Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

Properties ofProperties of
OrthodonticOrthodontic WiresWires
Part I
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.comwww.indiandentalacademy.com

IntroductionIntroduction
Moving teeth and craniofacial harmonyMoving teeth and craniofacial harmony
Forces and momentsForces and moments
WiresWires
Light continuous forcesLight continuous forces

HistoryHistory
1.1. Material Scarcity, Abundance of IdeasMaterial Scarcity, Abundance of Ideas
(1750-1930)(1750-1930)
noble metalsnoble metals
Gold, platinum, iridium and silver alloysGold, platinum, iridium and silver alloys
good corrosion resistancegood corrosion resistance
acceptable estheticsacceptable esthetics
lacked the flexibility and tensile strengthlacked the flexibility and tensile strength

Angle (1887)Angle (1887)  German silver (a type ofGerman silver (a type of
brass)brass)
OppositionOpposition Farrar – discoloredFarrar – discolored
Neusilber brass (Cu 65%, Ni 14%, Zn 21%)Neusilber brass (Cu 65%, Ni 14%, Zn 21%)
various degrees of cold work (diff prop)various degrees of cold work (diff prop)

jack screws,jack screws,

expansion arches,expansion arches,

BandsBands
HistoryHistory

HistoryHistory
Wood, rubber, vulcanite, piano wire andWood, rubber, vulcanite, piano wire and
silk threadsilk thread
No restrictions.No restrictions.

HistoryHistory
Stainless steel (entered dentistry -1920)Stainless steel (entered dentistry -1920)
Stahl and Eisen – Benno Strauss & EduardStahl and Eisen – Benno Strauss & Eduard
Maurer in 1914Maurer in 1914
By 1920 – Dr. F Hauptmeyer.By 1920 – Dr. F Hauptmeyer.
Simon, schwarz, Korkhous, De Coster-Simon, schwarz, Korkhous, De Coster-
orthodontic materialorthodontic material
ReplacedReplaced
OppositionOpposition  Emil HerbstEmil Herbst

gold wire was stronger than stainless steel. (1934)gold wire was stronger than stainless steel. (1934)
Steel as ligature wireSteel as ligature wire

HistoryHistory
2.2. Abundance of materials, RefinementAbundance of materials, Refinement
of Proceduresof Procedures (1930 – 1975)(1930 – 1975)
 Improvement in metallurgy and organicImprovement in metallurgy and organic
chemistry – mass production(1960)chemistry – mass production(1960)
 Farrar’s dream(1878)Farrar’s dream(1878)
Cobalt chrome (1950s)-Elgin watch coCobalt chrome (1950s)-Elgin watch co
Rocky Mountain Orthodontics- ElgiloyRocky Mountain Orthodontics- Elgiloy
Nitinol (1970s)- Buehler, intoNitinol (1970s)- Buehler, into
orthodontics- Andreasen. Unitekorthodontics- Andreasen. Unitek

HistoryHistory
3.3. The beginning of SelectivityThe beginning of Selectivity (1975 to(1975 to
the present)the present)
Orthodontic manufacturersOrthodontic manufacturers
Beta titanium (1980)Beta titanium (1980)
CAD/CAM – larger production runsCAD/CAM – larger production runs
Composites and CeramicsComposites and Ceramics
Iatrogenic damageIatrogenic damage

Nickel and bis-GMANickel and bis-GMA
New products- control of govt agencies, priNew products- control of govt agencies, pri
organizationorganization www.indiandentalacademy.comwww.indiandentalacademy.com

Basic Properties of MaterialsBasic Properties of Materials
Elements –all particles identicalElements –all particles identical
 Atoms-smallestAtoms-smallest
Electrons – orbits around nucleusElectrons – orbits around nucleus
Floating in shells of diff energy levelsFloating in shells of diff energy levels
Electrons form the basis of bondsElectrons form the basis of bonds
Atoms interact via electronsAtoms interact via electrons
In metals, the energy levels are veryIn metals, the energy levels are very
closely spaced and the electrons tend toclosely spaced and the electrons tend to
belong to the entire assembly rather thanbelong to the entire assembly rather than
a single atom.a single atom.

Array of positive ions in a “sea ofArray of positive ions in a “sea of
electrons”electrons”
Electrons free to moveElectrons free to move
electrical and thermal conductivityelectrical and thermal conductivity
Ductility and malleabilityDuctility and malleability
electrons adjust to deformationelectrons adjust to deformation

Molecules – 2 or more atomsMolecules – 2 or more atoms
Amorphous – similar properties in allAmorphous – similar properties in all
directions – isotropydirections – isotropy  GlassGlass
atoms organize themselves into specificatoms organize themselves into specific
latticeslattices  geometrygeometry
CRYSTALCRYSTAL

anisotropyanisotropy

CRYSTALSCRYSTALS
Perfect crystals: anion – cation –anion –Perfect crystals: anion – cation –anion –
cationcation
extremely strongextremely strong
Thin wiskersThin wiskers reinforcereinforce
If like ions are forced together, breakageIf like ions are forced together, breakage
results. Unlike metals, crystals cannotresults. Unlike metals, crystals cannot
deform.deform.

alloy crystals growalloy crystals grow
anion – cation –anion – cationanion – cation –anion – cation
Perfect crystals seldom existPerfect crystals seldom exist
Crystals penetrate each other such that theCrystals penetrate each other such that the
crystal shapes get deformed and cannotcrystal shapes get deformed and cannot
be discerned grainsbe discerned grains

GrainsGrains  microns to centimetersmicrons to centimeters
Grain boundariesGrain boundaries
Atoms are irregularly arranged, and thisAtoms are irregularly arranged, and this
leads to a weaker amorphous typeleads to a weaker amorphous type
structure.structure.
AlloyAlloy  combination of crystalline (grains)combination of crystalline (grains)
and amorphous (grain boundaries)and amorphous (grain boundaries)
Decreased mechanical strength andDecreased mechanical strength and
reduced corrosion resistancereduced corrosion resistancewww.indiandentalacademy.comwww.indiandentalacademy.com

Stages in the
formation of metallic
grains during the
solidification of a
molten metal
Polycrystalline- each
crystal - grain

VacanciesVacancies – These are empty atom sites– These are empty atom sites

InterstitialsInterstitials –– Smaller atoms that penetrateSmaller atoms that penetrate
the lattice Eg – Carbon, Hydrogen, Oxygen,the lattice Eg – Carbon, Hydrogen, Oxygen,
Boron. Often distort the metal structureBoron. Often distort the metal structure

Substitutial Element – another metal atom can
substitute one of the same or similar size. E.g. -
Nickel or Chromium substituting iron in stainless
steel.

Imperfections- although they lower theImperfections- although they lower the
cleavage strength of the metal , increasecleavage strength of the metal , increase
its resistance to deformationits resistance to deformation

LATTICELATTICE
The three dimensional arrangement ofThe three dimensional arrangement of
lines that can be visualized as connectinglines that can be visualized as connecting
the atoms in undisrupted crystals, is calledthe atoms in undisrupted crystals, is called
a lattice.a lattice.
Unit cellUnit cell
CrystalCrystal  combination of unit cells, incombination of unit cells, in
which each cell shares faces, edges orwhich each cell shares faces, edges or
corners with the neighboring cellscorners with the neighboring cells
14 crystal lattices14 crystal lattices

The atoms, which areThe atoms, which are
represented as points,represented as points,
are not static. Instead,are not static. Instead,
they oscillate about thatthey oscillate about that
point and are in dynamicpoint and are in dynamic
equilibrium.equilibrium.

Lattice deformations:Lattice deformations:
various defectsvarious defects  slipslip planesplanes--alongalong whichwhich
dislocation occursdislocation occurs

shear stressshear stress  atoms of the crystalsatoms of the crystals
can glide along these planescan glide along these planes
more the slip planesmore the slip planes easier is it toeasier is it to
deformdeform
Slip planes intercepted at grainSlip planes intercepted at grain
boundaries-increases the resistance toboundaries-increases the resistance to
further deformationfurther deformation

If the shearing force is:-If the shearing force is:-
SmallSmall - atoms slip, and return back to their- atoms slip, and return back to their
original position (elastic deformation)original position (elastic deformation)
Beyond the elastic limit -Beyond the elastic limit -
crystal suffers a slight deformationcrystal suffers a slight deformation
permanent (plastic deformation)permanent (plastic deformation)
Greater stressGreater stress - fracture- fracture

During deformation - atomic bonds withinDuring deformation - atomic bonds within
the crystal get stressedthe crystal get stressed
 resistance to more deformationresistance to more deformation
Number of atoms that get stressed alsoNumber of atoms that get stressed also
increasesincreases  resistance to moreresistance to more
deformationdeformation
Strain or work hardening or cold workStrain or work hardening or cold work

Work hardeningWork hardening
Forced interlocking of grains and atoms ofForced interlocking of grains and atoms of
metal.metal.
Locked in and under pressure/tensionLocked in and under pressure/tension
Carried at room temperature.Carried at room temperature.

