Ideal requisites of orthodontic wires

WIRES IN
ORTHODONTICS
www.indiandentalacademy.com

INTRODUCTIONINTRODUCTION
Recent advances in orthodontic wire alloys have resultedRecent advances in orthodontic wire alloys have resulted
in a varied array of wires that exhibit a wide spectrum ofin a varied array of wires that exhibit a wide spectrum of
properties up until the 1930’s the only orthodontic wiresproperties up until the 1930’s the only orthodontic wires
available were made of gold.available were made of gold.
Austenitic stainless steel, with itsAustenitic stainless steel, with its
greater strength, higher modulus of elasticity, goodgreater strength, higher modulus of elasticity, good
resistance to corrosion, and moderate costs wasresistance to corrosion, and moderate costs was
introduced as an orthodontic wire in 1929,and shortlyintroduced as an orthodontic wire in 1929,and shortly
afterward gained popularity over gold.afterward gained popularity over gold.
Since, then several other alloys withSince, then several other alloys with
desirable properties have been adopted in orthodontics.desirable properties have been adopted in orthodontics.
These include Cobalt – Chromium, Nickel – Titanium, BetaThese include Cobalt – Chromium, Nickel – Titanium, Beta
– Titanium and multi stranded stainless steel wires.– Titanium and multi stranded stainless steel wires.

Presently the orthodontist may select from all thePresently the orthodontist may select from all the
available wire types, one that best meets theavailable wire types, one that best meets the
demands of a particular clinical situation. Thedemands of a particular clinical situation. The
selection of an appropriate wire size and alloy typeselection of an appropriate wire size and alloy type
in turn would provide the benefit of optimum andin turn would provide the benefit of optimum and
predictable treatment results.predictable treatment results.
The clinician must therefore beThe clinician must therefore be
conversant with the mechanical properties and theconversant with the mechanical properties and the
relevant clinical applications of these properties forrelevant clinical applications of these properties for
these wires.these wires.

IDEAL REQUISITES OFIDEAL REQUISITES OF
ORTHODONTIC WIRESORTHODONTIC WIRES
► Wires used for active components should exert low and constantWires used for active components should exert low and constant
forcesforces
► Wires of retentive unit should be stiffWires of retentive unit should be stiff
► Low load deflection rate is desired for springs.Low load deflection rate is desired for springs.
► Wires should be ductile.Wires should be ductile.
► Ease of forming.Ease of forming.
► Ease of joining –weldable , solderableEase of joining –weldable , solderable
► Should be heat treatable.Should be heat treatable.
► Should have resistance to corrosion.Should have resistance to corrosion.
► Should be stable in the oral environment.Should be stable in the oral environment.
► Should be biocompatible.Should be biocompatible.
► Should be cold workable.Should be cold workable.
► Wires should have sufficient strength to withstand the forces appliedWires should have sufficient strength to withstand the forces applied
on it.on it.

Classification of orthodontic ArchClassification of orthodontic Arch
wireswires
► The classification is based on the material constituents.The classification is based on the material constituents.
Metallic NonmetallicMetallic Nonmetallic
1.1. Gold CompositeGold Composite
2.2. Stainless steel CoatedStainless steel Coated
3.3. Chrome cobaltChrome cobalt
4.4. Nickel-titanium alloysNickel-titanium alloys
NitinolsNitinols
► MartensiticMartensitic
► AusteniticAustenitic
► PseudoelasticPseudoelastic
► ThermoelasticThermoelastic
Beta titaniumBeta titanium
1.untreated1.untreated
2.Surface treated2.Surface treated
► Alpha titaniumAlpha titanium
► Niobium-titaniumNiobium-titanium
► TimoliumTimolium

WIRE CHARACTERISTICS OF CLINICAL RELEVANCEWIRE CHARACTERISTICS OF CLINICAL RELEVANCE
Several characteristics of orthodontic wires are considered desirableSeveral characteristics of orthodontic wires are considered desirable
for optimum performance during treatment. These include a largefor optimum performance during treatment. These include a large
spring back, low stiffness, high formability, high stored energy,spring back, low stiffness, high formability, high stored energy,
biocompatibility and environmental stability, low surface friction, andbiocompatibility and environmental stability, low surface friction, and
the capability to be welded or soldered to auxiliaries andthe capability to be welded or soldered to auxiliaries and
attachments. A brief description of each of these desirable wireattachments. A brief description of each of these desirable wire
characteristics is provided.characteristics is provided.
1. Spring back.1. Spring back.
This is also referred to as maximum elastic deflection,This is also referred to as maximum elastic deflection,
maximum flexibility, range of activation, range of deflection, ormaximum flexibility, range of activation, range of deflection, or
working range. Spring back is related to the ratio of yield strength toworking range. Spring back is related to the ratio of yield strength to
the modulus of elasticity of the material (YS/E).the modulus of elasticity of the material (YS/E).
Higher spring back values provide the ability to applyHigher spring back values provide the ability to apply
large activations with a resultant increase in working time of thelarge activations with a resultant increase in working time of the
appliance. This, in turn, implies that fewer arch wire changes orappliance. This, in turn, implies that fewer arch wire changes or
adjustments will be required. also a measure of how far a wire canadjustments will be required. also a measure of how far a wire can
be deflected without causing permanent deformation or exceedingbe deflected without causing permanent deformation or exceeding
the limits of the material.the limits of the material.

2. Stiffness or load deflection rate.2. Stiffness or load deflection rate.
This is the force magnitude delivered by an applianceThis is the force magnitude delivered by an appliance
and is proportional to the modulus of elasticity (E). Low stiffness orand is proportional to the modulus of elasticity (E). Low stiffness or
load deflection rates provide (1) the ability to apply lower forces, (2) aload deflection rates provide (1) the ability to apply lower forces, (2) a
more constant force over time as the appliance experiencesmore constant force over time as the appliance experiences
deactivation, and (3) greater ease and accuracy in applying a givendeactivation, and (3) greater ease and accuracy in applying a given
force.force.
3. Formability.3. Formability.
High formability provides the ability to bend a wire intoHigh formability provides the ability to bend a wire into
desired configurations such as loops, coils, and stops withoutdesired configurations such as loops, coils, and stops without
fracturing the wire.fracturing the wire.
4. Modulus of resilience or stored energy (MR)4. Modulus of resilience or stored energy (MR)
This property represents the work available toThis property represents the work available to
move teeth. It is reflected by the area under the line describing elasticmove teeth. It is reflected by the area under the line describing elastic
deformation of the wiredeformation of the wire

5. Biocompatibility and environmental stability.5. Biocompatibility and environmental stability.
Biocompatibility includes resistance to corrosion andBiocompatibility includes resistance to corrosion and
tissue tolerance to elements in the wire. Environmental stability ensures thetissue tolerance to elements in the wire. Environmental stability ensures the
maintenance of desirable properties of the wire for extended periods of timemaintenance of desirable properties of the wire for extended periods of time
after manufacture. This, in turn, ensures a predictable behavior of the wireafter manufacture. This, in turn, ensures a predictable behavior of the wire
when in use.when in use.
6. Joinability.6. Joinability.
The ability to attach auxiliaries to orthodontic wires byThe ability to attach auxiliaries to orthodontic wires by
welding or soldering provides an additional advantage when incorporatingwelding or soldering provides an additional advantage when incorporating
modifications to the appliance.modifications to the appliance.
7. Friction.7. Friction.
Space closure and canine retraction in continuous archSpace closure and canine retraction in continuous arch
wire techniques involve a relative motion of bracket over wire. Excessivewire techniques involve a relative motion of bracket over wire. Excessive
amounts of bracket/wire friction may result in loss of anchorage or bindingamounts of bracket/wire friction may result in loss of anchorage or binding
accompanied by little or no tooth movement. The preferred wire material foraccompanied by little or no tooth movement. The preferred wire material for
moving a tooth relative to the wire would be one that produces the leastmoving a tooth relative to the wire would be one that produces the least
amount of friction at the bracket/wire interface.amount of friction at the bracket/wire interface.

Gold Alloys-WireGold Alloys-Wire
The composition of gold alloys used in orthodontic wires in similar toThe composition of gold alloys used in orthodontic wires in similar to
that of type IV gold casting alloy. These alloys containsthat of type IV gold casting alloy. These alloys contains
15-55% Gold 5-10% Palladium15-55% Gold 5-10% Palladium
11-18% Copper 5-10% Platinum11-18% Copper 5-10% Platinum
10-25% Silver 1-2% Nickel10-25% Silver 1-2% Nickel
These wires can be potentially be strengthened with proper heatThese wires can be potentially be strengthened with proper heat
treatment although they are typically used in a drawn condition. Thetreatment although they are typically used in a drawn condition. The
yield strength of wrought gold wire ranges from 50,000 to 160,000 psiyield strength of wrought gold wire ranges from 50,000 to 160,000 psi
depending on alloy and composition.depending on alloy and composition.
The gold-copper alloys have a modulus of elasticityThe gold-copper alloys have a modulus of elasticity
of approximately 15,000,000psi.This combination makes gold veryof approximately 15,000,000psi.This combination makes gold very
formable and capable of delivering lower forces than stainless steel.formable and capable of delivering lower forces than stainless steel.
But they have a limited spring back.But they have a limited spring back.
They are easily joined by shouldering and areThey are easily joined by shouldering and are
highly corrosion resistant. The gold wires have decreased usage inhighly corrosion resistant. The gold wires have decreased usage in
orthodontics because of their low yield strength and increased cost.orthodontics because of their low yield strength and increased cost.

Stainless Stain Orthodontic WireStainless Stain Orthodontic Wire
This is the most popular wire inThis is the most popular wire in
orthodontics because of its low cost andorthodontics because of its low cost and
possesses many qualities that is desired forpossesses many qualities that is desired for
orthodontic treatment.orthodontic treatment.

Composition and PhysicalComposition and Physical
Characteristics Of Stainless SteelCharacteristics Of Stainless Steel
AlloyAlloy
In molten state metals usually show mutualIn molten state metals usually show mutual
solubility in one another. When the moltensolubility in one another. When the molten
components are cooled, the component metalscomponents are cooled, the component metals
may remain soluble in one another forming a solidmay remain soluble in one another forming a solid
a solution alloy.a solution alloy.
A type of solid solution alloy is theA type of solid solution alloy is the
interstitial solid a solution alloy in which for binaryinterstitial solid a solution alloy in which for binary
alloys the primary lattice sites are occupied by onealloys the primary lattice sites are occupied by one
metal atom and the atoms of the secondmetal atom and the atoms of the second
component do not occupy lattice sites but lie withincomponent do not occupy lattice sites but lie within
the interstices of the lattice.the interstices of the lattice.

Stainless Steel is an interstitial solidStainless Steel is an interstitial solid
solution alloy primarily of Iron and Carbonsolution alloy primarily of Iron and Carbon
and also contains Chromium, Nickel,and also contains Chromium, Nickel,
Manganese and perhaps other materials toManganese and perhaps other materials to
improve the properties and gives itsimprove the properties and gives its
stainless steel property. It is used instainless steel property. It is used in
dentistry in the wrought form as wires,dentistry in the wrought form as wires,
bands, bars, brackets and other.bands, bars, brackets and other.

