Titanium and its alloy /certified fixed orthodontic courses by Indian dental academy

Titanium and its alloy used in
orthodontics
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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INTRODUCTION
• Titanium was discovered by GREGOR
•
( England 1790 )
• Bothe et al implanted titanium in lab. animals
•
(1940)
• A light weight metal
• Atomic weight – 47.9
• Non magnetic

•
SUPERIOR CORROSION RESISTANCE
• A thin complex film Tio2 gives Ti affinity, a self
adherence that may cause friction.
•
•
•

Titanium is not esthetic
Laser aided depositions
Implantation of nitrogen ( IONGUARD )


• Alpha phase –
Hexagonal unit cells
•
At room
temperature
• Beta phase – Body
centered cubic cells
•
At temperatures
above 1620F or 882C


 Alpha type – ALPHA TITANIUM (A.J. Wilcock)
 Beta type – Beta II or ORMCO‘ TMA
Titanium-Niobium wires
TiMolium
Beta III wires.
Alloy that have both phases alpha and beta such as
Ti-5Al-2.5Fe or the widely used Ti-6Al-4V are
difficult to draw and bend but can be machined
easily to make implants and expansion screws.

Different forms used in orthodontics
Titanium
Implants
brackets

Nonnickel alloys
Beta type – Beta
II or ORMCO‘
TMA
TitaniumNiobium wires
TiMolium
Beta III wires.
Alpha Ti wires

Nickel
titanium
Orthodontic
arch wires
auxiliaries

Titanium as implant material


• Implant materials.
• requirements
• The material must be nontoxic and biocompatible,
possess excellent mechanical properties, and provide
resistance to stress, strain, and corrosion.
• Commonly used materials can be divided into 3
categories:
• biotolerant (stainless steel, chromium-cobalt alloy),
• bioinert (titanium, carbon), and
• bioactive (hydroxylapatite, ceramic oxidized
aluminum).


• Commercially pure titanium is the material
most often used in implantology. It consists
of 99.5% titanium, and the remaining 0.5%
is other elements, such as carbon, oxygen,
nitrogen, and hydrogen.
• .


• Because of titanium‘s characteristics (no allergic
and immunological reactions and no neoplasm
formation), it is considered an ideal material and is
widely used.
• Its mechanical characteristics, moreover, are well
suited to implant requirements: it is very
lightweight, and it has excellent resistance to
traction and breaking, enabling it to withstand
both masticatory loads and the stresses of
orthodontic forces.

• Bone grows along the titanium oxide surface,
which is formed after contact with air or tissue
fluid.
• Biocompatibility is attributed to the stable oxide
layer primarily TiO2 that spontaneously forms
when Ti is exposed to oxygen.
• This reaction converts the base metal into a
ceramic material that electrically and chemically
passivates the implant

• This biomaterial surface interacts with water, ions
and numerous biomolecules after implantation the
nature of these reactions will determine how cells
and tissue respond to the implant.
• Manufactures immerse these implants in acidic
solution to enhance the formation of passivating
oxide film.(2-6nm)
• However, pure titanium has less fatigue strength
than titanium alloys. A titanium alloy—titanium-6
aluminum-4 vanadium—is used to overcome this
disadvantage.

Surface design of Ti implants
• Machined finished
• Smooth surface
(Branemark System
<0.2µm
Nobel Biocare)
• Poor interaction with
• 0.5-1µm
tissue
• Poor mechanical
retention
• Allow epithelial
downward growth
deep per-iimplant
pockets

• Implants with different surface characteristics
continue to be developed in attempts to increase
the degree and rate of Osseo integration to allow
early and immediate loading and to promote
integration in anatomic sites with poor/insufficient
bone quality for conventional implants.
• uncoated implants might be preferred to prevent
excessive Osseo integration and complicated later
surgical removal.


• Ti implants with intermediate surface have
higher bone –implant contact. Furthermore
increase in roughness can lead to increase
plaque accumulation, peri-implantitis, and
failure.


Methods for altering surface texture
David et al DCNA,2006

• Ablative ( removal of material from the surface)
• Grit blasting
• Acid etching
• Grit blasting followed by acid etching

• Additive (deposit material on implant surface)
• Plasma spraying ;TPS ( one of the roughest dental implant
surface)
• coating Ti implants with hydroxy apatite– surface
chemistry dramatically changes from Ti02 to a bone like
ceramic with potential for chemically bonding to bone


Bone implant interface
interaction
Osseo integration

Osseo coalescence

Direct structural and
functional connection
between implant and load
carrying implant

Refer specifically to
chemical integration of
implants in bone tissue
by surface reactive
materials.

Largely refers to physical
integration or mechanical
fixation of an implant
into bone

Calcium phosphate,
bioactive glasses.
Exhibit resistance to
both shear and tension
loads

Good resistance to shear
load but poor resistance
to tension

i
m
p
l
a
n
t

t
i
s
s
u
e


• Osseo integrated implants can be used as a
firm osseous anchor for orthodontic
treatment because they are able to resist
continuous horizontal forces of at least 5 N
(about 510 gm) during a period of several
months.
• The implant must have a certain surface
area available for Osseo integration to
support the forces of orthodontic traction. If
the length is decreased, the diameter must
be increased.

• However practical consideration for the orthodontist is
whether some critical degree of implant stability is
required for functional efficiency?
• There are substantial differences between conventional
implants and temporary skeletal anchorage
devices(TSADs)
• conventional prosthodontic implants, generally loaded
after Osseo integration, are intended to be permanent,
whereas implants for orthodontic anchorage are usually
loaded long before osseointegration is achieved and are
intended to be removed relatively soon.

