Implant materials/ dental courses

Implant Materials
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Loss of teeth and has been a part of expected
course of aging in general population.
 Prevalence of edentulism has posed a great challenge
to dental surgeons encouraging them to devise most
acceptable prosthetic results to patients.
 The quest for replacement of natural teeth has intrigued
human kind since ancient times.
 Implant designs are traceable to early Egyptians and South
Central American cultures.
 Metal implant devices of gold, lead, iridium, tantalum,
stainless steel and cobalt alloy were developed in early
20th
century.

 The loosening of implants from bone
tissues has been a cause of problems in
reconstructive surgery and joint
replacement.
 The thought for decades has been that the layer
of fibrous tissue that develops around the implant
diminishes the integrity and mechanical stability of
the implant/bone interface
 During the 1950s it had been shown by Brånemark that the
living bone could become so fused with the titanium oxide
layer of the implant that the two could not be separated without
fracture
Brånemark introduced the term
"OSSEOINTEGRATION" to describe this modality for
stable fixation of titanium to bone tissue

CONTENTS
1. Classification Of Implant Materials
2. Events at Bone - Implant Interface
3. Characteristics Of Implantable
Materials
4. Methods Of Ceramic Coatings
5. Selection of Implant Materials
6. Sterilization
7. Recent Advances in Implant Materials
8. Summary and Conclusion

Metals Ceramics Polymers
316L stainless
steel
Co-Cr Alloys
Titanium
Ti6Al4V
Alumina
Zirconia
Carbon
Hydroxyapatite
Ultra high molecular
weight polyethylene
Polyurethane
Classification Of Implant Materials

The performance of any material in the human
body is controlled by two sets of characteristics:
biofunctionality and biocompatibility.
It is relatively easy to satisfy the requirements for
mechanical and physical functionality of implantable
devices.
Therefore, the selection of materials for medical applications is
usually based on considerations of biocompatibility
Events at Bone-Implant Interface
1. The response of the host to the implant, and
2. The behavior of the material in the host.

Host Response :
 Involves a series of cell and matrix events,
ideally culminating in tissue healing, leading
to intimate apposition of bone to the
biomaterial ---- osseointegration.
. For this intimate contact to occur, gaps that were
initially present between bone and implant must be filled
by a blood clot and bone damaged during preparation of
the implant site must be repaired

Material Response :
 The event that occurs almost immediately.. is
adsorption of proteins.
Oxidation of metallic implants both in vivo and in vitro.
 Surface analytic studies show that the chemical composition
of the oxide film is changed by incorporation…. calcium
phosphorus, and sulfur.
 Another consequence of these events is the release of
metallic ions into tissues. These corrosion by-products
accumulate locally but may also spread systemically.
These proteins come first from blood and tissue fluids
at the wound site and later from cellular activity in the
interfacial region.

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
Yield strength
Fatigue strength
Resistance to corrosion
Resistance to biodegradation
Metallurgy

Titanium and titanium alloys
 The element was discovered by wilhem.
Gregor in 1791
 Van Arkel in 1925 refined a metal using
titanium tetraiodide, producing a metal with
acceptable properties
 It is an extremely reactive metal that forms a
tenacious oxide layer that contributes to its passivity
 It is one of the most abundant element in the earth’s
crust
 There are two types of implantable materials
i) Commercially Pure Titanium (CpTi)
ii) Titanium alloys

Commercially pure titanium (CPTi)
Come in different grades – CP grade I to Cp grade
IV.
 Pure titanium is soft and non-magnetic
 It has relatively low modulus of elasticity and tensile
strength when compared to other alloys
•Strength and yield strength are slightly lower than Ti
alloys.
•Modulus of elasticity of titanium (102 GPa), is 5 times more
than that of compact bone
 Strength values for normal root and plate
form implant are 1.5 times more than
compact bone

-
•Titanium alloys :
I) Ti-6Al-4V
•II) Ti-6Al-4V Extra low interstitial (ELI).
Aluminium acts as an α stabilizer ,increasing the strength
and decreasing the mass.
Titanium alloys
Ti-6Al-4V ELI has low levels of oxygen and iron
which improve ductility.
Mod. of elasticity (117 GPa) closer to that of bone…(5.6
times>compact bone)….uniform distribution of stress.
Vanadium, copper and palladium are beta phase stabilizers;–
decrease susceptibility to corrosion.
 Wrought alloy is approx. 6 times stronger than compact
bone and hence provides more opportunities for design
with thinner sections.