Crystallographic Features ofCrystallographic Features of
Stainless SteelStainless Steel
At higher temperature ‘fe’ lattice exist in a AusteniteAt higher temperature ‘fe’ lattice exist in a Austenite
form – Lattice structure of Austenitic stainless steel-> faceform – Lattice structure of Austenitic stainless steel-> face
centered cubic unit cells (Fcc). This structure is morecentered cubic unit cells (Fcc). This structure is more
homogenous. If atoms of other elements are substituted,homogenous. If atoms of other elements are substituted,
the highly homogenous structure can be obtained even atthe highly homogenous structure can be obtained even at
room temperature.room temperature.
It austenitic form is cooled from higher temperature, 2It austenitic form is cooled from higher temperature, 2
types of SS occurs depending upon the type of coolingtypes of SS occurs depending upon the type of cooling
(i) ferrite structure (BCC) Body Centered Cubic form is(i) ferrite structure (BCC) Body Centered Cubic form is
obtained when Austenite is cooled slowly. Here carbon isobtained when Austenite is cooled slowly. Here carbon is
expressed as iron carbide.expressed as iron carbide.
(ii) If austenite is cooled rapidly (or) wrenched suddenly in(ii) If austenite is cooled rapidly (or) wrenched suddenly in
water, carbon is trapped inside the lattice and exist inwater, carbon is trapped inside the lattice and exist in
cartensite, body centered tetragonal form (BCT).cartensite, body centered tetragonal form (BCT).

Three Types of Stainless SteelThree Types of Stainless Steel
* Ferrite S.S* Ferrite S.S
* Martensitic S.S* Martensitic S.S
* Austenitic S.S* Austenitic S.S

Austenitic S.SAustenitic S.S
The austenitic S.S alloy are the mostThe austenitic S.S alloy are the most
corrosion resistant of the stainless steels. Thecorrosion resistant of the stainless steels. The
basic type is AISI 302, containing 18% chromiumbasic type is AISI 302, containing 18% chromium
8% nickel and 0.15% carbon.8% nickel and 0.15% carbon.
In orthodontics chiefly the AISI 302 and AISIIn orthodontics chiefly the AISI 302 and AISI
304 are used. Type 304 has a similar composition304 are used. Type 304 has a similar composition
of AISI 302 but has a reduced amount of carbon ofof AISI 302 but has a reduced amount of carbon of
0.08%. So both 302 + 304 S.S may be designated0.08%. So both 302 + 304 S.S may be designated
as 18.8 SS and are used by the orthodontist in theas 18.8 SS and are used by the orthodontist in the
form of wires and bands.form of wires and bands.

Generally Austenitic S.S is preferable to ferritic SSGenerally Austenitic S.S is preferable to ferritic SS
because of following characteristics.because of following characteristics.
* Greater ductility and ability to undergo more cold* Greater ductility and ability to undergo more cold
work without fracturing.work without fracturing.
► Substantial lengthening during cold working.Substantial lengthening during cold working.
► Greater ease of welding.Greater ease of welding.
► Ability to fairly readily overcome sensitization.Ability to fairly readily overcome sensitization.
► Comparative ease of forming.Comparative ease of forming.

ADA Specification No.32 forADA Specification No.32 for
Orthodontic WiresOrthodontic Wires
For wires not containing previous metals itFor wires not containing previous metals it
describesdescribes
(1)(1) Type I – low resilience.Type I – low resilience.
(2)(2) Type II – high resilience.Type II – high resilience.

I. Stainless Steel in OrthodonticsI. Stainless Steel in Orthodontics
S.S was introduced by Harry Brearly of sheffield.S.S was introduced by Harry Brearly of sheffield.
In early dental literature, piano wireIn early dental literature, piano wire
was recommended where strength and elasticity wherewas recommended where strength and elasticity where
required and the problem of corrosion was some howrequired and the problem of corrosion was some how
overcome by physically manipulating the wire.overcome by physically manipulating the wire.
The discovery of SS and itsThe discovery of SS and its
eventual production in wire as ribon form in Germany andeventual production in wire as ribon form in Germany and
Great Britain was followed by the development andGreat Britain was followed by the development and
refinement of methods for working, joining and exploringrefinement of methods for working, joining and exploring
the physical properties of the new material for orthodonticthe physical properties of the new material for orthodontic
appliance construction by FRUED in 1933.appliance construction by FRUED in 1933.

Round Arch wiresRound Arch wires
Mainly Australian wires (or) AJ Wilcock wires. EvenMainly Australian wires (or) AJ Wilcock wires. Even
the wires that one produced by other companies are alsothe wires that one produced by other companies are also
called Australian type of wires showing the Excellency ofcalled Australian type of wires showing the Excellency of
AJ Wilcock wires. Australian wires are introduced byAJ Wilcock wires. Australian wires are introduced by
A.J.Wilcock of whittlesea, Victoria, Australia. WilcockA.J.Wilcock of whittlesea, Victoria, Australia. Wilcock
Arch wires have been the main stay of Begg technique.Arch wires have been the main stay of Begg technique.
They are available in 2 type of manufacturing processThey are available in 2 type of manufacturing process
(i)(i) Spinner straightening Method.Spinner straightening Method.
(ii)(ii) Pulse straightening Method.Pulse straightening Method.

Spinner straightening WiresSpinner straightening Wires
Spinner straightening is a mechanical process ofSpinner straightening is a mechanical process of
straightening resistant materials, usually in the cold drawnstraightening resistant materials, usually in the cold drawn
condition by mechanical Bronze rollers.condition by mechanical Bronze rollers.
Earlier the manicuring process used was spinnerEarlier the manicuring process used was spinner
straightening. The resultant wire is heat treated (so Brownstraightening. The resultant wire is heat treated (so Brown
in colour) and cold drawn to its proper diameter. This givesin colour) and cold drawn to its proper diameter. This gives
it’s the property of resiliency, toughness and tensileit’s the property of resiliency, toughness and tensile
strength. Its marketed in diameter 0.012”, 0.014”, 0.016”,strength. Its marketed in diameter 0.012”, 0.014”, 0.016”,
1.018”, 0.020”. These wires are extensively used in Begg’s1.018”, 0.020”. These wires are extensively used in Begg’s
technique.technique.

Pulse straightened wiresPulse straightened wires
AJ Wilcock and engineering companyAJ Wilcock and engineering company
recently introduced a S.S. wire under a newrecently introduced a S.S. wire under a new
manufacturing process called pulse straighteningmanufacturing process called pulse straightening
as against the spinner straightening producer usedas against the spinner straightening producer used
earlier. Disadvantage spinner straighteningearlier. Disadvantage spinner straightening
method ismethod is
1. Resultant deformation1. Resultant deformation
2. Decreased yield strength values and it2. Decreased yield strength values and it
becomes strain softened.becomes strain softened.

In pulse straightened the wire is pulsed in a special machine whichIn pulse straightened the wire is pulsed in a special machine which
permits high tensile wires to be straightened and low diameter wirespermits high tensile wires to be straightened and low diameter wires
are possible. The material yield strength is not altered and the surfaceare possible. The material yield strength is not altered and the surface
has a smoother finish.has a smoother finish.
They are difficult to bend, but interestingly theyThey are difficult to bend, but interestingly they
remain stiffer inside the patients mouth, even after several months.remain stiffer inside the patients mouth, even after several months.
The pulsed wired are 3 times stiffer and are excellent base arches, asThe pulsed wired are 3 times stiffer and are excellent base arches, as
studies by Mollenhauer.studies by Mollenhauer.
The new grades and sizes available areThe new grades and sizes available are
Wires SizesWires Sizes
Premium 0.020”Premium 0.020”
Premium plus 0.018”,0.016’, 0.014”Premium plus 0.018”,0.016’, 0.014”
0.012”, 0.011”, 0.010”0.012”, 0.011”, 0.010”
Supreme 0.011”, 0.010”Supreme 0.011”, 0.010”
0.009”, 0.008”0.009”, 0.008”

Uses of Newer Wilcock WiresUses of Newer Wilcock Wires
1.Supreme Grade(0.008” to 0.011” wires)1.Supreme Grade(0.008” to 0.011” wires)
(i)(i) For unraveling crow drugFor unraveling crow drug
(ii)(ii) MAAMAA
(iii)(iii) Mini up righting springsMini up righting springs
► For torquing when it is made into boxesFor torquing when it is made into boxes
► Mollenhauer aligning auxiliary to control the teeth duringMollenhauer aligning auxiliary to control the teeth during
alignment Also used for breaking mechanicsalignment Also used for breaking mechanics
► Mini up righting springs for up righting teethMini up righting springs for up righting teeth
2.P.S. 0.010” Wires2.P.S. 0.010” Wires
Suitable for incisally activated mouse traps.Suitable for incisally activated mouse traps.

3. P.S. 0.011” Wire3. P.S. 0.011” Wire
Excellent for aligning second molar towards end of stage III.Excellent for aligning second molar towards end of stage III.
4. P.S. 0.014” Wire4. P.S. 0.014” Wire
Can be used in high angle cases as one way to minimize opening ofCan be used in high angle cases as one way to minimize opening of
the bite.the bite.
5. P.S. 0.016” Wires5. P.S. 0.016” Wires
Suitable for mesiofacial type.Suitable for mesiofacial type.
6. P.S. 0.018” Wires6. P.S. 0.018” Wires
Upper incisor intrusion and bypass arch wires.Upper incisor intrusion and bypass arch wires.
7. P.S. 0.020” Wire7. P.S. 0.020” Wire
Maintaining arch in stage III andMaintaining arch in stage III and

Heat Treatment of Stainless SteelHeat Treatment of Stainless Steel
The possibility of Heat treatment of stainless steel haveThe possibility of Heat treatment of stainless steel have
been possible known since 1949. (Baikofur and Yales –been possible known since 1949. (Baikofur and Yales –
1952) & Funk – 1981) have shown experimentally that 18-81952) & Funk – 1981) have shown experimentally that 18-8
hand drawn SS may be successfully heat treated after theyhand drawn SS may be successfully heat treated after they
have been forming to the required shape does not enhancehave been forming to the required shape does not enhance
physical properties.physical properties.
On the other hand, heat treatment ofOn the other hand, heat treatment of
stainless steel relieves the stresses induced due to the coldstainless steel relieves the stresses induced due to the cold
working of the alloy during fabrication of arches, loops andworking of the alloy during fabrication of arches, loops and
clasps. So, this heat treatment may be referred to asclasps. So, this heat treatment may be referred to as
stress- relief anneal.stress- relief anneal.

The Heat treatment procedure for orthodontic wiresThe Heat treatment procedure for orthodontic wires
can be briefly summarized as:can be briefly summarized as:
(1) By placing them in a temperature controlled over(1) By placing them in a temperature controlled over
for a specific time. Backofer and Glass(1952)for a specific time. Backofer and Glass(1952)
investigated the effect on stainless steel wires ofinvestigated the effect on stainless steel wires of
heat treatment at 500F for 20 minutes and 750Fheat treatment at 500F for 20 minutes and 750F
for 10 minutes showing the later combinationfor 10 minutes showing the later combination
(750F for 10 minutes) has a better effect. But the(750F for 10 minutes) has a better effect. But the
limitation to use such a method is the timelimitation to use such a method is the time
consumed.consumed.

