Wires in orthodontics


INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Introduction
Evolution of materials
Physical & Elastic properties
Requirements of an ideal arch wire
Composition, Heat treatment, manufacture of
1.Gold Alloy wires
2.Stainless Steel wires
3.Chrome Cobalt wires
4.Nickel Titanium wires
5.Copper Nickel Titanium wires
6.Alpha-Titanium wires

7.Beta-Titanium wires
8.Tooth colored wires
 Clinical importance of various wires
 Choice of wires in the clinical situation
 References

 Before Angle’s era.
 Noble metals and their alloys.
- Gold (at least 75%), platinum, iridium and silver
alloys
 Good corrosion resistance
 Acceptable esthetics
 Lacked flexibility and tensile strength
 Inappropriate for complex machining and joining.

 Angle (1887)  German silver (a type of brass)
 -To obtained desired properties --varied the
proportion of Cu, Ni & Zn and applied cold working
operation a.
 Neusilber brass (Cu 65%, Ni 14%, Zn 21%)
 jack screws (rigid)
 expansion arches (elastic)
 Bands (malleable)
 Opposition by Farrar – discolored

 Stainless steel
(introduced in dentistry -1919).
 Angle used steel ligature wires (1930).

 Opposition By,
 Emil Herbst
-Gold wire was stronger than stainless steel
(1934).
 Begg (1940s) with Wilcock-produced resilient
arch wires-Australian SS.

 Cobalt chrome (1950s)-Elgin watch company
developed a complex alloy-
Cobalt(40%),Chromium(20%),iron(16%)&nickel(15%).
 Rocky Mountain Orthodontics first introduced Co-Cr
wires by name ElgiloyTM
 1958-1961
various tempers
Red – hard & resilient
green – semi-resilient
Yellow – slightly less formable but ductile
Blue – soft & formable

 1962 - Buehler discovered nickel-titanium named
NITINOL (Nickel Titanium Naval Ordnance
Laboratory) . Developed for space program.
 1970-Dr.George Andreason (Unitek) introduced
NiTi to orthodontics.
 Late 1980s –NiTi with active austenitic grain
structure.
 β titanium –Burstone and Goldberg-1980

 Chinese NiTi (1985) –by Burstone et al
 Japanese NiTi (1986) – by Miura et al
 Cu NiTi – (1994) -by Rohit Sachdeva.

 Stress
 Strain
 Modulus of elasticity
 Proportional limit
 Elastic limit
 Yield strength
 Ductility
Richman G.Y. Practical metallurgy for
Orthodontist, AJO 1957;vol.42,573-576

 Malleability
 Elongation
 Formability
 Resilience
 Flexibility
 Spring back
Kohl R.w. Metallurgy in orthosontics,A.O.1964,Vol
34,37-52

Stress-
 It is the internal distribution of the load measured as
force per unit area i.e., Force/Original area.
 For simple compression or tension the stress is given
by the expression,
Stress =F/A
Where,
F= force applied
A= cross-sectional area

 Stress is measured in common units of psi or MPa
(Mega Pascal).
 1 Pascal – stress resulting from a force of 1
Newton (N) acting upon 1 sq. meter of surface and
is equal to 0.145 x 10–3 psi, (1000 psi = 6.894 MPa).

 By means of their directions ,stress can be classified
under three types
 TENSION OR TENSILE STRESS
 COMPRESSION OR COMPRESSIVE STRESS
 SHEAR STRESS
Sunil Kapila Sachdeva R.:Mechanical properties and clinical
applications of orthodontic wires.AJO 1989,Vol.96,100-109

TENSION OR
TENSILE STRESS
 Any induced force that
resists a deformation
caused by a load that
tends to stretch or
elongate a body

 COMPRESSION OR
COMPRESSIVE
STRESS
If a body is placed under
load that tends to
compress or shorten it ,
the internal forces that
resist such a load are
called compressive
stress.

 SHEAR STRESS
 A Stress that tends to
resist a twisting
motion ,or a sliding of
one portion of a body
over another ,is a
shear or shearing
stress

 Complex Stresses

 Poisson’s ratio (ν)
ν = - εx/ εz = -εy / εz
 Axial tensile stress (z axis) produces elastic tensile
strain and accompanying elastic contractions in x in y
axis.
 The ratio of x,y or x,z gives the Poissons ratio of the
material
 It is the ratio of the strain along the length and along the
diameter of the wire.

Strain-
It is the internal distortion produced by load or a
stress, i.e., change in length per unit length when
stress is applied.
 Strain = L’ = change in length
 L original length

• The common units of strain are inch per inch or
centimeter per centimeter.

 Strain may be either elastic or plastic or a
combination of two.
 Elastic strain is reversible ,it disappears after the
stress is removed.
 Plastic strain is permanent displacement of atoms
inside the material.