Dennis C. Smithin (1992) considered the various materials
and designs for the successful outcome of dental implant
treatment 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
Gregory r. parr, L. Kirk Gardner, Richard W. Tooth
(1985) stated that titanium and alloys particularly
alpha-beta alloys , posses favorable mechanical
properties that make them ideal implant materials

-
Surface characteristics of Ti and
Ti alloys
Low temp. thermal oxides are homogenous and
dense; with increasing temp., they become more
heterogeneous and porous.
If implant is scratched or abraded during placement, it
repassivates in vivo.
The oxide layer formed is primarily amorphous in nature and
thin in thickness dimensions. But if unalloyed Ti is processed
at elevated temp. or anodized , it forms a crystalline thicker
layer.
Ti oxidizes (passivates) upon contact with room
temp. air and normal tissue fluids – increases
corrosion resistance.

Cobalt-Chromium-Molybdenum based
alloys
High elastic modulus, high corrosion resistance, low ductility.
 Carbon acts as a hardener.
 Molybdenum provides strength and bulk corrosion resistance
 Chromium provides corrosion resistance through oxide
surface.
Cobalt provides the continuous phase for basic properties.
Major elements: Co - 63% ;Cr – 30% ;Mo – 5%

Used in an as-cast and cast-and-annealed
metallurgic conditions. This permits fabrication of
implants as custom designs like subperiosteal
frames.
 In general cast cobalt alloys are least ductile of all
alloy systems and hence bending of finished
implants should be avoided.

Iron-Chromium-Nickel Based Alloys
It has a long history of use for orthopaedic and
implant device.
Have some galvanic potentials that could result in coupling
and biocorrosion
This alloy is most subjected to pitting corrosion. Contains
nickel which may be allergic to some patients
The ramus blade, ramus frame, and some mucosal inserts
have been made from this alloy
This alloy with titanium systems is used most often in
wrought and heat treated metallurgic conditions-high
strength and high ductility

Ceramics and carbon
Based on their interaction with bone there are two types:
They were introduced for surgical implant devices because of
their inertness to biodegradation, high strength physical
characteristics such as minimal thermal and electrical
conductivity,
Ceramics are inorganic, non metallic, non polymeric
materials manufactured by compacting and sintering at
elevated temperatures.
Ceramics have been used in bulk forms and as coatings on
metals and alloys
a. Bioactive e.g. Hydroxyapatite and Bioglass
b. Non-reactive e.g. Aluminum oxide

Bioactive and Biodegradable Ceramics
based on Calcium Phosphate
Calcium phosphate ceramics are used in dental
reconstructive surgery
Hence they were used with internal reinforcement
through mechanical (central metallic rod) or
physiochemical (coating over another substrate)
techniques
First series of structural forms for dental implants had
limitations in mechanical property
Early investigation were on solid and porous particulates, the
compositions of which were similar to mineral phase of bone
 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

 Monetite
 Brushite
 Octacalcium 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.
Calcium Phosphate Materials

Coatings of calcium phosphate
concerns present regarding the fatigue strength,
under tensile and shear loading conditions.
 Solubility is greater for TCP than HA.
 Non conductors of heat & electricity .
 Variable micro structure compared with the solid portions
of the particulate forms of HA and Ca3PO4.
 Mixtures of crystalline and amorphous phases
Average thickness between 50 & 70micrometers
 Advantages: stimulate adaptation of bone
more intimate bone-to-implant contact
 Limitations :

METHODS OF CERAMIC COATINGS:
1. Plasma Spraying
2. Vacuum Deposition Techniques
3. Sol-gel and Dip Coating Methods
4. Electrolytic process
5. Hot Isostatic Pressing

It is the most common coating method for dental
implants because almost all the commercial HA
coatings are produced by this technique
The most stable of the plasma sprayed calcium phosphate
coatings is fluorapatite (FA),
Coatings around 50- 100 um are typically produced
This method involves the use of a carrier gas which ionizes
(generally HA), undergoes partial melting as they are
propelled toward the substrates to be coated (De Groot ).
Plasma Spraying:

Advantages:
 It is relatively inexpensive.
 The mechanical properties of the
metallic substrate are not compromised
during the coating process.
Limitation:
Forms mechanical bonding only with the
metallic implant surface.
The main source of contamination appears to be
copper from the nozzles of the sprayer.

Vacuum Deposition Techniques:
These techniques include ion beam sputtering, and pulsed
laser deposition all are relatively expensive and capable of
depositing coatings in the order of a few micrometers.
Involves bombarding a target in vacuum chamber
resulting in sputtered or abated atoms or particles
moving through the chamber to coat on properly
positioned substrates.
 Advantages:
 High quality coatings with good bonding to either
smooth or rough titanium surfaces.
Limitations:
The efficacy of these very thin coatings is
unknown.
There is some concern that the coating may
resorb in the body before causing the desired
effect.www.indiandentalacademy.com

 Sol-Gel and Dip coating methods:
Advantages:
Small crystalline size and
High strength.
The coating is fired at 800(degree) to 900(degree) C to melt
the carrier glass to achieve bonding to the metallic
substrate. This process is repeated until a relatively thick
coating (e.g.,100um) consisting of HA/glass mixture can be
obtained.
In this technique, precursors of the final product i.e the
metal implant to be coated is dipped into the solution,
withdrawn at the prescribed rate, and then heated to
create a more dense coating.