(2)(2) By passing electric current through the archwires provisions forBy passing electric current through the archwires provisions for
doing this is made on same orthodontic welder by means of twodoing this is made on same orthodontic welder by means of two
terminal blocks at which a potential of up approximately 3-4 volts isterminal blocks at which a potential of up approximately 3-4 volts is
available. The arch wire was treated by applying 2-5 volts at theavailable. The arch wire was treated by applying 2-5 volts at the
ends and carefully watching the colour of the wire.ends and carefully watching the colour of the wire.
Within a matter of seconds, the color changedWithin a matter of seconds, the color changed
to a “medium straw” colour at which stage the current was switchedto a “medium straw” colour at which stage the current was switched
off and heat treatment was complete. For a thicker and longer wiresoff and heat treatment was complete. For a thicker and longer wires
a higher potential may be used to compensate for resistance.a higher potential may be used to compensate for resistance.
Funk recommends the use of a colour index to determine whenFunk recommends the use of a colour index to determine when
adequate heat treatment is achieved. He suggests that a strawadequate heat treatment is achieved. He suggests that a straw
coloured wire indicates that optimum heat treatment has beencoloured wire indicates that optimum heat treatment has been
attained.attained.

Mechanical properties and their clinical implicationsMechanical properties and their clinical implications
of stainless steelof stainless steel
► Carbon interstitial hardening and cold working contribute to the highCarbon interstitial hardening and cold working contribute to the high
yield strength and modulus of elasticity of stainless steel.yield strength and modulus of elasticity of stainless steel.
► Residual stresses present in a wire subsequent to bending canResidual stresses present in a wire subsequent to bending can
markedly affect the elastic properties of the wire. Heat treatment ismarkedly affect the elastic properties of the wire. Heat treatment is
therefore used in stress-relieving stainless steel after bending the wiretherefore used in stress-relieving stainless steel after bending the wire
into an arch, loops, or coils. This helps to enhance the elasticinto an arch, loops, or coils. This helps to enhance the elastic
properties of the wire.properties of the wire.
► The recommended temperature-time schedule for stress-relievingThe recommended temperature-time schedule for stress-relieving
stainless steel is 750° F (399° C) for 11 minutes.stainless steel is 750° F (399° C) for 11 minutes.
► Funk recommends the use of a color index to determine whenFunk recommends the use of a color index to determine when
adequate heat treatment is achieved. He suggests that a straw-coloredadequate heat treatment is achieved. He suggests that a straw-colored
wire indicates that optimum heat treatment has been attained.wire indicates that optimum heat treatment has been attained.

► Commercially available stainless steel wires demonstrate aCommercially available stainless steel wires demonstrate a
range of values both for the modulus of elasticity and yieldrange of values both for the modulus of elasticity and yield
strengthstrength
► The large modulus of elasticity of stainless steel and itsThe large modulus of elasticity of stainless steel and its
associated high stiffness necessitate the use of smallerassociated high stiffness necessitate the use of smaller
wires for alignment of moderately or severely displacedwires for alignment of moderately or severely displaced
teeth. A reduction in wire size results in a poorer fit in theteeth. A reduction in wire size results in a poorer fit in the
bracket and may cause loss of control during toothbracket and may cause loss of control during tooth
movement. However, high stiffness is advantageous inmovement. However, high stiffness is advantageous in
resisting deformation caused by extra- and intra oralresisting deformation caused by extra- and intra oral
tractional forces.tractional forces.

► The yield strength to elastic modulus ratio (YS/E)The yield strength to elastic modulus ratio (YS/E)
indicates a lower spring back of stainless steelindicates a lower spring back of stainless steel
than those of newer titanium-based alloys . Thethan those of newer titanium-based alloys . The
stored energy of activated stainless steel wires isstored energy of activated stainless steel wires is
substantially less than that of beta-titanium andsubstantially less than that of beta-titanium and
nitinol wire.nitinol wire.
This implies that stainless steelThis implies that stainless steel
wires produce higher forces that dissipate overwires produce higher forces that dissipate over
shorter periods of time than either beta-titanium orshorter periods of time than either beta-titanium or
nitinol wires, thus requiring more frequentnitinol wires, thus requiring more frequent
activations or arch wire changes.activations or arch wire changes.

► Joinability with stainless steel is possible by soldering.Joinability with stainless steel is possible by soldering.
► Stainless steel wires also can be fused together by welding, but thisStainless steel wires also can be fused together by welding, but this
generally requires reinforcement with solder.generally requires reinforcement with solder.
► Corrosion resistance of stainless steel wires is good,although solderCorrosion resistance of stainless steel wires is good,although solder
joints may corrode in the oral cavity. Low levels of bracket/wire frictionjoints may corrode in the oral cavity. Low levels of bracket/wire friction
have been reported with experiments using stainless steel.Thishave been reported with experiments using stainless steel.This
signifies that stainless steel wires offer lower resistance to toothsignifies that stainless steel wires offer lower resistance to tooth
movement than other orthodontic alloys.movement than other orthodontic alloys.

Multistranded WiresMultistranded Wires
► Multistranded wires are made of stainless steelMultistranded wires are made of stainless steel
and composed of specified numbers of thin wireand composed of specified numbers of thin wire
sections coiled around each other to provide asections coiled around each other to provide a
round or rectangular cross-section.round or rectangular cross-section.
► Kusy and Dilley investigated the strength,Kusy and Dilley investigated the strength,
stiffness, and spring back properties ofstiffness, and spring back properties of
multistranded wires in a bending mode of stress.multistranded wires in a bending mode of stress.
► They noted that the stiffness of a triple-strandedThey noted that the stiffness of a triple-stranded
0.0175-inch (3 x 0.008-inch) stainless steel arch0.0175-inch (3 x 0.008-inch) stainless steel arch
wire was similar to that of 0.010-inch single-wire was similar to that of 0.010-inch single-
stranded stainless steel wire.stranded stainless steel wire.

► The multistranded wire was also 25% stronger than theThe multistranded wire was also 25% stronger than the
0.010-inch stainless steel wire. The 0.0175-inch triple-0.010-inch stainless steel wire. The 0.0175-inch triple-
stranded wire and 0.016-inch nitinol wire demonstratedstranded wire and 0.016-inch nitinol wire demonstrated
similar stiffnesses. However, nitinol tolerated more thansimilar stiffnesses. However, nitinol tolerated more than
50% greater activation than the multistranded-wire.50% greater activation than the multistranded-wire.
► The triple-stranded wire was alsoThe triple-stranded wire was also
half as stiff as a 0.016-inch beta-titanium wire.half as stiff as a 0.016-inch beta-titanium wire.
In a more recent Investigation,In a more recent Investigation,
Kusy and Stevens state that although the elastic propertiesKusy and Stevens state that although the elastic properties
of multistranded wires vary widely, several of these wiresof multistranded wires vary widely, several of these wires
compare favorably with some of the beta-titanium andcompare favorably with some of the beta-titanium and
nitinol wires.nitinol wires.

► Ingram, Gipe, and Smithl noted that titaniumIngram, Gipe, and Smithl noted that titanium
alloy wires and multistranded stainless steelalloy wires and multistranded stainless steel
wires have low stiffness when compared withwires have low stiffness when compared with
solid stainless steel wires.solid stainless steel wires.
The investigators also foundThe investigators also found
that most multistranded wires had a spring backthat most multistranded wires had a spring back
similar to that of nitinol, but a larger spring backsimilar to that of nitinol, but a larger spring back
when compared with solid stainless steel orwhen compared with solid stainless steel or
beta-titanium wires.beta-titanium wires.
Unlike stainless steel wires, inUnlike stainless steel wires, in
which spring back decreases with increasingwhich spring back decreases with increasing
thickness, the titanium and multistranded wiresthickness, the titanium and multistranded wires
have spring back properties that are relativelyhave spring back properties that are relatively
independent of wire size.independent of wire size.

ELGILOYELGILOY
► Elgiloy was developed by Elgin national company as the metal forElgiloy was developed by Elgin national company as the metal for
precision syringe. The main advantage of wire over stainless steel isprecision syringe. The main advantage of wire over stainless steel is
easier to bend in the received state. So it is preferred in techniqueseasier to bend in the received state. So it is preferred in techniques
where loops in arch wires are used. It can also be heat treated afterwhere loops in arch wires are used. It can also be heat treated after
manipulation to achieve a hardness approximately equal to that ofmanipulation to achieve a hardness approximately equal to that of
stainless steel.stainless steel.
► Composition of ElgiloyComposition of Elgiloy
► Cobalt 40% Manganese 2%Cobalt 40% Manganese 2%
► Chromium 20% Carbon 15%Chromium 20% Carbon 15%
► Nickel 15% Beryllium 0.04%Nickel 15% Beryllium 0.04%
► Molybdenum 7%Molybdenum 7%
Its manufactured in four tempers and each are color coded inIts manufactured in four tempers and each are color coded in
increasing order of resistance.increasing order of resistance.
Maximum strength of wire can be obtained by a heat treatmentMaximum strength of wire can be obtained by a heat treatment
at 1200F.at 1200F.

Mechanical Properties & ClinicalMechanical Properties & Clinical
Applications of ElgiloyApplications of Elgiloy
Cobalt chromium alloys are availableCobalt chromium alloys are available
commercially as Elgiloy, Azura, and Multicommercially as Elgiloy, Azura, and Multi
phase.phase.
(1) Blue Elgiloy is the softest of the four wire(1) Blue Elgiloy is the softest of the four wire
tempers and can be bent easily with fingerstempers and can be bent easily with fingers
or pliers. It is recommended for use whenor pliers. It is recommended for use when
considerable bending, soldering or weldingconsiderable bending, soldering or welding
in required. Heat treatment of blue Elgiloyin required. Heat treatment of blue Elgiloy
increases its resistance to deformation.increases its resistance to deformation.

(2) Yellow Elgiloy is relatively ductile and(2) Yellow Elgiloy is relatively ductile and
more resilient than blue Elgiloy. It can alsomore resilient than blue Elgiloy. It can also
be bent with relative case. Further increasesbe bent with relative case. Further increases
in its resilience and spring performance canin its resilience and spring performance can
be achieved by heat treatment.be achieved by heat treatment.
(3) Green Elgiloy is more resilient than yellow(3) Green Elgiloy is more resilient than yellow
elgiloy and can be shaped with pliers beforeelgiloy and can be shaped with pliers before
heat treatment.heat treatment.

(4) The most resistant elgiloy is marked red(4) The most resistant elgiloy is marked red
and provides high spring qualities. Carefuland provides high spring qualities. Careful
manipulation with pliers is recommendedmanipulation with pliers is recommended
when using this wires because it withstandswhen using this wires because it withstands
only minima working. Heat treatment makesonly minima working. Heat treatment makes
red elgiloy wire extremely resistant. Sincered elgiloy wire extremely resistant. Since
this wire fractures easily after heatthis wire fractures easily after heat
treatment, all adjustments should be madetreatment, all adjustments should be made
before this precipitation hardening process.before this precipitation hardening process.

