Implant materials final/prosthodontic courses

IMPLANT
MATERIAL
S
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Table of contents
•Introduction
•History
•Implantable materials
•Corrosion And Biodegradation
•Surface modifications
•Titanium and titanium alloys
•Cobalt-Chromium-Molybdenum based alloys
•Iron-Chromium-Nickel-based alloys
•Ceramics and carbon

•Polymers and composites
•Review of literature
•Tissue interactions
•Implant fixation and biomechanical properties
•Porous coatings
•Sterilization
•Selection of implant materials
•Summary and conclusion
•References

INTRODUCTION
•The restoration of missing teeth is an important aspect of
modern dentistry.
•Conventional methods of restoration…
•A look at the history of restorative dentistry shows that for
centuries, people have attempted to replace missing teeth
using the method of implantation.

•Implantation is defined as the insertion of an object
or material, such as an alloplastic substance or other
tissue, either partially or completely into the body, for
theraupitic,diagnostic,prosthetic,or experimental
purposes.
•Extensive research has since been done to develop the
ideal implant biomaterial that would elicit a positive
biological response.

HISTORY
•The origin of dental implants dates back to the
Egyptian and Greek civilizations.
•Albucasis de Condue (936-1013) attempted to use ox
bone to replace missing teeth and this was the first
documented placement of implants.
•This was followed through centuries by a series of
tooth transplants of either human or animal teeth.
•The increased failure rate of transplants brought about
interest in implantation of artificial roots.

•In 1809, Maggiolo fabricated gold roots that were
inserted in a fresh extraction site, although not truly
submerged into bone.the crowns were placed after
healing had occurred around the implant.
•This was followed by use of platinum posts coated with
lead,tubes of gold and irridium,silver capsule with
porcelain crown…..
•In 1913, Greenfield introduced a hollow basket implant
made from a meshwork of 24 gauge iridium-platinum
wires soldered with 24-karat gold.This was used to
support single implants as well as fixed partial dentures.

•In 1937,Strock et al analyzed the effects of metal on bone.
They proposed the use of Vitallium, a material composed
of cobalt, chromium and molybdenum. It was considered to
be inert, compatible with living tissue and resistant to body
fluids.
•In 1962, Chercheve
introduced a screw type
implant made of chrome-
cobalt.

•The use of ceramics as an implant material can be traced
back to the early 1890, and is still considered as a
biocompatible, inert material.
•Use of porcelain, alumina, sapphire, Bioglass and carbon
followed.
•In 1948,Goldberg and Gershkoff inserted the first viable
subperiosteal implant.

•In 1982, Dr. Per-Ingvar Branemark introduced the
concept of osseointegration. His studies involved
titanium implants placed into tibia of rabbit and jaws of
dogs, and he concluded that titanium was the best
material for artificial root replacement.

IMPLANTABLE MATERIALS
•Titanium and alloys
•Cobalt chromium alloys
•Stainless steel alloys
•Ceramics
•Carbon and carbon silicon compounds
•Polymers
•Composites

The longevity of a implant material depends on..
•Strength..
•Ductility
•Modulus of elasticity
•Thermal and electrical conductivity
•Yield strength
•Fatigue strength
•Creep
•Resistance to corrosion
•Resistance to biodegradation

Corrosion
•Chemical or electrochemical process where a solid,
usually a metal is attacked by an environmental agent,
resulting in partial or complete dissolution.
•..difference in electrolyte and oxygen composition…
•..increased range of ph…
•3 types:
- stress corrosion cracking
- galvanic corrosion -
- fretting corrosion

Fretting corrosion Crevice corrosion

•In metallic implants, passive oxide layer dissolves at
negligible slower rates….but irreversible local perforation by
chloride ions can cause localised pitting corrosion.
•In ceramic implants, chemical dissolution of the oxides into
ions…
•In synthetic polymers, it depends upon composition,
structural form and degree of polymerisation.

Surface modifications of implant materials
•Passivation – enhancement of the oxide layer to prevent
the release of metallic ions as a result of surface
breakdown
- immersion in 40% nitric acid.
- anodisation.
•Ion implantation – bombarding of implant surface by high
energy ions upto a surface depth of 0.1µm.
•Surface texturing – increasing surface roughness to
enhance osseointegration by increasing the area to which
bone can bond.
- plasma spraying with titanium
- blasting with alumina
- acid etching www.indiandentalacademy.com

Titanium and titanium alloys
•Density of 4.5gm/cm3
, low sp. Gravity, high heat
resistance, high strength.
•Low modulus of elasticity(97 GPa) and tensile strength.
Mod. Of elasticity is 5 times more than compact bone.
•Used in wrought and heat treated metallurgic
condition…..high strength and high ductility.
•Used for endosteal plate form devices because of their
ductility.
•Commonly used titanium products are pure titanium &
titanium alloys : Ti-6Al-4V
Ti-6Al-4V Extra low interstitial (ELI).

