wires in ortho.ppt

ORTHODONTIC WIRES
BY JITHIN JACOB
www.dentistpro.org to find more

INDEX
 INTRODUCTION
 EVOLUTION OF ORTHODONTIC WIRES
 PROPERTIES OF ORTHODONTIC WIRES
 MANUFACTURING OF ORTHODONTIC WIRES
 WIRE ALLOYS
GOLD ALLOYS
STAINLESS STEEL WIRES
AUSTRALIAN ARCH WIRES
BRAIDED WIRES
Co-Cr NICKEL WIRES
TITANIUM
ALPHA TITANIUM WIRES
BETA TITANUM WIRES(TMA)
NICKEL TITANIUM ALOY
NITINOL
CHINESE NITI
JAPANESE NITI
Cu NITI
ESTHETIC WIRES
 CONCLUSION
 BIBLOGRAPHY

INTRODUCTION
 Orthodontic wires, which generate the biomechanical forces
communicated through brackets for tooth movement, are
central to the practice of the profession.
 Ideally arch wires are designed to move the teeth with light
continuous force. It is important that these forces do not
decrease rapidly. Also an ideal arch wire should have
certain properties like esthetics, biohostability, formability,
resilience etc. but the search of a arch wire which meets all
this requirements and is perfect is still not over and the
search continuous…..
 For not abusing the material and for designing the
appliance to its full potential the proper understanding of its
physical and mechanical properties is required. The aim of
this seminar is to provide this basic knowledge of
orthodontic wire characteristics.

 Evans (BJO 1990) divided the phases of
archwire development into five phases on the
basis of (a) Method of force delivery, (b)
Force/Deflection characteristics and (c) Material.
PHASE I
 Method of force delivery: Variation in
archwire dimension
 Force/Deflection characteristics: Linear
force/deflection ratio
 Material: Stainless steel, Gold
EVOLUTION OF ORTHODONTIC WIRES
(PHASES OF ARCHWIRE DEVELOPMENT)

PHASE II
archwire material but same dimension
 Force/Deflection characteristics: Linear
force/deflection characteristics
 Material: Beta Titanium, Nickel titanium,
Stainless steel, Cobalt chromium
PHASE III
archwire diameter
 Force/Deflection characteristics: Non-
linear force deflection characteristic due to
stress induced structural change
 Material: Superelastic Nickel Titanium

PHASE IV
 Method of force delivery: Variation in structural
composition of archwire material
 Force/Deflection characteristics: Non-linear
force/deflection characteristic dictated by thermally
induced structural change
 Material: Thermally activated Nickel titanium
PHASE V
 Method of force delivery: Variation in archwire
composition/structure
 Force/Deflection characteristics: Non-linear
force/deflection characteristics dictated by different
thermally induced structural changes in the sections of
the archwire
 Material: Graded, thermally activated nickel titanium

THE EARLY ARCHWIRES
 The scarcity of adequate dental materials at
the end of the nineteenth century launched
E.H. Angle on his quest for new sources
 Angle listed only a few materials as
appropriate work. These included strips or
wires of precious metal, wood, rubber,
vulcanite, piano wire, and silk thread.
 Before Angle began his search for new
materials, orthodontists made attachments
from noble metals and their alloys Gold (at
least 75%, to avoid discoloration), platinum,
iridium, and silver alloys were esthetically
pleasing and corrosion resistant, but they
lacked flexibility and tensile strength

 In 1887 Angle tried replacing noble metals with German
silver, a brass. His contemporary, J.N. Farrar,
condemned the use of the new alloy, showing that it
discolored in the mouth, Farrar’s opinion was shared by
many
 To obtain the desired properties, Angle acted, as stated
in 1888, “by varying the proportion of Cu, Ni and Zn”
around the average composition of the Neusilber brass
(German silver, 65%Cu, 14%Ni,21%Zn), as well as by
applying cold working operations at various degrees of
plastic deformation.
 Besides its “unsightliness” and obvious lack of
reproducibility (variations in composition and
processing), the mechanical and chemical properties of
German silver were well below modern demands.
However, because it could be readily soldered, this
brass allowed Angle to design more complex appliances.

 The material that was to truly displace noble
metals was stainless steel. As with German
silver, it had its opponents. As late as 1934
Emil Herbst held that gold was stronger than
stainless steel without exfoliation. If forced to
choose, he even preferred German silver to
stainless steel. Eventually, better
manufacturing procedures and quality control
made stainless steel the material of choice.