Heat Treatment of ElgiloyHeat Treatment of Elgiloy
Elgiloy is received in a soft condition with excellent formability afterElgiloy is received in a soft condition with excellent formability after
orthodontic bending. Its then heat treated to 482F(900F) for 7 to 12 inorthodontic bending. Its then heat treated to 482F(900F) for 7 to 12 in
a dental furnace to obtain a stiffness comparable to stainless steel.a dental furnace to obtain a stiffness comparable to stainless steel.
In addition to solid solution hardening and coldIn addition to solid solution hardening and cold
working, they can be hardened by precipitation hardening, which is theworking, they can be hardened by precipitation hardening, which is the
mechanism responsible for effective heat treatment which increasesmechanism responsible for effective heat treatment which increases
the resilience.the resilience.
This causes precipitation hardening of theThis causes precipitation hardening of the
alloy increasing the resistance of the wire to deformation and results inalloy increasing the resistance of the wire to deformation and results in
a wire that demonstrate properties similar to those of stainless steel.a wire that demonstrate properties similar to those of stainless steel.
Heat treatment at temperature above 1200F(794 0) resultsHeat treatment at temperature above 1200F(794 0) results
in a rapid decline in resistance to deformation because of partialin a rapid decline in resistance to deformation because of partial
annealing. Optimum levels of heat treatment are confirmed by a darkannealing. Optimum levels of heat treatment are confirmed by a dark
straw coloured wire or by use of temperature indicating paste.straw coloured wire or by use of temperature indicating paste.

Mechanical PropertiesMechanical Properties
► Greater resistance of fatigue and distortionGreater resistance of fatigue and distortion
The advantage of co-cr wires over stainlessThe advantage of co-cr wires over stainless
steel wires include greater resistance to fatiguesteel wires include greater resistance to fatigue
and distortion and longer function as a resilientand distortion and longer function as a resilient
spring. In most other aspects, the mechanicalspring. In most other aspects, the mechanical
properties of co-cr wires are very similar to thoseproperties of co-cr wires are very similar to those
of S.S. wires.of S.S. wires.
Therefore, stainless steel wires mayTherefore, stainless steel wires may
be used instead of co-cr wires of the same size inbe used instead of co-cr wires of the same size in
clinical situation in which heat hardening capabilityclinical situation in which heat hardening capability
and added torsimal strength of co-cr wires are notand added torsimal strength of co-cr wires are not
required.required.

2. Modulus of elasticity2. Modulus of elasticity
The high moduli of elasticity of co-cr and stainless steelThe high moduli of elasticity of co-cr and stainless steel
wires suggest that these wires deliver twice the force ofwires suggest that these wires deliver twice the force of
Beta titanium wires and four times the force of nitinol wiresBeta titanium wires and four times the force of nitinol wires
for equal amounts of activation.for equal amounts of activation.
The resultant undesired forceThe resultant undesired force
vectors one therefore greater with co-cr and stainless steelvectors one therefore greater with co-cr and stainless steel
wires than with both types of titanium alloys.wires than with both types of titanium alloys.
Clinically, this may translate intoClinically, this may translate into
faster rats of mesial movement of posterior teeth, thusfaster rats of mesial movement of posterior teeth, thus
placing greater demands on internal and externalplacing greater demands on internal and external
anchorage.anchorage.

FormabilityFormability
► Co-Cr and stainless steel wires have goodCo-Cr and stainless steel wires have good
formability and can be bent into manyformability and can be bent into many
configurations relatively easily.configurations relatively easily.
Soldering and weldingSoldering and welding
► Caution should be exercised when solderingCaution should be exercised when soldering
attachments to these wires since highattachments to these wires since high
temperatures cause annealing with resultant losstemperatures cause annealing with resultant loss
in yield and tensile strengths. Low-fusing solder isin yield and tensile strengths. Low-fusing solder is
recommended for this purpose.recommended for this purpose.

Frictional forcesFrictional forces
► Although larger frictional forces have been notedAlthough larger frictional forces have been noted
previously between brackets and Co-Cr wires thanpreviously between brackets and Co-Cr wires than
between brackets and stainless steel wires, abetween brackets and stainless steel wires, a
recent report on zero torque/zero angulatedrecent report on zero torque/zero angulated
brackets indicates similar values for frictionbrackets indicates similar values for friction
between brackets and these two types of alloys.between brackets and these two types of alloys.
This implies that resistance to tooth movementThis implies that resistance to tooth movement
along stainless steel and Co-Cr wires may bealong stainless steel and Co-Cr wires may be
comparable.comparable.

TITANIUM WIRESTITANIUM WIRES
Alpha- Titanium arch wireAlpha- Titanium arch wire
► These wires were developed in 1988 and as the nameThese wires were developed in 1988 and as the name
suggest one nearly pure alpha titanium in alpha phase.suggest one nearly pure alpha titanium in alpha phase.
These wires have an interesting clinical property that theyThese wires have an interesting clinical property that they
become stiffer with passage of time, which is clinicallybecome stiffer with passage of time, which is clinically
useful. This is by the absorption of hydrogen ions by theuseful. This is by the absorption of hydrogen ions by the
surface layer and forming titanium hydride.surface layer and forming titanium hydride.
It is available as 0.016x.022and 0.018x0.022 sizes.It is available as 0.016x.022and 0.018x0.022 sizes.
Torque can be incorporated using a torquing turret. UsedTorque can be incorporated using a torquing turret. Used
mainly in refined Begg/modern Begg technique as amainly in refined Begg/modern Begg technique as a
furnishing wires. T pins used in conjuction with these wiresfurnishing wires. T pins used in conjuction with these wires
improve control .improve control .

Beta-titanium wiresBeta-titanium wires
► Beta titanium has been popularized as an orthodontic alloy only in the currentBeta titanium has been popularized as an orthodontic alloy only in the current
decade. It is commercially available as TMA (titanium-molybdenum alloy).decade. It is commercially available as TMA (titanium-molybdenum alloy).
Mechanical properties of wireMechanical properties of wire
► Beta titanium has a modulus of elasticity that is less than that of stainless steelBeta titanium has a modulus of elasticity that is less than that of stainless steel
and about twice that of Nitinol . This makes its use ideal in situations in whichand about twice that of Nitinol . This makes its use ideal in situations in which
forces less than those of stainless steel are necessary and in instances inforces less than those of stainless steel are necessary and in instances in
which a lower modulus material such as nitinol is inadequate to produce thewhich a lower modulus material such as nitinol is inadequate to produce the
desired force magnitudes.desired force magnitudes.
Furthermore, the relatively lower forces generatedFurthermore, the relatively lower forces generated
by beta-titanium wires imply that the counterproductive force vectors generatedby beta-titanium wires imply that the counterproductive force vectors generated
by beta-titanium wires can be counteracted by smaller forces than thoseby beta-titanium wires can be counteracted by smaller forces than those
required for comparable stainless steel wires.required for comparable stainless steel wires.
Extra oral anchorage demands with beta-titanium wires will thereforeExtra oral anchorage demands with beta-titanium wires will therefore
be less than those for stainless steel wires.be less than those for stainless steel wires.

► The spring back for beta titanium is superior to that ofThe spring back for beta titanium is superior to that of
stainless steel . A beta-titanium wire can therefore bestainless steel . A beta-titanium wire can therefore be
deflected almost twice as much as stainless steel wiredeflected almost twice as much as stainless steel wire
without permanent deformation.without permanent deformation.
► Beta-titanium wires also deliver aboutBeta-titanium wires also deliver about
half the amount of force as do comparable stainless steelhalf the amount of force as do comparable stainless steel
wire; for example, an 0.018 ´ 0.025-inch beta-titanium wirewire; for example, an 0.018 ´ 0.025-inch beta-titanium wire
delivers approximately the same force as a 0.014 ´ 0.020-delivers approximately the same force as a 0.014 ´ 0.020-
inch stainless steel wire in a second-order activation.inch stainless steel wire in a second-order activation.
► The former configuration has the addedThe former configuration has the added
advantage of full bracket engagement and a resultantadvantage of full bracket engagement and a resultant
greater torque control than the smaller stainless steel wire.greater torque control than the smaller stainless steel wire.

► The good formability of beta-titanium-wire allowsThe good formability of beta-titanium-wire allows
stops and loops to be bent into the wire.stops and loops to be bent into the wire.
However, Burstone and Goldberg recommendHowever, Burstone and Goldberg recommend
that these wires should not be bent over a sharpthat these wires should not be bent over a sharp
radius.radius.
► Helices that areHelices that are
commonly used with stainless steel to lower thecommonly used with stainless steel to lower the
load deflection rate of the appliance may not beload deflection rate of the appliance may not be
necessary with beta-titanium wires because ofnecessary with beta-titanium wires because of
their low modulus of elasticity and high springtheir low modulus of elasticity and high spring
back. This helps to simplify appliance design byback. This helps to simplify appliance design by
eliminating the need to place loops and heliceseliminating the need to place loops and helices
in the wire.in the wire.
►

► It is possible to attach stops, hooks, and active auxiliariesIt is possible to attach stops, hooks, and active auxiliaries
by welding to beta-titanium wires, thereby increasing theby welding to beta-titanium wires, thereby increasing the
versatility of the wire. However, adequate strength of theversatility of the wire. However, adequate strength of the
weld without loss in wire properties is achieved within aweld without loss in wire properties is achieved within a
narrow optimal voltage setting on a resistance spot welder.narrow optimal voltage setting on a resistance spot welder.
► Nelson, Burstone, and GoldbergNelson, Burstone, and Goldberg
have provided values for these optimal voltage settings. Ahave provided values for these optimal voltage settings. A
flat-to-flat electrode configuration is recommended forflat-to-flat electrode configuration is recommended for
welding because it produces a strong joint with low levelswelding because it produces a strong joint with low levels
of distortion. Overheating of the wire causes it to becomeof distortion. Overheating of the wire causes it to become
brittle.brittle.

►Beta-titanium has a corrosion resistanceBeta-titanium has a corrosion resistance
comparable to stainless steel and cobalt-comparable to stainless steel and cobalt-
chromium alloys.chromium alloys.
► Beta-titanium wires demonstrate higherBeta-titanium wires demonstrate higher
levels of bracket/ wire friction than eitherlevels of bracket/ wire friction than either
stainless steel or Co-Cr wires.stainless steel or Co-Cr wires.
This may imply slower ratesThis may imply slower rates
of tooth movement during canineof tooth movement during canine
retraction and space consolidation withretraction and space consolidation with
beta-titanium wires than with stainlessbeta-titanium wires than with stainless
steel or Co-Cr wires.steel or Co-Cr wires.

Ion guard TMAIon guard TMA
►The sliding technique is limited in beta-The sliding technique is limited in beta-
titanium. Ironically stainless steel stilltitanium. Ironically stainless steel still
remains the best alloy in this regard.remains the best alloy in this regard.
Recently ion implantation technologicallyRecently ion implantation technologically
has been used to reduce the coefficient ofhas been used to reduce the coefficient of
friction of beta- titanium. (Ion guard TMA)friction of beta- titanium. (Ion guard TMA)
In summary beta-titanium posses aIn summary beta-titanium posses a
unique ability of high spring back andunique ability of high spring back and
formability with low stiffness.formability with low stiffness.

Advantages of beta-titanium overAdvantages of beta-titanium over
stainless steelstainless steel
► For a given cross section, it can be deflectedFor a given cross section, it can be deflected
approximately twice as far as stainless steel wireapproximately twice as far as stainless steel wire
without permanent deformation.without permanent deformation.
► It delivers force values less than half of stainlessIt delivers force values less than half of stainless
steel and so as the advantage of light continuoussteel and so as the advantage of light continuous
force.force.
► Titanium is highly ductile, so can be formed inTitanium is highly ductile, so can be formed in
different configuration.different configuration.
► Wire can be welded together as required withoutWire can be welded together as required without
loss of mechanical properties similarly.loss of mechanical properties similarly.