Difference in nature of force
• Conventional implants are subject to high
intermittent forces of mastication, but forces
acting on orthodontic anchors are light and
continuous.
• The direction of loading and the size of the
implants also vary between the 2 systems


• Implant stability depends not only on Osseo
integration, but also on the mechanical
stability achieved at placement.
• Osseous contact with an implant as low as
5% was shown to resist orthodontic loads.
Ohmae et al reported that an integration
index of 25% would provide reliable
anchorage.

• Complete Osseo integration would clearly be
undesirable for a TSAD, and it is apparent that
implants can be functional, even with a very low
integration index.
• Clinical stability sufficient for orthodontic anchorage
can be achieved even with levels of Osseo integration
as low as 5%. Under 25% of Osseo integration, screws
remain easy to remove
• Osseo integration rates appeared lower around miniimplants, ranging from 10% to 58%, in contrast to the
reported Osseo integration index of 75.5% around
orthodontically loaded palatal implants in humans.

• For the clinician, a decrease in implant diameter will
both increase the number of potential insertion sites
and facilitate the surgical removal

Titanium Brackets
• Of all the different materials tested so far,
stainless steel brackets are preferred for their
low frictional force values
• However, concerns have been expressed in the
literature about the nickel content in the
stainless steel causing hypersensitivity and
corrosion in the oral environment. In addition,
there are instances where MRI or CT imaging
may have been distorted because of the stainless
steel alloys.

• To overcome these difficulties, pure titanium brackets have
been made available.
• These brackets have excellent corrosion resistance and are
biocompatible,
• As a consequence of its passivity over a broad pH range,
its high breakdown potential, and its low current density to
corrosion, Ti exhibits the minimum tissue response of all
commonly used metals.
• Only when the passive layer is broken down does galling
and fretting occur, problems common to all Ti alloys;
ultimately frictional and biocompatible breakdown occur.


• The currently available titanium bracket products
consists of two products a commercially pure
titanium and a titanium alloy ti-6al-4v
• Base-pure titanium
• Wing- titanium alloy --more prone to galvanic
corrosion
• Base + wing –pure titanium—low hardness than
stainless steel wear of slot—reduce transfer of
torque and plastic deformation of the wing—
require surface treatment


• Recently, Deguchi et al (J Dent Res 1996)
reported on the feasibility of manufacturing
titanium brackets by metal injection molding
(MIM).
• The brackets tested exhibited mechanical
properties and bond strengths equivalent to or
better than that of stainless steel brackets, while
providing better corrosion resistance and absence
of nickel leaching.


• Kusy et al (AJODO 1998) evaluated the static
and kinetic frictional coefficients of
commercially pure titanium brackets in the
passive configuration in the dry and wet states
against stainless steel, nickel-titanium, and betatitanium archwires.
• For comparison, stainless steel brackets were
evaluated under identical conditions.
• Titanium brackets were grayer in color and
rougher in texture than the stainless steel
brackets.

Scanning electron micrographs show overall
morphologies of as-received Ti bracket versus SS
bracket

• Remarkably, the static and kinetic frictional
coefficients of the couples formed by titanium
and stainless steel brackets were comparable.
• When evaluated against stainless steel and
nickel-titanium archwires in the dry state at
34°C, the static coefficient averaged .12 and .20,
respectively, independent of bracket alloy.
• When evaluated against stainless steel and
nickel-titanium wires in the wet state at 34°C
using human saliva, the static coefficient
averaged .15 and .20, respectively, independent
of bracket alloy.

• Kusy and O‘Grady
(AJODO 2000) tested
the hypothesis that in
the active configuration,
when brackets are
subjected to higher
levels of stress, the thin
passive layer of Ti
brackets will break
down causing the
archwire–bracket
couple to gall and
seize.


• Contrary to theoretical
reasoning, however, the testing showed that
this passive layer of Ti brackets does not
break down in the active configuration.
• Furthermore, the sliding properties of Ti
brackets remained comparable to SS
brackets and compared favorably with other
biocompatible brackets such as
monocrystalline and polycrystalline ceramic
brackets.
• The authors concluded that Ti brackets are a
suitable substitute for SS brackets in sliding
mechanics.

• Kapur, Sinha and Nanda (AJODO 1999) compared the
level of frictional resistance generated between
titanium (Rimatitan, Dentaurum) and stainless steel
brackets (Dentaurum and GAC).
• Both 0.018 and 0.022 inch slot size edgewise brackets
were tested with different sized rectangular stainless
steel wires in a specially designed apparatus.
• The titanium brackets showed lower static and kinetic
frictional force as the wire size increased, whereas
stainless steel brackets showed higher static and kinetic
frictional force as the wire size increased.


• A possible explanation could be offered by the
chemical structure and mechanical properties of
titanium and titanium-based alloys.
• Titanium brackets have a different chemical
structure or hardness compared with the stainless
steel brackets. In addition, frictional forces are due
largely to the atomic and molecular forces of
attraction at the small contact areas between
materials.
• For example, friction is greater between two
surfaces of the same material than two surfaces of
different materials.

• The desirable mechanical properties of titanium
for use in orthodontics are low rigidity, super
elasticity, and shape memory effect.
• These qualities allow early engagement of a full
size wire during treatment, it allows the bracket to
elastically deform and creates a reactive working
environment for three-dimensional control of
orthodontic tooth movement with rectangular
wires.