•Ti-6Al-4V most commonly used.
•Aluminium acts as an α stabiliser ,increasing the strength
and decreasing the mass.
•Vanadium, copper and palladium are beta phase
stabilisers; prevent formation of TiAl3 – decrease
susceptibility to corrosion.
•Mod. of elasticity (117 GPa)closer to that of bone…(5.6
times>compact bone)….uniform distribution of stress.
•Ti-6Al-4V ELI has low levels of oxygen and iron which
improve ductility.

Commercially pure titanium (CPTi)
•Come in different grades – CP grade I to Cp grade IV.
•The mod. of elasticity (102 GPa), strength and yield
strength are slightly lower than Ti alloys.

Surface characteristics of Ti and Ti alloys
•Ti oxidises (passivates) upon contact with room temp. air and
normal tissue fluids – increases corrosion resistance.
•The oxide layer formed is primarily amorphous in nature and
thin in thickness dimensions. But if unalloyed Ti is processed at
elevated temp. or anodised , it forms a crystalline thicker layer.
•If implant is scratched or abraded during placement, it
repassivates in vivo.
•The oxide layer grows homogenously and a inert coating of
stable insoluble oxide normally contacts the living tissues.
•Low temp. thermal oxides are homogenous and dense; with
increasing temp., they become more heterogenous and porous.

Cobalt-Chromium-Molybdenum based alloy
•Major elements: Co - 63% ;Cr – 30% ;Mo – 5%
Minor elements: Nickel, manganese, carbon.
•Cobalt provides the continous phase for basic properties.
Chromium provides corrosion resistance through oxide
surface.
Molybdenum provides strength and bulk corrosion reistnace
Carbon acts as a hardner.
•High elastic modulus, high corrosion resistance, low
ductility.
•Used in an as-cast and cast-and-annealed metallurgic
conditions. hence fabricated as custom designs like
subperiosteal frames.

STAINLESS STEEL ALLOY
(Iron-chromium-Nickel based alloy)
•18% chromium – corrosion resistance
8% nickel – stabilises austenitic structure.
•Used in a wrought and heat treated metallurgic
condition. Hence high strength and high ductility.
•Ramus blades,ramus frames,stabiliser pins,mucosal
insert systems.

•Limitations :
- crevice and pitting corrosion
- allergic reactions to nickel
- repassivation reqd. if modified before surgery
- galvanic corrosion and biocorrosion.. contact with
noble/base metal alloys.
- Corrosion products Fe,Cr,Ni,Mo accumulate in
surrounding tissues.
•But ,Co-Cr and stainless steel are sometimes preferred
over titanium, because of their low cost and castability.

CERAMICS AND CARBON
•Ceramics are inorganic non metallic, non polymeric
materials manufactured by compacting and
sintering at elevated temperatures.
•They can be divided into metallic oxides and other
compounds.
•Ceramics have been used in bulk forms and as
coatings on metals and alloys.

Alumina,titanium & zirconium oxides
•Used for root form, endosteal plate form and pin
type dental implants.
Advantages :
•Inertness to biodegradation…
•The compressive,tensile and bending strength
exceed the strength of the compact bone by 3-5
times.
•High moduli of elasticity.
•Minimal thermal and electrical conductivity.
•Minimal reactions with bone, soft tissue and
oralenvironment.
•They have a clear white,cream or light gray color
which is beneficial for applications in anterior root
form devices.
•Studies have exhibited direct interfaces with bone,
but they do not promote formation of .bone

Drawbacks:
•Brittleness, low ductility, low tensile strength.
•Low fracture resistance
•Scratches/notches may introduce fracture initiation sites.
•Chemical solutions may leave residues.;
•May abrade other materials leaving a residue on contact.
•Steam sterilisation decreases the strength of the
material.
•Long term studies have shown fractures at sites of
localised bending and tensile loading.

CALCIUM PHOSPHATE CERAMICS
•Lower moduli of elasticity ,lower strength and hardness.
•Used for : bone augmentation and replacement
endosteal and subperiosteal implants
rods & cones (ridge retainers), blocks, H bars.
•Physical properties are related to
surface area or form of the product… porosity..
Crystallinity.