Strain hardening- principleStrain hardening- principle
 Hard and strong, tensile strengthHard and strong, tensile strength
Brittle.Brittle.
Annealing – heat below melting point.Annealing – heat below melting point.

More the cold work, more rapid the annealingMore the cold work, more rapid the annealing

Higher melting point – higher annealing temp.Higher melting point – higher annealing temp.

½ the melting temperature (½ the melting temperature (oo
K)K)

ANNEALING:ANNEALING:
RecoveryRecovery
RecrystallizationRecrystallization
Grain GrowthGrain Growth

Before Annealing
Recovery – Relief of stresses
Recrystallization – New grains
from severely cold worked areas
-original soft and ductile condition
Grain Growth – large crystal “eat
up” small ones-ultimate coarse grain
structure is produced

AnnealingAnnealing
Smaller grains – harder and strongerSmaller grains – harder and stronger
Larger grain boundaries to oppose the slipLarger grain boundaries to oppose the slip
planes.planes.

Various methods of obtaining smaller grain sizeVarious methods of obtaining smaller grain size
1.1. Enhancing crystal nucleation by adding fineEnhancing crystal nucleation by adding fine
particles with a higher melting point, aroundparticles with a higher melting point, around
which the atoms gather.which the atoms gather.
2.2. Preventing enlargement of existing grains.Preventing enlargement of existing grains.
Abrupt cooling (quenching) of the metal.Abrupt cooling (quenching) of the metal.
Dissolve specific elements at elevatedDissolve specific elements at elevated
temperatures. Metal is cooledtemperatures. Metal is cooled
Solute element precipitatesSolute element precipitates barriers to thebarriers to the
slip planesslip planes..

Solution heat treatmentSolution heat treatment
Heat below the solidus tempHeat below the solidus temp
Held for sometime, - random solid solnHeld for sometime, - random solid soln
Cool rapidly to room temp. retained.Cool rapidly to room temp. retained.
Soft and ductileSoft and ductile
AGE HARDENINGAGE HARDENING
Below : ordered structureBelow : ordered structure
Time periodTime period
Stronger, harder but less ductile.Stronger, harder but less ductile.

TwinningTwinning
Closed packed hexagonal type of crystalsClosed packed hexagonal type of crystals
Two symmetric halvesTwo symmetric halves
Fixed angleFixed angle
NiTi - multipleNiTi - multiple
Subjected to a higher temperature,Subjected to a higher temperature,
de - twinning occurs (shape memory)de - twinning occurs (shape memory)

PolymorphismPolymorphism
Metals and alloys exist as more than oneMetals and alloys exist as more than one
type of structuretype of structure
Transition from one to the otherTransition from one to the other
Allotropy -Allotropy - reversiblereversible
At higher temperature, ironAt higher temperature, iron FCC structureFCC structure
(austenite)(austenite)
lower temperatures,lower temperatures,  BCC structureBCC structure
(ferrite)(ferrite)

Transition of IronTransition of Iron
IronIron  FCC stableFCC stable
(austenite), 912*c-(austenite), 912*c-
1394*c1394*c
Lattice spaces greater,Lattice spaces greater,
Carbon atom can easily beCarbon atom can easily be
incorporated into the unitincorporated into the unit
cellcell

On Cooling <912*cOn Cooling <912*c
FCCFCC  BCCBCC
Carbon diffusesCarbon diffuses
out as FeCout as FeC
FeC adds strengthFeC adds strength
to ferrite andto ferrite and
austeniteaustenite
TIMETIME

Rapidly cooledRapidly cooled
(quenched)(quenched)

Carbon cannot escapeCarbon cannot escape
Highly strained,Highly strained,
distorted bodydistorted body
centered tetragonalcentered tetragonal
lattice calledlattice called
martensitemartensite

Grain boundaries are more in numberGrain boundaries are more in number
Alloy is stronger and more brittle-Alloy is stronger and more brittle-
martensitic change – various types of steelmartensitic change – various types of steel
Interstitials are intentionally incorporatedInterstitials are intentionally incorporated
into the alloy to make it hard when it isinto the alloy to make it hard when it is
quenched.quenched.

Cooled slowlyCooled slowly
Other crystal structures are formed atOther crystal structures are formed at
intermediate temperaturesintermediate temperatures SofterSofter
Some are stable at room temperatureSome are stable at room temperature
Ultimately, the final structure is softer andUltimately, the final structure is softer and
more workablemore workable

Tempering –Tempering –
Reheat the alloy to intermediateReheat the alloy to intermediate
temperature(1000*F/525*c)temperature(1000*F/525*c)
Partial transformation into softer alloysPartial transformation into softer alloys
Remedy brittle martensiteRemedy brittle martensite
more workablemore workable

Some alloysSome alloys
FCC to BCC by rearrangement of atomsFCC to BCC by rearrangement of atoms

Diagonal plane of the BCC unit becomes theDiagonal plane of the BCC unit becomes the
face of the FCC unitface of the FCC unit

Shape memory alloys – Easy switchingShape memory alloys – Easy switching
from one type of structure to another.from one type of structure to another.
Bain distortionBain distortion
Over a range of temperature {hysteresis}Over a range of temperature {hysteresis}
unlike ironunlike iron

Elastic PropertiesElastic Properties
Stress and strainStress and strain
Stress- internal distribution of load.Stress- internal distribution of load.
F/AF/A
Strain- internal distortion produced by loadStrain- internal distortion produced by load
deflection/unit lengthdeflection/unit length

Force applied to wireForce applied to wire DeflectionDeflection
Internal force----Internal force---- (equal and opposite)(equal and opposite)
Internal forceInternal force = Stress= Stress
Area of actionArea of action
DeflectionDeflection change in lengthchange in length = Strain= Strain
Original lengthOriginal length

Types of stress/strainTypes of stress/strain
Tensile –Tensile –stretch/pullstretch/pull
Compressive –Compressive – compress/towards each othercompress/towards each other
Shear – 2 forcesShear – 2 forces opp direction, not in same line.opp direction, not in same line.
sliding of one part over anothersliding of one part over another
Complex force systemsComplex force systems

Strain
Stress
Elastic Portion
Wire returns back to original
dimension when stress is
removed

Hooke’s lawHooke’s law
Spring stretch in proportion to applied forceSpring stretch in proportion to applied force
(proportional limit)(proportional limit)
Modulus of elasticity – constant for a givenModulus of elasticity – constant for a given
materialmaterial

Strain
Stress
Elastic Limit
Proportional Limit
Yield strength
0.1%

Strain
Stress
Ultimate Tensile
Strength Fracture Point

ultimate tensile strengthultimate tensile strength is higher than theis higher than the
yield strengthyield strength
important clinicallyimportant clinically  maximum force thatmaximum force that
the wire can deliverthe wire can deliver
Ultimate tensile strength higher than theUltimate tensile strength higher than the
stress at the point of fracturestress at the point of fracture

reduction in the diameter of the wirereduction in the diameter of the wire

Strain
Stress
Slope α Stiffness
Stiffness α 1 .
Springiness

Strain
Stress
Range Springback
Point of arbitrary clinical loading
Yield point

Clinically, ortho wires are deformed
beyond their elastic limit.
Springback properties are important
Strength = Stiffness x Range

Resiliency -Resiliency -
When a wire is stretched, the space between theWhen a wire is stretched, the space between the
atoms increases. Within the elastic limit, there isatoms increases. Within the elastic limit, there is
an attractive force between the atoms.an attractive force between the atoms.
Energy stored within the wire.Energy stored within the wire.
Strength + springinessStrength + springiness

Strain
Stress
Resilience Formability
Proportional limit
Yield strength

FormabilityFormability - amount of permanent- amount of permanent
deformation that the wire can withstanddeformation that the wire can withstand
without breakingwithout breaking
Indication of the ability of the wire to takeIndication of the ability of the wire to take
the shapethe shape
Also an indication of the amount of coldAlso an indication of the amount of cold
work that they can withstandwork that they can withstand

FlexibilityFlexibility
large deformation (or large strain) withlarge deformation (or large strain) with
minimal force, within its elastic limit.minimal force, within its elastic limit.
Maximal flexibility is the strain that occursMaximal flexibility is the strain that occurs
when a wire is stressed to its elastic limit.when a wire is stressed to its elastic limit.
Max. flexibility =Max. flexibility = Proportional limitProportional limit
Modulus of elasticity.Modulus of elasticity.

