Titanium
The use of dental implants has increased dramatically in recent years, and is
expected to grow in the future. The high degree of success achieved with dental implants is
attributed to improved materials, designs and surgical techniques. There have been attempts to
replace missing teeth since the time of the early Egyptian and South American cultures.
Materials used in that purpose included natural teeth from man, animal teeth, ivory, wood,
plastic, carbon, and metals such as aluminium, steel, cobalt-chromium.
Nowadays, titanium and its alloys became prominent as dental and orthopaedic
materials because of titanium's excellent biocompatibility, corrosion resistance, and desirable
physical and mechanical properties.
The era of titanium had really started in the 1940s when noting some problems with SMo
stainless steel and Vitallium, preferred at this time as orthopaedic implants, many workers
and surgeons begun looking for even better materials that would join both physiological
inertion and good mechanical characteristics. The first recorded discovery of the element we
know as titanium is attributed to Wilhelm Gregor, a clergyman and amateur mineralogist who
in 1791 in Cornwell investigated black magnetic sand he named menachanite. It took,
nevertheless, 150 years to make titanium commercially available. The industrial process that
we, with small changes, use today to extract titanium from its rutile was developed in 1930s by
dr. Wilhelm Kroll. Attractive mechanical properties and excellent corrosion resistance made
titanium one of the most important industrial metals.
Indeed it is used today widely throughout the world in a multitude of applications
including aerospace and defence industry as well as medicine and dentistry.
However, the history of implementing titanium into surgery is not straightforward and though it
has become the material of choice for dental and orthopaedic implants there are still
controversies over precise composition design and suitability of use.
Titanium is a very light metal having a density of 4.505 g/cm3 at 25 ºC. The melting
point is about 1665 ºC though it may vary depending on impurities. The coefficient of thermal
expansion is 8,35 x 10-6/ ºC at 15 ºC and the electrical resistivity 42,0 x 10-6/g. It has a
hexagonal closed packed crystal structure referred to as alpha phase that undergoes an
allotropic modification at 883 ºC to a body centred cubic crystal structure known as beta phase.
The manipulation of these crystallographic variations through alloying and thermomechanical
processing results in a wide range of alloys and properties.
Commercially pure titanium, available in four different grades, is based on the incorporation of small
amounts of oxygen, nitrogen, hydrogen, iron, and carbon during purification process. The
microstructure consists of equiaxed alpha grains.
1601-01.04 Dyna Pushin Implant Manual GB 11 / 144
To attain higher strength, in commercially pure titanium, alloying elements are added. For medical
purposes alloy design criteria are not only based on changing the mechanical properties but on
biocompatibility of the resulting alloy. Alloying elements dictates the microstructure and determines
properties. Pure titanium, though, used in dental implantology is not strong enough to be used in
demanding circumstances. Therefore, different types of titanium alloys have been developed and
introduced into the market. Having better mechanical characteristics and the some biocompatibility
they give a wider range of applications also for dental implantology. Crystallographic variations
help to categorize these alloys. Based on the phase that can be produced by alloying titanium alloys
can be grouped as alpha, alpha-beta, and beta alloys. Particular elements stabilize particular phase
and so, for instance, aluminium, tin and zirconium act as alpha phase stabilizers whereas vanadium,
molybdenum, niobium, chromium, iron and manganese as beta phase stabilizers. The wide range of
mechanical properties is based on the transformation characteristics of the beta phase. The
transformation is sluggish and can be controlled to produce the desired properties. The structure
depends on the composition of the alloy and thermo-mechanical treatment and there are different
methods to achieve desirable properties. The most popular alloy is Ti-6Al-4V microstructurally
which consists of equiaxed alpha grains with only a small amount of residual beta in the matrix.
The mechanical properties of titanium and its alloys surpass the requirements for an implant material
(strength level greater than bone, comparable elastic modulus). The most commonly used and
important titanium alloy is Ti-6Al-4V, as of its favourable proportion and predictable producibility.
With the combination of biocompatibility, high strength, corrosion and wear resistance, attractive
weight to strength ratio Titanium and its alloys have become extremely popular materials of choice
for dental implants. The application of titanium to fixed and removable prostheses is still in the
development phase. Concerns regarding technology of machining, casting, welding, and veneering
have been reported in the literature. At present titanium is a useful and interesting material. It will
probably continue to dominate the dental implant market as one of the most biocompatible metals
expected to grow in the future. The high degree of success achieved with dental implants is
attributed to improved materials, designs and surgical techniques. There have been attempts to
replace missing teeth since the time of the early Egyptian and South American cultures.
Materials used in that purpose included natural teeth from man, animal teeth, ivory, wood,
plastic, carbon, and metals such as aluminium, steel, cobalt-chromium.
Nowadays, titanium and its alloys became prominent as dental and orthopaedic
materials because of titanium's excellent biocompatibility, corrosion resistance, and desirable
physical and mechanical properties.