• Chemical properties are related to
Calcium – Phosphate ratio
composition
elemental impurities (carbonates)
ionic substitution in atomic structure
pH of the surrounding region.
•Steam or water autoclaving can significantly change the
basic structure and properties of CaPO4 ceramics & thereby
provide an unknown biomaterial condition at the time of
implantation.
•Dry heat sterilisation or gamma sterilisation recommended.

Calcium phosphate materials
•Monetite
•Brushite
•Octa calcium phosphate
•Whitlockite
•Tri Calcium Phosphate (TCP)
•Hydroxyapatite (HA)
Among these HA and TCP are widely used as
particulates for bone augmentation and replacement and
coatings for Implants.

Hydroxyapatite
Particulate, non porous form
•spherical or angular shaped particles, are examples of
crystalline, high purity HA biomaterials.
•High compressive strength up to 500mPa.
•Tensile strength in the range of 50-70mPa.
•Ceramics are brittle materials and exhibit high compressive
strength compared with tensile strength.
•Less resistance to tensile and shear stresses limit their
application as dental implants because of mechanical
constraints of implant form & volume.

Macroporous(>50µm) or microporous(<50µm) HA
particulates
•Increased surface area/unit vol. This provides more
surface area for solution and cell ,mediated resorption
under static conditions and a significant reduction in
compressive & tensile strength.
•Provide additional regions for tissue ingrowth &
integration & thereby minimization of interfacial motion
and dynamic interfacial breakdown (mechanical
stabilisation).

Coatings of calcium phosphate
•Bulk form implant designs made from CaPO4 ceramics, which
were shown to be contraindicated for some implant designs
because of poor mechanical performance, have found a wide
range of indications as coatings of stronger implant materials.
•Applied by Plasma spraying
•Average thickness between 50 & 70micrometers
•mixtures of crystalline and amorphous phases
•variable micro structure compared with the solid portions of
the particulate forms of HA and Ca3PO4.
•Non conductors of heat & electricity .
•Solubility is greater for TCP than HA.

•Advantages: stimulate adaptation of bone
more intimate bone-to-implant contact
compared with metallic surface.
•Limitations : concerns present regarding the fatigue
strength, under tensile and shear loading
conditions.
•To avoid this, coatings are applied to diff. geometrical
designs such as porosities, screws, spirals, plateaus and
vents.

Factors affecting resorption of ceramic coating
•Particle size
•Porosity
•Chemical structure
Crystallinity
Purity
• Environmental conditions
pH

•Carbon compounds are often classified under
ceramics because of their chemical inertness &
absence of ductility, however they are conductors of
heat & electricity.
•Ceramic & carbonitic substances continue to be used
as coatings on metallic & ceramic materials.
•Lower modulus of elasticity closer to that of bone.
Carbon & Carbon Silicon Compounds

Advantages:
Tissue attachment
Opportunities for the attachment of active bio-
molecules/synthetic compounds.
Prevent elemental transfer, heat, or electric
current flow.
Color.
•Disadvantage:
Lack of mechanical strength properties.
time-dependent changes in properties.
Sensitive to handling, sterilisation and placing
methods.
Biodegradation .

Polymers
Advantages of Fiber reinforced polymers:
•Can be designed to match tissue properties
•Can be coated for attachment to tissues
•Can be fabricated at relatively low cost
•Polymers have low strength & elastic moduli and Higher
elongations to fracture compared with other classes of
biomaterials
•They are thermal & electrical insulators.
•They are relatively resistant to bio degradation

•Polymers have been fabricated in porous and solid forms
for tissue attachment, replacement, augmentation & as
coatings for force transfer to soft & hard tissue region.
•Cold flow characteristics, creep & fatigue strengths are
relatively low for some classes of polymers.
ex: Silicon Rubber
Polymethylmethacrylate
•In contrast some are extremely tough and fatigue cycle
resistant.
ex: Polypropylene (PP)
Polytetrafluoroethylene (PTFE)

•Polymers like PTFE,PP are extremely tough and fatigue
cycle resistant.
•The IMZ implants incorporate a polyoxymethylene
intramobile element ,which acts as an internal shock
absorber.

