Archwires in orthodontics

INTRODUCTION
EVOLUTION
IDEAL PROPERTIES
CLASSIFICATION
CLINICAL CONSIDERATIONS
ADVANCES IN ARCHWIRES

Over the last century material science has
made rapid progress
Not only have the materials but also the
philosophies have changed
Wires which had increased resilience and low
cost were favoured
Hence s.s prevailed over the noble metal alloys

The appliance philosophies and material
science progress is closely inter related
All the wires that were introduced and
newer ones have some very individualistic
and unique properties with them
In order to use newer wires its necessary
to know the material properties

Active
components of
fixed
appliances.
Inherent
capacity for
elastic storage
of applied
forces.
Bring about
tooth movement
through
medium of
bracket and
buccal tubes.
In the rational
selection of
wires-various
factors to be
considered

GOLD
Up until 1930’s the only orthodontic wires available were made of gold and
their alloys
1887-Angle tried replacing noble metals with german silver(neusilber)
They are esthetically pleasing
Excellent corrosion resisitance
Low proportional limit
The material that was to truly replace noble metals was stainless steel
With the rise in cost of gold Austenitic s.s began to displace gold

1940’s
Begg with wilcock introduced AUSTRALIAN STAINLESS STEEL
By 1960’s gold was universally abandoned in favour of S.S
1960’s
Cobalt-chromium alloys were introduced.
Their physical properties were very similar to s.s
Softer and more formable

1962
WILLIAM F.BUEHLER –Nitinol at Naval ordinance
laboratory, Maryland
ANDREASEN GEORGE F et al introduced Nitinol in
Orthodonitcs in 1971 through university of Lowa
The original alloy contained 55% Nickel and 45%
Titanium
Unitek company licensed the patent (1974) and offered a
stabilized martensitic alloy that doesn’t exhibit shape
memory effect under the name NITINOL

1977
Beta titanium was introduced to orthodontics by C.J
BURSTONE and JON GOLDBERG.
Modulus close to that of traditional gold
Good spring back
Good formability
Good weldability

1984
A.J WILCOCK jr. as per request of Dr.MALLENHAUER of
Melbourne Australia resulted in production of Ultra high
tensile s.s round wires—THE SUPREME GRADE
1985
BURSTONE reported an alloy,chineese NiTi developed by
Dr.TIENHUA CHENG and associates at the General Research
institute for nonferrous metals in Beijing China

1986
MIURA et al reported
JAPANESE NiTi
Developed at furukawa Electric
company limited Japan
Chinese and japanese NiTi are active
austenitic alloys that form stress induced
Martensite (SIM)

1988
A.J WILCOCK Jr—much harder,Alpha Titanium
1990
Neo-sentalloy introduced as true active martensitic alloy
1992
Optiflex arch wire— M.F TALASS
unique mechanical properties with high esthetic
appearance

1994
Copper NiTi –
Dr.ROHIT SACHDEVA
shows phase
transition
15⁰c,27 ⁰C,35⁰C,40⁰C
2000
Titanium Niobium--
DALSTRA et al
For tooth to tooth
finishing

EVANS(BJO 1990) divided the phases of arch wire
development into five phases on the basis of:
Method of force delivery
Force/deflection charecteristics
Material

Method of force
delivery:
• variation in arch
wire dimension
Force/Deflection:
• linear
force/deflection
charecteristics
Material :
• stainless
steel,Gold

Method of force
delivery:
•variation in arch
wire material but
same dimension
Force/Deflection:
•linear
force/deflection
charecteristics
Material :
•Beta
Titanium,Nickel
Titanium,Stainless
steel,Cobalt
chromium

Method of force
delivery:
• variation in arch
wire properties
Force/Deflection:
• Non-linear
force/deflection
charecteristics
due to stress
induced
structural
change
Material :
• super elastic
Nickel Titanium

Method of force
delivery:
• variation in
structural
composition of
arch wire
material
Force/Deflection:
• Non-linear
force/deflection
characteristics
dictated by
thermally
induced
structural
changes
Material :
• Thermally
activated nickel
Titanium

Method of force
delivery:
•variation in arch wire
composition/structure
Force/Deflection:
•Non-linear
force/deflection
characteristics dictated
by thermally induced
structural changes
Material :
•Graded,Thermally
activated nickel
Titanium

Basedon the materialconstituents
Metallic
Non metallic
Basedon the crosssection
Round
Round rectangular
Rectangular
coaxial
Twisted
woven

ROUND WIRES
 Initial and intermediate stages of treatment
to correct crowding,level the arch,close
spaces
SQUARE OR RECTANGULAR WIRES
 Final stages of treatment to position the
crown and root in the correct maxillary and
mandibular relationship

The arch wires used with standard edgewise
appliance and pre adjusted appliance were
round and rectangular stainless steel wires
Round wires were available in sizes
.014,.016,.018,.020
Rectangular wires were available in a number
of sizes with .018×.025,.019×.025 being
the most popular wires used with the .022
bracket slot