 Types of strains
1) Compressive strain-Contraction /original length
2) Tensile strain =Elongation/Original length
3) Shear strain =Shear angle

Proportional limit
 It may be defined as
the greatest stress
which may be
produced in a
material such that the
stress is directly
proportional to the
strain

Proportional limit
Hook’s law-
The stress is directly proportional to strain in elastic
deformation
 Proportional limit for
Tooth enamel - 225 MPa
Tooth dentin - 147 MPa
Acrylics - 27.5 MPa
Stainless steel - 1630 MPa

Yield Strength
 It is defined as the stress at which a material exhibits
a specified limiting deviation from proportionality
of stress to strain.
 It is a more practical indicator , at which a plastic
deformation of 0.1% is seen

 Bauschinger Effect
If the wires are straightened by the process of
reverse straining, meaning flexing in a direction
opposite to that of original bend ,the yield point of
the wire reduces. This phenomenon is known as
work softening due to reverse staining or the
Bauschinger effect.

Elastic Limit
The elastic limit of a material is the greatest stress to
which a material can be subjected ,such that it will
return to its original dimensions when the forces are
released

 Although the three terms, elastic limit, proportional
limit and yield strength are defined differently, their
magnitudes are so nearly the same that for all
practical purposes the terms can often be used
interchangeably.

MODULUS OF ELASTICITY (E)
If any stress value equal to or less than proportional
limit is divided by its corresponding strain value ,a
constant of proportionality will result, which is
known as the modulus of elasticity

Types of MODULUS OF ELASTICITY
 Young’s modulus (E)
 Bulk modulus
 Modulus of rigidity/stiffness (shear modulus-G)

 Usually expressed as force per unit area (MPa/psi)
It is an index of stiffness or flexibility of a material
within the elastic range.

Stress Fl
E = ---------- = ------
Strain eA
E-Young’s modulus
F-Applied force or load
A-Cross section of material under stress
e-Increased in length
l-Original length

FLEXIBILITY
 It is defined as the strain which occurs when
material is stressed to its proportional limit
or
 It is the measure of the strain that a wire can
withstand without undergoing plastic deformation

The relation between the proportional limit,
flexibility & modulus of elasticity
εm = P/E
Where,
E=Modulus of elasticity
P=Proportional limit
ε m =Maximal Flexibility

RESILIENCE ( stored or spring energy)
 It can be defined as the amount of energy absorbed
by a structure when it is stressed not to exceed its
proportional limit.
 The energy stored is released when the wire springs
back to its original shape after removal of an applied
stress.

Toughness
-It is defined as the energy required to fracture a
material
-Toughness is more dependent upon the ductility or
malleability of the material than upon its flexibility
-Tough material is generally strong

 It is the ability of a material to be plastically strained
in tension i.e., ability of a material to withstand
permanent deformation under a tensile load without
rupture
 Ductility decreases with increase in temperature

 The ability of a material to withstand permanent
deformation without rupture under compression ,as
in hammering or rolling into sheet is termed as
malleability
 Malleability increases with increase in temperature

 Creep (Visco-Elasticity)
 If a metal is held at a temperature near its melting
point and subjected to a constant applied force ,the
resulting strain will be found to increase as a
function of time. This time dependent plastic
deformation is referred to as creep

 Static creep-
It is the time dependent deformation produced in a
completely set solid subjected to a constant stress.
 Dynamic creep-
It refers to this phenomenon when applied stress is
fluctuating.

 It is the deformtion as a result of tensile force
application
 It is usually expressed as percentage elongation & is
equal to
Increase in length x 100/Original length

• Formability is the amount of permanent deformation that a
wire will withstand before failing i.e. before breaking or
fracture.

 It is expressed as YS/E i.e., the ratio of yield
strength to modulus of elasticity which represents
the approximate amount of strain released by the
wire on unloading.

ELASTIC PROPERTIES
 Strength
 Stiffness
 Range

Strength
 It is a force value, that is a measure of the
maximum possible load i.e. the greatest force that
a wire can sustain or deliver, if it is loaded to the
limit of the material.
 It is equivalent to the proportional limit (PL) or
approximately the yield strength (YS) of the wire
segment.

 Considering the
graphic representation
of the stress – strain
curve three points can
be taken as
representative of the
strength of a material
- elastic limit
- yield point
-ultimate tensile
strength

1. Esthetics
2. Stiffness
3. Strength
4. Range
5. Spring back
6. Formability
7. Resiliency
8. Coefficient of friction
9. Biocompatibility
10. Weldability

 It is the rate of force delivery required for a unit
activation .
 It is the measure of the force required to bend or
otherwise deform the material to a definite distance.

 Stiffness is proportional to the modulus of elasticity
and cross-section of a given wire and is not
appreciably influenced by any hardening treatment.
 Stiffness and springiness are reciprocal properties.
Springiness = 1 / stiffness.

 Stiffness = Ed/L, higher the elastic modulus, stiffer
the wire.

 Range is defined as the maximum amount of elastic
activation before the onset of a permanent or plastic
deformation.
 Range is usually determined from the 0.1% offset
point on the force – deflection diagram.

 Strength, Stiffness and Range have an important
relationship, i.e.,
Strength = Stiffness x Range

 The mechanical arrangement by which force is
applied to the teeth, e.g. length of archwire.
 The second factor is the form of the wire itself – the
size and shape of cross section.
 The material, including the alloy composition, its
hardness.

 The first wire introduced for orthodontic
purpose was made of gold.
 Gold arch wires were the ideal choice of arch
wires with good bio-compatibility.