ToughnessToughness ––force required to fracture aforce required to fracture a
material. Total area under the stress –material. Total area under the stress –
strain graph.strain graph.
BrittlenessBrittleness ––opposite of toughness. Aopposite of toughness. A
brittle material, is elastic, butbrittle material, is elastic, but cannotcannot
undergo plastic deformationundergo plastic deformation. eg: Glass. eg: Glass
FatigueFatigue –– Repeated cyclic stress of aRepeated cyclic stress of a
magnitude below the fracture point of amagnitude below the fracture point of a
wire can result in fracture. This is calledwire can result in fracture. This is called
fatigue.fatigue. www.indiandentalacademy.comwww.indiandentalacademy.com

Properties ofProperties of
OrthodonticOrthodontic WiresWires
Part I
Dr. Vijaya Lakshmi www.indiandentalacademy.comwww.indiandentalacademy.com

Requirements of an ideal archwireRequirements of an ideal archwire
(Kusy )(Kusy )
1.1. EstheticsEsthetics
2.2. StiffnessStiffness
3.3. StrengthStrength
4.4. RangeRange
5.5. SpringbackSpringback
6.6. FormabilityFormability
7.7. ResiliencyResiliency
8.8. Coefficient of frictionCoefficient of friction
9.9. BiohostabilityBiohostability
10.10. BiocompatibilityBiocompatibility
11.11. WeldabilityWeldability

1. Esthetics1. Esthetics
DesirableDesirable
No compromise on mechanical propertiesNo compromise on mechanical properties
White coloured wires discolourWhite coloured wires discolour
Destroyed by oral enzymesDestroyed by oral enzymes
Deformed by masticatory loadsDeformed by masticatory loads
Except the composite wiresExcept the composite wires

2. Stiffness / Load deflection Rate2. Stiffness / Load deflection Rate
Proffit:Proffit: - slope of stress-strain curve- slope of stress-strain curve
ThurowThurow - force:distance ratio, measure of- force:distance ratio, measure of
resistance to deformation.resistance to deformation.
BurstoneBurstone – Stiffness is related to – wire– Stiffness is related to – wire
property & appliance designproperty & appliance design
Wire property is related to – Material &Wire property is related to – Material &
cross section.cross section.
WilcockWilcock – Stiffness α– Stiffness α LoadLoad

Stiffness / Load deflection RateStiffness / Load deflection Rate
Magnitude of the force delivered by the applianceMagnitude of the force delivered by the appliance
for a particular amount of deflection.for a particular amount of deflection.
Low stiffness or Low LDR implies thatLow stiffness or Low LDR implies that:-:-
1) Low forces will be applied1) Low forces will be applied
2) The force will be more constant as the appliance2) The force will be more constant as the appliance
deactivatesdeactivates
3) Greater ease and accuracy in applying a given3) Greater ease and accuracy in applying a given
force.force.

3 point bending test3 point bending test

3. Strength3. Strength
Yield strength, proportional limit and ultimateYield strength, proportional limit and ultimate
tensile/compressive strengthtensile/compressive strength
KusyKusy - force required to activate an archwire- force required to activate an archwire
to a specific distance.to a specific distance.
ProffitProffit - Strength = stiffness x range.- Strength = stiffness x range.
Range limits the amount the wire can beRange limits the amount the wire can be
bent, Stiffness is the indication of the forcebent, Stiffness is the indication of the force
required to reach that limit.required to reach that limit.www.indiandentalacademy.comwww.indiandentalacademy.com

StrengthStrength
TheThe shapeshape andand cross sectioncross section of a wireof a wire
have an effect on the strength of the wire.have an effect on the strength of the wire.
The effects of these will be consideredThe effects of these will be considered
subsequently.subsequently.

4. Range4. Range
Distance that the wire bends elastically,Distance that the wire bends elastically,
before permanent deformation occursbefore permanent deformation occurs
((ProffitProffit).).
KusyKusy – Distance to which an archwire can– Distance to which an archwire can
be activated- working range.be activated- working range.
ThurowThurow – A linear measure of how far a– A linear measure of how far a
wire or material can be deformed withoutwire or material can be deformed without
exceeding the limits of the material.exceeding the limits of the material.www.indiandentalacademy.comwww.indiandentalacademy.com

KusyKusy -- The extent to which a wire-- The extent to which a wire
recovers its shape after deactivationrecovers its shape after deactivation
Ingram et alIngram et al – a measure of how far a wire– a measure of how far a wire
can be deflected without causingcan be deflected without causing
permanent deformation. (Contrast topermanent deformation. (Contrast to
ProffitProffit yield pointyield point).).

Large springbackLarge springback
Activated to a large extent.Activated to a large extent.
Hence it will mean fewer archwireHence it will mean fewer archwire
changes.changes.
Ratio –Ratio – yield strengthyield strength
Modulus of elasticityModulus of elasticity

6.6. FormabilityFormability
KusyKusy – the ease in which a material may– the ease in which a material may
be permanently deformed.be permanently deformed.
Ease of forming a spring or archwireEase of forming a spring or archwire
Proffit:Proffit: amount of permanent deformationamount of permanent deformation
a wire can withstand without breakinga wire can withstand without breaking

7.7. ResiliencyResiliency
Store/absorb more strain energy /unitStore/absorb more strain energy /unit
volume before they get permanentlyvolume before they get permanently
deformeddeformed
Greater resistance to permanentGreater resistance to permanent
deformationdeformation
Release of greater amount of energy onRelease of greater amount of energy on
deactivationdeactivation
High work availability to move the teethHigh work availability to move the teeth

8.8. Coefficient of frictionCoefficient of friction
Brackets (and teeth) must be able to slideBrackets (and teeth) must be able to slide
along the wirealong the wire
High amounts of frictionHigh amounts of friction  anchor loss.anchor loss.

9.9. Biohostability:- site for accumulation ofBiohostability:- site for accumulation of
bacteria, spores or viruses. An idealbacteria, spores or viruses. An ideal
archwire must have poor biohostability.archwire must have poor biohostability.
10.10.Biocompatibility:- Resistance ofBiocompatibility:- Resistance of
corrosion, and tissue tolerance to the wire.corrosion, and tissue tolerance to the wire.
11. Weldability:- the ease by which the11. Weldability:- the ease by which the
wire can be joined to other metals, bywire can be joined to other metals, by
actually melting the 2 metals in the area ofactually melting the 2 metals in the area of
the bond. (A filler metal may or may not bethe bond. (A filler metal may or may not be
used.)used.) www.indiandentalacademy.comwww.indiandentalacademy.com

Properties of WiresProperties of Wires
Before the titanium alloys wereBefore the titanium alloys were
introduced into orthodontics, theintroduced into orthodontics, the
practitioners used only steel wires. Sopractitioners used only steel wires. So
the way to control the stiffness of the wirethe way to control the stiffness of the wire
was:-was:-
1.1. Change the cross section of the wireChange the cross section of the wire
2.2. Increase the length of the wire (Increase the length of the wire ( interinter
bracket distance, incorporate loops.)bracket distance, incorporate loops.)

Effects of Wire Cross SectionEffects of Wire Cross Section
Wires of various dimensions and crossWires of various dimensions and cross
sections.sections.
Does the wire need to be move teeth overDoes the wire need to be move teeth over
large distances, or does it need to correctlarge distances, or does it need to correct
the torque of the tooth?the torque of the tooth?
Is it primarily going to be used to correctIs it primarily going to be used to correct
first order irregularities, or second order?first order irregularities, or second order?

primary factorprimary factor 
load deflection rate or stiffnessload deflection rate or stiffness
play of the wireplay of the wire
in the second order –in the second order –
0.016” wire in 0.022” slot is only 1.15 times the play of a0.016” wire in 0.022” slot is only 1.15 times the play of a
0.018” wire.0.018” wire.
The play in the second order becomes significant if theThe play in the second order becomes significant if the
wire dimensions are drastically different (0.010” andwire dimensions are drastically different (0.010” and
0.020”)0.020”)

Based on stiffness/load deflection rate
Force delivered by a wire with high load deflection rate

Force delivered by a wire with low load deflection rate
Force delivered by a wire with low load deflection rate

Load deflection rateLoad deflection rate
Shape Moment
of Inertia
Ratio to stiffness of
round wire
Пd4
64
1
s4
12
1.7
b3
h
12
1.7 b3
h:d4

Dimension of wire increases- LDRDimension of wire increases- LDR
increasesincreases
Round and square wire of sameRound and square wire of same
dimension-LDR of square wire is more.dimension-LDR of square wire is more.
Rectangular wire – maximum stiffnessRectangular wire – maximum stiffness

Stiffness of different dimensions of wiresStiffness of different dimensions of wires
can be related to each other.can be related to each other.
0
500
1000
1500
2000
2500
3000
3500
Stiffnessnumber
(Burstone)
14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 18x25 25x18 21x25 25x21 215x28 28x215
Wire dimension
Relative stiffness

Rectangular wiresRectangular wires  bending perpendicular tobending perpendicular to
the larger dimension (ribbon mode)the larger dimension (ribbon mode)
easier than bending perpendicular to the smallereasier than bending perpendicular to the smaller
dimension (edgewise).dimension (edgewise).
0
500
1000
1500
2000
2500
3000
3500
Stiffnessnumber
(Burstone)
14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 18x25 25x18 21x25 25x21 215x28 28x215
Wire dimension
Relative stiffness

The larger dimensionThe larger dimension  correction is needed.correction is needed.
The smaller dimensionThe smaller dimension  the plane in whichthe plane in which
more stiffness is needed.more stiffness is needed.
> first order, < second order – RIBBON> first order, < second order – RIBBON
> Second order, < first order - EDGEWISE> Second order, < first order - EDGEWISE

> 1> 1stst
order correction in anterior segmentorder correction in anterior segment
> 2> 2ndnd
order in the posterior segment,order in the posterior segment,
wire can be twisted 90wire can be twisted 90oo
If both, 1If both, 1stst
& 2& 2ndnd
order corrections are required toorder corrections are required to
the same extent, thenthe same extent, then squaresquare oror round wires.round wires.
The square wires - advantage -The square wires - advantage - simultaneouslysimultaneously
control torquecontrol torque
better orientation into a rectangular slot.better orientation into a rectangular slot.