KUSSY(1997)
Esthetics
Low Stiffness
High Strength
High Range
Spring back
High formability
Resiliency
Coefficient of friction
Biocompatibility
weldability

STRESS
Internal distribution of load
STRESS= FORCE
UNIT AREA
 Expressed as pascal
 3 types

Internal distortion produced by the load
STRAIN= CHANGE IN DIMENSION
ORIGINAL DIMENSION
No unit of measurement
Dimensionless quantity

ELASTICITY
Ability of a stressed material
to return to original form.
ELASTIC LIMIT
Greatest stress to which a
material can be subjected,
such that it will return to its
original dimensions when the
forces are released

 Stress is proportional to strain within the
elastic limit

Greatest stress that is produced in a material
such that the stress is directly proportional to
strain
 SUPER ELASTIC A-NiTi WIRES EXCEPTION!!

 strength at which material begins to function
in a plastic manner.
 Limiting deviation of 0.1% from
proportionality of stress to strain.

 Maximum load the wire can sustain,before
breaking.

 The point at which the wire breaks.

 Relative stiffness or rigidity of a material
 Ratio of stress to strain within proportional
limit
 Measured by slope of elastic region

Independent of ductility of material and not
measure of strength
Its inherent property of a material and cannot
be altered by heat treatment or work hardening
This property is called as STRUCTURAL
INSENSITIVITY

Modulus of elasticity of
GOLD wire is 1/2 to 1/3
of stainless steel wire.
Modulus of elasticity of
NITINOL wire is 1/3 to
¼ of stainless steel wire.

 : LATERAL STRAIN
AXIAL STRAIN
 For an ideal isotropic material,ratio is 0.5

 Force required to bend or deform the
material over a definite distance
STIFFNESS=FORCE
DISTANCE
 Proportional to the slope of the linear
portion of curve

Capacity of a material
to resist a deforming
load without
exceeding limits of
plastic deformation.

Maximum amount of energy material
can absorb without undergoing
permanent deformation

Amount of permanent bending the wire will
tolerate before it breaks or fails.

Distance the wire will bend elastically
before permanent deformation occurs

STRENGTH = STIFNESS × RANGE
SPRINGINESS= 1
STIFFNESS
Factors that influence strength,stiffness,range
 Mechanical arrangement by which force is
applied to teeth,eg.bracket width,length of
arch wire,span and loops
 Form of the wire itself-size and shape of
cross section,alloy formula,hardness

STIFFNESS STRENGTH RANGE
α Modulus of
elasticity
α Resiliency α Elastic
limit
α 1/L3 α 1/length α L2
α d4 α d3 α 1/d
α 1/no. of coils ---- α n. of coils
α 1/coil diameter3 ---- α coil
diameter2

Ability to undergo large deflections without
permanent deformation.

Strain that occurs when material is stressed to its proportional
limit
Non specific term denotes ease of bending
Indicate low stiffness,strength,working range,brittleness
FLEXIBILITY = PROPORTIONAL LIMIT
MODULUS OF ELASTICITY

Amount of energy required to fracture a material
Measure of the resistance to fracture

Inability of a material to sustain plastic deformation before fracture occurs
Opposite of toughness

Repeated cyclic stress of magnitude
below the fracture point of wire can
result in fatigue.

Ability of the material to with stand permanent
deformation under a tensile load without
rupture.

Ability of a material to withstand permanent
deformation under a compressive load without
rupture

 Describes functional charecteristics of
orthodontic appliance
LDR = LOAD
DEFLECTION
 Dependant on length and diameter of wire

 For orthodontic spring—LOW LDR
 For retentive units---HIGH LDR

Cantilever beams
 Beams supported on only one end
Eg: finger spring
Supported beams
 Beams supported on both the ends
Eg:arch wire segment b/w two teeth

• If a force is applied to such a beam, its response
can be measured as the deflection produced by the
force
Force and deflection are external measurements.
Internal stress and strain can be calculated from
force and deflection by considering the area and
length of the beam.

GEOMETRY:SIZE AND SHAPE
CANTILEVER BEAMS
 In orthodontic applications, this is the type of
spring often used in removable appliances, in
which a wire extends from the plastic body of
the removable appliance as a finger spring.
 When a round wire is used as a finger spring,
doubling the diameter of the wire increases its
strength eight times

Doubling the diameter
decreases springiness by a
factor of 16 and decreases
range by a factor of two.
Doubling the diameter of
a cantilever beam makes it
8 times as strong, but it is
then only1/16 as springy
and has half the range.

more complex
Supporting both ends makes
the beam stronger and less
flexible.
The principle is the same as
with a cantilever beam: as the
beam size increases, strength
increases as a cubic function,
springiness decreases as a
fourth power function and
range decreases
proportionately

 Torsion is actual twisting that take place in
the material
 STRENGTH α size of wire
 Springiness α 1
size of wire
 RANGE α 1
size of wire