• Kapur, Sinha and Nanda (AJODO 1999) evaluated
the distortion of brackets after the application of
torsional forces, and discovered that the titanium
brackets showed significantly lower bracket slot
widening.
• Thus, the titanium brackets demonstrated superior
structural stability compared with conventional
stainless steel brackets on application of torsional
forces


Non-nickel titanium archwires


Properties of archwire required during different stages
of treatment


Beta titanium (TMA) wires
• Beta titanium was introduced by Dr. CHARLES
BURSTONE and JON GOLDBERG in the
university of CONNECTICUT ( Early 1980s )
•
•
•
•
•

Composition
Titanium
- 73.5%
Molybdenum - 11.5% -to stabilize beta phase
Zirconium
- 6%
Tin
- 4.5 %

•

ADVANTAGES:

•
•
•
•
•
•
•

Low stiffness
Good formability
High spring back
Weldable
Ductile
Corrosion resistance

Composition (wt%)

Modulus
of
Elasticity (GPa)

Yield Strength
(MPa)a

Springbackb

17-20% Cr. 8-12% Ni. 0.15% C
(max), balance mainly Fe

160-180

1100-1500

0.0060-0.0094 (AR) 0.00650.0099 (HT)

Cobalt-chromiumnickel (Elgiloy Blue)

40% Co. 20%Cr. 15% Ni. 15.8%
Fe, 7% Mo, 2% Mn, 0.15% C,
0.04% Be

160-190

830-1.000

0.0045-0.0065 (AR) 0.00540.0074 (HT)

Beta-titanium (TMA)

77.8% Ti, 11.3% Mo, 6.6 %Zr,
4.3% Sn

62-69

690-970

0.0094-0.011

Nickel-titanium

55% Ni, 45%Ti (approx. and
may contain small amounts of
Cu or other elements)

34

210-410

0.0058-0.016

Wire Alloy

Austenitic
steel

stainless


Properties of beta titanium wires
• The modulus of elasticity of beta titanium is
approximately twice that of nitinol and less
than one half that of stainless steel.
• The forces that are produced are approximately
0.4 that of steel, producing a more gentle
delivery of forces with an edgewise wire; for
example, an 0.018 by 0.025 inch wire in beta
titanium delivers about the same force as an
0.014 by 0.020 inch stain steel wire when
activated in a second-order direction

• Its stiffness makes it ideal in applications where
less force than steel is required but where lower
modulus materials would be inadequate to develop
required force magnitudes
• Furthermore, it would have the advantage of full
bracket engagement and third order or torque
control if used in an 0.018 inch slot bracket
• Clinical application

• Initial tooth alignment
• Finishing arches

• Because of the much lower value of elastic
modulus, despite lower values for yield
strength, the beta-titanium wires have significantly
improved values of springback (YS/f), which
markedly increase their working range for tooth
movement.
• The high spring back properties [working range]
may offer simplification of the overall design of
loops


• A second clinical advantage of the betatitanium wires is excellent formability, which is
due to their BCC structure. The addition of
molybdenum to the alloy composition
stabilizes the high-temperature bcc -phase
polymorphic form of titanium at room
temperature, rather than the hexagonal closepacked alpha-phase.
• However, the titanium alloy cannot be bent
over as sharp a radius as stainless steel, so that
some care in the selection of pliers and bending
procedures is required.

• The many slip systems available for
dislocation movement in the bcc crystal
structure account for the high ductility of
the -titanium wires. The zirconium and
zinc in the alloy composition contribute
increased strength and hardness,


• The high ductility [ability
of the material to
withstand permanent
deformation without
rupture under tensile load]
of -Titanium allow it to
be formed into arches with
tieback loops or segments
with complicated loop
configuration.
• It also offers the
possibility of varying
force magnitude by a
choice of material rather
than cross section of the
wire. (variable modulus
orthodontics)

• Clinical use
• K-SIR ARCH
WIRE.0.019‘‘/0.025‘‘


Pendulum appliance – 0.032’’


• The third clinical advantage of -titanium is
that it is the only orthodontic wire alloy
possessing true weldability.
• The welded joints for stainless steel and
Elgiloy Blue appliances require additional
mechanical reinforcement with solder.
• Detailed optimum settings for welding titanium wires with the capacitance (singlepulse) and transformer (multiple-pulse)
welding apparatuses available to the
orthodontist have been published

• Springs for alignment or
retraction can be directly
welded to an arch wire
(Only TMA can be welded
to TMA; it is not possible
to weld stainless steel to
TMA
• Unlike steel, where too
much heat will produce
softness in the wire,
overheating of titanium
could lead to brittleness of
an energy-imparting finger
spring.

• Welding of TMA wire
•
•
•
•
•
•

5 basic principles;
1. Proper positioning
2. Minimum voltage
3. Small contact area
4. Single short pulse
5. Pressure


Biocompatibility
• With increased interest in the
biocompatibility of orthodontic
materials, another important feature of the
Beta-titanium wires is their absence of
nickel that is present in the other three
major wire alloy types.
• The excellent corrosion resistance and
biocompatibility of -titanium is due to the
presence of a thin, adherent, passivating
surface layer www.indiandentalacademy.com
of titanium oxide (TiO2).