Hot Isostatic Pressing:
Disadvantages:
Expensive
The necessity of removing the inert foil or other
encapsulating material
The potential for contamination.
 HA powder is applied to the implant surface, an inert foil
is placed over the powder to facilitate uniform
densification, then both heat and pressure are applied
 In this technique both heat and pressure are used to
enhance ceramic density (such as alumina or HA) into a
solid ceramic of high strength.
 Hot Isostatic Pressing (HIP) is used to produce the
highest density and strength possible in crystalline
ceramic materials.

Electrolytic process:
 Advantages
The porous surfaces materials can be uniformly coated, and
the original composition of the ceramic (e.g.,HA) can be
maintained in most cases.
Electrophoresis and electrolytic deposition are two
processes that deposit HA or suitable bioceramic
particles.

Yu-L iang 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.
HA coating of higher Crystallinity was found to be more
desirable in providing durability and maintaining
osteoconductive properties.
 They concluded that HA coatings on metal implants
enhance osseointegration and provide bone bending
capability.
Michael s. Block et al (1987) conducted comparative study
of bone response to HA coated Ti surface and other two
surfaces and found that bone formation and maturation
occurred at faster rate on HA coated implants than on
non coated implants

POLYMERS
The inert polymeric materials include polytetra
fluoroethelene (PTFE), polyethylene teraphthalate
(PET), polymethylmethacrylate (PMMA), polyprophylene
(PP), polysulfone (PF) or silicone rubber (SR)
• In general 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
Can be fabricated at relatively low cost
Can be designed to match tissue properties
Can be coated for attachment to tissues

COMPOSITES
These are intended as structural scaffolds, plates, screws or
other such applications.
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.
Most of the inert polymers have been combined with
particulate or fibers of carbon, Aluminum oxide, HA &
glass ceramics.
 Most polymeric materials electrostatic surface properties
that tend to gather dust and other particulates if exposed
to semiclean environment

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.

STERILIZATION
Radio Frequency Glow Discharge Treatment is the new
method being evaluated.
Radiation techniques, i.e., electron beam, gamma rays and UV
radiation, rarely contaminate the implant surfaces.
Conventional methods include steam autoclaving, dry heat
and ethylene oxide treatment. But each of these techniques
have the potential to alter the implant surface.
 Generally the manufacturer guarantees precleaned
and presterilised implants with high technology
procedures, with implants ready to be inserted .

SELECTING AN IMPLANT MATERIAL
Area of placement
Quality of bone
Habits of the patient
Strength of the implant material
Implant Design
Implant Size

Recent advances
Titanium Implants Derived from Nanocrystalline
Titanium Powders
 It is therefore now possible to use hollow implants that
more closely match natural bone.
These ultrafine-grained materials utilize the biocompatibility of
titanium but are approximately 10 times stronger than
conventional titanium implants.
More recent work has focused on nanocrystalline titanium
powders for bone implants.

PHOSPHOLIPID-BASED BIOMATERIALS.
One of the trends is to increasingly utilize microrough
titanium implants.
In recent years new implant surfaces have emerged, so-
called microrough titanium surfaces produced with reducing
techniques such as grit-blasting with Al2O3 or TiO2
particles, sandblasting and acid-etching, or acid-etching
alone.
Lipids play an important role in biomineralization.
Phospholipids-based materials may be
increasingly utilized as tools for the manipulation
of cell and tissue responses to biomaterials

Summary
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.
 Surface characterization and working knowledge
about how the biomaterial properties are inter related
to the dental implant biocompatibility represent an
important area in implant-based reconstructive surgery.

Conclusion:
All the materials in these categories have their
own virtues
Therefore it is sometimes advantageous to combine
the properties of different types of materials
Hence the choice of a particular implant is a
compromise between different requirements

References
Chang Y et al. Biochemical and Morphometric Analysis
of Hydroxyapatite-Coated Implants With Varying
Crystallinity. J Oral Maxillofac Surg 1999;57:1096-1108.
Lee J J. et al. Survival of Hydroxyapatite-Coated Implants :A
Meta-analytic review. J Oral Maxillofac Surg 2000;58:1372-
1379.
Osseointegration and Occlusal Rehabilitation, Sumiya
Contemporary Implant Dentistry, Carl E. Misch,
second edition, 1999.
Gregory R. Parr et al- Titanium- the myatery metal of implant
dentistry. Dental Material aspect. J Prosthet Dent
1985;54(3):410-413
Hobo

•Smith D C. Dental Implants: Materials and Design
Considerations. Int J Prosthodont 1993;6:106-117.
Phillips’ Science of Dental Materials, Anusavice,
eleventh edition,2004

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