Cross-sectional shape:Cross-sectional shape:

On range and strengthOn range and strength

Diameter increases-strengthDiameter increases-strength thirdthird powerpower
of diameterof diameter

Range increases proportional toRange increases proportional to
diameterdiameter

In torsion - absolute values of strength,In torsion - absolute values of strength,
stiffness and range are different,stiffness and range are different,
but the overall effect of changing thebut the overall effect of changing the
diameter of the wire is the same.diameter of the wire is the same.
1.1. Strength – Increases with increase inStrength – Increases with increase in
diameterdiameter
2.2. Stiffness – increasesStiffness – increases
3.3. Range –Range – decreases.decreases.www.indiandentalacademy.comwww.indiandentalacademy.com

Effects of LengthEffects of Length
Loops,Loops,
 the inter-bracket distancethe inter-bracket distance
For bendingFor bending
1.1. Strength – decreases proportionatelyStrength – decreases proportionately
2.2. Stiffness – decreases as aStiffness – decreases as a cubiccubic functionfunction
3.3. Range – increases as aRange – increases as a squaresquare..

In the case ofIn the case of torsiontorsion, the picture is, the picture is
slightly different.slightly different. Increase in length:Increase in length: ––
1.1. Stiffness decreases proportionatelyStiffness decreases proportionately
2.2. Range increases proportionatelyRange increases proportionately
3.3. Strength remains unchanged.Strength remains unchanged.

Way the beam is attached also affects theWay the beam is attached also affects the
valuesvalues
cantilever, the stiffness of a wire iscantilever, the stiffness of a wire is
obviously lessobviously less
wire is supported from both sides (as anwire is supported from both sides (as an
archwire in brackets), again, the stiffnessarchwire in brackets), again, the stiffness
is affectedis affected

Cantilever Beam supported on both ends Fixed at both ends

Stiffness is also affected by the method ofStiffness is also affected by the method of
ligation of the wire into the brackets.ligation of the wire into the brackets.
Loosely ligated, so that it can slide throughLoosely ligated, so that it can slide through
the brackets, it has ¼th the stiffness of athe brackets, it has ¼th the stiffness of a
wire that is tightly ligated.wire that is tightly ligated.

Clinical ImplicationsClinical Implications
LIGHT CONTINUOUS FORCESLIGHT CONTINUOUS FORCES
Stiff wires should be taboo to theStiff wires should be taboo to the
orthodontist?orthodontist?
Springier wire, can be easily distorted inSpringier wire, can be easily distorted in
the harsh oral environment.the harsh oral environment.
Aim atAim at balancebalance..

Removable applianceRemovable appliance cantilever springcantilever spring
The material of choice is usually steel. (StiffThe material of choice is usually steel. (Stiff
material)material)
Sufficiently thick steel wireSufficiently thick steel wire
Good strength to resist masticatory and otherGood strength to resist masticatory and other
oral forces.oral forces.
Increase the length of the wireIncrease the length of the wire 

ProportionateProportionate decrease in strength, but thedecrease in strength, but the
stiffness will decrease as astiffness will decrease as a cubiccubic functionfunction

Length is increased by eitherLength is increased by either bending the wirebending the wire
over itselfover itself, or by winding, or by winding helicalshelicals oror loopsloops intointo
the springthe spring www.indiandentalacademy.comwww.indiandentalacademy.com

In archwires of stiffer materials the sameIn archwires of stiffer materials the same
principle can be used.principle can be used.
The length of wire between brackets canThe length of wire between brackets can
be increasedbe increased

loops, or smaller brackets, or special bracketloops, or smaller brackets, or special bracket
designs.designs.
Also, the use of flexible wiresAlso, the use of flexible wires
Multistranded wiresMultistranded wires

Variable cross-section orthodontics.Variable cross-section orthodontics.
Variable modulus orthodontics.Variable modulus orthodontics.

NiTi – high springbackNiTi – high springback
Initial stages – NiTi instead of steelInitial stages – NiTi instead of steel
Towards the end- stiff steel wireTowards the end- stiff steel wire
TMA - intermediate properties- transitionTMA - intermediate properties- transition
wirewire

variable modulus orthodontics –variable modulus orthodontics –
Advantage-Advantage-

relatively constant dimensionrelatively constant dimension

important for the third order controlimportant for the third order control
variable stiffness approach,variable stiffness approach,

compromise control for getting a wire withcompromise control for getting a wire with
adequate stiffness,adequate stiffness,

had to spend clinical time bending loops intohad to spend clinical time bending loops into
stiffer archwires, which would offer less play.stiffer archwires, which would offer less play.

Requirements of arch wires in different stages of
treatment www.indiandentalacademy.comwww.indiandentalacademy.com

AppropriateAppropriate
wirewire
Take into account the amount of force that wireTake into account the amount of force that wire
can deliver.can deliver.
For example, a NiTi wireFor example, a NiTi wire  efficient in tippingefficient in tipping
teeth to get them into alignment, but may not beteeth to get them into alignment, but may not be
able to achieve third order corrections.able to achieve third order corrections.
After using rectangular NiTi wires for alignment,After using rectangular NiTi wires for alignment,
rectangular steel wire must always be used torectangular steel wire must always be used to
achieve the correct torque of the tooth.achieve the correct torque of the tooth.

NomogramsNomograms

AA rough idea can be obtained clinically as wellrough idea can be obtained clinically as well
Forming an arch wire with the thumb givesForming an arch wire with the thumb gives
an indication of thean indication of the stiffnessstiffness of the wire.of the wire.
Flexing the wires between the fingers,Flexing the wires between the fingers,
without deforming it, is a measure ofwithout deforming it, is a measure of
flexibilityflexibility
Deflecting the ends of an archwire betweenDeflecting the ends of an archwire between
the thumb and finger gives a measure ofthe thumb and finger gives a measure of
resiliency.resiliency.

CorrosionCorrosion
Nickel -Nickel -
1.1. Carcinogenic,Carcinogenic,
2.2. mutagenic,mutagenic,
3.3. cytotoxic andcytotoxic and
4.4. allergenic.allergenic.
 Stainless steels, Co-Cr-Ni alloys and NiTiStainless steels, Co-Cr-Ni alloys and NiTi
are all rich in Niare all rich in Ni

CorrosionCorrosion
Placement in the oral cavityPlacement in the oral cavity

Greater peril than implantingGreater peril than implanting

Implanted material gets surrounded by aImplanted material gets surrounded by a
connective tissue capsuleconnective tissue capsule

In the oral cavity, the alloy is free to reactIn the oral cavity, the alloy is free to react
with the environment.with the environment.www.indiandentalacademy.comwww.indiandentalacademy.com

CorrosionCorrosion
Stainless steel- Ni austenite stabilizer. NotStainless steel- Ni austenite stabilizer. Not
strongly bonded- slow releasestrongly bonded- slow release
Passivating filmPassivating film  traces of Fe ,Ni and Mo.traces of Fe ,Ni and Mo.
Aqueous environmentAqueous environment

inner oxide layerinner oxide layer

outer hydroxide layer.outer hydroxide layer.
CrO is not as efficient as TiO in resistingCrO is not as efficient as TiO in resisting
corrosioncorrosion some Ni releasesome Ni release
Improper handlingImproper handling  sensitizationsensitization

CorrosionCorrosion
1.1. Uniform attack –Uniform attack –
the entire wire reacts with thethe entire wire reacts with the
environment,environment,
hydroxides or organometallic compoundshydroxides or organometallic compounds
detectable after a large amount of metaldetectable after a large amount of metal
is dissolved.is dissolved.
2.2. Pitting CorrosionPitting Corrosion ––
manufacturing defectsmanufacturing defects
sites of easy attacksites of easy attack

CorrosionCorrosion
Stainless Steel
NiTi
Pitting corrosion

CorrosionCorrosion
3.3. Crevice corrosion or gasket corrosion -Crevice corrosion or gasket corrosion -
Parts of the wire exposed to corrosiveParts of the wire exposed to corrosive
environmentenvironment
Sites of tying to the bracketsSites of tying to the brackets
Plaque build upPlaque build up  disturbs the regeneration ofdisturbs the regeneration of
the passivating layerthe passivating layer
Reach upto 2-5 mmReach upto 2-5 mm
High amount of metals can be dissolved in theHigh amount of metals can be dissolved in the
mouth.mouth.