ROUND WIRES
 RANGE α 1
DIAMETER
 STIFFNESS depends on value called
MOMENT OF INERTIA, property of shape
that is used to predict deflection, bending
and stress in beams.
 STIFNESS α DIAMETER
4
 STRENGTH α DIAMETER
3

Width and thickness----vary independently
Width---dimension perpendicular to
direction of bending in plane of neutral axis
Thickness---dimensions in plane of bend

EFFECT OF WIDTH & THICKNESS ON RANGE
Range----- Width has no effect on range
Range α 1/Thickness
EFFECT OF WIDTH & THICKNESS ON STIFFNESS
stiffness α width
Stiffness α Thickness3
EFFECT OF WIDTH & THICKNESS ON STRENGTH
Strength α width
Strength α Thickness2

A supported beamlike arch wire is four times as springy if it can
slide over bracket if loosely tied rather than being tied tightly

Torsion is
actual
twisting that
take place in
the material
STRENGTH :
Length has
no effect
SPRINGINESS
α
LENGTH
RANGE
α
LENGTH

Metal is stretched along the
outside curvature and
compressed along the inside
curvature
Combination of tension and
compression that resists bending
and actually accomplishes energy
storage

Measure of bending effect at any specified point in
a beam, measured in units of force and distance

 Maximum bending moment in a cantilever is
at the supported end.
 In beam terminology the location of this
maximum bending moment is called
CRITICAL or DANGEROUS section.

 Part of beam that is niether elongated nor
compressed in bending
 Midway b/w outer and inner curved sides
 No longitudinal stress or Strain

Developed by Robert Kusy
Fixed charts that display mathemetical relation via
appropriately adjusted scales
Efficient method for comparing different wire
materials and sizes
Provide generalised comparison of S.S,M-NiTi and
beta titanium in bending and torsion

 1977—ADA specification number 32 was
published.
 Properties of orthodontic wires are commonly
determined by means of various laboratory
tests like
--BENDING TEST
--TORSION TEST

 Provides information on behaviour of wires
when subjected to 1st and 2nd order bends
METHOD
Bending couple is applied at one end of
the specimen where only rotation is
permitted; at the other end of test span
wire is held against fixed knife edge stop
--Angular deformation measured is rotation
of the shaft
--plot of applied couple versus angular
deformation is done

 Reflect wires characteristics in third order
direction

INGOT: initially the wire alloy is
cast in the form of an ingot
successive deformation stages
until cross section becomes
sufficiently small for wire
drawing
ROLLING: ingot is rolled into a
long bar.
This is done by series of rollers
gradually reduce the ingot to a
relatively small diameter

 Considerable work hardening of the alloy
occurs during rolling.
 It may fracture if rolling is continued beyond
this point
TO PREVENT THIS:
Rolling process is interrupted
Metal is ANNEALED by heating to suitably high
temperature

DRAWING
After rolling—wire is further reduced to its final size by drawing
Used to fabricate metal wiring and tubing.
Deformation accomplished by pulling the material through a die
by means of tensile force
Before reducing to orthodontic size, wire is drawn through
many series of dies and annealed several times along the way to
relieve work hardening

Rectangular cross section wires are fabricated from
round wires by rolling process using TURK’S HEAD which
contains series of rolls.
Rectangular and square wires have some degree of
rounding at corners ie.EDGE BEVEL

It becomes strain softened
Decreased yield strength due to Bauschinger effect
Resultant deformation
DISADVANTAGES
The wire is pulled through rotating bronze rollers that torsionally twist it into straight condition
Mechanical process of straightening resistant materials, usually in the cold drawn condition.
SPINNER STRAIGHTENING

Smoother appearance and hence less bracket friction
Yield strength is not suppressed
Permits high tensile wire to be straightened
ADVANTAGES
The wire is pulled in special machines that permit high tensile wires to be straightened
Found by A.J WILCOCK
PULSE STRAIGHTENING

 Greater flexibility
 Greater Resiliency
 Permits usage of small diameter wire
resulting in lighter and more constant force

Discovered by Dr. BAUSCHINGER in 1886
observed the relation ship between permanent deformation
and loss of yield strength
if the metal was permanently deformed in one direction then
it reduced its strength in opposite direction
The wire is more resistant to permanent deformation
because a certain residual stress remains in it,after
placement offirst bend

Hardness and spring properties depend almost entirely on
effects of work hardening during manufacture
If metal is almost in need of another annealing at its final
size—it will have maximum work hardening and spring
properties
If drawing is carried too far enough after last annealing—wire
will be brittle
If drawing is not carried far enough after last annealing—too
much residual softness and very low working range and
strength

Move freely within the brackets.
At least 2 mil clearance between the archwire and
the bracket is needed
4 mil clearance is desirable
Tightly fit rectangular, the position of the root apex
could be affected, normally should be avoided.