 Composition of many gold alloy wires
corresponds to the type IV gold casting alloys
 They are also subjected to softening and
hardening heat treatments.

 Their composition is very similar to the Type
IV gold casting alloys. The typical composition
of the alloy is as follows-
 Gold – 15 – 65% (55-65% more typical)
 Copper – 11 – 18%
 Silver – 10 – 25%
 Nickel – 5 – 10%

 Many wires appear to contain less than 60%
gold with some containing less than 25 to 30%
or even less.
 The palladium content of the alloy is relatively
high, which gives a composition closely
resembling white gold casting alloys.

 Palladium and platinum cause rise in the
melting point, improve corrosion resistance and
increase hardness and strength during heat
treatment.
 The copper content of most wires is well above
9%.

 Gold alloys used, can be called to a large
extent as binary alloys, as only gold and
copper are major metals used.
 These binary alloys to a large extent exhibit
severe grain growth on heating and have poor
ductility in the hardened state.

 The changes that are produced in the strength
and ductility of a wrought gold alloy by heat
treatment are due to the alterations in the gold
copper compound present in the alloy.
 Softening heat treatment is undertaken initially
by heating the wire to 1300° F, for
approximately ten minutes and then quenching
it.

 Softening of the alloys is produced as the gold
copper alloy enters into solid solution at 1300°
F.
 All of the hardening elements are completely
dissolved in each other in solid solution, the
space lattice is free to move on the slip planes
without interference.

 Increased number of slip planes, causes
increased ductility of the wire.
 This wire left at room temperature for several
days becomes harder.
 Alternatively, after the wire is heated to 1300°F,
it is reheated to 840°F and allowed to cool
slowly. This allows the gold copper compound
to come out of the solution.

 This causes the formation of segregated
molecules which produce a locking effect on
the space lattice and causes resistance to slip.
 The space lattice itself is also distorted to some
degree, thus decreasing the number of planes
on which slip can occur. In this way, the
material becomes stronger and more resilient.

 Besides (age) precipitation hardening, cold
working of gold alloys increases strength of the
wrought gold wires. The alloy hardens as the
grain structure becomes broken up and the
space lattice is distorted during cold working.

 This type of hardening is easily relieved by
heating the wire to recrystallization
temperatures, recrystallization will take place
and allow the atoms to return to normal
position in the space lattice.

 Yield strength of the gold wires range from
50,000 to 1,60,000 psi, depending on the alloy.
 Modulus of elasticity of gold copper alloys is
approximately 15,00,000 psi.
 The combination of these properties makes
gold very formable and capable of delivering
lower forces than stainless steel

 Stainless steel (SS) entered dentistry in 1919
 Introduced by R.Hauptmeyer in Garmany
 First it was known as Wipla-Like platinum
 Discovered by chance a few years before World
war I
 Angle used it in his last year (1930) as ligature
wire

 Stainless steel wires began to replace gold
wires in the 1930’s .
 Steels are iron – based alloys that usually
contain less than 1.2% carbon.
 When 12-30% chromium is added to steel the
alloy is commonly called STAINLESS STEEL.

 Silicon ,phosphorous ,sulphur, manganese,
tantalum, and niobium may also be present in
small amounts. The balance is iron.
 A variety of SS have been developed ,and at
least 10 are or were used to manufacture
orthodontic instruments & attachments.

 Steels are classified according to the American
Iron and Steel Institute ( AISI) System
 This classification parallels the United Number
System (UNS) & German Standards (DIN)
 Steel that have AISI numbers beginning with
the number 3 , for austenitic
 The higher this number ,the less ferrous the
alloy are
 The letter L signifies lower carbon content

 Scan page 358 vanarsdall

 The name derives from the fact that
microstructure of these steels is same as that
of iron at room temperature(bcc)
 These alloys are often designated as American
Iron and Steel Institute(AISI) Series 400
stainless steels.
 The ferritic alloys provide good corrosion
resistance at a low cost , provided that high
strength is not required

 Because temperature change induces no
phase change in the solid state , the alloy is not
hardenable by heat treatment.
 The modern “super ferritics”in which chromium
is substituted for some of the iron atoms in the
unit cells ,contain 19% to 30%chromium are
used in several nickel free brackets

 Ferrictic steels are highly resistant to chlorides
these alloys contain small amounts of
aluminum and molybdenum and very little
carbon
 This series of alloys finds little application in
dentistry.

 Martensitic stainless steel alloys share the AISI
400 designation with the ferritic alloys.
 Starting in 1970 ,in addition to carbon other
elements were added to SS to increase their
tensile strength
 Martensitic stainless steel have good tensile
strength but less corrosion resistance. Such
SS could only be used in oral environment for
short contact.

 They can be heat treated in the same manner
as plain carbon steels , with similar results.
 Because of their higher strength and hardness,
martensitic stainless steels are used for
surgical and cutting instruments.

 The austenitic stainless steel alloys are the
most corrosion resistant of the stainless steels.
 AISI 302 is the basic type , containing 18%
chromium , 8% nickel , and 0.15% carbon.
Type 304 has a similar composition , but the
chief difference is its reduced carbon content
(0.08%).