Medical Grade Titanium AlloyMedical Grade Titanium Alloy
It is a pure titanium alloy used in patientsIt is a pure titanium alloy used in patients
who have allergy to metals. It’s propertieswho have allergy to metals. It’s properties
are similar to stainless steel.are similar to stainless steel.

Titanium – Niobium Arch WireTitanium – Niobium Arch Wire
It is a innovative wire designed for precision toIt is a innovative wire designed for precision to
tooth alignment. Its unique metallurgical propertiestooth alignment. Its unique metallurgical properties
make it the most precise intra oral detailing optionmake it the most precise intra oral detailing option
available today.available today.
At 80% stiffness of TMA, it isAt 80% stiffness of TMA, it is
perfect for holding bends yet light enough not toperfect for holding bends yet light enough not to
over side the arch to arch relationship. It feels softover side the arch to arch relationship. It feels soft
and pliable but has resiliency equal to stainlessand pliable but has resiliency equal to stainless
steel.steel.

Nitinol WiresNitinol Wires
The nickel titanium wire was developed byThe nickel titanium wire was developed by
William Buehler, a research metallurgist at theWilliam Buehler, a research metallurgist at the
NAVAL ORDNANCE LABORATORY .NAVAL ORDNANCE LABORATORY .
The Nitinol acronym is derivedThe Nitinol acronym is derived
by the elements which comprises the alloy Ni-by the elements which comprises the alloy Ni-
Nickel, Ti-titanium and NOL- NAVAL ORDNANCENickel, Ti-titanium and NOL- NAVAL ORDNANCE
LABORATORY.LABORATORY.
It was introduced into the field ofIt was introduced into the field of
orthodontics by Dr. George Anderson in Mayorthodontics by Dr. George Anderson in May
1972.1972.
It is also called the space age alloyIt is also called the space age alloy
as it was used in the U.S. space shuttles byas it was used in the U.S. space shuttles by
NASA.NASA. www.indiandentalacademy.com

Metallurgical Properties of NickelMetallurgical Properties of Nickel
Titanium WiresTitanium Wires
Nickel Titanium wires have two importantNickel Titanium wires have two important
properties which gradually have been exploitedproperties which gradually have been exploited
for the field of orthodontics.for the field of orthodontics.
They areThey are
1.1. Shape memory or thermal martensitic memory.Shape memory or thermal martensitic memory.
2.2. Pseudo elasticity or super elasticity.Pseudo elasticity or super elasticity.
Shape memoryShape memory
Shape memory refers to the ability of theShape memory refers to the ability of the
material to remember it’s original shape aftermaterial to remember it’s original shape after
being plastically deformed while in thebeing plastically deformed while in the
martensitic form.martensitic form.

Thermo ElasticityThermo Elasticity
In a typical application, a certain shape is setIn a typical application, a certain shape is set
while the alloy is maintained at elevatedwhile the alloy is maintained at elevated
temperature, above the martensitic-austenitictemperature, above the martensitic-austenitic
transition temperature.transition temperature.
When the alloy is cooled belowWhen the alloy is cooled below
the transition temperature it can be plasticallythe transition temperature it can be plastically
deformed, but when it is heated again the originaldeformed, but when it is heated again the original
shape is restored. This property called Thermoshape is restored. This property called Thermo
Elasticity was important to the original nitinol’s useElasticity was important to the original nitinol’s use
in the space program but proved difficult to exploitin the space program but proved difficult to exploit
in orthodontic applications.in orthodontic applications.

There are two Niti phases in the Niti wires.There are two Niti phases in the Niti wires.
(i)(i) Austenitic NitiAustenitic Niti
a. it has an ordered BCC structure.a. it has an ordered BCC structure.
b. it occurs in high temperature and low stresses.b. it occurs in high temperature and low stresses.
(ii)(ii) Martensitic NitiMartensitic Niti
a. Has a distorted monoclinic triclinic, or hexagonal structures.a. Has a distorted monoclinic triclinic, or hexagonal structures.
b. It forms at low temperature and high stresses.b. It forms at low temperature and high stresses.
The shape memory effect is associated with a reversibleThe shape memory effect is associated with a reversible
martensitic <-> austenitic transformation, which occurs rapidly bymartensitic <-> austenitic transformation, which occurs rapidly by
crystallographic twining at the atomic level.crystallographic twining at the atomic level.
In some cases an intermediate R-phase having a rhombohedralIn some cases an intermediate R-phase having a rhombohedral
crystal structure may form during transformation process.crystal structure may form during transformation process.

Phase Transformation TemperaturesPhase Transformation Temperatures
for the Nickel Titanium Alloysfor the Nickel Titanium Alloys
Ms - the temperature at which martensiticMs - the temperature at which martensitic
transformation (martensitic start)transformation (martensitic start)
Mf - the temperature at which martensiticMf - the temperature at which martensitic
transformation (martensitic finish)transformation (martensitic finish)
As - (Austenite) start) – the temperature at which theAs - (Austenite) start) – the temperature at which the
transformation to austenite starts.transformation to austenite starts.
Af - (Austenite – finish) the temperature at whichAf - (Austenite – finish) the temperature at which
transformation to austenite completes.transformation to austenite completes.
Rs+Rf -> may be defined for the R phaseRs+Rf -> may be defined for the R phase
transformation temperatures.transformation temperatures.

Conventional Nitinol (or) MartensiticConventional Nitinol (or) Martensitic
stabilized Niti (or) M-Nitistabilized Niti (or) M-Niti
Nitinol is the first Niti wire introduced byNitinol is the first Niti wire introduced by
Unitek corporation around 1970. In this wireUnitek corporation around 1970. In this wire
shape memory effect was not used as it hadshape memory effect was not used as it had
work hardened martensitic phase (stabilizedwork hardened martensitic phase (stabilized
martensitic). Since it is exceptionally springymartensitic). Since it is exceptionally springy
and quite strong and low stiffness, it is beenand quite strong and low stiffness, it is been
very attractive.very attractive.

Mechanical Properties ofMechanical Properties of
conventional Niticonventional Niti
(i)(i) Nitinol is called as martensitic stabilized alloys because processingNitinol is called as martensitic stabilized alloys because processing
of the wire creates a stable martensitic structure.of the wire creates a stable martensitic structure.
(ii)(ii) Do not posses shape memory or super elasticityDo not posses shape memory or super elasticity
(iii)(iii) Wire has a high spring back and its stiffness was linear like a spring,Wire has a high spring back and its stiffness was linear like a spring,
resulting in equal loss of force for a fixed increment of deactivation.resulting in equal loss of force for a fixed increment of deactivation.
(iv)(iv) Solid solution hardening and cold working strengthen this alloy.Solid solution hardening and cold working strengthen this alloy.
(v)(v) Due to its low modulus of elasticity of 4,800,000 psi combined withDue to its low modulus of elasticity of 4,800,000 psi combined with
tensile strength of 2,40,000 psi this wire. Can sustain large elastictensile strength of 2,40,000 psi this wire. Can sustain large elastic
deflections as reflected by its high spring back characteristics.deflections as reflected by its high spring back characteristics.
(vi)(vi) But Nitinol has limited formability which contra indicates it is bendsBut Nitinol has limited formability which contra indicates it is bends
of small radius.of small radius.
(vii)(vii) Soldering and welding is not possible with NitinolSoldering and welding is not possible with Nitinol

Austenitic Niti – A NITIAustenitic Niti – A NITI
In the late 1980’s new Nickel titanium wires with an activeIn the late 1980’s new Nickel titanium wires with an active
austenitic grain structure appeared. These wires exhibitaustenitic grain structure appeared. These wires exhibit
the other remarkable property of Niti alloys superthe other remarkable property of Niti alloys super
elasticity – which is manifested by very large reversibleelasticity – which is manifested by very large reversible
strains and a non elastic stress strain or force deflectionstrains and a non elastic stress strain or force deflection
curve.curve.
2 types of A – Niti have been developed2 types of A – Niti have been developed
1.1. Chinese – Niti-> developed by Burrstone et al developedChinese – Niti-> developed by Burrstone et al developed
in China.in China.
2.2. Japanese Niti-> By Miura prepared in JapanJapanese Niti-> By Miura prepared in Japan
Presumably equivalent properties are found in otherPresumably equivalent properties are found in other
austenitic wires now marketed. Niti and Cu – Niti ->austenitic wires now marketed. Niti and Cu – Niti ->
Ormco / sybron; Nitinol – SE, unitek; and several others.Ormco / sybron; Nitinol – SE, unitek; and several others.
This group subsequently is referred to as A – Niti.This group subsequently is referred to as A – Niti.

Chinese Niti
A new nickel-titanium alloy has been developed
especially for orthodontic applications by Dr. Tien Hua
Cheng and associates at the General Research
Institute for Non-Ferrous Metals in Beijing, China.
This alloy has unique characteristics and offers
significant potential in the design of orthodontic
appliances.
Its history of little work hardening
and a parent phase which is austenite yield mechanical
properties that differ significantly from nitinol wire.
In addition, Chinese NiTi wire has a
much lower transition temperature than nitinol wire.

Clinical significanceClinical significance
Because of its high range of action or spring back, Chinese
NiTi wire is applicable in situations where large deflections
are required.
Applications include straight-wire
procedures when teeth are badly malaligned and in
appliances designed to deliver constant forces during major
stages of tooth movement.
The amount of deformation without
notable permanent set is remarkable— 4.4 times that of the
stainless steel wire and 1.6 times that of the nitinol wire
(based on 1° of permanent deformation).

Chinese NiTi wire was studied by means of a bending
test to determine wire stiffness, springback, and maximum
bending moments. Chinese NiTi wire has an unusual deactivation
curve (unlike steel and nitinol wires) in which relatively constant
forces are produced over a long range of action.
The characteristic flexural stiffness of NiTi wire is
determined by the amount of activation. At large activations NiTi
wires has a stiffness of only 7% that of a comparable stainless
steel wire, and at small activations 28% of steel wire. For the same
activation at large deflections, the forces produced are 36% that of
a comparable nitinol wire.

►Chinese NiTi wire demonstrates
phenomenal springback. It can be
deflected 1.6 times as far as nitinol
wire or 4.4 times as far as stainless
steel wire without appreciable
permanent deformation. NiTi wire is
highly useful in clinical situations
that require a low-stiffness wire with
an extremely large springback.

SUMMARY OF CHINESE –NITISUMMARY OF CHINESE –NITI
The new nickel-titanium alloy (Chinese Niti wire) describedThe new nickel-titanium alloy (Chinese Niti wire) described
here has the following unique mechanical properties:here has the following unique mechanical properties:
1. The wire has a springback that is 4.4 times that of1. The wire has a springback that is 4.4 times that of
comparable stainless steel wire and 1.6 times that of nitinolcomparable stainless steel wire and 1.6 times that of nitinol
wire, if springback is measured at yield based on a 5-mm spanwire, if springback is measured at yield based on a 5-mm span
cantilever test.cantilever test.
2. At 80° of activation the average stiffness of Chinese NiTi2. At 80° of activation the average stiffness of Chinese NiTi
wire is 73% that of stainless steel wire and 36% that of nitinolwire is 73% that of stainless steel wire and 36% that of nitinol
wire.wire.

