Arch wires

DDEEPPAARRTTMMEENNTT
OOFF
OORRTTHHOODDOONNTTIICCSS
www.indiandentalacademy.comwww.indiandentalacademy.com

Dr NIPUN T JOHN
II nd
M D Swww.indiandentalacademy.com

History of Orthodontic
Wires• Until 1930-orthodontic wires was made of
GOLD
• 1930-advent of stainless steel & refinement in
drawing process to form wires with more
improved properties, GOLD lost its ground.
Stainless steel was perfected for the
orthodontic use by Bresrley and Sheffield of
U.S
• By 1950- almost 300 different series of S/S
alloys were used in the field of orthodontics.
• Chromium 17-25%
• Nickel 8-25% with a balance being iron
www.indiandentalacademy.com

Introduction
• An ideal archwire is one which move
teeth with a light continuous force.
• These forces should not decay rapidly
because material loses its elasticity as
a small amount of tooth movement
causes a large change in the force
levels. Hence mechanotherapy
depends on elastic behavior of the
material and biochemical reaction of
the teeth.

Properties of ideal archwire
STRENGTH
SPRINGY
RESELIENT
WELDABLE
ESTHETIC
POOR BIOHOST
GOOD RANGE
SPRING BACK
LOW FRICTION
FORMABLE
TOUGH
BIOCOMPATABILE

Manufacturing of orthodontic wiresManufacturing of orthodontic wires
• These alloys are usually standardized
and formulated based on AISI
specifications.
MELTING
INGOT FORMATION
ROLLING
DRAWING

The selection and melting of the
components of alloys influence the
physical properties of wire
MELTING
type
Composition (as per AISI)
Cr Ni C Mn Si P S
302 17-19% 8-
10
0.15 2 1 0.045 0.03
304 18-20% 8-
12
0.08 2 1 0.045 0.03
416 12-14% - 0.15 1.25 1 0.06 0.15www.indiandentalacademy.com

• Pouring of the molten metal in to the
mold
• A non uniform chunk of metal is
produced
• Ingot- Granular structure, consist of
crystals of component metals called as
GRAINS.
• The mechanical properties of the ingot
is controlled by its granular structure.
• When the ingot is cooled, grains forms
at once.
• These growing crystals are surrounded
each another.
• INGOT – colony of irregularly shaped
grains of different materials.
INGOT FORMATION

• The rate of cooling and size of
ingot decide the size and
distribution of the grains.
• The pouring and cooling process
affect porosity.
• Porosity can be due to
– Gases dissolved in molten mass.
– By product of molten mass
– When ingot cools the inner mass
hardens later, inside the outside
hardened shell, which results in
additional vacuum voids.

 First mechanical step in process.
 Ingot is rolled in series of rollers to
reduce its diameter.
 The individual grains retain their
identity through rolling process, unless
some heat treatments are carried out.
Now the wire is actually an “distorted
ingot”.
 The squeezing and rolling of ingot
alters the shape and arrangement of
the crystals.
ROLLING

• Rolling will cause the elongation of
crystals into an finger like process,
closely meshed with each other.
• Hardness/ brittleness increases as the
grain positions and arrangements are
altered.
• The metal is annealed by heating into
high temperature, which relives the
internal stress formed by rolling.
• On cooling ,it resembles an original
casting.
• The grain size depends on the time
and temperature of annealing and the
rate of cooling.

• Ingot is reduced in to final size.
• The wire is pulled through a
small hole in a die.
• To relive work hardening, the
wire is drawn through and
annealed ,several times. This
will increase the strength and
make the wire resistant to
breakage.
DRAWING

Cr2O3
Properties of stainless steel
• When 12-30% chromium is added to steel---
-----STAINLESS STEEL.
• Yield strength at room temperature-
211-1760Mpa
• PASSIVATION- property of SS to resist tarnish
and corrosion.
Stainless steel
O2
O2 O2 O2 O2
Cr Cr
Cr Cr

Types of stainless steel
FERRITIC
AUSTENITIC
ROOM TEMP
912C
1394C
BCC
LOW IRON SOLUBILITY-0.02wt%
FCC
IRON SOLUBILITY- 2.1wt%
WHEN COOLED SLOWLY
EXCESS CARBON WHICH IS NOT
SOLUBLE FORMS IRON CARBIDE
WHEN COOLED SUDDENLY
SPONTANEOUS DIFFUSIONLESS
TRANSFORMATIOM INTO BCT-
HARD STRONG & BRITTLE
BCTMARTENSITIC