The era of titanium had really started in the 1940s when noting some problems with SMo
stainless steel and Vitallium, preferred at this time as orthopaedic implants, many workers
and surgeons begun looking for even better materials that would join both physiological
inertion and good mechanical characteristics. The first recorded discovery of the element we
know as titanium is attributed to Wilhelm Gregor, a clergyman and amateur mineralogist who
in 1791 in Cornwell investigated black magnetic sand he named menachanite. It took,
nevertheless, 150 years to make titanium commercially available. The industrial process that
we, with small changes, use today to extract titanium from its rutile was developed in 1930s by
dr. Wilhelm Kroll. Attractive mechanical properties and excellent corrosion resistance made
titanium one of the most important industrial metals.
Indeed it is used today widely throughout the world in a multitude of applications
including aerospace and defence industry as well as medicine and dentistry.
However, the history of implementing titanium into surgery is not straightforward and though it
has become the material of choice for dental and orthopaedic implants there are still
controversies over precise composition design and suitability of use.
Titanium is a very light metal having a density of 4.505 g/cm3 at 25 ºC. The melting
point is about 1665 ºC though it may vary depending on impurities. The coefficient of thermal
expansion is 8,35 x 10-6/ ºC at 15 ºC and the electrical resistivity 42,0 x 10-6/g. It has a
hexagonal closed packed crystal structure referred to as alpha phase that undergoes an
allotropic modification at 883 ºC to a body centred cubic crystal structure known as beta phase.
The manipulation of these crystallographic variations through alloying and thermomechanical
processing results in a wide range of alloys and properties.
Commercially pure titanium, available in four different grades, is based on the incorporation of small
amounts of oxygen, nitrogen, hydrogen, iron, and carbon during purification process. The
microstructure consists of equiaxed alpha grains.
1601-01.04 Dyna Pushin Implant Manual GB 11 / 144
To attain higher strength, in commercially pure titanium, alloying elements are added. For medical
purposes alloy design criteria are not only based on changing the mechanical properties but on
biocompatibility of the resulting alloy. Alloying elements dictates the microstructure and determines
properties. Pure titanium, though, used in dental implantology is not strong enough to be used in
demanding circumstances. Therefore, different types of titanium alloys have been developed and
introduced into the market. Having better mechanical characteristics and the some biocompatibility
they give a wider range of applications also for dental implantology. Crystallographic variations
help to categorize these alloys. Based on the phase that can be produced by alloying titanium alloys
can be grouped as alpha, alpha-beta, and beta alloys. Particular elements stabilize particular phase
and so, for instance, aluminium, tin and zirconium act as alpha phase stabilizers whereas vanadium,
molybdenum, niobium, chromium, iron and manganese as beta phase stabilizers. The wide range of
mechanical properties is based on the transformation characteristics of the beta phase. The
transformation is sluggish and can be controlled to produce the desired properties. The structure
depends on the composition of the alloy and thermo-mechanical treatment and there are different
methods to achieve desirable properties. The most popular alloy is Ti-6Al-4V microstructurally
which consists of equiaxed alpha grains with only a small amount of residual beta in the matrix.
The mechanical properties of titanium and its alloys surpass the requirements for an implant material
(strength level greater than bone, comparable elastic modulus). The most commonly used and
important titanium alloy is Ti-6Al-4V, as of its favourable proportion and predictable producibility.
With the combination of biocompatibility, high strength, corrosion and wear resistance, attractive
weight to strength ratio Titanium and its alloys have become extremely popular materials of choice
for dental implants. The application of titanium to fixed and removable prostheses is still in the
development phase. Concerns regarding technology of machining, casting, welding, and veneering
have been reported in the literature. At present titanium is a useful and interesting material. It will
probably continue to dominate the dental implant market as one of the most biocompatible metals
Hydroxyapatite
It has been well documented that living bone may show direct or almost direct apposition on the
surface of titanium implants. Due to this phenomenon implants may function well in the mouth
environment replacing natural elements of dentition. However, this type of connection between the
bone and the implant gives only a mechanical retention. Those kinds of implants are called bioinert
in contrast to implants that connect with the bone chemically and consequently called bioactive.
Sintered hydroxylapatite (HA) or Ca10(PO4)6(OH)2 is biologically very compatible
material to replace bony tissues. Numerous studies have proved its excellent bonding
properties with the bone. Unfortunately, due to its poor biomechanical characteristics it
can only be used where it is not subjected to high mechanical loads. Therefore, it has
been suggested that HA coated metallic devices might be useful for sites where heavy
loads can be expected. Such a “hybrid” implant would join both the properties of
titanium and HA giving a clinician attractive mechanical characteristics and bioactivity in
one.
The use of bioceramics dates back to 19th century when in 1894 the use of plaster
of Paris (calcium phosphate) to fill bone defects was reported. This first synthetic bone
filling material had the perceived advantage of being mouldable, setting in place and
would resorb releasing calcium. In practice it was weak and resorbed too quickly and
eventually fell into disuse. Further researches focused on biomaterials led the
bioceramics into the new era. Inert ceramics like aluminium-oxide have been tried
unsuccessfully as load-bearing implants and are no longer in use now. Glass ceramics are
silicon-dioxide glasses containing calcium-phosphate ions and being very similar to glass.
They have osteogenic properties but are not used because of their brittleness.
