ORTHODONTIC ARCHWIRES-DR RAKSHITHA [Autosaved].pptx

ORTHODONTIC
ARCHWIRES
DR. RAKSHITHA R
1ST
MDS

CONTENTS- PART 1
◦ INTRODUCTION
◦ EVOLUTION OF ORTHODONTIC ARCHWIRE
◦ MECHANICAL PROPERTIES OF METALS
◦ REQUIREMENTS OF AN IDEAL ARCHWIRE
◦ CLASSIFICATION OF ORTHODONTIC ARCHWIRES
◦ MANUFACTURING OF ORTHODONTIC WIRES
◦ GOLD ARCHWIRES
◦ STAINLESS STEEL ARCHWIRES
◦ AJ WILCOCK WIRE

INTRODUCTION
◦ Orthodontic wires which generate the biomechanical forces communicated
through brackets for tooth movement ,are central to the practice of orthodontic
profession.
◦ In the rational selection of wires for a particular treatment ,the orthodontist
should consider a variety of factors ,including the amount of force delivery that
is desired ,the elastic range or springback ,formability and the need for
soldering and welding to assemble the appliance

EVOLUTION OF ORTHODONTIC
ARCHWIRES
1. Material Scarcity, Abundance of Ideas (1750-1930)
Gold, German silver -Angle (1887)
Stainless steel- 1919
1919 – Dr. F Hauptmeyer –Wipla
Angle used steel as ligature wire (1930).
Begg in 1940s with Wilcock-ultimately resilient arch wires-Australian SS.
William A Brantley, Theodore Eliades; Orthodontic materials

2. Abundance of materials, Refinement of Procedures (1930 – 1975).
Improvement in metallurgy and organic chemistry
Cobalt chrome (1950s)- Elgiloy
Variable cross-section orthodontics- Burstone

VARIABLE CROSS SECTION
ORTHODONTICS
◦ Controlling wire stiffness by altering the cross section geometry of the wire
◦ In period prior to seventies, in which gold and SS were the only available
materials, change in requirements of the wire were affected by altering cross
section and geometry of the wire
◦ Complicated loop designs were required to alter stiffness of wire chosen for
tooth movement

◦ 1962 - Buehler discovers nickel-titanium dubbed NITINOL (Nickel Titanium
Naval Ordnance Laboratory)
◦ 1970-Dr.George Andreason (Unitek) introduced NiTi to orthodontics.
◦ 50:50 composition –excellent springback, no superelasticity or shape memory
(M-NiTi).
◦ Late 1980s –NiTi with active austenitic grain structure

◦ Superelasticity (pseudoelasticity in engineering).
◦ New NiTi by Dr.Tien Hua Cheng and associates at the General Research
Institute for non Ferrous Metals, in Beijing, China.
◦ Burstone et al–Chinese NiTi (1985).

◦ In 1978 Furukawa electric co.ltd of Japan produced a new type of alloy
1. High spring back.
2. Shape memory.
3. Super elasticity.
◦ Miura et al – Japanese NiTi (1986)
Variable modulus orthodontics-Burstone (1981)

Variable-modulus orthodontics
C J Burstone
◦ The concept was given by Burstone controlling wire stiffness by varying
material properties- namely the modulus of elasticity
◦ The overall stiffness of an appliance is determined by two factors:
- wire stiffness
- design stiffness
Appliance stiffness=wire stiffness X design stiffness
◦ As we change our appliance design by increasing wire between brackets or
adding loops, the stiffness can be reduced as the design stiffness factor is
changed
Burstone CJ. Variable-modulus orthodontics. American journal of orthodontics. 1981 Jul 1;80(1):1-6.

◦ Wire stiffness is determined by two factors:
- the cross section
-the material of the wire
◦ In general,
Wire stiffness= material stiffness X cross sectional stiffness
◦ Material stiffness is determined by modulus of elasticity
◦ Previously most orthodontists used only SS wire with identical modulus of
elasticity, it was only the size that was varied
◦ But later the intent was to maintain same cross section of wire but use different
material with different stiffness to produce wide range of forces and load
deflection required for comprehensive orthodontics
◦ Relationship between material stiffness for SS, CoCr, NiTi and Beta Titanium:
1: 1.2: 0.26:0.42
Burstone CJ. Variable-modulus orthodontics. American journal of orthodontics. 1981 Jul 1;80(1):1-6.