• Dental arch form varies among individuals
• Basic principle - the patient's original arch form
should be preserved
CATENARY CURVE
 It was first described by MacConaill who
suggested that normal human dental
arches conform closely to a catenary curve
 For all patients, the fit is not as good

 1972--BRADER
 Based on a trifocal ellipse.
• The anterior segment closely approximates
the anterior segment of a catenary curve
• Gradually constricts posteriorly
• More closely approximate the normal position
of the second and third molars.

 SPRING BACK
 LOAD DEFLECTION RATE
 FORMABILITY
 MODULUS OF RESILIENCE
 BIOCOMPATIBILITY AND ENVIORNMENTAL
STABILITY
 JOINABILITY
 FRICTION

 WILLIAM R PROFFIT,5TH EDITION
 GRABER,VANARSDALL
 PHILLIPS SCIENCE OF DENTAL
MATERIALS,11TH EDITION
 GOOGLE

Similar to type IV gold casting alloys.
composition
Gold:15-65%
Copper:11-18%
Silver:10-25%
Nickel:5-10%
Palladium:20-25%

FUNCTIONS OF CONSTITUENTS
Copper provides strength
Platinum &palladium raises the melting point and makes it corrosion
resistant
Nickel strengthens the alloy
Zinc act as scavenger agent
MECHANICAL PROPERTIES
Yield strength ---360 mpa
Percent elongation ---3 – 16%
Modulus of elasticity ---15 × 106 p.s.i

SOFTENING HEAT heating at 700⁰ for
10 min
TREATMENT followed by
quenching
AGE HARDENING heating b/w 200
and 450⁰
TREATMENT for 15 to 30 min.
followed by
quenching

If heat treatment is not advocated, maximum properties of
the alloy cant be obtained
Other methods to
increase the
strength of gold
alloy
•By cold working
•Vary the composition
The actual mechanism of
hardening is as a result
of several solid state
transformations

ADVANTAGES
 Good formability
 capable of delivering low forces
 corrosion resistant
 Excellent stability and biocompatibility
DISADVANTAGES
 High cost
 Low spring back
USES
 Only crozat appliance is still occasionally made
from gold

• Following World War II, returning servicemen
complained that their Elgin watches couldn't
take the corrosive environmental situations in
various theatres of the war.
• Developed by Dr.ROBERT RICKETTS

After four years of research, "Elgiloy", a non-
corroding watch spring material with an infinite
life span, was born.
• Introduced into orthodontics because their
properties are excellent for orthodontic purposes.

Fatigue resistance—more cycles than stainless steel
Greater spring efficiency
Corrosion resistance
Non-magnetic
Available in different degrees or tempers
High formability

COMPOSITION
 COBALT 40 %
 CHROMIUM 20 %
 NICKEL 15 %
 MOLYBDENUM 7 %
 MANGANEESE 2 %
 CARBON 0.15 %
 BERYLLIUM 0.4 %
 IRON 15 %

• Available commercially as
• Elgiloy (Rocky Mountain Orthodontics),
• Azura (Ormco Corporation) and
• Multiphase (American Orthodontics).
• Elgiloy is manufactured in four tempers.
• Blue – soft.
• Yellow – ductile.
• Green –semi resilient
• Red-resilient

 Blue(soft)
 Softest –high formability.
Recommended when considerable bending
soldering or welding is required.
Heat treatment increases its resistance to
deformation.
 Yellow (Ductile)
 More resilient than blue Elgiloy.
 Good formability.
heat treatment increases its strength and
spring performance.

 Green (Semi resilient)
 More resilient than yellow
 can be shaped with pliers before heat
treatment.
 Red (Resilient)
 Most resilient with high spring qualities.
Withstands only minimal working.
 Fractures easily after heat treatment, all
adjustments should be made before this
precipitation hardening process.

 Finishing arches for post treatment provide
long term stability
 Five arch forms
 Delivered unheat-treated allowing complex
bends and loops to be easily made
After bending eligloy arches can be heat
treated to increase their springiness

 ROUND
.016
.018
 SQUARE
.016 × .016
.019 × .019
 RECTANGULAR
.016 × .022
.017 × .025
.018 × .025

MAXILLARY AND MANDIBULAR CUSPID
RETRACTOR
 Blue eligloy .016 × .016 ,unheat treated

Green eligloy heat treated
Applies continues torquing action to individual anterior
teeth
Placement ofarch wires in the bracket activates the
spring providing single contact with tooth surface

 0.38” blue eligloy
 Coil springs Red eligloy

 WILLIAM F BUEHLER in 1960’s invented
Nitinol
Ni—nickel
Ti—titanium
Nol—naval ordinance laboratory,U.S.A
 ANDREASEN G.F and coworkers introduced
the use of nickel titanium alloys for
orthodontic use in 1970

55% nickel,45 % titanium resulting in a
stochiometric ratio of these elements
1.6% cobalt is added to bring lower transition
temperature
Like stainless steel,NiTi can existin more than
one form or crystal structure
The martensite form exist at lower temperatures
the austenite form at higher temperature