The biggest and the most investigated group is Calcium Phosphate Ceramics. Two major
representatives are:
Hydroxylapatite (HA)
Tricalcium Phosphate (TCP)
HA is in its composition equivalent to the hard mineral matrix of bone. It shows both the features of
osteoconductivity and osteointegration and it allows the bone to bridge gaps up to 1mm without
forming intervening fibrous tissue layer. HA is available in two main forms: porous blocks and
granulate, and can be produced or synthetically or by sintering xenograft type materials like bovine
bone or coral. It is also available as amorphous (soluble) and crystalline (insoluble) material. Dense
HA is strong in compression but brittle when subjected to fatigues shear and tensile forces so it is not
indicated as a pure material for dental implants but it can be successfully used as a covering for
titanium cores. Several methods exist to coat a metallic surface with a thin (less then 50microns)
coating of metallic or ceramic origin, but two of them are most popular:
Electrolytically – by suspending colloidal particles of coating material in non conducting liquid,
whereafter an immersion of oppositely charged substrate will result in a transport of particles toward
the surface covering it loosely. To get a dense surface an appropriate heat treatment is needed.
1601-01.04 Dyna Pushin Implant Manual GB 13 / 144
Plasma spraying – HA powder is suspended in a carrier gas stream which is fed into the plasma
flame. The plasma flame is achieved by burning the flammable gas or mixture of gases (in presence
of oxygen) when passing through electric arc. This results in ionised gas of high temperature up to
30000OC, and a high speed approaching the speed of sound (due to large thermal expansion). In this
way suspended particles of HA reach the surface of titanium with great speed and elevated
temperature allowing to create a firm chemical bond between coating and substrate.
One of the most important factors influencing the quality of HA coating is the HA
powder. Dyna implants have the covering made of powder produced to assure the
consistency of the highest quality coating. Some of the Dyna HA features are shown in
the table below.
surface of titanium implants. Due to this phenomenon implants may function well in the mouth
environment replacing natural elements of dentition. However, this type of connection between the
bone and the implant gives only a mechanical retention. Those kinds of implants are called bioinert
in contrast to implants that connect with the bone chemically and consequently called bioactive.
Sintered hydroxylapatite (HA) or Ca10(PO4)6(OH)2 is biologically very compatible
material to replace bony tissues. Numerous studies have proved its excellent bonding
properties with the bone. Unfortunately, due to its poor biomechanical characteristics it
can only be used where it is not subjected to high mechanical loads. Therefore, it has
been suggested that HA coated metallic devices might be useful for sites where heavy
loads can be expected. Such a “hybrid” implant would join both the properties of
titanium and HA giving a clinician attractive mechanical characteristics and bioactivity in
one.
The use of bioceramics dates back to 19th century when in 1894 the use of plaster
of Paris (calcium phosphate) to fill bone defects was reported. This first synthetic bone
filling material had the perceived advantage of being mouldable, setting in place and
would resorb releasing calcium. In practice it was weak and resorbed too quickly and
eventually fell into disuse. Further researches focused on biomaterials led the
bioceramics into the new era. Inert ceramics like aluminium-oxide have been tried
unsuccessfully as load-bearing implants and are no longer in use now. Glass ceramics are
silicon-dioxide glasses containing calcium-phosphate ions and being very similar to glass.
They have osteogenic properties but are not used because of their brittleness.
The biggest and the most investigated group is Calcium Phosphate Ceramics. Two major
representatives are:
Hydroxylapatite (HA)
Tricalcium Phosphate (TCP)
HA is in its composition equivalent to the hard mineral matrix of bone. It shows both the features of
osteoconductivity and osteointegration and it allows the bone to bridge gaps up to 1mm without
forming intervening fibrous tissue layer. HA is available in two main forms: porous blocks and
granulate, and can be produced or synthetically or by sintering xenograft type materials like bovine
bone or coral. It is also available as amorphous (soluble) and crystalline (insoluble) material. Dense
HA is strong in compression but brittle when subjected to fatigues shear and tensile forces so it is not
indicated as a pure material for dental implants but it can be successfully used as a covering for
titanium cores. Several methods exist to coat a metallic surface with a thin (less then 50microns)
coating of metallic or ceramic origin, but two of them are most popular:
Electrolytically – by suspending colloidal particles of coating material in non conducting liquid,
whereafter an immersion of oppositely charged substrate will result in a transport of particles toward
the surface covering it loosely. To get a dense surface an appropriate heat treatment is needed.
1601-01.04 Dyna Pushin Implant Manual GB 13 / 144
Plasma spraying – HA powder is suspended in a carrier gas stream which is fed into the plasma
flame. The plasma flame is achieved by burning the flammable gas or mixture of gases (in presence
of oxygen) when passing through electric arc. This results in ionised gas of high temperature up to
30000OC, and a high speed approaching the speed of sound (due to large thermal expansion). In this
way suspended particles of HA reach the surface of titanium with great speed and elevated
temperature allowing to create a firm chemical bond between coating and substrate.
One of the most important factors influencing the quality of HA coating is the HA
powder. Dyna implants have the covering made of powder produced to assure the
consistency of the highest quality coating. Some of the Dyna HA features are shown in
the table below.
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