DISADVANTAGES
• High coefficient
of friction
• Unaesthetic
• costly


• Studies indicated( Kusy RP et al AJO 1990, Kapila S et al
AJO 1990) that TMA wires have higher coefficients of
friction and produce significantly greater frictional resistance
to sliding through orthodontic brackets than stainless steel.
• As the titanium content of an alloy increases, its surface
reactivity increases and the surface chemistry is a major
influence on frictional behavior. KUSY RP 1989
• Thus, β-titanium, at 80% titanium, has a higher coefficient of
friction than nickel-titanium at 50% titanium, and there is
greater frictional resistance to sliding with either than with
steel


• Under laboratory conditions, the surface of the
titanium wire can become cold-welded to stainless
steel brackets, making sliding closure of even small
spaces difficult. ―stick-slip‖ phenomena
• REMEDY
• A recently developed Nitrogen ion implantation
technique for beta-titanium (Ormco) has markedly
improved the measured values of in vitro sliding
friction.
• Implantation of nitrogen ions into the surface of this
wire causes surface hardening and can decrease
frictional force by as much as 70%.

MECHANISM
• The ions penetrate the surface of the wire on impact,
building up a structure that consists of both the original
wire and a layer of tin compounds (TiN and TiO) on the
surface and immediate subsurface. This layer is extremely
hard and creates a considerable amount of compressive
forces in the material at the atomic level
• The compressive forces and increased surface hardness
improve the fatigue resistance and ductility and reduce the
coefficient of friction of the wire. The superficial
compressive forces also minimize any detrimental effects
of surface flaws


Low-Friction And Coloured TMA
Burstone CJ, Farzin-Nia JCO 1995
• Two varieties of TMA—
low-friction and colored—
were produced by varying
the type and thickness of
ions.
• Low-friction TMA has a
light golden hue, and
several different wire
colors are also being
manufactured

• Results of a friction study by Burstone and Farzin-Nia JCO
1995 showed the static coefficient of friction of untreated
TMA (.52) to be significantly higher than stainless steel
(.19).
• However, the static coefficient of friction of treated TMA
was significantly reduced (.13). Concerning friction in a
wet environment, such as the mouth versus the laboratory
bench, wet ion-induced TMA (honeydew color) had
slightly lower coefficients than wet stainless steel.
• This study concluded that the frictional forces of treated
TMA are likely to be less than 40 percent that of stainless
steel because of the above-cited differences in frictional
force and the fact that TMA is only 40 percent as stiff as
stainless steel.
• There was no significant difference in the modulus of
elasticity or the tensile strength of the treated and untreated
TMA wires.

Clinical Applications
of
Low-Friction And Coloured TMA
• In Early Treatment
• extremely useful in the early stages of
treatment where the bracket slides along
the archwire during initial leveling and
rotation of single-tooth discrepancies.
These irregularities can be corrected
much more efficiently when the frictional
force is only 60 percent that of stainless
steel.

• With Ceramic Brackets
•
Another simple extrapolation concerning
efficient utilization of Low Friction and
Colored TMA is in its incorporation with
ceramic brackets without metal slots, where
friction can be quite a problem.
• When the Low Friction and Colored TMA
can be adequately engaged in the bracket, it
will likely outperform nickel titanium wires.


• 3.With Mildly Crowded, Bimaxillary Protrusive
Four-Bicuspid Extraction Cases

• since its flexibility allows for ideal bracket
engagement right from the inception of
treatment. Once initial leveling and aligning
are complete, retraction of the cuspids can
begin


precaution
• It is at this point that certain treatment concepts should be
considered. First, when employing this technique, as with
most cuspid retraction, it is advisable to retract the
maxillary cuspid before retracting the mandibular cuspid
.By doing so, the Class I cuspid relationship is preserved or
even established. If the lower is fully retracted before the
upper, it is likely to create a Class II relationship, which is
difficult to convert.
• Second, in maximum anchorage situations, it is advisable
to use a Nance palatal button during retraction. Due to the
low friction of this wire, it can protract molars if particular
caution is not exercised. The Nance button has been
efficiently used with this wire with no unfavorable side
effects.

ALPHA TITANIUM
• The composition of α-titanium include 88.9%
titanium, 7.86% Aluminum and 4.05% Vanadium.
• The elastic modulus and yield strength at room
temperature for α-titanium is approximately 110
GPa and 40 MPa respectively
• Certain elements, such as
aluminum, carbon, oxygen and nitrogen, stabilize
the α-titanium structure. That is, they raise the
temperature for transformation to β-titanium

• Hexagonal lattice possesses fewer slip planes making it
less ductile than β-titanium.
• Alloy is strictly near alpha phase of titanium rather than
pure alpha titanium alloy because there is certain amount
of beta phase retained in them at room temperature.
• The wires are soft enough for initial gentle action on teeth
in spite of large wire dimension as also for intraoral
activation.
• They seem to harden and become brittle with passage of
time in the mouth, possibly due to the absorption of
hydrogen and formation of titanium hydrides.

• A.J. Wilcock produces
combination wires, which are
rectangular in the anterior
segment to maintain torque
while the round posterior
segments allow sliding
mechanics. Rectangular
section wire is also available
in preformed arches.
• Rectangular wires of sizes of
0.022‖ x 0.018‖ (Ribbon
mode) or 0.020 x 0.020‖
(square) for finishing stage
are recommended.