 Titanium was discovered by w.Gregor and
named by KLAPORTH
 Atomic number 22,atomic weight 47.9,9th
place in abundance of metals in earth crust

Resembles steel when polished
Low density and light weight
Non-magnetic
low modulus and high strength
Can be coupled with other metals without losing its passivity

FIRST GENERATION
 Reported by ANDREASEN in 1971
 Marketed as nitinol by unitek/3M
 Did not exhibit super elastic behaviour,but
possessed two features
A very low elastic modulus
An extremely wide working
range
SECOND GENERATION
 Super elastic chineese NiTi
 Exhibits non-linear loading and unloading
characteristics more pronounced than
those of original nitinolwire

THIRD GENERATION
 Japaneese NiTi marketed as SENTALLOY
 Super elastic behaviour and shape memory
characteristics of these alloys are based on
reversible transformation between the
austenitic and martensitic NiTi phases
FOURTH GENERATION
 In 1990’sthermally activated NiTi wire
introduced
 Transition temperature close to thebody
temperature

MARTENSITIC-STABILIZED ALLOYS
•Do not possess shape memory or super elasticity
•They are non super elastic wire alloys such as originally
developed Nitinol
MARTENSITIC-ACTIVE ALLOYS
•Employ thermo elastic effect to achieve shape memory
Deformed arch
wire with
martensitic form
Oral
environment
Transforms
back to
austenite , to
starting
shape
AUSTENITIC-ACTIVE ALLOYS
•Undergoes SIM transformation when activated
• Display super elastic behaviour

STABILIZED MARTENSITIC FORM
 No application of phase transition effects
 The family of stabilized Martensitic alloys
now commercially available are referred to
as M-NiTi
ACTIVE AUSTENITIC FORM
 Appeared in late 1980’S
 Exhibited the remarkable property of NiTi
alloys-SUPER ELASTICITY
 Referred to A-NiTi

Spring back and flexibility
Load deflection rate
Formability
Shape memory
Joinability
Friction
Transition temperature range (TTR)
Super elasticity

SPRINGBACK AND FLEXIBILITY
 Good spring back and flexibility
 Low stiffness
 High spring back is useful in situations
that require large deflections but low
forces
LOAD DEFLECTION RATE
 Produce lower,constant,continuous forces
JOINABILITY
 Not joinable
 Hooks cannot be bent or attached to
Nitinol,crimpable hooks and stops are
used

Poor formability
Bending of loops and stops in Nitinol is not
recommended
Cinch backs distal to molar tubes can be obtained by
flame annealing the end of wire
Should not over heat the wire as it makes it brittle

SHAPE MEMORY
 ANDREASEN and MORROW described
the “shape memory” phenomenon as
capabilty of wire to return to a
previously manufactured shape when it
is heated through TTR
FRICTION
 Garner,Allai and Moore(1986) and kapila
et al(1990)
 Bracket wire frictional forces with Nitinol
wires are higher than those with SS wire
and lower than those with β-Ti,in 0.018
inch slot

In 0.22 inch slot NiTi and β-Ti wires demonstrated similar
levels of friction
Although NiTi has greater surface roughness β-Ti has
greater frictional resistance
CLINICAL APPLICATIONS
More difficult to deform during handling
Seating into bracket slots is easier than S.S arch wires
Reduces loops formerly needed to level dentition
Can be used for longer periods of time without changing

 Specific temperature range when the alloy
nickel titanium on cooling undergoes
martensitic transformation from cubic
crystallographic lattice(AUSTENITIC PHASE)
 Range for most binary NiTi alloys 40-60⁰ c
 Transformation from austenite to
martensite can occur by
 Lowering the temperature
 Applying stress (SIM)

Below TTR,----MARTENSITE
Above TTR----AUSTENITE
One of the first application of nitinol was developed by
NASA
Dr.GEORGE ANDREASEN applied the wire to orthodontics above
and below mouth temperature
Mouth temperature would be the TTR
More the Nickel—lower the TTR

 Shape memory refers to the ability of
material to “remember” its original shape
after being plastically deform while in
martensitic form
 Also called THERMOELASTICITY
 There are two major NiTi phases in the
nickel titanium wires
 Austenitic NiTi
 Martensitic NiTi

AUSTENITIC NiTi
---has an ordered BCC structure
---forms at high temperatures and low stresses
MARTENSITIC NiTi
---has distortedmonoclinic,triclinic or hexogonal structure
---forms at low temperature
Shape memory effect is associated with reversible martensite-austenite
transformation, which occurs by twinning at the atomic level
In some cases intermediate R-phase may form

 Controlling low and high temperature,a
change in crystal structure called martensitic
transformation can be produced
 The phenomenon causes change in physical
properties
 in martensitic phase,the metal is ductile
 in austenitic phase,it is difficult to induce
deformation

FORMING THE ARCH WIRE IN THE DESIRED SHAPE AT AN ELEVATED
TEMPERATURE
WIRE COOLED BELOW TRANSITION TEMPERTURE,WIRE CAN BE
PLASTICALLY DEFORMED
TAKING WIRE AGAIN THROUGH TTR WILL RESULT IN ORIGINAL
SHAPE