► 3. The unusual nonlinear loading curve builds into the NiTi wire a constant3. The unusual nonlinear loading curve builds into the NiTi wire a constant
force mechanism in the middle range of deactivation. This is potentially aforce mechanism in the middle range of deactivation. This is potentially a
significant design feature for constant-force appliances.significant design feature for constant-force appliances.
4. Unlike wires of other orthodontic alloys, the characteristic stiffness is4. Unlike wires of other orthodontic alloys, the characteristic stiffness is
determined by the amount of activation. The load-deformation rate at smalldetermined by the amount of activation. The load-deformation rate at small
activations is considerably higher than that at large activationsactivations is considerably higher than that at large activations..

The super-elasticThe super-elastic
property of the Japanese NiTi alloy wire for use inproperty of the Japanese NiTi alloy wire for use in
orthodonticsorthodontics
A new Japanese nickel-titanium (NiTi) alloy
wire was developed by the Furukawa
Electric Co., Ltd. of Japan

The "super-elastic property" is a phenomenon
that can be described briefly. The stress value
remains fairly constant up to a certain point of
wire deformation.
At the same time, when the
wire deformation rebounds, the stress value
again remains fairly constant.
Because of such unique
properties, NiTi alloy has been widely used in
the industrial, medical, and other scientific fields

The Japanese NiTi wire exhibited an unusual propertyThe Japanese NiTi wire exhibited an unusual property
termed "super-elasticity," which no other orthodontic wiretermed "super-elasticity," which no other orthodontic wire
has shown.has shown.
The wire delivered a constant force overThe wire delivered a constant force over
an extended portion of the deactivation range. Among allan extended portion of the deactivation range. Among all
the wires compared, Japanese NiTi alloy wire was the leastthe wires compared, Japanese NiTi alloy wire was the least
likely to undergo permanent deformation during activation.likely to undergo permanent deformation during activation.
The new alloy exhibited a specificThe new alloy exhibited a specific
stress-strain curve unlike those of the other testedstress-strain curve unlike those of the other tested
materials. Stress remained nearly constant despite thematerials. Stress remained nearly constant despite the
strain change within a specific range.strain change within a specific range.
This unique feature is the manifestation ofThis unique feature is the manifestation of
so-called super-elasticity.so-called super-elasticity.

Heat treatment enabled the load magnitude at which super-elasticity isHeat treatment enabled the load magnitude at which super-elasticity is
reflected to be influenced and controlled by both temperature and time.reflected to be influenced and controlled by both temperature and time.
A unique and useful process was alsoA unique and useful process was also
developed so that an arch wire delivering various magnitudes of forcedeveloped so that an arch wire delivering various magnitudes of force
for a given activation could be fabricated from the wire of the samefor a given activation could be fabricated from the wire of the same
diameter.diameter.
The clinical application of wires of this new alloyThe clinical application of wires of this new alloy
should be more likely to generate a physiologic tooth movementshould be more likely to generate a physiologic tooth movement
because of the relatively constant force delivered for a long period ofbecause of the relatively constant force delivered for a long period of
time during the deactivation of the wire.time during the deactivation of the wire.
Japanese NiTi alloy should be considered anJapanese NiTi alloy should be considered an
important material addition to clinical orthodontic metallurgy.important material addition to clinical orthodontic metallurgy.

► CONCLUSION OF JAPANESE -NITICONCLUSION OF JAPANESE -NITI
► Since the Japanese NiTi alloy arch wire possesses many desirableSince the Japanese NiTi alloy arch wire possesses many desirable
properties for physiologic tooth movement, there are sufficient reasonsproperties for physiologic tooth movement, there are sufficient reasons
to believe that similar properties could also be obtained if this alloy wireto believe that similar properties could also be obtained if this alloy wire
is fabricated into coil springs: For this reason, an intensive study on theis fabricated into coil springs: For this reason, an intensive study on the
tensile and compression properties of the coil springs was conducted.tensile and compression properties of the coil springs was conducted.
► From the findings gathered by the comparative study of the JapaneseFrom the findings gathered by the comparative study of the Japanese
NiTi alloy coil springs and the commercially available stainless steelNiTi alloy coil springs and the commercially available stainless steel
coil springs, it is concluded that the Japanese NiTi alloy coil spring hascoil springs, it is concluded that the Japanese NiTi alloy coil spring has
desirable springback and super-elastic properties that are not possibledesirable springback and super-elastic properties that are not possible
with the stainless steel-type coil springs.with the stainless steel-type coil springs.
From the study the following key statements can be made.From the study the following key statements can be made.
► 1. When the lumen of the coil spring remains constant, the load value1. When the lumen of the coil spring remains constant, the load value
of super-elastic activity increases as the wire diameter increases.of super-elastic activity increases as the wire diameter increases.

2. When the diameter of the wire remains constant, the load value of super-elastic2. When the diameter of the wire remains constant, the load value of super-elastic
activity increases as the lumen of the coil becomes smaller.activity increases as the lumen of the coil becomes smaller.
3. When the martensite transformation temperature elevates, the load value of3. When the martensite transformation temperature elevates, the load value of
super-elastic activity is reduced.super-elastic activity is reduced.
4. When the pitch of coils of the open coil spring is changed from fine to coarse, the4. When the pitch of coils of the open coil spring is changed from fine to coarse, the
load value of superelastic activity can still remain the same and the range of super-load value of superelastic activity can still remain the same and the range of super-
elastic activity increases.elastic activity increases.
By correlating these observations gained pertaining toBy correlating these observations gained pertaining to
the diameter, the lumen, martensite transformation temperature, and the pitch of thethe diameter, the lumen, martensite transformation temperature, and the pitch of the
coils, it is now possible to use the Japanese NiTi alloy coil springs selectively tocoils, it is now possible to use the Japanese NiTi alloy coil springs selectively to
obtain ideal and optimal tooth movement.obtain ideal and optimal tooth movement.

Mechanical properties of A-NitiMechanical properties of A-Niti
A- niti, over a considerable range of deflection, the force produced by A-NitiA- niti, over a considerable range of deflection, the force produced by A-Niti
hardly varies. This means that an initial arch wire would exert about the samehardly varies. This means that an initial arch wire would exert about the same
force whether it were deflected a relatively small or a large distance, which is aforce whether it were deflected a relatively small or a large distance, which is a
unique and extremely desirable characteristic.unique and extremely desirable characteristic.
► The unique force deflection curve for A-Niti wire occurs because of aThe unique force deflection curve for A-Niti wire occurs because of a
phase transition in grain structure from austenite to martensite. This responsephase transition in grain structure from austenite to martensite. This response
is not to a temperature change but due to applied force i.e. the austenitic –is not to a temperature change but due to applied force i.e. the austenitic –
active alloys undergo s Stress induced martensitic (SIM) transformation whenactive alloys undergo s Stress induced martensitic (SIM) transformation when
activated.activated.
► These alloys display super elastic behaviour (termedThese alloys display super elastic behaviour (termed
pseudo elastic in the materials science literature) which is the mechanicalpseudo elastic in the materials science literature) which is the mechanical
analogue of the thermo elastic shape-memory effect (SME). These alloys areanalogue of the thermo elastic shape-memory effect (SME). These alloys are
the super elastic wires that don’t posses thermo elastic shape memory at thethe super elastic wires that don’t posses thermo elastic shape memory at the
temperature of the oral environmental, such as Nitinol SE.temperature of the oral environmental, such as Nitinol SE.

The reverse deformation from martensitic back to austenite takes place duringThe reverse deformation from martensitic back to austenite takes place during
unloading (deactivation).unloading (deactivation).
Part of the universal nature of a super elastic material like A-Niti isPart of the universal nature of a super elastic material like A-Niti is
that its unloading cure differs from its loading curve (i.e the reversibility has anthat its unloading cure differs from its loading curve (i.e the reversibility has an
energy loss associates with it (hysteresis). This means the force it delivers isenergy loss associates with it (hysteresis). This means the force it delivers is
not the same as the force applied to activate it.not the same as the force applied to activate it.
The different loading and unloading curves produce theThe different loading and unloading curves produce the
even more remarkable effect that the force delivered by an A-Niti wire can beeven more remarkable effect that the force delivered by an A-Niti wire can be
changed during clinical use merely by releasing and retrying.changed during clinical use merely by releasing and retrying.
Wire bending is not possible with A-Niti wire because they do notWire bending is not possible with A-Niti wire because they do not
indergo plastic deformation until remarkably high force is applied. The wiresindergo plastic deformation until remarkably high force is applied. The wires
can be shaped and their properties can be altered, however by heat treatment.can be shaped and their properties can be altered, however by heat treatment.
This can be done in the orthodontic office by passing an electric currentThis can be done in the orthodontic office by passing an electric current
between electrodes attached to the wire or a segment of it.between electrodes attached to the wire or a segment of it.

A – Niti versus M - NitiA – Niti versus M - Niti
The properties of A – Niti have quickly made it the preferred materialThe properties of A – Niti have quickly made it the preferred material
for orthodontic applications in which a long range of activation withfor orthodontic applications in which a long range of activation with
relatively constant force is needed (i.e. for initial wires and coilrelatively constant force is needed (i.e. for initial wires and coil
springs).springs).
M-Niti remains useful primarily in the later stages ofM-Niti remains useful primarily in the later stages of
treatment when flexible but larger and somewhat stiffer wires aretreatment when flexible but larger and somewhat stiffer wires are
needed. At this point, small round Nickel- titanium wires usually shouldneeded. At this point, small round Nickel- titanium wires usually should
be A-Niti, while larger rectangular ones often perform better if madebe A-Niti, while larger rectangular ones often perform better if made
from M-Niti.from M-Niti.
Thermoelastic Niti wires –Copper NitiThermoelastic Niti wires –Copper Niti
Copper Niti is a new quaternary alloy of nickel,titanium,copperandCopper Niti is a new quaternary alloy of nickel,titanium,copperand
chromiumalloy with distinct advantages over the formerly availablechromiumalloy with distinct advantages over the formerly available
nickel titanium alloys.nickel titanium alloys.

► Copper Niti demonstrate smaller loading force for the same degree ofCopper Niti demonstrate smaller loading force for the same degree of
deformation. So its useful to engage severely malposed teeth withdeformation. So its useful to engage severely malposed teeth with
less patient discomfort and less potential for root resorption.less patient discomfort and less potential for root resorption.
► It provides consistent forces over a larger working range and reduciedIt provides consistent forces over a larger working range and reducied
hysterics makes it possible tp avoid undue loading force.hysterics makes it possible tp avoid undue loading force.
► At lower degrees of deformation or activation, copper Niti demonstrateAt lower degrees of deformation or activation, copper Niti demonstrate
a greater force to deformation relationship and greater degree ofa greater force to deformation relationship and greater degree of
recovery.This important quality that enables the Niti arch wire torecovery.This important quality that enables the Niti arch wire to
,maintain an effecyive level of force for continued tooth movement as it,maintain an effecyive level of force for continued tooth movement as it
returns to its original shape.returns to its original shape.
► The copper Niti exhibits a more constant force /deformationThe copper Niti exhibits a more constant force /deformation
relationship which provides superior constency from arch wire to archrelationship which provides superior constency from arch wire to arch
wire.wire.
► The cu- niti demonstrate consistent transformation temperature thatThe cu- niti demonstrate consistent transformation temperature that
ensure consistency of force.ensure consistency of force.