CorrosionCorrosion
4.4. GalvanicGalvanic //Electrochemical CorrosionElectrochemical Corrosion
two metals are joinedtwo metals are joined
or even the same metal after different type ofor even the same metal after different type of
treatment (soldering etc)treatment (soldering etc)
difference in the reactivitydifference in the reactivity 
Galvanic cell.Galvanic cell.
 
Less ReactiveLess Reactive More ReactiveMore Reactive
(Cathodic)(Cathodic) (Anodic(Anodic) less) less noble metalnoble metal

CorrosionCorrosion
AnodicAnodic

Looses ElectronsLooses Electrons

Soluble ionsSoluble ions

Leach outLeach out
Cathodic (nobel)Cathodic (nobel)

Accepts electronsAccepts electrons

Even less reactiveEven less reactive
S.Steel- active and passive areas : depletion &
regeneration of passivating film

CorrosionCorrosion
5.5. Intergranular corrosionIntergranular corrosion
Sensitization - ppt of CrCSensitization - ppt of CrC
6.6. Fretting corrosionFretting corrosion
Wire and brackets contactWire and brackets contact
FrictionFriction  surface destructionsurface destruction
PressurePressure  rupture of the oxide layerrupture of the oxide layer
Debris get deposited at grain boundaries, grainDebris get deposited at grain boundaries, grain
structure is disturbed.structure is disturbed.

CorrosionCorrosion
7.7. Microbiologically influenced corrosionMicrobiologically influenced corrosion
AdhesiveAdhesive
Craters at the base of bracketsCraters at the base of brackets
Or wires directly bonded on to teethOr wires directly bonded on to teeth
shown by Matasa.shown by Matasa.
Certain bacteria dissolve metals directlyCertain bacteria dissolve metals directly
form the wires.form the wires.
Others affect surface structure.Others affect surface structure.

Micro-0rganisms on various dentalMicro-0rganisms on various dental
materialsmaterials

CorrosionCorrosion
8.8. Stress corrosionStress corrosion
Similar to galvanic corrosionSimilar to galvanic corrosion
Bending of wiresBending of wires  different degress ofdifferent degress of
tension and compression.tension and compression.
Alter theAlter the electrochemical behaviorelectrochemical behavior
 
anode cathodeanode cathode

CorrosionCorrosion
9.9. CorrosionCorrosion Fatigue:Fatigue:
Cyclic stressing of a wireCyclic stressing of a wire
Resistance to fracture decreasesResistance to fracture decreases
Accelerated in a corrosive medium suchAccelerated in a corrosive medium such
as salivaas saliva

CorrosionCorrosion
Analysis of used wires also indicated that aAnalysis of used wires also indicated that a
biofilmbiofilm was formed on the wire.was formed on the wire.
Eliades et alEliades et al
CalcificationCalcification

Shielding the wireShielding the wire

Protecting the patient from the alloyProtecting the patient from the alloy
Stainless steel: Fe, Ni, Cr. Allergic potentialStainless steel: Fe, Ni, Cr. Allergic potential

OrthOdOntic Arch Wire
MAteriAls

Precious MetalsPrecious Metals
Upto about the 1950sUpto about the 1950s
Gold alloysGold alloys
Only wire which would tolerate the oralOnly wire which would tolerate the oral
environmentenvironment
Crozat appliance – according to originalCrozat appliance – according to original
designdesign

Stainless SteelStainless Steel
1919 – Germany1919 – Germany  used to makeused to make
prostheses.prostheses.
Extremely chemically stableExtremely chemically stable
High resistance to corrosion.High resistance to corrosion.
Chromium content.Chromium content.
The chromium gets oxidized,The chromium gets oxidized,

Impermeable, corrosion resistant layer.Impermeable, corrosion resistant layer.

Variety of stainless steelsVariety of stainless steels
Varying the degree of coldVarying the degree of cold
work and annealing duringwork and annealing during
manufacturemanufacture
Fully annealed stainlessFully annealed stainless
steelsteel  extremely soft, andextremely soft, and
highly formablehighly formable
Ligature wireLigature wire
““Dead soft”Dead soft” www.indiandentalacademy.comwww.indiandentalacademy.com

stainless steel arch wires are cold workedstainless steel arch wires are cold worked
to varying extents,to varying extents,  yield strengthyield strength
increases, at the cost of their formabilityincreases, at the cost of their formability
The steel with the highest yield strength,The steel with the highest yield strength,
the Supreme grade steels, are also verythe Supreme grade steels, are also very
brittle, and break easily when bentbrittle, and break easily when bent
sharply.sharply.

Structure and compositionStructure and composition
Chromium (11-26%)–Chromium (11-26%)–improves the corrosionimproves the corrosion
resistanceresistance
Stabilizes BCC phaseStabilizes BCC phase
Nickel(0-22%) – austenitic stabilizerNickel(0-22%) – austenitic stabilizer
copper, manganese and nitrogen - similarcopper, manganese and nitrogen - similar

amount of nickel added to the alloyamount of nickel added to the alloy

adversely affect the corrosion resistance.adversely affect the corrosion resistance.

Carbon (0.08-1.2%)– provides strengthCarbon (0.08-1.2%)– provides strength
Reduces the corrosion resistanceReduces the corrosion resistance
SensitizationSensitization..
During soldering or welding, 425-815During soldering or welding, 425-815oo
cc
Chromium diffuses towards the carbonChromium diffuses towards the carbon
rich areas (usually the grain boundaries)rich areas (usually the grain boundaries)

Chromium carbidesChromium carbides
Amount of chromium decreasesAmount of chromium decreases
Chromium carbide is soluble,Chromium carbide is soluble, 
intergranular corrosion.intergranular corrosion.
StabilizationStabilization

Stabilization –

Element which precipitates carbide moreElement which precipitates carbide more
easily than Chromium.easily than Chromium.

Usu. Titanium.Usu. Titanium.

Ti 6x> CarbonTi 6x> Carbon

No sensitization during soldering.No sensitization during soldering.

Most steels used in orthodontics are notMost steels used in orthodontics are not
stabilized.stabilized.

SiliconSilicon – (low concentrations) improves the– (low concentrations) improves the
resistance to oxidation and carburization at highresistance to oxidation and carburization at high
temperatures.temperatures.
SulfurSulfur (0.015%) increases ease of machining(0.015%) increases ease of machining
Phosphorous – allows sintering at lower– allows sintering at lower
temperatures.temperatures.
But both sulfur and phosphorousBut both sulfur and phosphorous reduce thereduce the
corrosion resistance.corrosion resistance.

Manufacture: AISI ,Manufacture: AISI ,specially for orthodontic purposesspecially for orthodontic purposes
Various steps –Various steps –
1.1. MeltingMelting
2.2. Ingot FormationIngot Formation
3.3. RollingRolling
4.4. DrawingDrawing
MANUFACTUREMANUFACTURE

MeltingMelting

Various metals of the alloy are meltedVarious metals of the alloy are melted

Proportion influences the propertiesProportion influences the properties
Ingot formationIngot formation

Molten alloy into mold.Molten alloy into mold.

Non uniform chunk of metalNon uniform chunk of metal

Porosities and slag.Porosities and slag.

Grains seen in the ingot – control ofGrains seen in the ingot – control of
mechanical propertiesmechanical properties
stepssteps


Porosities due to dissolved gases (produced /Porosities due to dissolved gases (produced /
trapped)trapped)

Vacuum voids due to shrinking of late coolingVacuum voids due to shrinking of late cooling
interior.interior.

Important to control microstructure at thisImportant to control microstructure at this
stage – basis of its phy properties andstage – basis of its phy properties and
mechanical performancemechanical performance
Ingot formationIngot formation

Rolling –Rolling –

First mechanical process.First mechanical process.

Ingot reduced to thinner barsIngot reduced to thinner bars

Finally form a wireFinally form a wire

Different wires from the same batch, differ inDifferent wires from the same batch, differ in
propertiesproperties
stepssteps


Retain their property even after rollingRetain their property even after rolling

Shape & arrangement alteredShape & arrangement altered

Grains get elongated, defects get rearrangedGrains get elongated, defects get rearranged

Work hardening – structure locked up.Work hardening – structure locked up.

Wires start to crack if rolling continuedWires start to crack if rolling continued

AnnealingAnnealing is done- mobileis done- mobile

Cooling – structure resembles original ingot, uniformCooling – structure resembles original ingot, uniform
RollingRolling

DrawingDrawing

More preciseMore precise

IngotIngot  final size.final size.

Wire pulled through small hole in a dieWire pulled through small hole in a die

Progressively smaller diameter-uniform squeezing.Progressively smaller diameter-uniform squeezing.

Same pressure all around, instead of from 2 oppositeSame pressure all around, instead of from 2 opposite
sides.sides.
stepssteps


Series of diesSeries of dies

Annealing at regular intervals.Annealing at regular intervals.