 Transformation from austenite to
martensite and reverse do not take place
at the same temperature.
 The range for most binary NiTi alloys is
40⁰cto 70⁰c

Angular movement of atoms parallel and
symmetric towards a specific plane that divides
the lattice into two symmetric parts
These parts are not in same plane,rather at a certain
angle
NiTi is charecterized by multiple twinning through out
the metal
These alloys subjected to high temperature,detwinning
occurs and alloy reverts to original shape

 Also referred as A-NiTi
 This group Includes
---chineseNiTi
---japanese NiTi
---27⁰super elastic cu-NiTi
 In Austenitic active alloy both Martensitic and
austenitic phases play an important role
during mechanical deformation

Refers to very large reversible strains that NiTi wires can
withstand due to martensitic –austenitic phase transition
Also referred to PSEUDO ELASTICITY due to non linear
stress-strain curve,which is not typical of elastic
behaviour

Stress induced martensitic transformation
Phase transition in grain structure from Austenite to
martensite
In response to applied force,not to temperature
This transformation is mechanically analogue to thermally
induced shape memory effect
This mechanism is possible as their TTR is close to room
temperature

THE UNLOADING CURVE CHANGES AT DIFFERENT ACTIVATIONS

Wire bending impossible with A-NiTi
Wires can be shaped by heat treatment
Done by passing electric current between
electrodes attached to the wire
Miura et al –possible to reposition the
teeth using A-NiTi
A-NiTi has long range of activation with
relatively constant force

Developed by Dr.TIEN HUA CHENG
At general Research Institute for Non Ferrous metals in
Beijing,China.
Reported by BURSTONE in 1985
Much lower transition temperature than Nitinol wire
Highly suitable if low stiffness and large deflections are needed
Large cross section wires are capable of delivering large
moments required for major tooth movement

SPRING BACK
 At 80⁰ of activation
--1.4 times the spring back of Nitinol wire
--4.6 times the spring back of SS wire
 STIFFNESS is 36% that of Nitinol wire and
73% ss wire

Exhibits small differences at
varying temperatures
Increased temperature=increased
stiffness=reduced spring back
Temperature dependant changes
are clinically insignificant

TIME
DEPENDANT
CHANGES
over 1
minute
chinese NiTi
deformed a
limited
amount
compared to
nitinol nd
stainless
steel wire
which
deformed
considerably
CLINICAL
SIGNIFICANC
E
Applicable in
situation
where large
deflections
are required
When tooth
are badly
malpositione
d

1978—Furukawa Electric Co.Ltd of Japanproduced a new type of
Japanese NiTi alloy
1986—MIURA et al reported on Japanese NiTi
Super elasticity is produced by stress,not by temperature
change and is called stress induced Martensitic transformation
Provides light continuous for physiologic tooth movement
Marketed as SENTALLOY

Japanese NiTi possess good spring back
property,shape memory and super elasticity
Manufactured by different process than nitinol
and has got active austenitic grain structure
Subjecting to heat treatment ,at 500⁰ super
elasticity reduced
At 600⁰ superelasticity got eliminated

 Alignment of badly malposed teeth
 Distalize the molar
 Expansion of arch
 Gain/close space
 Periodontally compromised pts

 Constant force over wide range of
deflection
 Low stiffness
 High Spring back
 More effective in initial toothalignment
 Less patient discomfort
LIMITATIONS OF SUPERELASTIC NiTi
 Cannot be soldered or welded
 Poor formability
 Tendency for dentoalveolar expansion
 Expensive

 Invented by Dr.ROHIT SACHDEVA
COMPOSITION
 Nickel
 Titanium
 Copper (5-6%)
 Chromium (0.2-0.5%)

COPPER
 Icreases strength
 Reduces hysteresis
 These benefits occur at expense of
increasing TTR above that of oral cavity
CHROMIUM
 To compensate for the above mentioned
unwanted effect 0.5% chromium is added
to return TTR close to oral temperature

TYPE I - AF 15⁰ C
-Not used for clinical application due to
high force
TYPE II -AF 27⁰ C
-This generates heavy force than type III,IV
wires
-Best used in pts with average or high pain
threshold
-patients with normal periodontal health
-patients in whom rapid tooth movement is
required

TYPE III-AF-35⁰ C
-this generates mid range of forces
-used in periodontally compromised
patients
-patients with low to normal pain threshold
-whn reltively low forces are requested
TYPE IV-AF-40⁰ C
-generates tooth moving forces when
mouth temp exceeds 40⁰c
-patients sensitive to pain
-Periodontally compromised patients
-beneficial as an initial rectangular wire

CU-NiTi generates more constant force over long activation
spans
More resistant to permanent deformtion
Exhibits better spring backproperties
Reduced hysteresis
Enables clinician to select archwires on a case specific