 Both 302 and 304 stainless steel may be
designated as 18-8 stainless steel ; they are
the types most commonly used by the
orthodontist in the form of band and wires .
 Type 316L (0.03% maximum carbon) is the
type ordinarily employed for implants.

 The alloying elements Chromium, Nickel ,Mn
(austenizing elements) maintains austenite at
room temperature and prevents conversion of
face centered cubic lattice structure of
austenite to a martensitic cubic lattice
structure.

 By nature austenite is malleable and ductile
whereas martensite is hard and brittle. By
maintaining austenite at room temperature,
several uses of austenitic stainless steel are
made use of in orthodontics, such as wires,
bands, instruments etc.

Passivating effect-Chromium when exposed
to atmosphere, immediately gets oxidised to
form a very thin atomic layer of chromium
oxide which is firmly bonded to the
substrate.This film prevents further oxidation by
penetration of oxygen and thus protects the
material from corrosion
 Tarnish and corrosion are resisted by stainless
steel due to the passivating effect of chromium

 This protective oxide layer prevents tarnish and
corrosion, but can be ruptured by mechanical
or chemical means resulting in corrosion.
 However ,the passivating oxide layer
eventually forms again in an oxidizing
environment.

 Sensitization-Loss of corrosion resistance(due
to loss of chromium) When SS is heated
between 400 c to 900 c
 These temperatures are within the range of
soldering & welding temperatures. Corrosion
taking place at the soldered joints & weld
nuggets is due to loss of passivation &
localised stress in the welded or soldered
interface .These lead to failures known as weld
decay

 stabilization. A procedure to introduce some
element that precipitates carbide in preference
to chromium.
 Titanium is often used for this purpose

 Titanium introduced in amount approximately
six times the carbon content, the precipitation
of chromium carbide can be inhibited for a
short time at the temperature ordinarily
encountered in soldering .
 SS that have been treated in this manner are
said to be stabilized

 The physical properties of orthodontic stainless
steel wires improve by heat treatment at low
temperatures between 750° C to 820° C for ten
minutes and at a lower temperature of 250° C
for twenty minutes.
 By heat treatment residual stresses are
removed.

 Biocompatibility
 High corrosion resistance
 Chemically Stable in oral & implant
environment
 Superior mechanical properties
Yield strength-11oo-1759 MPa
Ultimate tensile strength upto 2200 MPa
Modulus of elasticity about 170,000-200,000
MPa
Density -8.5 gm/cc

 Arthur. J. Wilcock of Victoria, Australia,
produced the orthodontic archwire to meet Dr.
Begg’s needs for use in Begg technique.
 The wire produced has certain unique
characteristics different from usual stainless
steel wires .

 REGULAR GRADE : White label. Lowest grade
and easiest to bend. Used for practice bending
or forming auxillaries. It can be used for
archwires when distortion and bite opening are
not a problem.

 REGULAR PLUS GRADE : Green Label
Relatively easy to form, yet more resilient than
regular grade. Used for auxillaires and
archwires when more pressure and resistance
to deformation is required.

SPECIAL GRADE : Black Label.
Highly resilient, yet can be formed into intricate
shapes with little danger of breakage.
SPECIAL PLUS GRADE : Orange Label
Hardness and resiliency of the wire are
excellent for supporting anchorage and
reducing deep overbites.

 EXTRA SPECIAL PLUS GRADE :Blue Label.
Highly resilient and hard, difficult to bend and
subjects to fracture.
 Supreme Grade : Blue Label.
Primarily used in early treatment for correction
of rotations, alignment and levelling. Its yield
strength exceeds that of E.S.P.

 Each grade of wire is available in diameters of
0.010″, 0.012″, 0.014″, 0.016″, 0.018″, 0.020″,
0.022″. They are supplied in the form of spools
or cut lengths of the wire.
 With the demand for harder wires , even higher
grades , premium and premium plus wires
were developed .

 The new grades and sizes of wire made
available are:
Sizes Available
Premium : .020″
Premium Plus : .010″,.O12″,.014″,.016″,
Supreme : .008″, .009″, .010″, .011″.

 The low and medium grade wires exhibit better
formability as they are subjected to less work
hardening and hence are more ductile.
 The wires were straightened by spinner
straightening. The wire is pulled through high
speed rotating bronze rollers which twist the
wire into a straightened condition.

 Presently the premium and supreme wires are
straightened by a process called pulse
straightening .Though the exact procedure
remains a trade secret , it enables to straighten
these high yield strength wires , without
structural deformation and altering the physical
properties.

 These are ultra high tensile austenitic stainless
steel arch wires.
 The wires are resilient, certain bends when
incorporated into the arch form and pinned to
the teeth become activated by which stresses
are produced within the wires which generates
forces.

 The wires must be sufficiently resilient to resist
permanent deformation and maintain their
activation, for maximum control of anchorage.
 All these properties make these wires very
hard and brittle.

 The properties of the wire are affected by the
way the wire is straightened before bending it
to form any component of the appliance .
 If the wires are straightened by the process of
reverse straining, meaning flexing in a direction
opposite to that of the original bend, the yield
point of the wire reduces.

 The phenomenon is known as work softening
due to reverse straining or the ‘Bauschinger
Effect’ , named after the person who described
it for the first time .