DESIRABLE PROPERTIES OF
ORTHODONTIC WIRES:
 The ideal properties for an orthodontic purpose according to Proffit5 are:
1. High strength.
2. Low stiffness.
3. High range.
4. High formability.
 Kusy11 (1997) in a review of contemporary arch wires listed a few ideal
characteristics desired in an archwire as follows:
1. Esthetics
2. Stiffness
3. Strength
4. Range
5. Springback
6. Formability
7. Resiliency (Resilience)
8. Coefficient of friction
9. Biohostability
10. Biocompatibility
11. Weldability

PROPERTIES
OF
ORTHODONTIC ARCH WIRES
 Strength
-Proportional limit
-Yield strength
-Ultimate tensile strength
 Stiffness
 Range
 Resilience
 Formability

There are three points on a force-deflection curve that
represent strength. Studying materials using a graph is
very helpful because
"a picture is worth a thousand words."

Strength:
 Strength is the measure of the force a material can
withstand before the material permanently deforms. (is the
maximal stress required to fracture a structure)Strength may be
viewed in these three ways:
1. Proportional Limit: the point at which any permanent
deformation first occurs.
2. Yield Strength: the point at which 0.1% deformation is
measured.
3. Ultimate Tensile Strength: the maximum load that the
wire can sustain.
 strength is in units of force

Stiffness:
 Stiffness is proportional to the slope
of the linear portion of the graph of
the force-deflection curve of a
material. The linear portion ranges
from zero to the proportional limit.
The steeper the slope, the stiffer the
material. (defined as the ratio of
force to deflection of a member)

Range:
 Range(flexibility) is the deflection the material
will encounter before any permanent deformation
occurs - from zero to the proportional limit.
Beyond the proportional limit, the material will
bend, but it will not return to its original shape.
There is, however, a limit to the amount of
bending beyond the proportional limit to which
you can bend a material - the failure point is
were it breaks (Range is defined as the distance the wire will bend
elastically before deformation occurs, and is measured in millimeters)
 range is in units of length

Internal stresses and external strains are characteristics of a material
that can be calculated from the force-deflection curve. This relationship
explains the similarity in the shapes of the force-deflection and stress-
strain curves. The slope of the stress-strain curve is the elastic
modulus (E) and is proportional to the stiffness.

Resilience
 Resilience is the area under the
curve out to the proportional limit.
 Resilience represents the energy
capacity of the material that is a
combination of the strength and
stiffness

Formability:
 Formability is the amount of permanent
deformation that a material can withstand
before breaking.
(It represents total amount of permanent
bending a wire will tolerate before it
breaks)
 It is represented by the area under the
curve between yield stress and tensile
strength.

Bauschinger Effect as described by A.J.
Wilcock:
 This phenomenon was discovered by Dr. Bauschinger in
1886 (Mugharabi 1987). He observed the relationship
between permanent deformation and loss of yield strength
and found that if the metal was permanently deformed in
one direction then, it reduced its yield strength in the
opposite direction. If a straight wire of wire is bent so that
permanent deformation occurs and an attempt is made to
increase the magnitude, bending in the same direction as
had originally be done, the wire is more resistant to
permanent deformation than if an attempt had been made
to bend in the opposite direction. The wire is more resistant
to permanent deformation because a certain residual stress
remains in it, after placement of first bend. A flexibly
member will not deform as easily if it is activated in the
same direction as the original bends were made to form the
configuration. If a bend is made in an orthodontic appliance
the maximum elastic load is not the same in all direction: it
is greatest in the direction identical to the original direction
of bending or twisting. The phenomenon responsible for
this difference is known as Bauschinger Effect.

Two noteworthy points about this effect are:
1. Plastic prestrain increases the elastic limit of deformation in
the same direction as the prestrain.
2. Plastic prestrain decreases the elastic limit of
deformation in the direction reverse to prestrain. If the
magnitude of prestrain is increased, the elastic limit in the
reverse direction can reduce to zero.
Dr. Bauschinger said that plastic deformation in the absence
of dislocation locking will not achieve as high a yield point.
Furthermore if the material is subjected to reverse straining
it will posses an even lower yield point in the reverse
direction.
This effect can be used to advantage after wire bending
because of the residual stresses left in the material,
improving its elastic properties in the direction to which the
wire has been deformed.

MANUFCTURING OF ORTHODONTIC
WIRES

Manufacture: AISI ,specially for orthodontic
purposes
Various steps –
1. Melting
2. Ingot Formation
3. Rolling
4. Drawing

 Melting : The selection and melting of the components
of alloys influence the physical properties of metals.
 Ingot formation : An ingot is produced by the
pouring of molten alloy into a mold. It is one of the
critical operations.
 Rolling : It is the first mechanical step in the
manufacture of a wire from the ingot. The ingot is rolled
into a long bar by a series of rollers that gradually
reduce it to a relatively small diameter.
 Drawing : It is a more precise process by which the
ingot is reduced to its final size. The wire is pulled
through a small hole in a die. The size of the hole is
slightly smaller than the starting diameter of the wire,
in order to facilitate uniform squeezing of the wire from
all sides by the walls of the die as it passes through,
reducing the wire to the diameter of the die.