• Cr-11.5-27% Ni-0% C-0.2%
• AISI 400 series.
• Good corrosion resistance .
• Low cost.
• Low strength.
• Not hardenable by heat treatment.
• Not readily work hardenable.
• Little application in dentistry.
FERRITIC-BCC

• Cr-11.5-17% Ni-0-2.5% C-0.15-1.2%
• Can be heat treated
• High strength, high hardness
• Yield strength-492Mpa(annealed)-
1898Mpa(hardened)
230-600BHN
• Less corrosion resistance.
• Reduced ductility.
MARTENSITIC-BCT

• Cr-16-26% Ni-7-22% C-0.25%
• AISI 302 is basic type 18:8:0.05
• AISI 304 18:8:0.08
• AISI 316L- implants 18:8:0.03
• Commonly used by ORTHODONTIST
AUSTENITIC-FCC

ADVANTAGES
 Greater ductility and ability to undergo
cold working without fracture.
 Substantial strengthening during cold
working.
 Ease of welding
 Ability to readily overcome sensitization
 Less critical grain growth.
 Ease of forming.

CORROSION RESISTANCE OF S/S
• SENSITIZATION
Cold working of SS, carbide
precipitates along the slip planes. as a
result areas deficient in carbon will be
less and carbide is uniformly
distributed. they precipitate only in
grain boundaries. This increases
corrosion resistance
• STABILIZATION
Titanium ,when added 6 times to
carbon, inhibits formation of chromium
carbide

Stress relief in SS
• It is a level of heat treatment at which the
internal stresses are relived by minute
slippages & rearrangement in the inter-
granular relations with out loss of hardening
that accompanies the higher temp process of
annealing.
– Work hardening.
– Cold working.
– Annealing.
– Recovery.
– Recrystalization.
– Grain growth.

• Stainless steel archwires manufactured by
A. J. WILCOCK SCIENTIFIC &
ENGINEERING.LTD of Victoria, Australia,
(founded in 1946 by the
Late Arthur J. Wilcock, who had previously
been employed at the Melbourne
University Metallurgy School)
have been the backbone of Begg treatment
ever since Dr BEGG started his technique.
• The manufactures are continuously trying to
improve the mechanical properties of these
wires.
• High tensile wires are available today.
• Till recently, no other wire was found to be
capable of duplicating their properties.

Properties of A J WILCOCK
wires.
• Round Austenitic S/S wire which
is heat treated and cold drawn to
its proper diameter from round
wires of larger dimension.
• High tensile strength.
• Greater stiffness(load – deflection
rate) than same size wire made of
other materials like NiTi and TMA.
• High resiliency.

• Toughness.
• 0.008”-0.022”
• Coiled and straight. (straight ones
are not so resilient as coiled ones
due to the process of
straightening)
• Regular grade to supreme grade
(color coded)

REGULAR
REGULAR PLUS
SPECIAL PLUS
SPECIAL
PREMIUM SUPREME
PREMIUM PLUS
RESILIENCERESILIENCE
YEILD STRENGTHYEILD STRENGTHwww.indiandentalacademy.com

Regular grade
• Lowest grade
• Easier to bend
• Used for practice bending and
auxiliaries.
• Can be used when archform
distortion is not a problem or
bite opening is not required.

Regular plus
• Relatively easy to form.
• More resilient than regular.
• Used for making auxiliaries.
• Used for making an archform
when more pressure and
resistance to deformation are
desired.

Special grade
• Highly resilient
• Can be formed to intricate
shapes with little danger of
breaking.
• Used as starting arches mostly

Special plus
• Hardness and resiliency of
0.016” size is excellent for
maintaining anchorage and for
reducing overbites.
• Chances of fracture is more.
• Should be bent with caution.

Extra special plus
• Unequalled in resiliency and
hardness.
• More difficult to bend.
• More prone to fracture.

0.009
0.008
0.010
0.011
0.012
0.014
0.016
0.018
0.020
PREMIUM
PREMIUM PLUS
SUPREME

PROCESS OF
MANUFACTURING
SPINNER STRAIGHTENING
PULSE STRAIGHTENING

Mechanical process of
straightening resistant materials
usually in the cold drawn condition.
the wire is pulled through high
speed, rotating bronze rollers that
torsionally twist into straight
condition.
The resultant deformation and
decreased yield stress value
makes it strain softened.
SPINNER STRAIGHTENING

• The wire is pulsed in special
machines the permit high tensile
wires to be straightened.
• The advantages
–It permits highest tensile wire to
be straightened.
–Tensile yield stress is not
altered.
–Smoother surface of wire hence
less friction.
PULSE STRAIGHTENING

–Greater flexibility of springs
fabricated.
–Greater resiliency
–Permits the usage of smaller
diameter wire resulting in a light
continuous force with minimal
relaxation.