◦ Cu NiTi – (thermoelasticity) - Rohit Sachdeva.
◦ Quaternary metal – Nickel, Titanium, Copper,
Chromium.
◦ Copper enhances thermal reactive properties and creates a consistent
unloading force.
Variable transformation temperature orthodontics

Variable transformation temperature
orthodontics
◦ This concept was given by Dr. Rohit Sachdeva
◦ By 90s NiTi archwire that are superelasric and thermodynamic were available
◦ By taking advantage of body temperature and setting the alloy’s TTR for
martensitic transformation, precise control of memory phenomenon can be
utilized.
Sachdeva R. Variable transformation temperature orthodontics. Copper NiTi
Makes it a Reality: Clinical Impressions. 1995:1-6

3. The beginning of Selectivity (1975 to the present)
◦ CAD/CAM – larger production runs
◦ Composites and Ceramics
β titanium- Burstone and Goldberg-1980
TMA – Titanium Molybdenum alloy – ORMCO
Titanium-Niobium- M. Dalstra et al.
TiMolium wires (TP Lab)-Deva Devanathan (late 90s)
β III- Ravindra Nanda (2000-2001)

MECHANICAL
PROPERTIES OF
ARCHWIRES

MECHANICAL PROPERTIES
◦ Stress & strain
◦ Elastic properties
◦ Young’s modulus (modulus of elasticity)
◦ Range
◦ Springback
◦ Formability
◦ Resiliency
◦ Flexibility
◦ Strength properties
◦ Proportional limit (elastic limit)
◦ Yield strength
◦ Plastic deformation
◦ stiffness/load deflection rate

STRESS
◦ stress is the force acting on the unit area
of a material
STRAIN
◦ Strain is described as the change in
length per unit area of the body when it
Is subjected to stress

18
TYPES OF STRESS/STRAIN
◦ Tensile –stretch/pull
◦ Compressive – compress towards each other
◦ Shear – 2 non linear forces in opp direction which
causes sliding of one part of a body over another

STRESS STRAIN CURVE
◦ The graph showing the relationship of stress strain as a material is subjected to
increasing load.
◦ The curve produced in the diagram may also be called elastic curve

20
ELASTIC PROPERTIES –
STRENGTH ANALYSIS
3 points on the stress strain graph can be represented to explain
“STRENGTH”
1. Proportional limit
2. Yield strength
3. Ultimate tensile strength

21
◦ Proportional limit
Maximum stress at which stress is proportional to strain and
above which plastic deformation occurs
 At this point if the stress is
removed the wire returns
back to its original form

22
◦ Yield strength
 The stress at which a test specimen exhibits a specific amount
of plastic strain
 Usually the point at which a deformation of 0.1% is
measured is taken into account

23
◦ Ultimate tensile strength
 It is defined as the maximum stress that a material can withstand before
failure in tension
 Is greater than the yield
Strength & occurs after
Some plastic deformation
 Clinically imp – determines
Max force a wire can deliver

24
ELASTIC PROPERTIES
Modulus of elasticity (Young’s modulus)
 Measures the relative stiffness
or rigidity of the wire
 Hooke’s law – stress and strain
(elastic or compressive) are proportional
to each other
 Represented by a st.line designated as ‘E’
◦ Spring stretch in proportion to applied force until the proportional limit
◦ Modulus of elasticity – constant for a given material

25
◦ Stiffness and springback
-are proportional to ‘E’
stiffness α E ie load / deflection
springiness α 1/ E
stiffness = 1/ springiness
The more horizontal the slope the
more springier the wire, the more
vertical the slope the more stiffer
the wire

26
◦ Range – distance the wire will bend elastically
before permanent deformation occurs
 measured upto the yield strength on X axis

27
Clinical implication
Relationship b/w strength, stiffness & range
Clinically optimal springback occurs when the wire is bent b/w its elastic limit
and ultimate strength
The greater the springback, the more the wire can be activated
Ultimate strength = stiffness x range

28
Resiliency & formability
 Are 2 other characteristics of some clinical importance
 Resiliency – represents the energy storage capacity of
the wire
Strength + springiness
 wire is stretched- space between the atoms increases.
 Within the elastic limit, there is an attractive force
between the atoms.

