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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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Contemporary Archwires
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
Contemporary Archwires
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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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