PULSE STRAIGHTENED
TENSILE STRENGTH 8-12%
LOAD DEFLECTION RATE
10% FOR 0.016”
235% FOR 0.020”
FRICTIONAL RESISTANCE 50%
INITIAL YEILD STRENGTH 33%
COST

• Pulse Straightened wires have a
smooth low friction surface with
the same resilient properties as
the coiled product, giving the
added benefit of saving time to
straighten the arch posterior
segments and provide ease of
use. Available in Special Plus,
Premium, Premium Plus and
Supreme.

• The increase in the yield strength of
the Australian wire is achieved by
– Careful selection of materials with
appropriate composition and properties
– Cold working.
Add refined begg fig 3.13

High yield strength influences
• Working range
• Resiliency
• Zero-stress relaxation
• Formability

• Working range (max flexibility,
spring back, elastic strain)
Working range= Yield strength
Modulus of elasticity
Higher grade wire can be
deflected over a greater
distance without permanent
deformation. They have more
springy back. they have better
spring back than lower grade
wires.
Working range

Resiliency
• MODULUS OF ELASTICITY α 1/2 YIELD STRENGTH2.
ELASTIC MODULUS
• Same material with same modulus of
elasticity higher yield strength results
in higher resiliency.
• High grade wires absorbs or store
more energy per unit area before it
get deformed.
• Higher resilient wire can work more
to move the teeth.

Zero-stress relaxation
• This is a form of slip by dislocation
movement takes place at atomic level,
which is resisted by high yield
strength.
• Ability of the wire to deliver constant
force when subjected to external load,
over a long period.
• Newer wires maintain their
configuration over along periods
against deforming forces and forces
generated by the wires also remain
practically unaffected over a long
period

Formability
F
o
r
c
e
Deflection
Failure point
RESILIENCE FORMABILITY

• For the same material, greater the
resiliency, greater the formability.
• GREATER RESILIENT wires are
more brittle than low grade wires.
• So special care should be taken
while bending these wires

• The properties of A J Wilcock wires are
affected by the way, how it is
straightened.
• If the wires are straightened by reverse
straining, the yield point of the wires
reduces.
(the way we straighten the wire manually)
• In conventional manufacturing wire is
straightened using rollers and spinners.
This process is called as work
softening due to reverse straining or
Bauschinger effect.

Working range V/s resiliency
TMA SMALLER DIAMETER
SUPREME WIRE
TMA
SUPREME
S
T
R
E
S
S
STRAIN
MORE RESILIENT
LESS ABILITY TO
CORRECT ROTATIONS
NiTi wires have a greater range than supreme and TMA
wire
But formability is poor
Supreme wires are more ecconomical than TMA and
NiTi wires.

Clinical tips and facts
• The higher grade wires especially
pulse straightened are excellent for
applying constant force for a longer
time without undergoing softening.
• For a careless patient and patients
with occlusal interference, chance of
wire fracture is more. So low grade
wire is preferred.
• The wire used for making arches is
selected according to the load
deflection, we required.

HIGH LOAD
DEFLECTION REQUIRED
LOW LOAD
DEFLECTION REQUIRED
IN STAGE 1
0.016” / 0.018 PREMIUM
OR PREMIUM PLUS
THIRD STAGE
TO MAINTAIN ARCH FORM
0.018” P AND P+ OR 0.020P
TO AVOID UNDESERIABLE EFFECT
OF TORQUING AUXILLARY
0.020” P IS INDICATED
For smaller forces for alignment
0.014” PREMIUM
0.014” SPECIAL PLUS
OR
Sectionals of 0.012” PREMIUM PLUS
OR
smaller supreme wire
according to malalignment
during root torque and uprighting
0.012” P+ OR SMALLER SUPREME
To attain high resiliency
and spring back

Clinical application
• Unravelling of crowded anterior teeth
• Opening deep overbite.
• Auxiliaries
• Tooth uprighting.
• Rotations corrections
• Maintaining anchorage.
• Maintaining correction.
• Root torquing.
• Resistant overbites.
• Finishing.

