Archwires Alloy

8/3/2019 Archwires Alloy

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Contemporary Archwires

DR. GHULAM RASOOL


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Strong

Resilient

Biocompatible

Formable

Springy

Weldable

Low Friction

Good SpringBack

Poor Biohost

Tough

Good Range

Esthetics

IdealIdeal

ArchwireArchwire


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Some definitions

Range

The distance that an arch wire can be

activated by a specific force


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Resilience

The capicity of a material to absorbenergy, when the material is elastically

deformed


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Shape memory

The combination of thermoelasticity andpseudoelasticity in which, following a

force induced phase transformation, thereverse transformation occurs, when theAW temp is increased to oral temp.


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Spring back

Theextent to which the range recoversupon deactivation of an activated wire


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stiffness

In AW the ratio of force required to exceedtheelastic region to the distance that an

AW can be activated elastically


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Strngth

The force required to activate an AW aspecific distance


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Weldability

Theease by which metals may be joined

by actally melting the work piece in thevicinity of bond


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pseudoelasticity

The mech analog of thermoelasticity inwhich at constant temterature phasetransition occurs with applied load


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Thermoelasticity

The thermal analog of pseudoelasticity inwhich the martensitephase transformaion

occurs from austenite as temp isdecreased.


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Formability

Theease with which a mat may bepermanantly deformed as measured


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Biohostility

Theease with which a mat will culture

MO


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Cold working

The process of plastically deforming ametal at a temp below that at which it

recrystalise new grains


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Contemporary Aechwires


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Gold

Stainless steel

Cobalt-Chromium Nickel Titanium

Beta Titanium (TMA)

Plastic Composites


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GOLD


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Gold

Gold Alloyed withPt, Pd, Cu

Good biocompatibilty and stability

Superseded by stainless steel in 1950 Used only in Crozat Appliance nowadays


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STAIN

LESSSTEEL


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Stainless Steel

Invented in World War 1

Chromium forms a Shiny Layer Rendering theSteel Stainless.

Typical 18/8 wire contains

18 % Chromium: Passivate theIron

8 % Nickel: Stabilize SS in Austinite form

Both these metals increse the corrosion resistence Carbon Content is kept below 0.2 % to reduce

the formation of Chromium Carbides


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Strong

Resilient

Bio-

compatible

Formable

Springy

Weldable

Low

Friction

Good

Spring

Back

Poor

Biohost

Tough

Good

Range

Esthetics

STAIN-

LESS

STEEL

X

XX

X


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COB

ALT

CHROM

IUM


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Cobalt Chromium

Invented by Elgin WatchCo. in 1950s thusnamed Elgiloy

Alloy of Cobalt

Chromium

Iron

Nickel


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Cobalt Chromium

Supplied in a soft state

Formability modified by heat treatment

(482o

for 7-12 min.) After heat treatment the properties are

comparable to that of Stainless Steel


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NICKEL

T

IT

ANIUM


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Nickel Titanium

Nickel titanium has three types

Conventional NITINOL

M-NiTi A-NiTi

Thermoelastic NiTi


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NITINOL

Invented by theNaval Ordinance Laboratoriesfor the space program thus named NiTi NOL

It had the phase transition property

Apart from being very springy it has a peculiarproperty i.eThermoelasticity or Shape MemoryEffect (SME)

theuse was in satellites and magicians tricks,kettles, fireextinguishers etc. no use inorthodontics


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M-NiTi

1970 marketed by Unitek as Nitinol inorthodontics

50:50 of Ni & Ti It was a martensitic stable alloy that is it

did not had the property of phase change.

The SME was further depressed by coldworking the alloy


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M-NiTi

The wire was quite springy and had alarge range & Spring Back

This produced light continuous forces

The ideal wire was discovered but not forlong

Brittleness and lack of formability plagued

the space age wire Brittleness has been rectified in the

modern wires


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M-NiTi

Strong

Resilient

Bio-

compatible

Formable

Springy

Weldable

Low

Friction

Good

SpringBack

Poor

Biohost

Tough

Good

Range

Esthetics

M-NiTii

X

X

XX

X

X


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A-NiTi

a.k.a Pseudoelastic nitinol

Contemporary NiTi in use today

No Thermoelasticity Superelastic

Active alloy with phase transition from

austenitic to martensitic response to force


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A-NiTi

Stress strain curve of A-NiTi Showing phasetransition and superelasticity


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A-NiTi

Activation and de activation curves for A-NiTi

differ


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A-NiTi

Reactivation increases the force


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Thermoelastic NiTi

HANT


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Thermoelastic NiTi

The latest in HANTs is BioForceBy GACDentsply

Single rooted anteriors need far less force to

move than long, multi-rooted molars. If the forceexerted by a wire is too light, desired movementwill take far longer. If a wires force is greatenough to move molars, then anteriors will be

subjected to traumatic forces that cause patientdiscomfort, root resorption, and roundtripping


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Thermoelastic NiTi

BioForce provides this gradual increase inforce with one wire, so there is no need tostart with light wires and work up.


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Bioforce

The latest of Ortho wires


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BET

A-T

IT

ANIUM


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Beta-Titanium

Introduced by Ormco in 1980s as TMA

The last major system of alloy to have an

impact on contemporary orthodontics. Meets the criteria of Burstone.

Contains

80% Titanium 11.5% molybdenum

Zinc & Tin


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Beta-Titanium

The advantages of this alloy were that itwas inherently smoother, could be weldedand had good formability. It producedgentle linear forces and had more rangeand springback than S.S.

The ideal alloy was finally discovered

with the formability of steel andspringback and range of NiTi.


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Beta-Titanium

But not for long

Beta-Ti too had a latent flaw

Friction


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Beta-Titanium

Strong

Resilient

Bio-

compatible

Formable

Springy

Weldable

Low

Friction

Good

Spring

Back

Poor

Biohost

Tough

Good

Range

Esthetics

TMA

X

X


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E

sthetic Archwires


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Composites are replacing alloys in the spaceindustry, its time for us to follow

Composite wires are the future of orthodontic

wires With the process ofpultrusion (forming of wires

by curing the fiber and the resin withelectrochemical radiation) has led to the

formation of orthodontic wires with morestrength and elasticity than the non superelasticwires.


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In Search ofThe Ideal

Orthodontic Wire


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The search is still on

Every wirehas its advantages and short

comings The treatment philosophy of todayrevolves around use of multiple wiresduring the orthodontic treatment

All wires have a place in contemporaryorthodontics


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Comparison of



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Strength Stiffness Range.016 .018 .016 .018 .016 .018

1 1 1 1 1 1

0.6 0.6 0.3 0.3 1.8 1.8

0.6 0.6 0.2 0.2 3.9 3.9


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Effect ofLength


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Documents

Archwires Alloy