29
Resiliency
Strain
Stress
Resilience Formability
Proportional limit
Yield strength
It is represented by the area under the stress strain graph upto
the proportional limit.

30
Formability -
◦ amount of permanent deformation that the wire can withstand
before breaking
◦ Indication of the permanent bending the wire will tolerate while
bent into springs , archforms etc
◦ Also an indication of the amount of cold work that they can
withstand

31
Formability
Strain
Stress
Resilience Formability
Proportional limit
Yield strength
It is represented by the area under the stress strain graph b/w the
yield strength and fracture point.
Fracture point

32
Other mechanical properties
1. Flexibility
2. Toughness
3. Brittleness
4. Fatigue
Flexibility
◦ Maximal flexibility is the strain that occurs when a wire is stressed to
its elastic limit.
Max. flexibility = Proportional limit
Modulus of elasticity.

33
Other mechanical properties
◦ Toughness –force required to fracture a material. Total area
under the stress – strain graph.
◦ Brittleness –opposite of toughness. A brittle material, is
elastic, but cannot undergo plastic deformation.
◦ Fatigue – Repeated cyclic stress of a given magnitude
below the fracture point. This is called fatigue.

34
◦ Process of softening the
metal to reverse the effect
of cold working
◦ heat below melting point.
◦ More the cold work, more
rapid the annealing
◦ Higher melting point – higher
annealing temp.
◦ ½ the melting temperature
ANNEALING

35
ANNEALING:
STAGES
⊙ Recovery ⊙Recrystallization ⊙ Grain Growth

36
Before Annealing
Recovery – Relief of stresses
Recrystallization – New grains from
severely cold worked areas
-original soft and ductile condition
Grain Growth – large crystal “eat up”
small ones-ultimate coarse grain structure is
produced

REQUIREMENTS OF AN IDEAL ARCH
WIRE- ROBERT P.KUSY
Kusy RP. A review of contemporary archwires: their properties and characteristics. The Angle Orthodontist.
1997 Jun 1;67(3):197-207.

CLASSIFICATION OF ARCHWIRES
1. Depending on material used:
Gold wires
Stainless Steel wires
Cr Co wires(Elgiloy)
Nickel Titanium
Conventional NiTi
Japanese NiTi
Chinese NiTi
Cu NiTi
Alpha Titanium
Beta Titanium(TMA wires)
Esthetic wires

2. Depending on cross section:
Round
Rectangular
Combination of round & rectangular
3. Wires may be
Single stranded
Multistranded
Twisted or braided

MANUFACTURE OF ORTHODONTIC
WIRES
MELTING
INGOT
FORMATION
DRAWING
ROLLING

◦ Melting : The selection and melting of the components
of alloys influence the physical properties of metals.

◦ Ingot formation : An ingot is produced by the pouring of molten alloy into a
mold. It is one of the critical operations.
◦ It differs from any other casting, by being a non-uniform chunk of metal.
Different parts of the ingot possess varying degrees of porosities and
inclusions of slag.
◦ In a magnified view, the ingot has a granular structure, made up of crystals of
the component metals called "grains". The mechanical properties of the ingot
are controlled by its granular structure.

◦ Rolling : It is the first mechanical step in the manufacture of a wire from the
ingot. The ingot is rolled into a long bar by a series of rollers that gradually
reduce it to a relatively small diameter
◦ The squeezing and massaging action of rolling the ingot, alters the shape and
arrangement of the crystals
◦ The structure becomes so locked-up that it can no longer adjust enough to
adapt to the squeezing of the rollers.
◦ If rolling is continued beyond this point, small cracks start to appear on the
surface and the ingot will begin to crumble.