Wires used in different stages of begg
treatment
0.016”-Space present / space to be
created.
Average to deep bite cases-0.018 P+/P
because it provides intrusive force on upper
anteriors, resist lingual rolling of lower
molars.
Anterior open bite cases
upper arch- 0.014P/P+
lower arch- 0.016P/P+
STAGE 1

Rotational control
MINIMUM
MODERATE
SEVERE
0.016” ss with V bends or offset bends
0.014” ss with V bend produces lesser forces
Next visit- 0.016 ss
0.016/0.014” Niti with 0.014 SS base wire
which is not engaged to
malpositioned tooth.
After correction NiTi is ommitedwww.indiandentalacademy.com

• A J Wilcock wires, due to its greater
stiffness is beneficial for the
objectives like bite opening and
maintenance of archform,it is
undesirable for the objective of
alignment of crowded teeth.
• This necessities the use of multi-
looped arch form or sectional small
diameter SS wire during alignment.
• Another way is to use NiTi or TMA
wire in conjunction with Australian
wires.

STAGE II
0.018 P/P+
0.020 P
If stage 1 corrections involved extreme deep bite
Distorted arch forms,
Severe rotations
They resist distobuccal rotational tendency
of molars on the effect of class 1 elastics
The degree of anchor bend should be reduced
when using 0.020” than when using 0.018”www.indiandentalacademy.com

Usually completed within 1 month.
0.016”
If discrepancy between premolar and
molar positions are excessive it may
require 2 months to reach 0.020” wire.
PRESTAGE III

Base wire used is of 0.020 premium grade
Three times stiffer than 0.020” special
plus which used earlier.
This will resist the vertical and horizontal
reactions of auxiliaries and springs.
STAGE III

MAA
• Manufactured by Mollenhauer’s
request-1984
• REQUIREMENTS
• Light root moving force
• Resist deformation
• Base arch wire should resist vertical &
transverse reactions of MAA- 0.018
premium plus
0.009 supreme

 Jenner auxiliary
-0.012 supreme
 Lingual root torquing auxiliary
–0.012 P+ (refined begg)
–0.014/0.016 special plus – conventional
begg
 Spec auxiliary
– 0.009/0.010P+
–In stage III, if needed- 0.012P+
Reverse torquing auxiliary
0.012P+ on a 0.018/0.020 base wire
 Uprighting spring
0.014P+
0.019 supreme- Mollenhauers Mini
uprighting spring

BENDING OF WIRE
• Warm the wire by pulling
through the fingers, because
this wire have a brittle
transition period slightly above
the room temperature.
• Wilcock pointed out that this
wire is more likely to break
when using round beak of the
pliers.

More strain on the
crystalline structures
of the wire
The point of stress on the
wire are directly opposite
to each other
Greater force on
one particular area
TOO MUCH PRESSURE
Damage to
crystalline structures
Fracture of wire
Round beak of pliers
When using a square beak,
it produces an moment arm
between the thumb and beak,
reducing stress.

Crack propagation theory
There exist an relation between applied stress
and internal stress at the head of dislocation
pile ups seen in high and sharp yield point
materials
POINT DEFECT AT HEAD OF DISLOCATION HEAD
MINUTE CRACK
TRANS GRANULAR CRACK PROPAGATION
HIGH STRESS CONCFORCE

CARBIDE PRECIPITAES
GRAINS ARE SPLITTED AND ENERGYN IS RELEASED
CRACK CONTINUES
BLUNTING OF CRACK HEAD BY PLASTIC DEFORMATION
CRACK PROPAGATION STOPS

AJO 1984 Nov Force relaxation in orthodontic arch wires -
Hazel, et al
Measurements of the force relaxation
have been made in stainless steel,
Elgiloy, and nitinol wires at 21° C and 37°
C. All the wires were found to relax at 21°
except NiTi. The rates of relaxation were
found to vary widely; stainless steel wires
produced by A J Wilcock relaxed
significantly less than Elgiloy wires.

AJO 1984 Nov Force relaxation in orthodontic arch wires -
Hazel, et al
0.016 round wires

The Wilcock wires were found to relax less than the other
round wires tested,

A J WILCOCK
Alpha Titanium wires
Ti - 90%
Al- 6%
Va-4%
• Ni – 0% so can be used in Ni sensitive
patient
• These wires have a molecular
structure that resembles closely
packed hexagonal lattice (TMA- BCC
lattice). so easy deformation is not
possible.
• Absorbs Hydrogen and forms Titanium
Hydride with passage of time .Alloy
becomes stiffer.

For over fifty years, "Australian Wire" has
been a household name in orthodontics. The
extra ordinary properties of these wires are
due to the research and fine engineering
skills employed in the processing of the
wires. Wilcock wires are well known for
their resilience and ability to withstand
masticatory forces as well as being able to
maintain their shape even when auxiliaries
and elastics are used. There is no other
wire which opens the bite as effectively as
Wilcock wire.www.indiandentalacademy.com

THANK YOU

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