TITANIUM-NIOBIUM
• Nickel free Titanium alloy
• COMPOSITION
•
Ti - 82%
•
Mo - 15%
( or)
•
Nb - 3%

Ti - 74%
Nb - 13%
Zr - 13%


•
•
•
•
•
•

PROPERTIES
Easy to bend, formability is less than TMA
Stiffness - ¼ of SS
Load deflection rate is lower than TMA
Yield strength is lower than SS
Indicated when lower forces than those exerted by
TMA are needed.


• ADVANTAGES;
•
•
•

Substitute for SS
No leaching of nickel
CLINICAL IMPLICATIONS

• Finishing wire with multiple bends
• Fixed retainers ( Biocompatible )


TIMOLIUM WIRES
•
•
•
•
•

Improved titanium wires
Smooth surface texture
Less friction
Accelerate treatment time
Resistance to breakage

BETA –III WIRES
•
•
•
•
•
•
•
•

Introduced by RAVINDRA NANDA
Bendable
High force
Low deflection rate
Co-efficient of friction is more
Nickel free titanium wire with memory
Ideal for multilooping, cantilever, utility arches
First choice of wire for finishing stages where tip &
torque corrections fully accomplished during initial stages.

BASIC CONCEPTS ABOUT NICKEL
TITANIUM ALLOYS


AUSTENITE :High temperature phase of Nickel titanium alloys is called
Austenite . Like many ferrous alloys this austenite can
transform to Martensite. It has got Body centered cubic (BCC)
structure. It is the stronger, higher temperature phase present in
NiTi.
MARTENSITIC TRANSFORMATION :Process of phase transformation which is DIFFUSIONLESS,
occurring from within and without any chemical change which
results in transformation of Austenite (parent phase) to
Martensite following rapid cooling.
• MARTENSITE has got distorted monoclinic, triclinic or HCP
structure More deformable, lower temperature phase present in
NiTi.


• The relative concentration of the 2 phases in
the alloy will determine the resultant
stiffness of the wire and the amount of force
delivered


HYSTERESIS

Hysteresis: The temperature difference between a phase
transformation upon heating and cooling. In NiTi alloys, it
is generally measured as the difference between Ap and
Mp.

TWINNING :In
certain
metals that crystallize in Hexagonal
closed
pack
(HCP)
structure,
(martensite) deformation occurs by
twinning.
• It refers to a movement that divides
the lattice into two symmetric parts;
these parts are no longer in the same
plane but rather at a certain angle.
• responsible for the alloy‘s ―Shape
Memory‖
and
Superelasticity,
properties that derive from the
twinning-detwinning mechanism
e.g., :- NiTi alloys are characterized
by multiple rather than single twining
throughout the metal


Austenite and Martensite have different crystal
structure and mechanical properties the most
notable mechanical properties of Nitinol wires
i.e. super elasticity and shape memory are result
of reversible nature of Martensitic
transformation


Martensitic transformations do not occur at a precise
temperature but rather within a range known as
temperature transition range(TTR).
Range for most binary NiTi alloys

40 - 60 C.

Transformation from Austenite to Martensite can occur
by.
Lowering the temperature.- Martensitic-active alloys
Applying stress (Stress induced Martensite) SIM.
-Austenitic-active alloys

EFFECTS OF ADDITIONS AND IMPURITIES ON
TTR :Adding a third metal can lower the TTR
to as low as - 330 F ( - 200 C).
Narrow the difference b/w cooling and heating
(Narrow Hysteresis).
For thermally activated purposes most common
third metals are Cu and Co .
Reduce the hysteresis
Bring TTR close to body temperature.


•
•
•
•

Kusy ( 1991) classified NiTi alloys into :
Martensitic-stabilized alloys
Martensitic-active alloys
Autenitic-active alloys


• Martensitic-stabilized alloys - do not possess
shape memory or super elasticity, because the
processing of the wire creates a stable
martensitic structure.
• These are the non superelastic wire alloys such
as originally developed- Nitinol.


• CONVENTIONAL NITINOL - Original alloy 55% Nickel, 45% Titanium ratio of elements.
To modify mechanical properties and transition
temp. 1.6% Cobalt was added to it
CRYSTAL STRUCTURE:
Stabilized Martensitic form.
- No application of phase transition effects.
The family of Stabilized Martensitic alloys now
commercially available are referred to as M –
NiTi.

Conventional Nitinol is available as
- Nitinol classic Unitek corporation.
- Titanal
Lancer pacific.
- Orthonol -Rockymountainorthodontics.


PROPERTIES
1. Springback and Flexibility
Most advantageous properties of Nitinol .
Nitinol wires have greater springback and larger
recoverable energy than Stainless Steel or Ti when activated to same extent.
High spring back is useful in circumstances that
require large deflections but low forces.
.

• Bending also adversely effects springback property of this
wire.
• Bending of loops and stops in nitinol is not recommended.
• Any 1st, 2nd and 3rd order bends have to be over prescribed
to obtain desired permanent bend
• Cinch backs distal to molar tubes can be obtained by flame
annealing the end of wire. This makes the wire dead soft
and it can be bent into the preferred configuration.
•

A dark blue color indicates the desired annealing
temperature. Care should be taken not to overheat the wire
because this makes it brittle.