PROCESS OF MANUFACTURE:
 Spinner Straightening:
It is the mechanical process of straightening resistant materials,
usually in the cold drawn condition. The wire is pulled through rotating
bronze rollers that torsionally twist it into straight condition
 Pulse Straightening:
It was founded by Mr. A.J. Wilcock. The wire is pulsed in special machines
that permit high tensile wires to be straightened.
 Stress Relief Of Stainless Steel
One of the steps in manufacture or at the time of clinical application is
“Stress Relieving” . It is a level of heat treatment at which internal
stresses are relieved by minute slippages and readjustments in
intergranular relations without the loss of hardening that accompanies the
higher temperature process of annealing.
 Work Hardening / Strain Hardening
In a polycrystalline metal there is a build up of dislocations at the grain
boundaries and occurs on intersecting slip planes. Later point defect
increases and entire grain gets distorted leading to increased stress
required to cause further slip, leading to stronger, harder and less ductile
metal with less resistance to tarnish and corrosion.

 Cold Working
It is the process of deforming a metal at room temperature.
 Annealing
It is the process in which the effects associated with cold
working (for example: strain hardening, lowered ductility and
distorted grains) can be reversed by simply heating the metal.
Annealing generally comprises of 3 stages:
Recovery
Recrystallization
Grain growth
 Tempering:
It is the process of reheating steel to intermediate temperature
ranges (usually below 1000°F [525 °C] under carefully
controlled conditions to permit a partial transformation into
softer forms. This is done to remedy steel which when quenched
in water results in very brittle martensite that is unsuitable for
most mechanical applications.

Forms of Steel
 At high temperatures (more than 1400 to 1500°F / 750 to
800°C) steel is a homogenous material with all of the
carbon in solid solution in the iron. At this temperature, the
iron carbide is completely decomposed. This form of steel is
called "Austenite".
 At low temperatures (less than 450°F / 225°C), an almost
pure cementite, the hardest and most brittle form of iron-
carbon combination called "Martensite" is formed.
 Between these high and low extremes of temperature many
intermediate phases are formed. These are various
mixtures of ferrite and cementite, with crystal structures
tending toward hardness in the low temperature ranges and
toward softness and ductility at higher temperatures.

GOLD ALLOYS
 Their composition is very similar to
the Type IV gold casting alloys. The
typical composition of the alloy is as
follows-
 Gold – 15 – 65% (55-65% more
typical)
 Copper – 11 – 18%
 Silver – 10 – 25%
 Nickel – 5 – 10%

 The alloys contain quite a high amount
about (20 – 25%) of palladium.
Platinum is also present and in presence
of palladium, it raises the melting point
of the alloys, and makes it corrosion
resistant.
 Copper incorporates strength to the
wire. They acquire additional
strengthening through cold working,
which is incorporated during the wire
drawing process

 This combination of properties makes
gold very formable and capable of
delivering lower forces than stainless
steel. These wires are easily joined by
soldering and the joints are very
corrosion resistant.
 The gold wires are not used anymore in
orthodontics mainly because of their
low yield strength and increasing cost
has made its use prohibitive.

HEAT TREATMENT OF GOLD WIRE
 The changes that are produced in the
strength and ductility of a wrought gold
alloy by heat treatment are due to the
alterations in the gold-copper compound
present in the alloy.
 In order to uniformly soften most wrought
gold wire it is heated to 1300° F. for
approximately 10 minutes and then
quenched

 The wire is very soft and ductile and
may be easily manipulated
 If left standing at room temperature
for several days, will become much
harder. This phenomenon is known as
“age-hardening” or “precipitation-
hardening”.

 Other method: If, after quenching from
1300° F. The wire is reheated to
approximately 840° F. and allowed to
cool slowly from this temperature, the
gold-copper compound tends to come
out of solution.
 By not using heat treatment procedures
the orthodontist is not obtaining the
maximum properties from this alloys.

 Besides precipitation hardening
there are two other ways by which
the strength of wrought gold wire
may be increased. One of these
methods is cold working. The
other method is to vary the
composition of the alloy
constituents.

STAINLESS STEEL
 Stainless Steel is defined as a alloy of iron
that is resistant to corrosion. It was
discovered accidentally in U.K. during
second world was by a Sheffield
metallurgist BREARLEY. It was patented
in 1917.
 Later chromium was added to it so that it
gets a protective coating of chromium
oxide on it, hence improving the corrosion
resistantance.