Exact number of drafts and annealing cyclesExact number of drafts and annealing cycles
depends on the alloy (gold <carbondepends on the alloy (gold <carbon
steel<stainless steel)steel<stainless steel)
DrawingDrawing

Stress reliefStress relief
During manufacture, wire highly stressed.During manufacture, wire highly stressed.
Adverse effects on mechanical propertiesAdverse effects on mechanical properties
Annealing heat treatmentAnnealing heat treatment
By minute slippages & readjustments inBy minute slippages & readjustments in
intergranular relations without the loss ofintergranular relations without the loss of
hardening higher temp of annealinghardening higher temp of annealing
Alternate sequence of cold working & heatAlternate sequence of cold working & heat
treatment—improve strengthtreatment—improve strength

Clinical implicationsClinical implications
Soldering attachments to arch wire:Soldering attachments to arch wire:

Raise in temp----wire deadRaise in temp----wire dead

Quick and well controlled.Quick and well controlled.

Cinch back, heatCinch back, heat

Wire #Wire #

ClassificationClassification
American Iron and Steel Institute (AISI)American Iron and Steel Institute (AISI)
Unified Number System (UNS)Unified Number System (UNS)
German Standards (DIN).German Standards (DIN).

The AISI numbers used for stainless steel rangeThe AISI numbers used for stainless steel range
from 300 to 502from 300 to 502
Numbers beginning withNumbers beginning with 33 are all austeniticare all austenitic
Higher the numberHigher the number 

More the iron contentMore the iron content

More expensive the alloyMore expensive the alloy

Numbers having a letter L signify a low carbonNumbers having a letter L signify a low carbon
contentcontent www.indiandentalacademy.comwww.indiandentalacademy.com

Austenitic steels (the 300 series)Austenitic steels (the 300 series)
Better corrosion resistance -attachmentsBetter corrosion resistance -attachments
FCC structureFCC structure  non ferromagneticnon ferromagnetic
Not stable at room temperature,Not stable at room temperature,
Austenite stabilizersAustenite stabilizers Ni, Mn and NNi, Mn and N
Known as the 18-8 stainless steelsKnown as the 18-8 stainless steels..

Martensitic steelMartensitic steel
FCCFCC  BCCBCC
BCC structure is highly stressed.BCC structure is highly stressed.
More grain boundaries,More grain boundaries,

StrongerStronger

Less corrosion resistantLess corrosion resistant
Making instrument edges which need toMaking instrument edges which need to
be sharp and wear resistant.be sharp and wear resistant.

Ferritic steelsFerritic steels – (the 400 series)– (the 400 series)
Good corrosion resistanceGood corrosion resistance
Low strength.Low strength.
Not hardenable by heat treatment.Not hardenable by heat treatment.
Not readily cold worked.Not readily cold worked.

Austenitic steels more preferableAustenitic steels more preferable :-:-
Greater ductility and ability to undergo more coldGreater ductility and ability to undergo more cold
work without breaking.work without breaking.
Substantial strengthening during cold work.Substantial strengthening during cold work.
(Cannot be strengthened by heat treatment).(Cannot be strengthened by heat treatment).
Strengthening effect is due partial conversion toStrengthening effect is due partial conversion to
martensite.martensite.
Easy to weldEasy to weld
Easily overcome sensitizationEasily overcome sensitization
Ease in forming.Ease in forming.

Duplex steelsDuplex steels
Both austenite and ferrite grainsBoth austenite and ferrite grains
Increased toughness and ductility thanIncreased toughness and ductility than
Ferritic steelsFerritic steels
Twice the yield strength of austeniticTwice the yield strength of austenitic
steelssteels
Lower nickel contentLower nickel content
Manufacturing low nickel attachmentsManufacturing low nickel attachmentswww.indiandentalacademy.comwww.indiandentalacademy.com

Stainless steelStainless steel
Precipitation hardened steelsPrecipitation hardened steels
Certain elements added to themCertain elements added to them 
precipitate and increase the hardness onprecipitate and increase the hardness on
heat treatment.heat treatment.
The strength is very highThe strength is very high
Resistance to corrosion is low.Resistance to corrosion is low.
Used to make mini-brackets.Used to make mini-brackets.

General properties of StainlessGeneral properties of Stainless
SteelSteel
Relatively stiff materialRelatively stiff material
Yield strength and stiffness can be variedYield strength and stiffness can be varied

Altering the carbon content andAltering the carbon content and

Cold working andCold working and

AnnealingAnnealing
High forces - dissipate over a very shortHigh forces - dissipate over a very short
amount of deactivation (amount of deactivation (high loadhigh load
deflection ratedeflection rate).).www.indiandentalacademy.comwww.indiandentalacademy.com

Clinical terms:-Clinical terms:-
Loop - activated to a very small extent soLoop - activated to a very small extent so
as to achieve optimal forceas to achieve optimal force
Deactivated by only a small amount (0.1Deactivated by only a small amount (0.1
mm)mm)
Force level will drop tremendouslyForce level will drop tremendously
Not physiologicNot physiologic
More activationsMore activationswww.indiandentalacademy.comwww.indiandentalacademy.com

Force required to engage a steel wire intoForce required to engage a steel wire into
a severely mal-aligned tooth.a severely mal-aligned tooth.

Either cause the bracket to pop out,Either cause the bracket to pop out,

Or the patient to experience pain.Or the patient to experience pain.
Overcome by using thinner wires, whichOvercome by using thinner wires, which
have a lower stiffness.have a lower stiffness.
Fit poorlyFit poorly loss of control on the teeth.loss of control on the teeth.

High stiffnessHigh stiffness 
Maintain the positions of teethMaintain the positions of teeth
Hold the corrections achievedHold the corrections achieved
Begg treatment, stiff archwire, to dissipateBegg treatment, stiff archwire, to dissipate
the adverse effects of third stagethe adverse effects of third stage
auxiliariesauxiliaries

Lowest frictional resistanceLowest frictional resistance
Ideal choice of wire during space closureIdeal choice of wire during space closure
with sliding mechanicswith sliding mechanics
Teeth be held in their corrected relationTeeth be held in their corrected relation
Minimum resistance to slidingMinimum resistance to sliding

High Tensile Australian WiresHigh Tensile Australian Wires
HistoryHistory
Early part of Dr. Begg’s careerEarly part of Dr. Begg’s career
Arthur Wilcock Sr.Arthur Wilcock Sr.

Lock pins, brackets, bands, wires, etcLock pins, brackets, bands, wires, etc
Wires which would remain active for longWires which would remain active for long
No frequent visitsNo frequent visits
This lead Wilcock to develop steel wires of highThis lead Wilcock to develop steel wires of high
tensile strength.tensile strength.

Beginners found it difficult to use theBeginners found it difficult to use the
highest tensile wireshighest tensile wires
Grading systemGrading system
Late 1950s, the grades available were –Late 1950s, the grades available were –

RegularRegular

Regular plusRegular plus

SpecialSpecial

Special plusSpecial plus

Newer grades were introduced after the 70s.Newer grades were introduced after the 70s.
Premium, premium +, supremePremium, premium +, supreme
Raw materials directly from the suppliers from out ofRaw materials directly from the suppliers from out of
AustraliaAustralia
More specific ordering and obtaining better raw materialsMore specific ordering and obtaining better raw materials
Premium grade-high tensile strengthPremium grade-high tensile strength
Brittle.Brittle.
Softening , loss of high tensile propertiesSoftening , loss of high tensile properties

Bauschinger effectBauschinger effect..
Described by Dr. Bauschinger in 1886.Described by Dr. Bauschinger in 1886.
Material strained beyond its yield point inMaterial strained beyond its yield point in
one direction,one direction,
then strained in the reverse directionthen strained in the reverse direction,,
its yield strength in the reverse direction isits yield strength in the reverse direction is
reducedreduced..

1.1. Plastic prestrain increases the elastic limit ofPlastic prestrain increases the elastic limit of
deformation in the same direction as thedeformation in the same direction as the
prestrain.prestrain.
2.2. Decreases in oppositeDecreases in opposite
If the magnitude of the prestrain is increased,If the magnitude of the prestrain is increased,
the elastic limit in the reverse direction canthe elastic limit in the reverse direction can
reduce to zero.reduce to zero.

Straightening a wireStraightening a wire  pulling through apulling through a
series of rollersseries of rollers
Prestrain in a particular direction.Prestrain in a particular direction.
Yield strength for bending in the oppositeYield strength for bending in the opposite
direction will decrease.direction will decrease.
Premium wirePremium wire  special plus or specialspecial plus or special
wirewire www.indiandentalacademy.comwww.indiandentalacademy.com

Spinner straighteningSpinner straightening
It is mechanical process of straighteningIt is mechanical process of straightening
resistant materials in the cold drawnresistant materials in the cold drawn
condition.condition.
The wire is pulled through rotating bronzeThe wire is pulled through rotating bronze
rollers that torsionally twist it into straightrollers that torsionally twist it into straight
condition.condition.
Disadv:Disadv:
Decreases yield strengthDecreases yield strength
Creates rougher surfaceCreates rougher surface

Pulse straighteningPulse straightening
Special methodSpecial method
Placed in special machines that permitsPlaced in special machines that permits
high tensile wires to be straightened.high tensile wires to be straightened.
Advantages:Advantages:
1.1. Permits the straightening of high tensile wiresPermits the straightening of high tensile wires
2.2. Does not reduce the yield strength of the wireDoes not reduce the yield strength of the wire
3.3. Results in a smoother wire, hence less wire –Results in a smoother wire, hence less wire –
bracket friction.bracket friction.