2. Spring Rate / Load Deflection Rate:
Load deflection rate of Stainless Steel is twice that
of Nitinol.
Delivers 1/5th – 1/6th force per unit of deactivation
Clinically this means that for any given
malocclusion nitinol wire will produce a lower,
more constant and continuous force on teeth than
would a stainless steel wire of equivalent size


Formability : Nitinol has poor formability.
Therefore best suited for preadjusted systems.
- Joinability:
• Not joinable
• Since hooks cannot be bent or attached to
Nitinol, crimpable hooks and stops are
recommended for use


.
Friction:
Garner, Allai and Moore (1986) and Kapila et al
(1990):
• Noted that bracket wire frictional forces with nitinol
wires are higher than those with SS wires and lower
than those with -Ti, in 0.018 inch slot.
• In 0.022 inch slot – NiTi and
-Ti wires
demonstrated similar levels of friction.
• Although NiTi has greater surface roughness Beta –
Ti has greater frictional resistance


CLINICAL APPLICATIONS:
Leveling and Aligning:
• Nitinol wire is much more difficult to deform during
handling and seating into bracket slots is easier than
Stainless Steel arch wires.
• Reduces loops formerly needed to level dentition.
• Can be used for longer periods of time without
changing.


ADVANTAGES :
Fewer arch wire changes.
Less chair side time.
Less patient discomfort.
Reduction in time to accomplish rotations.


LIMITATIONS:
•

Poor formability.
Poor joinability.
• By its very nature nitinol is not a stiff wire which means that
it can easily be deflected. Low stiffness of nitinol provides
inadequate stability at completion of treatment. Such stability
is often best maintained by using stiffer Stainless Steel wires
tailored to the desired finished occlusion.
• Tendency for dentoalveolar expansion.
• Expensive.


Martensitic-active alloys
• CHARACTERISTIC FEATURE
• employ the thermoelasticity to achieve shape memory;
• By lowering the temperature the alloy is transformed into
martensite and becomes pliable and easily deformed
• the oral environment raises the temperature of the deformed
arch wire with the martensitic structure so that it transforms
back to the austenitic structure and returns to the starting
shape. (An orthodontic archform )
• The clinician can observe this thermoelastic shape memory if a
deformed archwire segment is warmed in the hands.

Active martensite thermodynamic
wire
• Neo Sentalloy
• CO NiTI 37
• CO NiTI 40


• Orthodontic clinical application requires setting
the TTR of these alloys very close to the intraoral
temperature or even corresponding to it, so that a
greater amount of martensite is constantly
available. (Sachdeva,1990)
• According to the data available in the literature,
most of the commercially available the
thermoelastic wires TTRs are set at higher
temperatures, from 35°C to 40°C
• This type of thermoelastic alloy, however, will be
completely austenitic at oral temperature, and the
austenite presents a higher modulus of elasticity
that results in a greater stiffness of the wire.

advantages
• This wire is pliable both intraorally and
extraorally and it will accept bends. The
forces exerted on the dentoalveolar
structures are remarkably low; therefore the
alloy is recommended for the treatment of
patients with periodontal problems


drawback
• The low stiffness of copper NiTi 40°C also
presents the mechanical disadvantage of not
allowing for complete dental alignment or
full control of transverse dimensions.
• A second wire with a larger diameter or
greater stiffness is usually required.


Active Austenitic Nickel Titanium
Alloys
• undergo a stress-induced martensitic (SIM)
transformation when activated. These alloys display
superelastic behavior , which is the mechanical
analogue of the thermoelastic shape-memory effect
(SME).
• Chinese NiTi
• Japanese NiTi [Sentalloy]
• Copper NiTi 27 C


• The unique force – deflection curve of A-NiTi
wire occurs because of a phase transition in grain
structure from austenite to martensite, in response
not to a temperature change but to applied force
• When the austenite is transformed into stress
induced Martensite SIM, a horizontal plateau
appears as an indicator of the expression of
superelastic properties.

•
•

SIM is unstable
In orthodontic clinical applications, SIM forms
where the wire is tied to brackets on malalligned
teeth so that the wire becomes pliable in deflected
areas. A LOCALISED STRESS RELATED
SUPERELASTIC PHENOMENON

•

In those areas the wire will be super elastic until
tooth movement occurs.


• Superelastic compounds
generally present a high
stiffness in the initial
segment of the slope of the
stress-strain graph when
the deflection of the wire is
still minimum.
• The initial activation force
required for autenitic NiTi
can be 3 times greater than
the force required to deflect
a classic work hardened
martensitic wire (Nitinol).

• However, once the SIM is
formed, the horizontal
plateau appears and the alloy
‗absorbs‘ any additional
load stress and releases it in
constant amounts during the
deactivation phase.
• This means that an initial
archwire would exert about
the same force whether it
were deflected a relatively
small or a large distance,
which is a unique and
extremely desirable
characteristics

• Actually, the linear
region corresponding to
the deactivation plateau
is lower than the
activation plateau and
parallel to it. This
phenomenon is called
mechanical hysteresis.
• The main clinical
interest of hysteresis is
that the force delivered
to the periodontal
structures is lower than
the force necessary to
activate the wire.