Types of stainless steels
 FERRITIC STAINLESS STEEL (AISI series 400) It has good corrosion
resistance, is cheaply made. Disadvantage of this type of stainless steel
is that it is not hard nor can it be hardened.
 MARTENSITIC STAINLESS STEEL: (AISI series 400) Alloys in the 400
series contain little or no Nickel and are primarily alloys of Iron and
Chromium. They can be heat treated much the same as carbon steel to
form martensite at room temperature. The low resistance to fracture
and high corrosion resistance of these alloys render them useful in the
construction of orthodontic instruments. They are used in making
surgical and cutting instruments. The disadvantage in such type of steel
is its brittle nature.
 AUSTENITIC STAINLESS STEELS (AISI series 302 & 304) They contain
Iron, Chromium 18%, Nickel 8% and 0.15% Carbon. The Nickel content
has a stabilizing effect on austenite only at high temperatures, but in
the Chromium-Nickel steels, the austenite is stable even at room
temperature. Hence these alloys are called "Austenitic stainless steel".
Presence of Chromium in the alloy provides the austenite with the
necessary strength and high resistance to corrosion. Types 302 and 304
are commonly used in orthodontic appliances. They contain about 18%
chromium and 8% Nickel and hence constitute the 18-8 group of
stainless steels.

The austenitic stainless steel, because of the presence of
austenite, cannot be hardened by quenching or similar heat
treatment. The only way to harden such steels is by "cold
working". Under cold working, the austenitic stainless
steels harden rapidly with the usual realignment of the
crystalline structure. Work hardening also brings about
some transformation of part of the austenite to martensite,
which adds to the hardening effect.
The advantages of austenitic stainless steel are:
1. Most corrosion resistant form.
2. Greater ductility.
3. Strengthening during cold working.
4. Ease of welding.
5. Readily overcome sensitization.
6. Less critical grain growth.
7. Ease of forming.

SENSITIZATION
 The 18-8 stainless steels may lose its
resistance to corrosion if it is heated
between 400-9000 C due to
precipitation of chromium carbide at
the grain boundaries

Overcoming Sensitization
 Reduce the carbon content
 Cold working
 STABILIZATION: Addition of
Titanium

HEAT TREATMENT OF STAINLESS
STEEL
Done(400-500degree C) to
 Eliminate some residual stress
resulting from wire manufacturing
and to
 Prevent premature breakage of
complex appliances during assemly.

 Kemler: 700-8000F for 5-15
minutes
 Backofen and Gales: 750-8200F for
10 minutes
 Funk: 8500F for 3 minutes

Properties:
 The modulus of elasticity ranges
from 23 X 106 to 24X106 psi. The
wires have a very high yield
strength of 50,000-280,000 psi.
 This wire is strong, has excellent
formability, adequate springback,
offers low frictional resistance, can
be soldered, has good corrosion
resistance & moderate cost.

 By The 50’s Rocky Mountain
Orthodontics offered two tempers
of cold worked stainless steels:
Standard and extra hard grade
 Today American Orthodontics
advertises three grades of
stainless steel wires:
Standard,
Gold Tone,
Super Gold Tone

AUSTRALIAN ARCHWIRES
 Developed by Mr. A. J. Wilcock & Dr.
P. R. Begg
 Acquaintance goes back to the war
years at the University of Melbourne.
 Dr. Begg demanded a wire that
remained active in the mouth for
long periods.
 High Tensile wires were developed

 Difficulties faced with high
tensile wires(1970s):
 Impossible to straighten.
 Work softening
 Breakage of wire

OVERCOMING THE DIFFICULTIES
 Old method - Spinner
straightening: Yield stress
decreases due to Bauschinger
effect
 New method - Pulse
straightening(1980s) : No plastic
deformation whatsoever.

Advantages of Pulse
straightening
 Permits the highest tensile wire to
be straightened, previously not
possible.
 The material tensile yield stress is
not suppressed in any way.
 The wire has a much smoother
appearance and hence less bracket
friction.

Mr. Wilcock, Jr.’s recommendations to
decrease breakage:
 Use the flat beak
 Round the edges of the pliers
 Warm the wire

Grades of wire available
The wires are marked in various sizes and grades ranging
from 0.008” to 0.002” and regular to supreme grade.
Regular with white label
Regular plus with green label
 Special grade with black label
 Special plus with orange label
 Extra special plus (ESP) with blue label
 Premium with blue label
 Premium plus
 Supreme with blue label
Regular grade is the least resilient and premium grade is
the most resilient of all the wires

Properties
 The ultimate tensile strength for
pulse-straightened wires is 8-12%
higher than stainless steel wires.
 The load-deflection rate is higher
 The pulse-straightened wires have a
significantly higher working range
and recovery patterns.
 Frictional resistance of the pulse-
straightened wires is lesser

Zero Stress Relaxation
 This is the ability of a wire to deliver
a constant light elastic force when
subjected to an external force or
forces of occlusion.
 This indicates that the wire should
have a very high and sharp yield
point with low elongation.
 This is probably in the region of
‘special plus’ and above