Methods of increasing yield strength ofMethods of increasing yield strength of
Australian wires.Australian wires.
1.1. Work hardeningWork hardening
2.2. Dislocation lockingDislocation locking
3.3. Solid solution strengtheningSolid solution strengthening
4.4. Grain refinement and orientationGrain refinement and orientation

By alternate sequence of
cold working and heat
treatment the yield point
of wire can be increased
to as much as
200tons/sq inch as
shown in this graph.

Higher yield strengthHigher yield strength 
more flexible.more flexible.
Supreme gradeSupreme grade
flexibility = β-flexibility = β-
titanium.titanium.
Higher resiliencyHigher resiliency 
nearly three times.nearly three times.
NiTiNiTi  higher flexibilityhigher flexibility
but it lacks formabilitybut it lacks formability

MollenhauerMollenhauer 
Supreme grade wireSupreme grade wire  faster and gentlerfaster and gentler
alignment of teeth.alignment of teeth.
IntrusionIntrusion  simultaneously with the basesimultaneously with the base
wireswires
Gingival health seemed betterGingival health seemed better
Originally in lingual orthodonticsOriginally in lingual orthodontics
Equally good for labial orthodontics asEqually good for labial orthodontics as
well.well. www.indiandentalacademy.comwww.indiandentalacademy.com

Clinical significance of high yield strength
1. Increased working range:1. Increased working range:
Yield strengthYield strength
modulus of elasticitymodulus of elasticity
2.2. Increased resiliency:Increased resiliency:
(( yield strength)2yield strength)2
elastic moduluselastic modulus
Stiffness remains the sameStiffness remains the same

3. Zero Stress Relaxation3. Zero Stress Relaxation
If a wire isIf a wire is deformeddeformed and held in aand held in a fixed positionfixed position, the, the
stressstress in the wire mayin the wire may diminishdiminish with time, but thewith time, but the strainstrain
remains constantremains constant..
Engineering terms, implies that a form of slip by dislocationEngineering terms, implies that a form of slip by dislocation
movement takes place at the atomic levelmovement takes place at the atomic level
Property of a wire to giveProperty of a wire to give constant light forceconstant light force, when, when
subjected to external forces (like occlusal forces).subjected to external forces (like occlusal forces).

external forcesexternal forces

particles slip over each otherparticles slip over each other

activation of the wire is lostactivation of the wire is lost
OvercomeOvercome
 
Internal frictionInternal friction
Between particlesBetween particles
 yield strength

Zero stress relaxation in springs.Zero stress relaxation in springs.
To avoid relaxation in the wire’s workingTo avoid relaxation in the wire’s working
stressstress
Diameter of coil : Diameter of wire = 4Diameter of coil : Diameter of wire = 4
smaller diameter of wiressmaller diameter of wires  smallersmaller
diameter springs (like the mini springs)diameter springs (like the mini springs)
Midi springsMidi springs

Twelftree, Cocks and Sims (AJO 1977)Twelftree, Cocks and Sims (AJO 1977)
Premium plus, Premium and Special plusPremium plus, Premium and Special plus
wires showed minimal stress relaxation.wires showed minimal stress relaxation.
Special,Special,
Remanit,Remanit,
Yellow Elgiloy,Yellow Elgiloy,
Unisil.Unisil.

Hazel, Rohan & West (1984)Hazel, Rohan & West (1984)

Stress relaxation of Special plus wires after 28Stress relaxation of Special plus wires after 28
days was less than Dentaurum SS and Elgiloydays was less than Dentaurum SS and Elgiloy
wires.wires.
Barrowes (1982) & Jyothindra KumarBarrowes (1982) & Jyothindra Kumar
(1989)(1989)

Higher working range among steel wires.Higher working range among steel wires.

Pulse straightened wires – SpinnerPulse straightened wires – Spinner
straightened wiresstraightened wires
(Skaria 1991)(Skaria 1991)

Strength, stiffness and Range higherStrength, stiffness and Range higher

Coeff. of friction higherCoeff. of friction higher

Similar surface topography, stress relaxation andSimilar surface topography, stress relaxation and
Elemental makeup.Elemental makeup.

A study of the metallurgical properties of newlyA study of the metallurgical properties of newly
introduced high tensile wires in comparison to theintroduced high tensile wires in comparison to the
high tensile Australian wires for various applicationshigh tensile Australian wires for various applications
in orthodontic treatmentin orthodontic treatment
Dr.Dr. Anuradha Acharya (2000)Anuradha Acharya (2000)

Super Plus (Ortho Organizers) – between SpecialSuper Plus (Ortho Organizers) – between Special
plus and Premiumplus and Premium

Premier (TP) – Comparable to SpecialPremier (TP) – Comparable to Special

Premier Plus – Special PlusPremier Plus – Special Plus

Bowflex – PremiumBowflex – Premium

Highest yield strength and ultimate tensileHighest yield strength and ultimate tensile
strength as compared to the correspondingstrength as compared to the corresponding
wires.wires.
Higher rangeHigher range
Lesser coefficient of frictionLesser coefficient of friction

Surface area seems to be rougher than that of theSurface area seems to be rougher than that of the
other manufacturers’ wires.other manufacturers’ wires.
Lowest stress relaxation.Lowest stress relaxation.

Clinical implicationsClinical implications
Stage I:Stage I:
1.1. Wilcock (P) / S+ base wire(.014”)Wilcock (P) / S+ base wire(.014”)
2.2. Ortho organizers (super +)Ortho organizers (super +)

Wilcock (P) & S+; T.P. Bowflex .016”Wilcock (P) & S+; T.P. Bowflex .016”

Ortho organizers ( super +) T.P P+Ortho organizers ( super +) T.P P+
 Latter part of Stage I and most of Stage IILatter part of Stage I and most of Stage II
1.1. T.P (Premier), Wilcock P ,S+ .018” diaT.P (Premier), Wilcock P ,S+ .018” dia
2.2. Ortho Organizers (super +) T.P BowflexOrtho Organizers (super +) T.P Bowflex
 Base wires in Stage III , torquing auxiliaries,Base wires in Stage III , torquing auxiliaries,
uprighting springsuprighting springs
1.1. Wilcock S+ / P .020” base wireWilcock S+ / P .020” base wire

Wilcock P and Supreme in .012”, .010” diaWilcock P and Supreme in .012”, .010” dia
respectivelyrespectively

Dislocation lockingDislocation locking

High tensile wires have high density ofHigh tensile wires have high density of
dislocations and crystal defectsdislocations and crystal defects

Pile up, and form a minute crackPile up, and form a minute crack

Stress concentrationStress concentration

Small stress applied with the plier beaksSmall stress applied with the plier beaks

Crack propagationCrack propagation

Elastic energy is releasedElastic energy is released

Propagation accelerates to the nearest grainPropagation accelerates to the nearest grain
boundaryboundary

Ways of preventing fractureWays of preventing fracture
1.1. Bending the wire around theBending the wire around the flat beakflat beak ofof
the pliers.the pliers.
Introduces aIntroduces a momentmoment about the thumbabout the thumb
and wire gripping point, which reducesand wire gripping point, which reduces
the applied stress on the wire.the applied stress on the wire.

2.2. The wire should not be held tightly in theThe wire should not be held tightly in the
beaks of the pliers.beaks of the pliers.
Area of permanent deformation to beArea of permanent deformation to be
slightly enlarged,slightly enlarged,
Nicking and scarring avoided.Nicking and scarring avoided.
The tips of the pliers shouldThe tips of the pliers should notnot be ofbe of
tungsten carbide.tungsten carbide.

3.3. The edges roundedThe edges rounded  reduce the stressreduce the stress
concentration in the wire.concentration in the wire.
4.4. Ductile – brittle transition temperatureDuctile – brittle transition temperature
slightly above room temperature.slightly above room temperature.
Wire should be warmed.Wire should be warmed.
Spools kept in oven at about 40Spools kept in oven at about 40oo
, so that, so that
the wire remains slightly warm.the wire remains slightly warm.