 In 1979 β titanium was introduced
 In 1981 it was introduced to orthodontics
by CHARLES J BURSTONE and JON
GOLDBERG
COMPOSITION
 Titanium -77.8%
 Molybdenum-11.3%
 Zirconium-4.3%

At room temp. it is stable in alpha phase and is HCP
lattice
At temp. above 1625⁰F titanium rearranges into a BCC-
beta phase
By adding molybdenum, the beta form of titanium
can be stabilized even when cooled to room
temperature
Such alloys are referred as beta stabilized titaniums
These alloys are strengthened by coldworking or precipitation
of HCP

ALLOY MODULUS OF
ELASTICITY
YIELD
STRENGTH
ULTIMATE
TENSILE
STRENGTH
Β-Titanium 71.7 ×103 931 1276
High spring back and formability with low stiffness
Low elastic modulus yields large deflections for low forces
It has high elastic strain
For a given cross section,it can be deflected twice as far as S.S wire
without permanent deformation
LIGHT CAPACITANCE WELD -Allows direct welding of auxillaries
into arch wire without reinforced by solder

 Rectangular TMA used
during retraction
 K-SIR arch wire .019”
 Utility arches

 Developed by A J WILCOCK jr IN 1988
 Possess closely packed hexagonal lattice
 Manufactured by a process called feed
centerless grinding
 Supplied as square and rectangular wires
COMPOSITION
 Titanium 88.9%
 Aluminium 7.86%
 Vanadium 4.05%

Readily absorbs free hydrogen in the oral enviornment and become
titanium hydrides
Hence,it becomes brittle soon
The HCP structures of alpha titanium has only one active slip plane
making it less ductile
Can be welded
Stiffness lies between SS and nitinol wires
Nickel 0% ,so can be used in Ni sensitive patient
MAINLY USED FOR ROOT TORQUING IN FINISHING STAGES

This alpha-beta titanium alloy introduced recently by
TP orthodontics
More resistant to breakage
Smoother for reduced friction
Brightly polished and esthetically pleasing
Nickel free for sensitive patients
Easier to bend and shape

Excellent for all phase of treatment
During initial alignment its excellent for tooth
alignment,levelling and bite opening
Early torque control during intermediate treatment
Timolium is the wire of choice during the final
treatment phase

OPTIFLEX
POLYNORBOGEN
TEFLON COATED WIRES
BIOFORCE ARCH WIRES
ORGANIC POLYMER WIRE
(QCM)

• Optiflex is a non metallic arch wire
• It was designed by DR. TALASS in the year 1992
& manufactured by Ormco.
• It has got unique mechanical properties with a
highly aesthetic appearance made of clear
optical fiber

Silicon dioxide core that provide force for moving
teeth
Silicon resin middle layer that protects the core
from moisture and adds strength
Strain resistant nylon outer layer that prevents
damage and increase strength

 It the most aesthetic orthodontic archwire.
 It is completely stain resistant, and will not stain or
loose its clear look even after several weeks in
mouth.
 Its effective in moving teeth using light continuous
force
 Its very flexible
 it has an extremely wide range of actions
 when indicated it can be tied with elastomeric
ligatures to severely malaligned teeth without fear
of fracturing the arch wire.
 Due to superior properties optiflex can be used
with any bracket system

clinical applications
 It is used in adult patients where
esthetics is chief concern
 Can be used as initial archwire in cases
with moderate amounts of crowding in
one or both arches.
 ideal for non extraction cases and also
cases with no partially edentulous areas
 Optiflex can be used in presurgical stage
in cases which require orthognathic
intervention


Precaution’s while using optiflex archwires
 Optiflex archwires should be tied into brackets
with elastomeric ligatures.
 Metal ligatures should never be used since
they will fracture the glass core.
 Sharp bends should never be attempted with
optiflex, as these bends will immediately
fracture the glass core.
 Using instruments with sharp edges, like the
scaler etc should be avoided
 To cut the end of the archwire distal to the
molar, it is recommended to the use the mini
distal end cutter which is designed to cut all 3
layer’s of optiflex.

Shape memory plastic developed in Japan
If temperatre exceeds the transition temperature it began
to display an elastic property and then returns to original
shape
At 50⁰ c it can be stretched to 2 to 3 times its original
length

EPOXY COATED ARCH WIRE
 Tooth colored arch wire
 Superior wear resistance and color stability
of 4 to 8 weeks
LEE WHITE WIRE
 Manufactured by lee pharmacuetical
 It’s a resilient ss or NiTi arch wire bonded
to a colored coating

Introduced by DENTSPLY
• It was possible to produce variation in force delivery between archwires
of identical dimension
This was possible by specifying transition temperatures
within given ranges.
• graded as thermodynamic arch wires.
This property was further advanced to produce variable
transition temperatures within the same archwire
• This arch wire was called Bioforce archwire

It is aesthetic
• Is the first and only family of biologically
correct archwires
• It applies low and gentle forces to anteriors
• Increasingly stronger forces across the
posteriors until plateauing at the molars.