 The stiffness of an archwire can be
varied in three ways.
 The first and traditional approach has
been to vary the dimensions of the
wire. Small changes in dimensions can
result in large variations in stiffness.The
difference between .016” and .014”
diameter is approximately 40%.
 The second approach to vary the elastic
modulus E. That is, use various
archwire materials such as Nitinol ,
Beta-Titanium, Gold alloys and stainless
steel.
BRAIDED WIRES

 A third approach, which is really an extension
of the second, is to build up a strand of
stainless steel wire, for example, a core wire
of .0065” and six .0055” wrap, wires will
produce an overall diameter approximately
.0165 inches. The reason why the strand has a
more flexible feel is due to the contact slip
between adjacent wrap wires and the core
wire of the stand.(COAXIAL WIRES)
 When the strand is deflected the wrap wires,
which are both under tension, and torsion will
slip with respect to the core wire and each
other. Providing there is only elastic
deformation each wire should return to its
original position.

 Kusy and Dilley noted that the stiffness of a triple
stranded 0175” ( 3 X 008”) stainless steel arch wire
was similar to that of 0.010” single stranded
stainless steel arch wire. The multistranded
archwire was also 25% stronger than the .010”
stainless steel wire.
 The .0175” triple stranded wire and .016” Nitinol
demonstrated a similar stiffness. However nitinol
tolerated 50% greater activation than the
multistranded wire.
 The triple stranded wire was also half as stiff as
.016” beta-titanium.
 Multistranded wire can be used as a substitute to
the newer alloy wire considering the cost of nickel
titanium wire.

COBALT-CHROMIUM-NICKEL
ALLOY
 Initially it was manufactured for watch springs
by Elgin Watch Company, hence the name
Elgiloy.
CONTENTS
 40% Cobalt
 20% Chromium
 15% Nickel
 7% Molybdenum
 2% Manganese
 0.15% Carbon
 0.4% Beryllium
 15% Iron.

Types of Elgiloy
Available in four tempers (levels of resilience)
 Blue Elgiloy(soft) – can be bent
easily with fingers and pliers.
 Yellow Elgiloy(ductile) – Relatively
ductile and more resilient than blue
Elgiloy.
 Green Elgiloy(semi-resilient) – More
resilient than yellow Elgiloy
 Red Elgiloy(resilient) -Most resilient
of Elgiloy wires

 All four alloy tempers have the same
composition. (last three tempers have mechanical
properties similar to less expensive SS wires)
 Differences in mechanical properties arise from
variations in the wire processing.
 As with SS alloys, the corrosion resistance of
Elgiloy arises from a thin passivating chromium
oxide layer on the wire surface.
 Popular because the as-received wire can easily
be manipulated into desired shapes and then
heat treated to achieve considerable increases in
strength and resilience.

HEAT TREATMENT
 The ideal temperature for heat
treatment is 900°F or 482°C for 7-12
min in a dental furnace.
 This causes precipitation hardening
of the alloy increasing the resistance
of the wire to deformation.

Disadvantages
 Greater degree of work hardening
 High temperatures (above 1200°F)
cause annealing
Advantages
 Greater resistance to fatigue and
distortion
 Longer function as a resilient
spring
 High moduli of elasticity

Comparison with stainless steel
 Values of modulus of elasticity (elastic
force delivery) for the Elgiloy Blue and SS
orthodontic wires are very similar
 Force delivery and joining characteristics
are similar.
 Contain comparable amount of nickel to
that found in the SS wires, which may
present concerns about biocompatibility.

Clinical application
 Elgiloy Blue wires is used for
fabrication of the fixed lingual quad-
helix appliance, which produces slow
maxillary expansion for the
treatment of maxillary constriction or
crossbite in the primary and mixed
dentitions.

ALPHA TITANIUM
Pure titanium:
 Below 885° C - hexagonal closed
packed or alpha lattice is stable
 At higher temperature the metal
rearranges into body centered cubic
or beta crystal.
 HCP- possesses fewer slip planes

 Gets hardened by absorbing
intraoral free hydrogen ions, which
turn it into titanium hydride, at the
oral temperature of 37°C and
100% humidity.
 Any modifications if required
should be done within six weeks
(Mollenhauer)

BETA TITANIUM
(TITANIUM MOLYBDENUM ALLOY OR T.M.A.)
 Introduced by Dr. Burstone (1980)
Composition
80% Titanium
11.5% Molybdenum
6% Zirconium
4.5% Tin

Advantages of TMA v/s Nitinol
 Smoother
 Can be welded
 Good formability
Advantages of TMA v/s S.S.
 Gentler forces
 More range
 Higher springback
 Drawback: High coefficient of
friction

Low friction TMA:
 Introduced by Ormco
 Done by ion implantation beam
mechanism
TMA Colours:
 Also developed by Ormco
 Implantation of oxygen and
nitrogen ions
 Ensures colour fastness

Welding of TMA wire
 POSITIONING
- Set down of 80%
- 25 - 60 % recommended
Broad, flat electrodes One wire"set down" into the other.