COMPOSITES
•Most of the inert polymers have been combined with
particulate or fibers of carbon, Aluminum oxide, HA & glass
ceramics.
•In some cases, bio degradable polymers such as polyvinyl
Alcohol,,polylactides or glycolides,cyanoacralates or other
hydratable forms have been combined with bio degradable
CaPO4 particulate or fibers.
•These are intended as structural scaffolds, plates, screws
or other such applications.

•Advantages :
excellent biocompatibility
ability to control properties through composite
structures
•Limitations :
sensitive to sterilisation and handling techniques.
•Uses:
For bone augmentation and periimplant defect repairs,
due to biodegradation properties.

Review of literature

•Dennis C. Smithin (1992) considered the various materials
and designs for the successful outcome of dental implant
treatment. He discussed different designs of implants and
concluded that long term clinical effectiveness was lacking
for several implant designs. He also discussed various
materials and concluded that Ti-6Al-4V had the maximum
desirable properties and that surface treatments like glow
discharge cleaning of implant, precoating with osteogenic
protein and anti bacterial coatings (chlorhexidine) needed
further research.

•Bundy (1993) exposed implant alloys simultaneously to
tensile stress & corrosive environments. In vivo, stainless
& Ti alloy demonstrated cracks when loaded to yield
stress & re-implanted under lab conditions for 8 weeks.
Crack like features were also seen in stainless steel & Ti
alloys loaded to or beyond the yield stress & subsequently
electrochemically polarized for 38 weeks in the in-vitro
part of the study
None of the samples actually failed by completely
cracking but the author presumed that it would have
occurred with a longer exposure time.

•Yu-Liang Chang et al (1999) compared the in vivo bony
response to HA coatings of varying levels of crystallinity and
determined the optimum composition to promote
osseointegration.
They concluded that HA coatings on metal implants
enhance osseointegration in the early stage of bone healing
and provide bone bending capability. HA coating of higher
crystallinity was found to be more desirable in providing
durability and maintaining osteoconductive properties.

•Jessica J.Lee and O. Ross Beirne (2000) conducted a study
on the reported survival of HA coated implants.
A systematic Medline computer search of literature was
conducted which yielded 45 human clinical trials on HA
coated implants.
They concluded on the basis of the analysis of reported
trials that the survival rates reported for HA coated implants
were similar to the survival rates reported from uncoated
titanium implants.

Tissue interactions

Integration with Titanium
•Although Ti is known to exhibit better corrosion resistance,
independent of the surface preparation, in vivo & in vitro
studies have shown that Ti may interact with recipient living
tissues over several years.
•This results in release of small quantities of corrosion
products even though there is a thermodynamically stable
oxide film.
•The presence of impurities like iron on implant parts can lead
to loss of bone-implant integration in areas exposed to
corrosion products.
•The long term presence of corrosion products could lead to
fracture at affected alloy-abutment interface, the abutment or
implant body itself.

Cobalt & Iron Alloys
•The alloys of Co & Fe exhibit oxides of chromium under
normal implant surface finishing conditions after acid or
electro-chemical passivation.
•These chromium oxides as with Ti alloys result in significant
reduction in chemical activity & environmental ion transfer.
•The chromium oxide covers the matrix phase (metallic
regions ),while the carbides stand as secondary components
at the microscopic level.
•Hence, tissue integration is described by tissue-to-oxide and
tissue-to-metallic carbide zones.

•If stainless steel implant surfaces are mechanically altered
during implantation, the iron alloy will biodegrade.
•However, in the absence of surface damage, the chromium
oxide on stainless steel biomaterials have shown excellent
resistance to breakdown & multiple examples of tissue &
host compatibility have been shown for implants removed
after long term implantation.

Ceramics
•Ceramic coatings have been shown to enhance the corrosion
resistance & biocompatibility of metal implants like surgical
stainless steel, Ni-Cr, Co-Cr alloys.
•However, studies in orthopedics cautioned that the Al2O3 may
cause demineralization phenomenon caused by a high local
concentration of substrate ions in the presence of metallic
bone disease.

Hydroxy Apatite
•No local or systemic toxicity
•No inflammatory or foreign body reaction
•Functional integration with bone.
•No alteration to natural mineralisation process.
•Chemical bonding to bone via natural bone cementing
mechanisms.

Implant fixation methods and biomechanical properties
•….provide better surgical fit and stress distribution at the
implant-bone interface.
These methods include:
•Direct bone apposition
Smooth finish – interfaces show fibrous encapsulation.
Grit blasted finish – direct bone apposition.
•Porous Ingrowth attachment
The interface attachment strength of porous implants
relying on bone ingrowth for fixation are atleast an
order of magnitude higher than that of nonporous
implants relying on direct bone apposition for fixation.