Providing greater patient comfort
Reducing the number of wire changes
It provides the right force to each tooth
increasing to approximately 300 grams
Beginning at approximately 100 grams

 Made from 1.6 mm diameter round
polytheline terephthalate
 Easy to fabricate and fit into dental arches
 Can be used as esthetic maxillary retainers

 1993-HANSON combined advantages of
multistranded cables and super elastic wires
to create super elastic NiTi coaxial wire
 Comprises seven individual strands that are
woven together in a long, gentle spiral form
 Maximize flexibility and minimize force
delivery.

Very small diameter SS wire can be
braided or twisted together
Comprised of five or seven wrapped
around a central wire of same diameter.
Affords extreme flexibility and delivers
extremely light forces

• Available in both round and rectangular
shape.
• Different type
 Triple stranded – 3 wires twisted
Coaxial – 5 wires wrapped
around core wire
 Braded – 8 strand rectangular wire.
• Used at the beginning of the treatment to
align labiolingually displaced
or rotated anterior teeth.

 Excellent combination of high
elastic recovery, high tensile
strength and low weight.
 Excellent formability
 Allow for flexural and torsional properties.
 Excellent aesthetics because of their
translucency.
 Ability to form wires of different stiffness values
for the same cross-section.

 Made of glass fibres and acrylic resin
 Manufactured by photopulstration or
electromagnetic radiation

This would facilitate the practice of Constant Cross- section
Orthodontics.
• Ability to directly bond attachments to these
wires
• Eliminating the need for soldering and electrical resistance w
welding
• Such wires can also be directly bonded to
• teeth, obviating the need for brackets

 Recent Reports on Fiber
Reinforced Composite Archwires
 Recent modification (Reports by Zufall,
Kennedy and Kusy, Angle Orthod 2000;
70: 34-47)
 They compared the frictional
characteristics of composite archwires
against stainless steel and nickel titanium
 They found composite archwires had
higher kinetic coefficients of friction
than stainless steel but lower than nickel-
Titanium or beta titanium.

 The key to success in a multi attachment straight
wire system is
 To have the ability to use light tipping movements
in combination with rigid translation
 They used three specific combined wires for the
technique
1. Dual Flex-l,
2. Dual Flex-2, and
3. Dual Flex-3 (Lancer Orthodontics).

The Dual Flex-1
 it consists of a anterior section made of 0.016-inch
round Titanal and a posterior section made of 0.016-inch
round steel.
 The flexible front part easily aligns the anterior teeth
and the rigid posterior part maintains the anchorage and
molar control by means of the “V” bend, mesial to the
molars.

It is used at the beginning of treatment.

The Dual Flex-2
 it consists of a flexible anterior segment composed of an
0.016 ´ 0.022-inch rectangular Titanal and a rigid posterior
segment of round 0.018-inch steel.
The Dual Flex-3,
• consists of a flexible anterior part of an 0.017 ´ 0.025-inch Titanal
rectangular wire and a posterior part of 0.018 round steel wire.
The Dual Flex-2 and 3 wires establish anterior anchorage and control
molar rotation during the closure of posterior spaces.
They also initiate the anterior torque

.021 × .025 pre-form rectangular arch wire formed
with multiple strands of titanium super elasticwire
Low force and low stiffness with excellent flexibility
Used in the beginning of treatment as it facilitate
levelling and aligning while also controlling torque

 Nitanium is a special hybrid non-heat-
treated form of Chromoly steel that
contains trace elements of Titanium and
Niobium
 Stain and crack resistant
 Plastic and friction reducing tooth colored
coating blend with natural dentition as well
as ceramic and composite brackets
 Blend with tooth anatomy
 Delivers 29 to 150 gms of
force on teeth

 Makes titanium more esthetic
 Delivers force constantly
 Pre programmed wire to deliver the right
amount of force for each area of mouth
 Delivers high force on molar,medium force
to bicuspids,light forces to incisors
 Prevents unwanted rotations of premolar
 Provides 3 dimensional controls from
beginning of treatment

 BROUSSARD and GRAHAM in 2001
introduced SS triangular wire
 Equilateral in cross sectionof .030” to a
side with rounded edges
 Used for making retainer,removable
appliance and bonded lingual retainer

 NiTI wire is coated with super hard gold
24carat
 Allows silky smooth sliding mechanics and
give a fabulous rich look

• It is important to know the properties of the
archwires as it is widely used in orthodontics.
• Proper handling of the material gives the best
result.
• Materials with excellent aesthetics and strength
expected to replace metals in orthodontics in the
near future

 William R Proffit, Henry Fields, David M
Server; Contemporary Orthodontics, 5th
edition
 Phillips’science of dental materials, 11th
ed, Anusavice
 Graber, Vanarsdall, Vig; Orthodontics -
Current principles and Techniques
 Recent modification (Reports by Zufall, Kennedy and
Kusy, Angle Orthod 2000; 70: 34-47
 Google

Archwires in orthodontics

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