Welding of TMA wire
Below optimal - low strength, separation of
wire
Optimal welding - good ductility strength
atleast 90% of unweld wire
Higher than optimal - good strength, low ductility
High voltage - Wire become brittle
Complete burnout

Welding of TMA wire
Round wires - Simple to weld.
- Require lower voltages
 SMALLER CONTACT AREA
- Low voltage
- Point contact
- ‘T’ joint
 SINGLE PULSE
- Short duration.
TMA wire can be welded to TMA wire
Not possible to weld TMA to SS

Welding of TMA wire
Improper Welding
Low voltage - The parts may
delaminate
High voltage - Wire become brittle
Cracks
Melting

NICKEL-TITANIUM ALLOYS
 CONVENTIONAL - NITINOL
 SUPERELASTIC
 Pseudoelastic-Japanese NiTi
 Thermo elastic-Cu NiTi.

2 forms of NiTi alloys
1. Martensite – Face centered (close
packed hexagonal).
2. Austenite – Body centered
cubic/tetragonal lattice.

NICKEL-TITANIUM
HYSTERESIS
• The transformation at different
temperatures.
• The difference between cooling and
heating.
• The range for most binary alloys is 400
– 600

NITINOL
 Was invented in early 60’s by William F. Buchler,
a researcher metallurgist of the Naval Ordinance
Laboratory in Silver Springs, Maryland
 The name Nitinol is given for NI for nickel, TI for
titanium and NOL for Naval Ordinance
Laboratory.
 It was initially developed for space programs but
was first introduced into dentistry by Unitek
cooperation in 1970’s .
 Clinical use of Nitinol wire started in May 1972 by
G.F.ANDREASEN et al.

NITINOL
NiTi wires have two remarkable properties which makes its
use in dentistry:
SHAPE MEMORY
 The characteristic of being able to return to a previously
manufactured shape when it is heated to a TTR.
 Ability of the material to remember its original shape after being
plastically deformed while in the martensitic form.
Superelasticity:
Superelasticity means the ability of the wire to exert the same
force whether it is deflected a relatively small or a large
distance. This can be produced by stress, not by temperature
difference and is called stress induced martensitic
transformation.

NITINOL
In orthodontic applications
1. Requires fewer arch wire changes.
2. Requires less chair time.
3. Shortens the time required to accomplish the
rotations and leveling
4. Produces less patient discomfort.

NITINOL
PHYSICAL PROPERTIES
Material
property
Nitinol Stainless
steel
Alloy Nickel, Titanium Iron,
Chrome,Nickel
Ultimate strength 230,000 to
250,000 p.s.i
280,000 to
300,000 p.s.i
Modulus of
elasticity
4.8 x106 p.s.i 28.5 x 106 p.s.i

NITINOL
STORED ENERGY COMPARISONS
Stored energy of Nitinol wire is significantly
greater than an equivalent SS wire.this
comparison was based upon the wires being
bent 90 degrees

NITINOL
CLINICAL APPLICATIONS
Class I ,II,III malocclusions in both
extraction and non extraction cases

NITINOL
 Primary criterion – Amount of malalignment
from the ideal arch form.
 More the deflection – more the benefit.

NITINOL
 Imp benefits - a rectangular wire is inserted
early in the treatment.
 Simultaneous rotation, leveling, tipping and
torquing can be accomplished earlier with a
resilient rectangular wire,
Cross bite correction
Uprighting impacted canines
Opening the bite

NITINOL LIMITATIONS
1.Can`t be bent with sharp – cornered
instruments.
2.It will readily break when bent over a sharp
edge.
3.The bending of loops or omega bends are
not recommended. ( especially closing
loops ).
4.Can`t be soldered or welded to itself
without annealing the wire.

5. Bending of tie-back hooks entails a high risk
of failure.
6. Cinch – backs.
- Annealing - Dark blue color flame.
- Cherry red flame – brittle.

Phase - Transformation
 AUSTENITE PHASE
 MARTENSITE PHASE
 Martensite start(MS)
 Martensite finish(MF)
 Austenite start(AS)
 Austenite finish(AF)

 SUPERELASTIC
 Chinese NiTi
 Pseudoelastic-Japanese NiTi
 Thermo elastic-Cu NiTi.

CHINESE NITI WIRE
 CHINESE NiTi wire - A new orthodontic wire
- C. J. BURSTONE ( AJO
JUNE 1985)
 New NiTi by Dr.Tien Hua Cheng and
associates at the General Research Institute
for non Ferrous Metals, in Beijing, China.
 Austenitic parent phase + Little work
hardened
 Chinese NiTi wire has much lower transitional
temperature than NiTi wire.