◦ Prior to this, the rolling process is interrupted and the metal is annealed by
heating to a suitable high temperature.
◦ At this annealing temperature the atoms become mobile and move within the
mass, breaking the crystalline structure and relieving some of the internal
stresses brought about by the rolling process.
◦ On cooling, the annealed structure resembles the original casting, but it is more
uniform.

◦ Drawing : It is a more precise process by which the ingot is reduced to its final
size.
◦ The wire is pulled through a small hole in a die.
◦ Drawing is a more precise process than rolling, as it subjects the entire surface
of the wire to the same pressure instead of squeezing it from only two opposite
sides as in rolling.

GOLD ALLOY WIRES
◦ Initially, in 1887, Edward Angle used nickel-silver alloys in his
orthodontic accessories.
◦ Subsequently, he replaced them with copper, nickel and silver-
free zinc alloys.
◦ Eventually, gold alloys became his favorite choice.
1997 Jun 1;67(3):197-207.

◦ Until the early 1930s, type IV gold alloys were the most widely
employed in the manufacture of orthodontic accessories.
◦ In those days, 14 to 18-carat gold was routinely used for wires,
bands, hooks and ligatures as well as iridium-platinum bands
and wires.
1997 Jun 1;67(3):197-207.

Composition:
Component percentage
Gold 65%
Copper 11-18%
Nickel 5-10%
Silver 25%
Palladium 25%
Platinum
1997 Jun 1;67(3):197-207.

Advantages:
1. Inertness
2. can be heat treated
3. corrosion resistant
Disadvantages:
1.Low yield strength
2.Limited spring back
3.High cost
Although they had good corrosion resistance, and acceptable esthetics, they lacked
the flexibility and tensile strength needed for complex machining.
1997 Jun 1;67(3):197-207.

STAINLESS STEEL WIRES
◦ In metallurgy, STAINLESS STEEL is defined as an Iron--Carbon
alloy with a minimum of 10.5% Chromium.
◦ The name originates from the fact that Stainless Steel doesn't
STAIN or CORRODE easily as ordinary steels. This material is
also known as Corrosion--Resistant Steel.
◦ Elements other than iron, carbon, and chromium may be present,
resulting in wide variation in composition and properties of the
stainless steels.
1997 Jun 1;67(3):197-207.

HISTORY
◦ The corrosion resistance of Fe--Cr alloy was first recognized
in1821 by French Metallurgist ‘Dirre Beithier’ who noted their
resistance against attack by some acids and suggested their use
in cutlery
◦ It was discovered accidentally when a batch of steel
contaminated with Cr was thrown on the scrap heap where it did
not rust.
1997 Jun 1;67(3):197-207.

◦ Stainless steel entered dentistry in 1919, being introduced at
Krupp’s Dental Polyclinic in germany by R.Hauptmeyer.
◦ He first used stainless steel to make a prosthesis and called the
alloy “Wipla”.
◦ After world war 1 ,stainless steel become widely available.
◦ Angle used it in his last year(1930) as ligature wire
◦ By 1937 the value of stainless steel as an orthodontic material
had been confirmed.
1997 Jun 1;67(3):197-207.

CLASSIFICATION
◦ Steels are classified according to the American Iron and Steel
Institute system(AISI).
◦ Higher this number, less ferrous the alloys are.
STAINLESS
STEEL
FERRITE
(400)
AUSTENTITE
(300)
MARTENSITE
(400)

COMPOSITION(WT %) OF THREE TYPES OF
STAINLESS STEEL
Type of stainless
steel
Chromium Nickel Carbon
Ferritic (bcc) 11.5 - 27.0 0 0.20 max
Austenitic(fcc) 16.0 - 26.0 7.0 - 22.0 0.25 max
Martensitic(bct) 11.5 - 17.0 0 - 2.5 0.15 - 1.20
Silicon, phosphorous, sulfur, manganese, tantalum, and niobium
may also be present in small amounts. The balance is iron.
1997 Jun 1;67(3):197-207.