 1)The ultimate tensile strength for Premium
Plus wire is 8-12% higher than SS wire
indicating greater resistance to fracture in oral
cavity
 2)The pulse straightened wires have
significantly higher working range and show
good recovery patterns.

 3) Frictional resistance of the P.S. wires is lesser
by a factor of 50% than SS wire
 4)There is no significant difference in stress
relaxation properties

 A cobalt-chromium-nickel orthodontic wire
alloy was developed during the 1950’s by the
Elgiloy Corporation (Elgin, IL,USA).
 Initially it was manufactured for watch springs
by Elgin watch company, hence the name
Elgiloy.
 Rocky Mountain Orthodontics first introduced Co-
Cr wires by name ElgiloyTM

 Chrome cobalt alloy is a cobalt base alloy
containing
 40% cobalt,
 20% chromium,
 15% nickel,
 7% Molybdenum,
 2% manganese,
 0.16% carbon,
 0.04% beryllium ,
 15.8% iron.

 Elgiloy is manufactured in four tempers
Red – hard & resilient
green – semi-resilient
Yellow – slightly less formable but ductile
Blue – soft & resilient

 Blue(soft) elgiloy : Can be bent easily with
finger pressure and pliers. Heat treatment of
blue elgiloy increases its resistance to
deformation.

 Yellow elgiloy : Relatively ductile and more
resilient than blue elgiloy. Further increase in
its resilience and spring performance can be
achieved by heat treatment.

 Green elgiloy : More resilient than yellow
elgiloy and can be shaped with pliers before
heat treatment.

 Red elgiloy : Most resilient of elgiloy wires,
with high spring qualities. Heat treatment
makes it extremely resilient

 William F. Buehler in 1960’s invented Nitinol
Ni – Nickel
ti-titanium
Nol-Naval Ordinance
Laboratory,U.S.A.

Andreasen G.F. and co-workers introduced the
use of nickel-titanium alloys for orthodontic use
in the 1970’s.

 55% nickel, 45% titanium resulting in a
stoichiometric ratio of these elements.
 1.6% cobalt is added to obtain desirable
properties.

 Like stainless steel ,NiTi can exist in more than
one form or crystal structure
 The martensite form exist at lower
temperatures, the austenite form at higher
temperatures

 Transition Temperature Range : TTR
 Shape Memory
 Super elasticity

 Transition temperature range is a specific
temperature range when the alloy nickel
titanium on cooling undergoes martensitic
transformation from cubic crystallographic
lattice.( Austenitic phase of the alloy.)
 In martensitic phase, the alloy cannot be
plastically deformed.

 At higher temperatures the alloy is found to be
in cubic crystallographic lattice consisting of
body centered cubic crystallographic
structures.
 It is also known as Austenitic phase of the alloy.
 Plastic deformation can be induced, in
austenitic phase of the alloy.

 The same plastic deformation induced at the
higher temperature returns back when the alloy
is heated through a temperature range known
as reverse transformation (transition)
temperature range, RTTR.
 Any plastic deformation below or in the TTR is
recoverable when the wire is heated through
RTTR.

 Shape memory refers to the ability of the
material to "remember” its original shape after
being plastically deform while in martesitic
form

 It is the property of the wire explained as even
when the strain is added, the rate of stress
increase levels off ,due to the progressive
deformation produced by the stress induced
martinsitic transformation

 This property can be produced by stress and
not temperature difference. Therefore it is
called as stress induced martensitic
transformation.

 Japanese Niti wire introduced by Fujio Miura
in 1986 & is manufactured by a different
process and demonstrates super elasticity.
 Fujio Miura et al:The super elastic property of
Nickel titanium wire for use in orthodontics
AJO 1986,Vol 90,1-10

 A new type of heat treatment was reported by
Fujio Miura and associates which is known as
Direct Electric Resistance Heat Treatment
(DERHT).
 An electric current is directly passed through
the wire, thus generating enough heat to make
it possible to bend it as well as impart change
in the super elastic property of the wire.

 Heat treating equipment consists of an electric
power supply, a pair of electric pliers, an
electric arch holder.
 The amount of heat can be controlled by
amperage and the heating time.
 The DERHT method utilizes the electric
resistance of the wire to generate heat.

 In spite of resulting molecular re-arrangement,
the mechanical properties of the wire are
unchanged.
 On testing it was found that the heat treated
segments demonstrated better super elastic
properties in relation to time.

 Hence it is possible to heat treat any desired
section of the archwire by DERHT method and
utilize optimally the super elastic property of
the wire.
 For smaller diameter wires lesser current is
required. For eg : 0.022” wire requires 8.0A for
2.0 seconds, 0.014” wire requires 3.5A for 2.0
seconds.

 Another nickel titanium alloy introduced by
Burstone and developed by Dr Tien Hua Cheng is
called as Chinese Niti alloy in1985
 It has a springback that is 4.4 times that of
comparable stainless steel wire and 1.6 times that
of nitinol wire
Burstone C.J.et al:Chinese NiTi wore,a new
orthodontic alloy AJO 1985 Vol 87 ,445- 452

 At 80° of activation the average stiffness of
Chinese NiTi wire is 73% that of stainless steel
wire and 36% that of nitinol wire.