• The different loading and unloading curves
produce the even more remarkable effect that the
force delivered by an A-NiTi wire can be changed
during clinical use merely by releasing and retying
it.
• The amount of force exerted by a niti-A wire that
had been previously activated to 80 could be
considerably increased by untying it from a
bracket and then retying again
• CUNiTi 27 C wire generates high force 137g/mm
(Segner, 1994) and best indicated for patients with
average or high pain threshold. Also a small,
round wire is preferable for most application

TTR FOR AUTENITIC ACTIVE NiTi ALLOYS
• In austenitic alloys, the formation of SIM will guarantee
the presence of the superelastic behavior necessary for the
release of light and continuous forces.
• Therefore, the Af of the alloy should not be set at a
temperature considerably below oral temperature or the
formation of SIM will not occur.
• It would actually be advisable to evaluate alloys on the
basis of their stress related TTRs because the application of
stress usually raises the Af of the alloy.
• According to the data available in the literature, most of
the commercially available superelastic wires exhibit
stress-related Afs ranging from 22°C to 28°C,

Recent advances in NiTi wires
• Bioforce sentalloy
• Nitrogen coated archwires
• Nitinol Total Control


• Bioforce Sentalloy – (Miura F,EJO-1988)
• A Graded Thermodynamic Wire The heat treatment
of selected sections of the archwire by means of
different electric current delivered by electric pliers
modified the values of the deactivation forces by
varying the amount of austenite present in the alloy.
• After heating the anterior segment for 60 minutes, the
linear plateau of the deactivation force dropped to 80
g in a 3-point bending test at room temperature.


• Similar manufacturing procedures have been
perfected to produce wires such as Bioforce Sentalloy
(GAC) that are able to deliver selective forces
according to the needs of the individual dental arch
segments

• BioForce (GAC) offers 80 grams of force for
anteriors and up to 320 grams for molars


NITROGEN COATED ARCHWIRES:
Implanting Nitrogen on surface of NiTi alloys by Ion
implantation process – NITRIDING.
Advantages:
- Make Titanium more esthetically pleasing giving it
gold like aspect.
Hardens surface.
Reduces friction.
Reduces Nickel release into mouth.
e.g : Bioforce Ionguard - 3 m Nitrogen coating.

The IONGUARD process actually alters the wire’s
surface to provide a dramatically reduced
coefficient of friction for sliding mechanics that
are better than the same size stainless steel wire
and half the friction of competitive NiTi wire.
It also seals the occlusal surface of the wire to
eliminate breakage and reduce nickel leaching.
While the IONGUARD process alters the surface
of the wire, none of the wire’s unique properties
is changed.


Nitinol Total Control .A new
Orthodontic alloy.
• TODD A. THAYER, KARL FOX,ERIC
MEYER ( JCO1999) developed a new
pseudo-superelastic nickel titanium,alloy,
Nitinol Total Control,
• Accepts specific 1st-, 2nd-, and 3rd-order
bends while maintaining its desirable
superelastic properties.

• Combines the ability of
superelastic nickel titanium
to deliver light, continuous
forces over a desired
treatment range with the
bend ability required to
account for variations in
tooth morphology, archform,
and bracket prescriptions
• ―Residual strain‖ is the
amount of permanent
deformation that remains in
the archwire material after
unloading.
• In other words, bendability is
indicated by increased levels
of residual strain.

Frictional and bending tests verify that the force levels
produced by them are within accepted ranges for optimal
tooth movement. Furthermore, wire properties are not
temperature dependent.


It can avoid the need to change archwires, , into he
following situations:

• Repositioning due to improper bracket placement
• Repositioning brackets to maintain torque control]
• Placement of extrusion, intrusion, or utility arches
•Functional finishing with detailing bends that address
variations in tooth morphology and interarch occlusal
relationships


• Filling the bracket slot with controlled, lightforce
(torque without shearing the bracket)
• Reduces archwire inventory without compromising
treatment mechanics. Lower forces are generally
associated with less patient discomfort. In addition,
by reducing the number of archwire changes required,
allows the clinician to treat more patients effectively
and efficiently.
• Precaution
• Because of relatively low stiffness, it should not be
used for space closure.

SELECTION OF NITI
WIRES
• The rationale for making an educated clinical choice of a
NiTi alloy includes two primary considerations
• (1) a proper stress-related TTR, corresponding to or
slightly below oral temperature and
• (2) a low deactivation force released to the dentoalveolar
structures to prevent deleterious side effects, such as pain
after bone hyalinization and possible root resorption.
• the delivery force is strictly correlated to the presence of
martensite in the alloy and is therefore dependent on the
TTR as well as on the amount of stress induced.


Selection related to severity of
crowding
•

•

The amount of loading used to test the
superelastic behavior has shown that at least 2
mm of deflection are necessary for the
formation of SIM in austenitic wires.
A deflection below the 2-mm threshold may
translate into a higher force delivery correlated
with the constant presence of the stiffer
austenitic phase..


• An optimal performance of austenitic superelastic
NiTi wires will be obtained in cases of severe
dental crowding, when an accentuated deflection
due to the irregular interbracket span
will generate SIM in a localized area of the arch,
usually the lower incisor area.
• Mild crowding does not necessarily require the
use of superelastic wires, and a classic small
diameter work-hardened alloy or a wellestablished multistranded round stainless steel
wire will generally perform as well


Selection related to periodontal
status


• In periodontally compromised patients, and
some-times in the lower incisor area, it would be
advisable to maintain the force level delivered to each
tooth below 100 g.
• Data available from properly designed experi-ments
with 2 mm or more of wire deflection at oral
temperature show that the average delivery force of
an austenitic superelastic NiTi .016 x .022-in ranges
between 200 g and 300 g.
• Co NiTi 27 C wire generates high force 137g/mm
(Segner, 1994) not preferred and best indicated for
patients with average or high pain threshold. Also a
small, round wire is preferable for most application

• Instead, 35°C and 40°C Thermo-Active Copper
Ni-Ti rectangular, Nitinol SE and Nitinol XL, and
Neo Sentalloy F240 wires of similar diameters
deliver forces around 100 g
• In order to obtain lower forces from austenitic
NiTi or multi-braided stainless steel, it is
necessary to select smaller diameters and abandon
the use of rectangular wires during the alignment
phase of treatment


Force level related to torque
• True pseudoelastic behavior generated by torquing
forces at nominal oral temperature has not been
demonstrated, even in copper NiTi alloys and with
a considerable increase of the twist.
• Only with a lowering of the temperature, with
cold rinses for example, can the baseline torque be
consistently reduced; in 40°C Thermo-Active
Copper Ni-Ti the delivery force can be dropped to
200 g/mm for a less than transient time interval.