Multistranded WiresMultistranded Wires
2 or more wires of smaller diameter are2 or more wires of smaller diameter are
twisted together/coiled around a core wire.twisted together/coiled around a core wire.
Diameter - 0.0165 or 0.0175, but theDiameter - 0.0165 or 0.0175, but the
stiffness is much less.stiffness is much less.
On bendingOn bending  individual strands slip overindividual strands slip over
each other and the core wire, makingeach other and the core wire, making
bending easy. (yield point)bending easy. (yield point)www.indiandentalacademy.comwww.indiandentalacademy.com

Multi stranded wiresMulti stranded wires
Co-axial
Twisted wire
Multi braided

Multi stranded wiresMulti stranded wires
Strength – resist distortionStrength – resist distortion
Separate strands - .007” but final wire canSeparate strands - .007” but final wire can
be either round / rectangularbe either round / rectangular
Sustain large elastic deflection in bendingSustain large elastic deflection in bending
Thurow: rough idea – multiplyThurow: rough idea – multiply

As the diameter of a wire decreases –As the diameter of a wire decreases –
Stiffness – decreases as a function of the 4Stiffness – decreases as a function of the 4thth
powerpower
Range – increases proportionatelyRange – increases proportionately
Strength – decreases as a function of the 3Strength – decreases as a function of the 3rdrd
powerpower
Multistranded wiresMultistranded wires  Small diameter wires,Small diameter wires,
High strengthHigh strength
Gentler forceGentler force

Elastic properties of multistranded archwiresElastic properties of multistranded archwires
depend on –depend on –
1.1. Material parametersMaterial parameters – Modulus of elasticity– Modulus of elasticity
2.2. Geometric factorsGeometric factors – wire dimension– wire dimension
3.3. Constants:Constants:

Number of strands coiledNumber of strands coiled

The distance from the neutral axis to theThe distance from the neutral axis to the
outer most fiber of a strandouter most fiber of a strand

Plane of bendingPlane of bending

Poisson’s ratioPoisson’s ratio

Deflection ofDeflection of
multi stranded wire=multi stranded wire= KPLKPL33
kknEInEI
K – load/support constantK – load/support constant
P – applied forceP – applied force
L – length of the beamL – length of the beam
K –K – helical spring shape factorhelical spring shape factor
n- no of strandsn- no of strands
E – modulus of elasticityE – modulus of elasticity
I – moment of inertiaI – moment of inertia

Helical spring shape factorHelical spring shape factor
Coils resemble the shape of a helical spring.Coils resemble the shape of a helical spring.
The helical spring shape factor is given as –The helical spring shape factor is given as –
2sin α2sin α
2+ v cos2+ v cos22
αα
α - helix angle andα - helix angle and
v - Poisson’s ratio (lateral strain/axial strain)v - Poisson’s ratio (lateral strain/axial strain)
Angle α can be seen in the following diagram :-Angle α can be seen in the following diagram :-

Kusy ( AJO-DO 1984)Kusy ( AJO-DO 1984)
Compared the elastic properties of tripleCompared the elastic properties of triple
stranded S.Steel wire with S.Steel, NiTi &stranded S.Steel wire with S.Steel, NiTi &
BB-TMA-TMA

ResultsResults
ResultsResults

ResultsResults

ResultsResults
0.0175” S.Steel wire had stiffness equal to0.0175” S.Steel wire had stiffness equal to
0.016”NiTi & 40% of 0.016”TMA0.016”NiTi & 40% of 0.016”TMA
Did not resemble the 0.018” SS wire except :Did not resemble the 0.018” SS wire except :
SizeSize
Wire-bracket relation.Wire-bracket relation.

Ingram, Gipe and Smith (AJO 86)
Range of 4 diff wiresRange of 4 diff wires
Results: NiTi>MS S.Steel>CoCr>SteelResults: NiTi>MS S.Steel>CoCr>Steel

Nanda et al (AO 97)Nanda et al (AO 97)
……. stiffness. stiffness
Increase in No. ofIncrease in No. of
strandsstrands  stiffnessstiffness
Varies as the amountVaries as the amount
of deflectionof deflection

Kusy (AJO-DO 2002)Kusy (AJO-DO 2002)
Interaction between individual strands wasInteraction between individual strands was
negligible.negligible.
Range and strengthRange and strength Triple strandedTriple stranded ΞΞ Co-Co-
axial (six stranded)axial (six stranded)
StiffnessStiffness  Coaxial < Triple strandedCoaxial < Triple stranded
Range of single stranded SS wire, tripleRange of single stranded SS wire, triple
stranded and co-axial were similar.stranded and co-axial were similar.

Welding of SteelWelding of Steel
3 useful properties3 useful properties ––
1.1. Comparatively low melting point,Comparatively low melting point,
2.2. High electrical resistance andHigh electrical resistance and
3.3. Low conductivity of heat.Low conductivity of heat.

Sensitization - between 425 and 815Sensitization - between 425 and 815oo
CC
Chromium carbides need time for theirChromium carbides need time for their
formation.formation.
Important toImportant to

minimize the time of passing the currentminimize the time of passing the current

minimize the area of heatingminimize the area of heating

Join twoJoin two thin sheetsthin sheets of metalof metal
Same thicknessSame thickness
Joining tubes, wires and springs, solderingJoining tubes, wires and springs, soldering
is generally recommended.is generally recommended.
Electrodes - small tips, not exceedingElectrodes - small tips, not exceeding
1mm in diameter.1mm in diameter.

Cobalt ChromiumCobalt Chromium
1950s the Elgin Watch1950s the Elgin Watch
Rocky Mountain OrthodonticsRocky Mountain Orthodontics
ElgiloyElgiloy
CoCr alloys - stellite alloysCoCr alloys - stellite alloys

superior resistance to corrosion, comparablesuperior resistance to corrosion, comparable
to that of gold alloys.to that of gold alloys.

Cobalt – 40-45%Cobalt – 40-45%
Chromium – 15-22%Chromium – 15-22%
Nickel – for strength and ductilityNickel – for strength and ductility
Iron, molybdenum, tungsten and titaniumIron, molybdenum, tungsten and titanium
to form stable carbides and enhanceto form stable carbides and enhance
hardenability.hardenability.

Strength and formability modified by heatStrength and formability modified by heat
treatment.treatment.
The alloy is highly formable, and can beThe alloy is highly formable, and can be
easily shaped.easily shaped.
Heat treated.Heat treated.

StrengthStrength 

FormabilityFormability 

Heat treated at 482Heat treated at 482oo
c for 7 to 12 minsc for 7 to 12 mins
Precipitation hardeningPrecipitation hardening

 ultimate tensile strength of the alloy,ultimate tensile strength of the alloy,
without hampering the resilience.without hampering the resilience.
After heat treatment, elgiloy had elasticAfter heat treatment, elgiloy had elastic
properties similar to steel.properties similar to steel.

BlueBlue – soft– soft
YellowYellow – ductile– ductile
GreenGreen – semiresilient– semiresilient
RedRed – resilient– resilient
No adjustmentsNo adjustments

After heat treatmentAfter heat treatment 
Strength:Strength:
BlueBlue andand yellowyellow ≡≡ normal steel wirenormal steel wire
GreenGreen andand redred temperstempers ≡≡ higher gradehigher grade
steelsteel

Heating above 650Heating above 650oo
CC

partial annealing, and softening of the wirepartial annealing, and softening of the wire
Optimum heat treatmentOptimum heat treatment  dark straw colordark straw color
of the wireof the wire
Advantage of Co-Cr over SS is –Advantage of Co-Cr over SS is –

Greater resistance to fatigue and distortionGreater resistance to fatigue and distortion

longer function as a resilient springlonger function as a resilient spring

Properties of Co-Cr are very similar to thatProperties of Co-Cr are very similar to that
of stainless steel.of stainless steel.
ForceForce

2x2x of β titanium andof β titanium and

44 times of NiTi.times of NiTi.

Ingram ,Gipe and Smith (AJO 86)Ingram ,Gipe and Smith (AJO 86)
Non heat treated Co-CrNon heat treated Co-Cr

Range < stainless steel of comparable sizesRange < stainless steel of comparable sizes
But after heat treatment, the range wasBut after heat treatment, the range was
considerably increased.considerably increased.

Frank and Nikolai ( AJO 1980)Frank and Nikolai ( AJO 1980)

Co-Cr alloysCo-Cr alloys ≡≡ stainless steel.stainless steel.
Stannard et al (AJO 1986)Stannard et al (AJO 1986)

Co-Cr highest frictional resistance in wet andCo-Cr highest frictional resistance in wet and
dry conditions.dry conditions.

Kusy et al (AJO
2001)
The elasticThe elastic
modulus did notmodulus did not
vary appreciablyvary appreciably 
edgewise oredgewise or
ribbon-wiseribbon-wise
configurations.configurations.

Round wiresRound wires 
higher ductility thanhigher ductility than
square orsquare or
rectangular wires.rectangular wires.

The modulus ofThe modulus of
elasticity 4 diffelasticity 4 diff
tempers of 0.016”tempers of 0.016”
elgiloy is almostelgiloy is almost
similarsimilar

Elastic propertiesElastic properties (yield strength and(yield strength and
ultimate tensile strength and ductility) wereultimate tensile strength and ductility) were
quite similar for different cross sectional areasquite similar for different cross sectional areas
and tempers.and tempers.
This does not seem to agree with what isThis does not seem to agree with what is
expected of the wires.expected of the wires.

Different tempers with different physicalDifferent tempers with different physical
properties – attractiveproperties – attractive
More care taken during the manufactureMore care taken during the manufacture
of the wires.of the wires.

Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

Viewers also liked

Viewers also liked (19)

Similar to Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

Similar to Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

Editor's Notes