 In 1994 Ormco Corporation introduced a new
orthodontic wire alloy, Copper NiTi.
 Copper Ni Ti is a new quaternary
( nickel, Titanium copper and chromium ) alloy.

 Orthodontic archwires fabricated from this alloy
have been developed for specific clinical
situations and are classified as follows:
Type I Af 15 0C
Type II Af 27 0C
Type III Af 35 0C
Type IV Af 40 0C

 These variants would be useful for different
types of orthodontic patients.
 For example,
the 27oC variant would be useful for
mouth breathers;
the 35oC variant is activated at normal
body temperature;
and the 40 o C variant would provide
activation only after consuming hot food and
beverages.

 With the exception of red temper non heat
treated Co-Cr wires have a smaller spring back
than SS of comparable sizes. This property can
be removed by adequate heat treatment .
 The ideal temperature for heat treatment is 900
F for 7-12 minutes . This causes precipitation
hardening of the alloy, increasing the resistance
of the wire to deformation
 This type of wire shows properties similar to SS

 In the 1960’s an entirely different “high
temperature” form of titanium alloy became
available.
 At temperature above 1625°F pure titanium
rearranges into a body centered cubic lattice
(B.C.C.), referred to as ‘Beta’ phase.
Charles J.Burstone & A.J. Goldberg,Beta Titanium:A
new Orthodontic alloy AJO-DO Feb 1980(121-132)

 With the addition of such elements as
molybdenum or columbium, a titanium based
alloy can maintain its beta structure even when
cooled to room temperature.
 Such alloys are referred as beta stabilized
titaniums.

 Goldberg and Burstone demonstrated that with
proper processing of an 11% molybdenum, 6%
Zirconium and 4% tin in beta titanium alloy, it is
possible to develop an orthodontic wire with a
modulus of elasticity of 9.4 x 10 6 psi and yield
strength of 17 x 10 4 psi.
 The resulting YS/E ratio (springback) of 1.8 x
10 -2 is superior to 1.1 x 10 -2 for stainless steel.

Alloy Modulus
of
Elasticity
(10³
MPa)
0.2% Offset
Yield
Strength(MP
a)
Ultimate
Tensile
Strength
(MPa)
Number
90-degree
Cold Ben
without
fracture
β-
Titanium
71.7 931 1276 4
Alloy Modulus
of
Elasticity
(10³
MPa)
0.2% Offset
Yield
Strength(MP
a)
Ultimate
Tensile
Strength
(MPa)
Number
90-degree
Cold Ben
without
fracture
β-
Titanium
71.7 931 1276 4
AlloyAlloy Modulus
of
Elasticity
(10³
MPa)
Modulus
of
Elasticity
(10³
MPa)
0.2% Offset
Yield
Strength(MP
a)
0.2% Offset
Yield
Strength(MP
a)
Ultimate
Tensile
Strength
(MPa)
Ultimate
Tensile
Strength
(MPa)
Number
90-degree
Cold Ben
without
fracture
Number
90-degree
Cold Ben
without
fracture
β-
Titanium
β-
Titanium
71.771.7 931931 12761276 44

 The low elastic modulus yields large
deflections for low forces.
 The high ratio of yield strength to elastic
modulus produces orthodontic appliances that
can sustain large elastic activations when
compared with stainless steel devices of the
same geometry
( Kenneth Nelson,Charles Burstone ,Optimal welding of
beta titanium orthodontic wire.AJO-DO 1987;213-219)

 β- titanium can be highly cold worked . The
wrought wire can be bent into various
orthodontic configurations and has formability
comparable to that of austenitic stainless steel .
 Clinically satisfactory joints can be made by
electrical resistance welding of β- titanium
(light-capacitance weld). Such joints need not
be reinforced with solder.

 Beta titanium wire possesses a unique balance
of high spring back & formability with low
stiffness ,making it particularly suitable for a
number of treatment modalities.

 The alpha titanium alloy is attained by adding
6% aluminium and 4% vanadium to titanium
 Because of its hexagonal lattice, it possesses
fewer slip planes making it less ductile from β-
titanium.
 The hexagonal closed packed structures of
Alpha-Titanium has only one active slip plane
along its base rendering it less ductile.

 Composotion
 Alpha-Beta alloy with
titanium,aluminum,vadadium
 A smooth surface structure
 Less friction at the archwire bracket inter
 Better strength than existing titanium based alloy
 Poor in its weld characteristics
 Vinod Krishnan,Weld charactristics of Orthodontic
Archwire Material,AO2004,Vol 84,No 4

 Optiflex is a new orthodontic archwire that is
designed to combine unique mechanical
properties with a highly esthetic appearance
 M.F. Talass,Optiflex Archwire Treatment of a
Skeletal Class III Open Bite,JCO 1992,April,245-
252)

 Made of three clear optical fiber
- A silicon dioxide core that provides the force
for moving teeth
- A silicon resin middle layer that protect the
core from moisture & adds strength
-A strain resistant nylon layer that prevent the
damage to the wire

 It is used in adult patients with high aesthetic
requirements
 It can be used as an initial wire in cases with
moderate amounts of crowding in one or both
arches.