• True thermoelastic alloys may therefore be
indicated for early torque control during the
alignment phase of treat-ment and in
periodontally compromised patients.


• Randomized clinical trials, at least those
conducted with austenitic NiTi, on the rate
of tooth movement and pain experienced,
failed to demonstrate a significantly better
performance of superelastic wires compared
with conventional alloys, such as
multistranded stain-less steel wires

Property

Stainless Steel

Cobalt-Chromium-Titanium
Nickel (Elgiloy Blue) (TMA)

Nickel-Tita

Cost

Low

Low

High

High

Force delivery

High

High

Intermediate

Light

Elastic range
(springback)
Formability

Low

Low

Intermediate

High

Excellent

Excellent

Excellent

Poor

Ease of joining

Can be soldered.
Welded joint m
ust be reinforced
with solder.
Lower

Can be soldered.
Welded joints must
be reinforced with
solder.
Lower

Only wire alloy
that has true
weldability

Cannot be
welded

Higher

Higher

Some

Some

None

Some

Archwire-bracket
friction
Concern about
biocompatibility


Corrosion Susceptibility of Titanium
alloys Archwires
• The use of fluoride-containing rinses and gels might
be harmful to titanium devices if the pH of these
prophylactic materials is below neutral Thus the
corrosion of titanium seems to depend not only on
fluoride concentration but also on pH. {Nakagawa J D
R 1999}
• A recent study by Watanabe{ AJO 2003} reported on
the effect of fluoride prophylactic agents on the
surfaces of titanium based Orthodontic wires. The βtitanium wires, particularly the TMA wire showed less
tarnish resistance to APF agents than did the nickelwww.indiandentalacademy.com
titanium alloy wires.

Recycling & Sterilization of Nickel
Titanium Archwires
• Recycling of nitinol wires is often practiced
because of their favorable physical
properties and the high cost of the wire.
Recycling involves (1) repeated exposure of
the wire for several weeks or months to
mechanical stresses and elements of the oral
environment and (2) sterilization between
uses

• For effective sterilization, steam autoclaving
(ideally at 134ºC, 32 psi for 3 minutes) is the
method recommended.
• For instruments unable to withstand
autoclaving, an effective cold disinfection
solution such as 2% glutaraldehyde is an
alternative.


• Mayhew and Kusy;AJO1988 and Buckthal and
Kusy AJO1988 have demonstrated no appreciable
loss in properties of nitinol wires after as many as
three cycles of various forms of heat sterilization
or chemical disinfection,
• In a recent in vitro investigation on the effects of a
simulated oral environment on 0.016‖ nickel
titanium wires, Harris et al(1988) noted a
significant decrease in yield strength of these
wires over a period of four months
• the effects of the oral environment on the wire
properties are still inconclusive.

Intra oral aging
• For brackets & archwires, issue of interest is the in
vivo alteration of material due to the expected
long period of performance, with possible effects
on mechanical properties.
• Main focus of the alterations induced on
orthodontic wires is on Ni Ti archwires because
stainless steel & Co-Cr-Ni archwires are usually
replaced in an escalating stepwise process as
treatment progresses.

• Generally it has been shown that intra oral exposure
of Ni Ti wires alter the topography & structure of the
alloy surface through surface attack in form of
pitting, crevice corrosion, or formation of
integuments.
• Retrieved Ni Ti wires demonstrated signs of
corrosion after more than 2 months of in vivo
placement.
• Signs of pitting corrosion have been detected in
retrieved wires after at least 6months exposure.


• Adsorption of intraoral integuments might greatly
reduce the coefficient of friction ( salivary protein
adsorption, plaque accumulation) .
• Alternatively calcified integuments might increase
surface resistance & resistance to shear forces.
• Also intraorally exposed Ni Ti wires do break more
frequently than expected : Variations in intra oral
temprature might affect their properties & fracture
resistance.
• Also the force delivery of superelastic coil springs
can be substantially affected by small changes in
temprature

Other uses of Ti alloys in
orthodontics
• Open and close coil
springs (Gain/Close
the space)
• Molar distalizer
• Expansion of arch
• Individualized
presurgical archforms


Ni Ti Palatal expander
William Arndt
( JCO 1993)
Nickel titanium
expanders come
in eight different
intermolar
widths, ranging
from 26mm to
47mm, that
generate forces
of 180-300g.

Miura et al

Jco 1990

Individualized
presurgical archforms


conclusion
• Titanium is a new orthodontic material with
unique properties and an excellent balance of
properties suitable for many orthodontic
applications
• Titanium not only offers an improvement in the
properties of presently designed orthodontic
appliances with its increased springback, reduced
force magnitudes, good ductility, and weldability,
but its excellent balance of properties should
permit the design of future appliances which
deliver superior force systems with simplified
configuration

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