CHINESE NITI WIRE
1. Applicable in situations where large
deflections are required.
2. When tooth are badly malpositoned.
3. Niti wire deformation is not time
dependent
CLINICAL SIGNIFICANCE

JAPANESE NITI
The super - elastic property of the Japanese
NiTi alloy wire for use in orthodontics.
- Fujio Miura
et al ( AJODO July 1986 )
In 1978 Furukawa electric co.ltd of Japan
produced a new type of alloy
1. High spring back.
2. Shape memory.
3. Super elasticity.

CLINICAL IMPLICATIONS
 Alignment of badly malposed
teeth
 Distalize the molar
 Expansion of arch
 Gain/Close the space
 Periodontally compromised pts

CLINICAL APPLICATIONS
INITIAL
TWO MONTHS LATER

COPPER NiTi
• Introduced by Rohit sachdeva
• It has the advantage of generating
more constant forces than any other
super elastic nickel titanium alloys.
• More resistant to deformation

QUATERNARY METAL –
Nickel, Titanium, Copper, Chromium.
Copper enhances thermal reactive
properties and creates a consistent
unloading force.

COPPER NiTi
VARIABLE TRANSFORMATION
TEMPERATURE ORTHODONTICS
-
ROHIT C. L. SACHDEVA.

COPPER NiTi
CLASSIFICATION
 Type I Af – 150 c
 Type II Af - 270 c-MOUTH BREATHERS
 Type III Af - 350c-
 Type IV Af - 400c-ONLY AFTER
CONSUMING HOT FOOD AND BEVERAGES

COPPER NiTi
ADVANTAGES OF COPPER NiTi ALLOYS
OVER OTHER NiTi WIRES
- Smaller loading force for the same degree
of deformation. (20% less )
- Reduced hysteresis makes to exert
consistent tooth movement and reduced
trauma.

Clinical Applications
 Provides 3 dimensional control
 Effective in surgical orthodontic cases
 Eliminates need to change arch wires
frequently
DISADVANTAGES
 Bracket friction will be more when large wires
are used
ADVANTAGES

ESTHETIC ARCHWIRES
 Composites: can be composed of
ceramic fibers that are embedded
in a linear or cross-linked
polymeric matrix.
 Developed by a process known as
pultrusion

A prototype (reported by Kusy) shows the following
characteristics:
 Tooth coloured
 Adequate strength
 Variable stiffness
 Resilience and springback comparable to Niti
 Low friction (beta staging)
 Enhanced biocompatibility (beta staging)
(Formability, weldability are unknown)

OPTIFLEX
Made of clear optical fibre; comprises of three
layers:
1. A silicon dioxide core
2. A silicon resin middle layer
3. A stain resistant nylon outer layer
Silicon
Dioxide Core Nylon Outer Layer
Silicon
resin
Middle
Layer

Properties
 The most esthetic orthodontic arch
wire to date.
 Completely stain resistant
 Exerts light continuous forces
 Very flexible

Precautions to be taken with
Optiflex
 Use elastomeric ligatures.
 No Sharp bends
 Avoid using instruments with sharp edges,
like the scalers etc., to force the wire into
the bracket slot.
 Use the (501) mini distal end cutter (AEZ)
 No rough diet
 Do not “cinch Back”

Other esthetic archwires
 E.T.E. coated Nickel Titanium: E.T.E.
is an abbreviation for ELASTOMERIC
POLY TETRA FLORETHYLENE
EMULSION
 Stainless steel or Nickel titanium
arch wire bonded to a tooth coloured
EPOXY coating

Cross-section
1970s: Only S.S.;
varying the cross-sectional diameter)
v/s
Modulus
(1980s: S.S., Niti, B-Ti; varying the
elastic modulus)
v/s
Transition temperature
(1990s: Cu Niti; Varying TTR/Af)

PROPERTY SS ELGILOY TMA NiTi
Cost Low Low High High
Force
Delivery
High High Intermediate Light
Springback Low Low Intermediate High
Formability Excellent Excellent Excellent Poor
Ease of
joining
Must be
reinforced
with solder
Must be
reinforced
with
solder
Weldable Cannot be
soldered or
welded
Friction Lower Lower Higher Higher
Biocompati
bility
Concern Concern Excellent Concern

Wire
alloy
Composition
(Wt%)
Modulus
of
elasticity
(Gpa)
Yield
strength
(MPa)
Springback
Austenit
ic
SS
17-20%Cr ,8-
12%Ni
0.15%C(max)
Rest-Fe
160-
180
1100-
1500
0.0060-0.0094
Ar
0.0065-0.0099
Ht
Co-Cr-
Ni
(Elgiloy
-Blue)
40%Co, 20%Cr
15%-Ni,
15.8%Fe, 7%Mo,
2%Mn 0.15%C,
0.04%Be
160-
190
830-
1000
0.0045-0.0065
Ar
0.0054-0.0074
Ht
β-
titanium
(TMA)
77.8%Ti,
11.3%Mo, 6.6%Zr,
4.3%Sn
62-69 690-970 0.0094-0.011
NiTi 55%Ni, 45% Ti
(Approx)-& may
contain small
amounts of Cu
34 210-410 0.0058-0.016