Physical PropertiesPhysical Properties
Cu – Niti are Martensitic Active Alloys which employ theCu – Niti are Martensitic Active Alloys which employ the
thermo elastic effect to achieve shape memory; the oralthermo elastic effect to achieve shape memory; the oral
environment raises the temperature of the deformed archenvironment raises the temperature of the deformed arch
wire with the martensitic structure so that it transformswire with the martensitic structure so that it transforms
back to the austenitic structure and returns to the startingback to the austenitic structure and returns to the starting
shape.shape.
This thermo elastic shape memory canThis thermo elastic shape memory can
be observed by the clinician if a deformed arch wirebe observed by the clinician if a deformed arch wire
segment is warmed in the hands. These are the shape –segment is warmed in the hands. These are the shape –
memory wire alloys such as Neosent alloy and copper Ni –memory wire alloys such as Neosent alloy and copper Ni –
Ti.Ti.
Low temperature -> exist in martensitic active formLow temperature -> exist in martensitic active form
When temperature rises -> transforms to austeniticWhen temperature rises -> transforms to austenitic
structure & (e.g. - oral environment).structure & (e.g. - oral environment).

Neosent alloy (GACNeosent alloy (GAC
International)International)
It exist in martensitic form in cool temperature. At the temperature of oralIt exist in martensitic form in cool temperature. At the temperature of oral
environment, Neosentalloy has essentially a complete austeniticenvironment, Neosentalloy has essentially a complete austenitic
structure.structure.
Copper Niti(Ormaco Corporation – 1994)Copper Niti(Ormaco Corporation – 1994)
It is available in three temperature variants of 270C, 35C and 40C.It is available in three temperature variants of 270C, 35C and 40C.
Corresponding to the austenitic finish temperature for theCorresponding to the austenitic finish temperature for the
completion of the martensitic austenitic transformation.completion of the martensitic austenitic transformation.
Shape memory behaviour is reported by the manufacturer toShape memory behaviour is reported by the manufacturer to
occur for each variant at temperature exceeding the specifiedoccur for each variant at temperature exceeding the specified
temperature.temperature.

Variable TransformationVariable Transformation
Temperature Mechanics of CopperTemperature Mechanics of Copper
NitiNiti
Stress induced martensitic is responsible for superStress induced martensitic is responsible for super
elastic property of Niti alloys. However martensiticelastic property of Niti alloys. However martensitic
transformation here is temperature dependent.transformation here is temperature dependent.
To exploit super elasticity to itsTo exploit super elasticity to its
fullest potential the working temperature of the orthodonticfullest potential the working temperature of the orthodontic
appliance should be greater than the austenitic finishappliance should be greater than the austenitic finish
temperature (Af)temperature (Af)
The difference between (Af) temperature and mouthThe difference between (Af) temperature and mouth
temperature determines the force generated by Niti alloys.temperature determines the force generated by Niti alloys.
This Austenitic finish temperature (Af) can be controlled aThis Austenitic finish temperature (Af) can be controlled a
wide range affecting the composition, thermo mechanicalwide range affecting the composition, thermo mechanical
treatment and manufacturing process of the alloy. It is atreatment and manufacturing process of the alloy. It is a
martensitic active alloy.martensitic active alloy.

Cu-NitiCu-Niti
Wires of (Af) 27CWires of (Af) 27C
It generates the highest forces of the two other types and is bestIt generates the highest forces of the two other types and is best
used.used.
1)1) In patients with high pain thresholdIn patients with high pain threshold
2)2) In normal periodontal healthIn normal periodontal health
3)3) Inpatients where rapid tooth movement is required and the forceInpatients where rapid tooth movement is required and the force
system generated is constant.system generated is constant.
Cu-Niti Wires of AF 35CCu-Niti Wires of AF 35C
This wire generates force in the mid range and is best used.This wire generates force in the mid range and is best used.
1)1) Patients who have normal or low pain thresholdPatients who have normal or low pain threshold
2)2) If periodontium is slightly compromisedIf periodontium is slightly compromised
3)3) Where relatively low forces are desiredWhere relatively low forces are desired

Cu-Niti Wires AF-40CCu-Niti Wires AF-40C
These wires generate tooth driving forces onlyThese wires generate tooth driving forces only
when the mouth temperature exceeds 40C.when the mouth temperature exceeds 40C.
These forces are intermittent in nature. Used inThese forces are intermittent in nature. Used in
1)1) Patients sensitive to painPatients sensitive to pain
2)2) Patients with compromised periodontalPatients with compromised periodontal
conditionsconditions
3)3) Where tooth movement is deliberately slowedWhere tooth movement is deliberately slowed
downdown
4)4) The wire is beneficial as initial rectangular wireThe wire is beneficial as initial rectangular wire

Copper Niti wire represent a major advancement in shape memoryCopper Niti wire represent a major advancement in shape memory
wires by reducing Hysteresis (amount of energy lost betweenwires by reducing Hysteresis (amount of energy lost between
unloading and loading forces) and by providing precise transformationunloading and loading forces) and by providing precise transformation
temperatures at different levels.temperatures at different levels.
Cu Niti develops approximately 20% less loadingCu Niti develops approximately 20% less loading
force than other Nickel titanium wires which permits easierforce than other Nickel titanium wires which permits easier
engagement of wires with less fauma and discomfort to the patient.engagement of wires with less fauma and discomfort to the patient.
At rear tooth positions, the decrease in forceAt rear tooth positions, the decrease in force
generated0 is less in Cu-Niti which explains its clinical efficiency togenerated0 is less in Cu-Niti which explains its clinical efficiency to
continue working as teeth near their intended positions. The addition ofcontinue working as teeth near their intended positions. The addition of
Cu, gives more accurate control over the TTR (TemperatureCu, gives more accurate control over the TTR (Temperature
Transformation Range), lower friction of the wire and reduce theTransformation Range), lower friction of the wire and reduce the
hysterisis.hysterisis.
Composition – It contains alloy conditions of normally 5 to 6%Composition – It contains alloy conditions of normally 5 to 6%
copper and 0.2 to 0.5% chromium to the conventional super elasticcopper and 0.2 to 0.5% chromium to the conventional super elastic
Nickel titanium alloy.Nickel titanium alloy.

Primary use of Cu-Niti is inPrimary use of Cu-Niti is in
► Extreme leveling problems as in engagements of high caninesExtreme leveling problems as in engagements of high canines
► Use of sectional Cu-Niti for cupid retractionUse of sectional Cu-Niti for cupid retraction
► In periodontally compromised patientsIn periodontally compromised patients
Reverse Curve NitiReverse Curve Niti
It is useful in opening the lute and simultaneous corrections of rotations,It is useful in opening the lute and simultaneous corrections of rotations,
intrusions and to control anterior and upright motors. There are 3 typesintrusions and to control anterior and upright motors. There are 3 types
► Original styleOriginal style
► Short leg styleShort leg style
► L – Shaped styleL – Shaped style
Gold NitiGold Niti
The Nickel titanium wires are coated with super hard gold of 24 karat that willThe Nickel titanium wires are coated with super hard gold of 24 karat that will
not get brushed off. It has a golden finish and smooth sliding mechanics.not get brushed off. It has a golden finish and smooth sliding mechanics.

Aesthetic Arch WiresAesthetic Arch Wires
One promising approach towards achieving an esthetic arch wire withOne promising approach towards achieving an esthetic arch wire with
excellent overall properties involves the use of composites, which can beexcellent overall properties involves the use of composites, which can be
composed of ceramic fibers that are embedded in a linear or cross linkedcomposed of ceramic fibers that are embedded in a linear or cross linked
polymeric matrix.polymeric matrix.
Existing photo types are tooth coloured with varyingExisting photo types are tooth coloured with varying
stiffness, which is possible during manufacture by a process called pultruism, instiffness, which is possible during manufacture by a process called pultruism, in
which the relative proportions of the fiber and matrix materials are adjustedwhich the relative proportions of the fiber and matrix materials are adjusted
approximately and cured by electromagnetic radiation.approximately and cured by electromagnetic radiation.
Mechanical tests have shown that such wires remainMechanical tests have shown that such wires remain
elastic until failure occurs. When compared with Niti, resilience and spring backelastic until failure occurs. When compared with Niti, resilience and spring back
are comparable.are comparable.
Although other characteristics are still under study,Although other characteristics are still under study,
performed arch wires and rectangular cross sections are said to be possible byperformed arch wires and rectangular cross sections are said to be possible by
a process called beta staging and low coefficients of friction, bio compatibilitya process called beta staging and low coefficients of friction, bio compatibility
possible by altering the surface chemistry of, the polymer. Such compositespossible by altering the surface chemistry of, the polymer. Such composites
are termed as UFRF’S or unidirectional fiber reinforced polymeric composites.are termed as UFRF’S or unidirectional fiber reinforced polymeric composites.

Composite Plastics – Opti flexComposite Plastics – Opti flex
(ormco/sybron)(ormco/sybron)
It is a composite structure found by topIt is a composite structure found by top
coating optical glass fibers made of pure siliconcoating optical glass fibers made of pure silicon
dioxide with a hot melt adhesive and nylon skin.dioxide with a hot melt adhesive and nylon skin.
The result is a 0.017 wire with 0.008 glass core.The result is a 0.017 wire with 0.008 glass core.
The advantages areThe advantages are
1.1. Light force for initial alignmentLight force for initial alignment
2.2. Highly aesthetically pleasingHighly aesthetically pleasing
Composite are expected to take over theComposite are expected to take over the
field of orthodontic in a few years.field of orthodontic in a few years.

Newer Miscellaneous Arch WireNewer Miscellaneous Arch Wire
MaterialsMaterials
1.Dual Flex Arch Wire Materials1.Dual Flex Arch Wire Materials
Its been divided intoIts been divided into
a.a. Type IType I
The dual flex arch wire has an anterior segment of 0.016sThe dual flex arch wire has an anterior segment of 0.016s
Fitanol and posterior segment made of 0.016 S.S. thus providingFitanol and posterior segment made of 0.016 S.S. thus providing
different stiffness anteriorly and posteriorly.different stiffness anteriorly and posteriorly.
The flexibility of titanol in anterior segment greatlyThe flexibility of titanol in anterior segment greatly
simplifies bracket engagement in the crowed anterior segment whilesimplifies bracket engagement in the crowed anterior segment while
rigidity of S.S. posteriorly controls rotation movements, preventsrigidity of S.S. posteriorly controls rotation movements, prevents
tipping from elastic fraction and permit lute opening. It is ideal fortipping from elastic fraction and permit lute opening. It is ideal for
lingual appliance.lingual appliance.
b.b. Type IIType II
It has 0.016 x 0.022 rectangular titanol in anterior segment andIt has 0.016 x 0.022 rectangular titanol in anterior segment and
0.016” S.S. in posterior segment. Useful in retraction of anterior0.016” S.S. in posterior segment. Useful in retraction of anterior
teeth to upright position and space closure by aerial movement ofteeth to upright position and space closure by aerial movement of
posterior teeth.posterior teeth.