 The wire can be round or rectangular & is
manufactured in various sizes.
 Mechanical properties includes a wide range of
action & ability to apply light continuous force.
 Sharp bends must be avoided ,since they could
fracture the core.
 Highly resilient wire that is especially effective
in the alignment of crowded teeth

 Flexibility of stainless steel wire can be
increased by building up a strand of stainless
steel wire around a core of 0.0065” wire along
with 0.0055” wires used as wrap wires.
 This produces an overall diameter of
approximately 0.165”.

 The strand of stainless steel wire is more
flexible due to the contact slip between
adjacent wrap wires and the core wire of the
strand.
 When the strand is deflected the wrap wires
will slip with respect to the core wire and each
other. If there is no elastic deformation each
wire returns to its normal position, giving
elasticity to the strand of the wire.

 According to studies conducted by Kusy ,a multi-
stranded wires have elastic properties similar to
nickel-titanium arch wires. Hence they can be used
as a substitute to the newer alloy wires considering
the cost of the nickel titanium wires .
 The 0.0175” triple stranded wire and 0.016” Nitinol
demonstrated a similar stiffness
 Robert Kusy, A review of contemporary Archwire,AO
1997,No.3,(197-207)

 CV(tm) Niti wires are introduced by Masel
 It is used as an alternative to the copper NiTi
wires in many orthodontic procedures
 When cold ,CV NiTi is very soft & workable
 When it warms up in patient’s mouth ,it
returns to its perfect arch shape,moving the
teeth along the way

 CV NiTi comes in three types
-27 c CV NiTi for maximum force activation
-35 c CV NiTi for moderate force activation
-40 c CV NiTi for the most gentle activation
Each type of CV NiTi gives consistent,
predictable force which the clinician can use
to affect tooth movement

 REQUIREMENTS OF AN IDEAL ARCH
WIRE
 A Review of Contemporary Arch Wires
Robert P.Kusy
Angle Orthod 1997;67(3);197-208

 No ideal arch wire exists.
 The demands of the treatment plan require
different characteristic stiffness and ranges.
 Nonetheless, several desirable characteristics
would be appropriate to list.

 Wires should be esthetic.
 Although esthetics are important to the
orthodontist, function is paramount

 Wires should have poor biohostability. This
characteristic goes beyond biocompatibility.
 As a poor biohost, the ideal archwire should
neither actively nurture nor passively act as a
substrate for micro-organisms that will smell
foul, cause color changes that detract from
esthetics, or remove and/or build up material
that compromise mechanical properties.

 Wires should possess low coefficients of
friction.
 Finally, wires should have formability,
weldability, resilience, and springback so that
they may be deformed into loops or bends,
fused onto a clasp, employed to maximize their
stored elastic energy, and ultimately return to
their initial shape.

Robert P.Kusy
Angle Orthod 1997;67(3);197-208

 CLINICAL IMPORTANCE OF VARIOUS
WIRES

 Stainless steel wires began to replace gold
wires from 1930. Stainless steel is the most
widely used alloy in orthodontics. It finds its
application as arch wires, auxiliaries,
orthodontic appliances, bands, etc.
 These wires are available both in round as well
as rectangular cross-sections

 The Australian stainless steel wires described
previously are used in the Begg’s technique as
well as in the preadjusted edgewise technique.
 These wires are available both in round as well
as rectangular cross-sections

 NiTi is the ideal wire for initial aligning
&levelling due its superior spring back,
superelasticity, shape memory
 Rectangular NiTi allows full engagement of the
bracket slot and give better torque control in
the initial phase of treatment.

 NiTi is also available in the form of coil springs.
These NiTi coil springs greatly enhance
efficiency in both - space closure and space
opening.
 NiTi coil springs are also used for distalization
of molars.

 The advantage of elgiloy over SS wires include
greater resistance to fatigue and distortion &
longer function as a resilient spring
 The blue elgiloy is very popular because it can
be easily manipulated into desired shapes and
then heat treated to achieve considerable
increases in strength and resilience

 This heat treatment can be performed easily
with the aid of an electrical resistance welding
apparatus.
 The other three tempers of Elgiloy have
mechanical properties that are similar to
tempers that are available with the less
expensive stainless steel wire alloys.

 Type I wire – Af 15 0C
Dr. Sachdeva does not recommend the
frequent use of this alloy because it generates
very heavy forces and clinical indications are
few.

Type II wire Af 270C
 In patients where rapid tooth movement is
required ; the force system generated by this
orthodontic arch wire is constant.

 Type III wire – Af 350C
This wire generates force in the midrange and is
best used :
1. In patients who have a low to normal pain
threshold.
2. In patients whose periodontium is normal to
slightly compromised.
3. When relatively low forces are desired.

 Type IV wire – Af 40 0C
These wires generate forces when the mouth
temperature exceeds 400C.
These forces are intermittent in nature. Used in :-
 Patients who are sensitive to pain.
 Patients who have compromised periodontal
conditions.

 It is used in adult patients with high aesthetic
requirements
 It can be used as an initial wire in cases with
moderate amounts of crowding in one or both
arches
 Optiflex can be used in presurgical stage in
cases which require orthognathic intervention
as part of the treatment s
 .