•Chemical bonding between bone and surface coated
implants
The HA coated implants have shown direct bone
mineralisation, whereas the uncoated surface have shown
areas of fibrous tissue at the interface.

Porous coatings

Titanium Plasma Spray
•Porous or rough Ti surfaces have been fabricated by a
plasma spraying a powder form of molten droplets at high
temperatures.
•At temperatures of 15,000° C, an argon plasma is
associated with a nozzle to provide very high velocity
600m/s partially molten particles of Ti powder projected
onto a metal or an alloy substrate.
•The porous Ti surface thus obtained produce attachment
by osteoformation and attachment is enhanced by
increasing ionic interactions , thus introducing a dual
physical & chemical anchor system.

Hydroxy Apatite Coating
•HA coating by plasma spray was brought to the dental
profession by DeGroot.
•A greater surface area of bone apposition with a high
degree of mineralisation has been seen around Ha coated
implants.
•Acts a s protective shield to reduce potential slow ion
release from Ti alloy substrate.

Other Surface Modifications
•Methods include controlled clinical reactions with nitrogen
or other elements or surface ion implantation procedures.
•The reaction of Nitrogen with Ti alloys at elevated
temperatures results in Ti-Nitride compounds being formed
along the surface.
•Electrochemically the Ti-Nitrides are similar to the oxides
and no adverse electrochemical behavior has been noted if
the Nitride is lost regionally.
•The Ti substrate re-oxidizes when the surface layer of
nitride is removed.
•Nitrogen implantation & carbon doped layer deposition
have been recommended to improve the physical properties
of stainless steel without affecting its bio compatibility.

Surface Energy
•Measurements of surface property values of an
implant’s ability to integrate within bone include contact
angle with fluids, local pH and surface topography.
•An intrinsically high surface energy is said to be most
desirable. High surface energy implants showed a 3 fold
increase in fibroblast adhesion and higher surface
energy surfaces such as metals, alloys & ceramics are
best suited to achieve cell adhesion.
•Surface tension values of 40 dyne/cm & higher are
characteristic of very clean surfaces and excellent
biologic integration conditions.

•The shift in contact angle is related to contamination of
the surface by hydrophobic contaminants & decreases
the surface tension parameters.
•A spontaneously deposited host dependent
conditioning film is pre-requisite to the adhesion of any
biologic element
•It is suggested that the wetting of the surface by blood
at the time of placement can be a good indication of the
high surface energy of the implant.

Sterilization
•Conventional methods include steam autoclaving, dry
heat, glassbead sterilisation and ethylene oxide treatment.
But each of these techniques have the potential to alter the
implant surface.
•Radiation techniques, i.e., electron beam, gamma rays
and UV radiation, rarely contaminate the implant surfaces.
•Radio Frequency Glow Discharge Treatment and liquid
solution techniques are new methods being evaluated.

Selecting an implant material
•Strength of the implant material
•Area of placement
•Quality of bone
•Better bone-implant integration
•Long term stability

Summary and Conclusion
•Surface characterization and the knowledge about how the
biomaterial properties are inter related to the dental implant
biocompatibility, represent an important area in implant-
based reconstructive surgery.
•The biomaterials discipline has evolved significantly over
the past few decades, and synthetic biomaterials are now
fabricated that have a high predictability of success when
used appropriately within the surgical disciplines.www.indiandentalacademy.com

References
•Contemporary Implant Dentistry, Carl E. Misch, second
edition, 1999.
•Phillips’ Science of Dental Materials, Anusavice,
eleventh edition,2004
•Osseointegration and Occlusal Rehabilitation, Sumiya
Hobo,1988.
•Implants in Dentistry, Michael S.Block,1997.
•Dental Implants: Principles and Practice, Charles
A.Babbush,1991.
•Oral Implantology, Andre Schroeder,1991.

•Smith D C. Dental Implants: Materials and Design
Considerations. Int J Prosthodont 1993;6:106-117.
•Lee J J. et al. Survival of Hydroxyapatite-Coated
Implants :A Meta-analytic review. J Oral Maxillofac Surg
2000;58:1372-1379.
•Chang Y et al. Biochemical and Morphometric Analysis of
Hydroxyapatite-Coated Implants With Varying Crystallinity.
J Oral Maxillofac Surg 1999;57:1096-1108.

Thank Youwww.indiandentalacademy.com

Implant materials final/prosthodontic courses

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