces along the force
transfer regions could be systems of
choice, depending on the clinical
situation.
• Unquestionably, the trend for
conservative treatment of oral diseases
will continue. Thus it can be anticipated
that dental implants will frequently be a
first-treatment option.
m

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