 27 c CV NiTi is a high activation force wire
used to move a severely malpositioned tooth
 27 c CV NiTi wire can be readily deformed
when the wire is colder than about 10 c, but
wire recovers its original shape after the wire
has been in patients mouth for about two
weeks

 350 c CV NiTi is a moderate force activation
wire used to level ,align and rotate teeth
 This type of wire can be readily deformed
when the wire is colder than about 20 o c but
the wire recovers original shape when the
wires warms up in the patients mouth.
 The wire is set at body temperature ,so the
patient needs to drink warm fluids to activate
the wire.
 Rectangualr 350 c CV NiTi is ideal for a
“settling in”arch

 400 c NiTi is used as an initial arch wire .It is
designed to level & align malposed teeth with
minimal gentle force .
 400 c NiTi is body heat activated & is
stimulated by hot liquids .Therefore ,the
patient need to be told to drink hot liquids to
activate the wire
 To use 400c CV NiTi wire cool the wire by
storing the wire in a freeze for an hour or more

 THE CHOICE OF ARCH
WIRES IN FIRST STAGE

 In nearly every patient with malaligned teeth,
the root apices are closer to the normal
position than the crowns.
 This is so as malalignment almost always
develops as the eruption paths of teeth are
deflected.

 To bring teeth into alignment, a combination of
labiolingual and mesiodistal tipping guided by
an archwire is needed, but root movement is
usually not.
 Several important consequences for
orthodontic mechanotherapy follow from this.

 Initial arch wires should provide light,
continuous force of approximately 50 grams, to
produce the most efficient tooth tipping.
 Arch wire should be able to move freely within
the brackets (2 mil clearance required).
 In an 18-slot edgewise bracket, 16 mil can be
used.

 Rectangular arch wires that tightly fit within the
bracket should be avoided as the position of
the root apex can be affected.
 Although a highly resilient 0.017” X 0.025” NiTi
could be used, it will create undesirable root
movement at this stage.

 The springier the arch wire, more important it is
that the crowding should be at least reasonably
symmetric.
 Otherwise, there is a danger that archform will
be lost as asymmetrically irregular teeth are
brought into alignment.

 If only one tooth is crowded and out of line, a
rigid wire is needed that maintains the arch
form, and an auxillary wire should be used to
correct the malaligned tooth.

 Arch wire materials appropriate for initial
alignment stage are round cross-section wires
as follows:
1. Nickel- titanium (preferably in its superelastic
form)
2. Multistranded stainless steel
3. Australian premium and supreme grade wires.

 Where tooth displacements are marked , the
first arch wire should be particularly low in
stiffness and high in range .
 ‘Superelastic’ nickel titanium wire of 0.014” to
0.016” diameter or six- strand multistranded
stainless steel wire of 0.0175” diameter may be
chosen.

 In most cases, initial alignment is complete
within two months of commencing treatment.
 Considering the poor control offered and the
dangers of producing unwanted tooth
movement , initial archwires should be
exchanged for the archwires of mid-treatment
as soon as possible.

MID-TREATMENT ARCH WIRES

 The highly flexible arch wires used for initial
alignment are replaced by a series of arch
wires of increasing stiffness, offering
progressively greater control over tooth
position.

 In the early stages of mid-treatment single
strand , round, stainless steel arch wires of
small diameter are appropriate .
 Arch wires of 0.016” and then 0.018” diameter
are used.

 Inter and intra-maxillary elastic forces can be
used safely with stainless steel single strand
round wires of 0.016” diameter and above.

 These wires are used for the purpose of canine
retraction using sliding mechanics.
 Australian ss arch wires are sufficiently stiff to
enable the molars to resist unwanted
movement, and they therefore play an
important part both in molar control and in
anchorage management.

 After canine retraction, 0.016” X 0.022” NiTi
progressing to 0.017” X 0.025” NiTi or 0.017” X
0.025” NiTi is directly given for levelling and
alignment.
 Then 0.016” X 0.022” ss closing loop arch wire
is given for anterior retraction.

 In case of enmass retraction, after the first
stage, 0.016” X 0.022” NiTi progressing to
0.017” X 0.025” NiTi is given for completing
the levelling and alignment.
 Then 0.016” X 0.022” ss closing loop arch wire
is given for anterior retraction.

 ARCH WIRES FOR FINISHING STAGE

 If preadjusted edgewise brackets have been
used then theoretically the detailing stage will
be unnecessary because of the activation
programmed into the brackets.
 However, minor errors in bracket positioning
will become obvious in these final stages of
treatment , and arch wire modification may still
be required.

 The arch wire requirements at this stage are
for high stiffness and low range.
 When rectangular wire has been used at the
end of mid-treatment stage the detailing arch
wire should also be rectangular ,of increased
stiffness

 With the 18-slot appliance, the finishing arch
wire is either 0.017” X 0.022” or 0.017” X
0.025” ss.
 They are flexible enough to engage brackets
even if mild tipping has occurred.
 These arch wires generate the necessary root
paralleling moments

 If greater tipping has occurred, a more flexible
full-dimension rectangular arch wire is required.
 In such cases, a β-Ti or M-NiTi 0.017” X 0.025”
wire may be needed initially.

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