2. Triforce Arch Wire2. Triforce Arch Wire
It has been programmed to deliver the rightIt has been programmed to deliver the right
amount of force to each area of the mouth. Theamount of force to each area of the mouth. The
strongest force to deeply rooted molars, mediumstrongest force to deeply rooted molars, medium
at bicuspids and gentle at anteriors. It is made ofat bicuspids and gentle at anteriors. It is made of
austenitic wire.austenitic wire.
3. Drift Free Arch Wire3. Drift Free Arch Wire
A built in then guideline stop presents lateralA built in then guideline stop presents lateral
arch wire shift and drifts can be detected early.arch wire shift and drifts can be detected early.

OPTIMAL CLINICAL APPLICATIONS OF ORTHODONTIC WIRESOPTIMAL CLINICAL APPLICATIONS OF ORTHODONTIC WIRES
The practical applications of orthodontic wiresThe practical applications of orthodontic wires
can be optimized by carefully selecting the appropriate alloy typecan be optimized by carefully selecting the appropriate alloy type
and wire size to meet the demands of a specific clinical situation.and wire size to meet the demands of a specific clinical situation.
Kusy and Kusy and Greenberg have recommended a sequentialKusy and Kusy and Greenberg have recommended a sequential
use of arch wires selected for optimal use of the mechanicaluse of arch wires selected for optimal use of the mechanical
properties of their constituent alloys.properties of their constituent alloys.
For initial levelingFor initial leveling
► The authors suggest that for initial leveling requiring wide-rangingThe authors suggest that for initial leveling requiring wide-ranging
tooth movements, a 0.016-inch nitinol wire outperforms a 0.0175-tooth movements, a 0.016-inch nitinol wire outperforms a 0.0175-
inch triple-stranded stainless steel wire,inch triple-stranded stainless steel wire,
► an 0.018-inch round nitinol wire is superior to a 0.014-inch roundan 0.018-inch round nitinol wire is superior to a 0.014-inch round
stainless steel wire, andstainless steel wire, and
► an 0.018-inch square nitinol wire outperforms a 0.014-inch roundan 0.018-inch square nitinol wire outperforms a 0.014-inch round
stainless steel wirestainless steel wire

► . However, in a recent report, Kusy and Stevens. However, in a recent report, Kusy and Stevens
noted that 0.015-inch triple-stranded wiresnoted that 0.015-inch triple-stranded wires
demonstrate a greater working range than eitherdemonstrate a greater working range than either
nitinol or beta-titanium wires of similar or greaternitinol or beta-titanium wires of similar or greater
dimensions.dimensions.
► The authors also indicate that multistranded wiresThe authors also indicate that multistranded wires
compare more favorably with titanium wires thancompare more favorably with titanium wires than
suggested by previous research56 and maysuggested by previous research56 and may
provide a viable alternative to the more expensiveprovide a viable alternative to the more expensive
titanium wires for initial leveling.titanium wires for initial leveling.

Wires for intermediate stageWires for intermediate stage
► The intermediate stages of treatment requireThe intermediate stages of treatment require
closing loops, gable bends, and attachments.closing loops, gable bends, and attachments.
► Beta-titanium wires meet these demands whileBeta-titanium wires meet these demands while
providing greater range of activation thanproviding greater range of activation than
stainless steel or Co-Cr wires.stainless steel or Co-Cr wires.
► The lower friction between stainlessThe lower friction between stainless
steel or Co-Cr wires and brackets suggest thatsteel or Co-Cr wires and brackets suggest that
these wires may be more suitable than otherthese wires may be more suitable than other
alloys for movement of teeth along a wire.alloys for movement of teeth along a wire.

Wires for Finishing stageWires for Finishing stage
In torsion, the formability and stiffness ofIn torsion, the formability and stiffness of
stainless steel and Co-Cr wires far exceedstainless steel and Co-Cr wires far exceed
those of the titanium wires, thereby makingthose of the titanium wires, thereby making
these alloys the finishing wires of choice.these alloys the finishing wires of choice.

Variable cross-section orthodonticsVariable cross-section orthodontics
►Until the recent introduction of new typesUntil the recent introduction of new types
of orthodontic alloys, increments in wireof orthodontic alloys, increments in wire
stiffness during treatment were institutedstiffness during treatment were instituted
by progressively increasing the cross-by progressively increasing the cross-
section of stainless steel wires. Burstonesection of stainless steel wires. Burstone
refers to this as "variable cross-sectionrefers to this as "variable cross-section
orthodontics."orthodontics."

Variable Modulus orthodonticsVariable Modulus orthodontics
►The author further states that advances inThe author further states that advances in
orthodontic wire alloys have made itorthodontic wire alloys have made it
possible to control wire stiffness by varyingpossible to control wire stiffness by varying
material properties— namely, the modulusmaterial properties— namely, the modulus
of elasticity. This is known as "variableof elasticity. This is known as "variable
modulus orthodontics."modulus orthodontics."

► Burstone formulates his concepts by stating that the overall stiffness ofBurstone formulates his concepts by stating that the overall stiffness of
the orthodontic appliance (S) is determined by the wire stiffness (Ws)the orthodontic appliance (S) is determined by the wire stiffness (Ws)
and design stiffness (As) as represented by:and design stiffness (As) as represented by:
S = Ws ´ AsS = Ws ´ As
► Design stiffness (As) is dependent on factors such as interbracketDesign stiffness (As) is dependent on factors such as interbracket
distance and the incorporation of loops and coils into the wire.distance and the incorporation of loops and coils into the wire.
Changes in wire stiffness (Ws), on the other hand, can be broughtChanges in wire stiffness (Ws), on the other hand, can be brought
about by altering the cross-sectional stiffness (Cs) and/or the materialabout by altering the cross-sectional stiffness (Cs) and/or the material
stiffness (MS) as designated by the formula:stiffness (MS) as designated by the formula:
Ws = Ms ´ CsWs = Ms ´ Cs

► where the cross-sectional stiffness is determined by awhere the cross-sectional stiffness is determined by a
cross-sectional property such as moment of inertia of thecross-sectional property such as moment of inertia of the
wire and the material stiffness is dependent on thewire and the material stiffness is dependent on the
modulus of elasticity of the alloy.modulus of elasticity of the alloy.
► Therefore, an increase inTherefore, an increase in
appliance stiffness (S) can be brought about not only byappliance stiffness (S) can be brought about not only by
change in appliance design or increase in cross-change in appliance design or increase in cross-
sectional thickness of the wire, but also by selecting asectional thickness of the wire, but also by selecting a
material with a higher modulus of elasticity.material with a higher modulus of elasticity.
► The relationships of material stiffThe relationships of material stiff
nesses for stainless steel, cobalt-chromium, nickel-nesses for stainless steel, cobalt-chromium, nickel-
titanium and beta-titanium wires are in the ratio oftitanium and beta-titanium wires are in the ratio of
1:1.2:0.26:0.42. Material stiffness for multistranded wires1:1.2:0.26:0.42. Material stiffness for multistranded wires
range from 1/25 to 1/5 of that for single-strandedrange from 1/25 to 1/5 of that for single-stranded
stainless steel wires.6stainless steel wires.6

► Several advantages of "variable modulusSeveral advantages of "variable modulus
orthodontics" have been suggested as follows:orthodontics" have been suggested as follows:
1.1. The amount of play between bracket and wireThe amount of play between bracket and wire
is not dictated by the desired wire stiffness, butis not dictated by the desired wire stiffness, but
is under full control of the clinician. This impliesis under full control of the clinician. This implies
that the orthodontist determines the amount ofthat the orthodontist determines the amount of
bracket/wire play desired before selection ofbracket/wire play desired before selection of
the wire.the wire.
Once the cross-Once the cross-
sectional size and shape have beensectional size and shape have been
established, the desired stiffness can beestablished, the desired stiffness can be
implemented by selecting an alloy with animplemented by selecting an alloy with an
appropriate material stiffness.appropriate material stiffness.
..

2. The low moduli of elasticity of the newer orthodontic alloys2. The low moduli of elasticity of the newer orthodontic alloys
permit the use of light, rectangular wires even during thepermit the use of light, rectangular wires even during the
early stages of treatment.early stages of treatment.
Rectangular wires are preferableRectangular wires are preferable
over round wires because they can be better oriented inover round wires because they can be better oriented in
the bracket in such a way that forces work out in the properthe bracket in such a way that forces work out in the proper
directions.directions.
They further aid in patientThey further aid in patient
comfort by preventing loops from turning into the cheekscomfort by preventing loops from turning into the cheeks
and gingiva. Rectangular wires also maintain better controland gingiva. Rectangular wires also maintain better control
over root position by delivering both moments and forcesover root position by delivering both moments and forces

3. The use of newer orthodontic alloys with their3. The use of newer orthodontic alloys with their
lower moduli of elasticity offers substantiallower moduli of elasticity offers substantial
advantages with a 0.022-inch bracket slot.advantages with a 0.022-inch bracket slot.
4. The selection of an appropriate alloy type and4. The selection of an appropriate alloy type and
wire size may reduce the number of arch wireswire size may reduce the number of arch wires
needed for alignment by reducing bracket/wireneeded for alignment by reducing bracket/wire
play early in treatment.play early in treatment.
In addition, since the titaniumIn addition, since the titanium
wires also work more efficiently and over longerwires also work more efficiently and over longer
periods of time because of their greater springperiods of time because of their greater spring
back, the number and frequency of arch wireback, the number and frequency of arch wire
changes are reduced.changes are reduced.

CONCLUSIONCONCLUSION
► In the last few decades , a variety of new wire alloys have beenIn the last few decades , a variety of new wire alloys have been
introduced in orthodontics. These wires demonstrate a wide spectrumintroduced in orthodontics. These wires demonstrate a wide spectrum
of mechanical properties and have added to the versatility ofof mechanical properties and have added to the versatility of
orthodontic treatment. Appropriate use of all the available wire typesorthodontic treatment. Appropriate use of all the available wire types
may enhance patient comfort and reduce chair side time and themay enhance patient comfort and reduce chair side time and the
duration of treatment.duration of treatment.
The restricted use of only stainless steelThe restricted use of only stainless steel
wires to treat an entire case from start to finish therefore may bewires to treat an entire case from start to finish therefore may be
indicated only in relatively few patients. It may be beneficial instead toindicated only in relatively few patients. It may be beneficial instead to
exploit the desirable qualities of a particular wire type that isexploit the desirable qualities of a particular wire type that is
specifically selected to satisfy the demands of the presenting clinicalspecifically selected to satisfy the demands of the presenting clinical
situation. This, in turn, would provide the most optimal and efficientsituation. This, in turn, would provide the most optimal and efficient
treatment results.treatment results.
..

ReferencesReferences
►Brantly and Elaides: orthodontic materialsBrantly and Elaides: orthodontic materials
►Profit: Contemporary orthodonticsProfit: Contemporary orthodontics
►Graber and vanarsdallGraber and vanarsdall
►AJO:1989 August volume 2AJO:1989 August volume 2
►Biomechanics: NandaBiomechanics: Nanda
►Skinner: Dental materialsSkinner: Dental materials

Ideal requisites of orthodontic wires

More Related Content

What's hot

Viewers also liked

Similar to Ideal requisites of orthodontic wires

More from Indian dental academy

Recently uploaded

Ideal requisites of orthodontic wires