IN SEARCH OF THE IDEAL
ARCHWIRE..by Kusy

CONCLUSION
 It can be seen that there is not a single arch wire
that meets all the requirements of the
orthodontist. We still have a long way to go, in
terms of finding the ‘ideal’ archwire. But, with
such rapid progress being made in science and
technology, I am sure that we will see significant
improvements in arch wires in the near future.
 Also, we must consider ourselves fortunate to
have such a wide array of materials to choose
from. Just imagine working with just a single
type of Gold alloy wire, like they used to not so
long ago. So we should appreciate this fact and
try to make the most of what we have.

THANK YOU

LIST OF REFERENCES
 Applied Dental Materials: John F. Mc Cabe 7th Edition 1990
Blackwell Scientific Publication. Pg. 69.
 The Clinical handling of Dental Materials: Bernard G.N. Smith,
Paul S. Wright, David Brown. WRIGHT Publications, 2nd
Edition, 1994; Pg. 195-199.
 Howe G.L. Greener E.H., Crimmins D.S.: Mechanical
properties and stress relief of stainless steel orthodontic wire.
AO 1968; 38: 244-249.
 Andreasen G. Heilman H., Krell D.: Stiffness changes in
thermodynamic NiTinol with increasing temperature AO 1985;
55:120-126.
 Edie J.W.: Andreasen G.F., Zaytoun M.P.: Surface corrosion of
Nitinol and stainless steel under clinical conditions AO 1981;
51:319-324.
 Miura F, Mogi M. Yoshiaki O: Japanese NiTi alloy wire use of
electric heat resistance treatment method EJO 198; 10; 187-
191.
 Andreasen G.F., Murrow R.E. : Laboratory and clinical
analyses of nitinol wire AJODO 1978; 73: 142-151.
 Evans T.J.W, Durning P: Orthodontic Product update –
Aligning archwires, the shape of things to come? – A fourth
and fifth phase of force delivery. BJO 1996; 23:269-275.
 Kusy R.P. : A review of contemporary archwires-Their
properties and characteristics AO 1997; 67: 197-207.

 Wilcock A.J., Jr. : Applied materials engineering for
orthodontic wires. Aust. Jor. Orthod. 1989; V:22-29.
 Burstone C.J. Bai Q., Morton J.Y. : Chinese NiTi Wire – A
new orthodontic alloy AJODO 1985; 87; 445-452.
 Fillmore G.M., Tomlinson J.L.: Heat treatment of Cobalt
chromium alloys of various tempers AO : 1979; 49:
126-130.
 Kohl R.W. : Metallurgy in orthodontics. AO 1964; 34:
37-42.
 Waters N.E.: Orthodontic product update-Super elastic
Nickel-Titanium wires. BJO 1992; 19: 319-322.
 Andreasen G.G., Hilleman T.B.: An evaluation of 55
Cobalt substituted NiTinol wire for the use in
orthodontics. JADA 1971; 82: 1373-1375.
 Beckoten W.A., Gales G.F.: Heat treated stainless steel
for orthodontics. AJODO 1952; 38: 755-765.
 Wilcock A..J., Jr: JCO Interview, JCO 1988; 22: 484-
489.
 Burstone C.J., Goldberg A.J.: Beta Titanium. A new
orthodontic alloy. AJODO 1980; 77; 121 –132.
 Kapilla S., Sachdeva R: Mechanical properties and
clinical applications of orthdontic wires.

 Miura F, Mogi M., Ohura Y and Humanaka H: The super-
elastic property of Japanese NiTi alloy wire for use in
orthodontics AJODO 1986; 90:1-10.
 Proffit W.R., Fields H.W Jr.: Contemporary orthodontics
– Mosby 3rd Edition 2000 Pg 326-334.
 Thurow R.C.: Edgewise orthodontics. The C.V.Mosby
Company 1982 4th Edition. Graber T.M., Vanarsdall R.L.
Jr: Orthodontics – Current principles and Techniques.
Mosby 1994 2nd Edition.
 Philips R.W.: Skinner’s Science of dental Materials Prism
Books Pvt. Ltd. 1991 – 9th Edition.
 Craig R.G. : Restorative dental materials. The C.V.
Mosby Co. 1989 8th Edition.
 Hudgine J.J.: The effect of long-term deflection on
permanent deformation of Nickel titanium archwires AO
1990: 283-293.
 Kusy R.P., Sterens L.E: Triple Stranded stainless steel
wires 1987: 18-32.
 Sachdeva R.C.L.: Orthdontics for the next millennium.
ORMCO Publishing.

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