◦ Chromium-increases tarnish & corrosion resistance, increases hardness, tensile
strength & proportional limit
◦ Nickel-strengthens the alloy, increases tarnish & corrosion resistance
◦ Cobalt-decreases hardness
◦ Manganese-acts as Sulphur scavenger &increases hardness during quenching
◦ Titanium-inhibits precipitation of Chromium carbide (Stabilization of sensitized
Stainless steel)
◦ Molybdenum - increases resistance to corrosion. Molybdenum is added to
martensitic stainless steel to improve the high temperature strength.
◦ Nitrogen – increases strength and corrosion resistance
1997 Jun 1;67(3):197-207.

FERRITIC STAINLESS STEELS
◦ Pure iron at room temperature has body centered cubic (BCC) structure and is
referred to as ‘ferrite’.
◦ This phase is stable upto 9120
C.
◦ The spaces between atoms in BCC structure are small and oblate, hence carbon
has very low solubility in ferrite (0.02wt%).
1997 Jun 1;67(3):197-207.

◦ These alloys are designated as American Iron and Steel Institute
(AISI) series 400 stainless steel.
◦ This series number is shared with martensitic stainless steels
◦ Provide good corrosion resistance at low cost, provided that high
strength is not required.
◦ Not hardenable by heat treatment and are not readily work-
hardenable.
◦ The modern “super ferritics” contain 19% - 30% chromium, and
are used in several nickel free brackets.
1997 Jun 1;67(3):197-207.

AUSTENITIC STAINLESS STEELS
◦ At temperature between 9120
C and 13940
C the stable form of iron in face
centered cubic structure (FCC) called austenite.
◦ The interstices in (FCC) are larger than BCC structure.
◦ Maximum carbon solubility is 2.11 wt%
1997 Jun 1;67(3):197-207.

◦ Austenitic steels are used for the purpose of orthodontic wires
and bands
◦ This family of alloys was named after the British metallurgist
Robert Austen.
◦ All AISI numbers in the series of 300 are austenitic.
◦ These alloys are the most corrosion resistant of all the stainless
steels
1997 Jun 1;67(3):197-207.

MARTENSITIC STAINLESS STEELS
◦ When austenite is cooled very rapidly (quenched) it will undergo a
spontaneous, diffusion less transformation to body centered tetragonal (BCT)
structure called ‘Martensite’.
◦ This lattice is highly distorted and strained, resulting in very strong hard and
brittle alloy.
1997 Jun 1;67(3):197-207.

◦ Advantages
High strength
High hardness
◦ Disadvantage
Less corrosion resistance
Mainly used for surgical and cutting instruments
1997 Jun 1;67(3):197-207.

PROPERTIES OF STAINLESS STEEL WIRES
◦ Good formability and can be bent into various designs without fracture
◦ Low coefficient of friction
◦ Low flexibility and low range of action
◦ Steep load deflection curve (forces delivered by the stainless steel wires
dissipate over a very short amount of deactivation)
◦ Good biocompatibility and high corrosion resistance in the oral environment
1997 Jun 1;67(3):197-207.

SENSITIZATION
◦ At temperatures between 800 and 1200°F (425-650°C), carbon in the stainless
steel reacts with chromium to form chromium carbide, which precipitates in the
grain boundaries.
◦ The carbon inactivates the chromium at the grain boundaries increasing the
susceptibility of the stainless steel to corrosion.
◦ This process is called sensitization and can be prevented by controlling the
sensitizing temperature range or by stabilization.
◦ Sensitization of stainless steel commonly occurs during soldering.Quenching
the stainless steel immediately after soldering brings it down to a safe
temperature rapidly reducing the degree of sensitization.
◦ Low-temperature silver solder can be used to maintain the soldering
temperature at a lower level.

STABILIZATION
◦ Stabilization is the process by which carbon is made unavailable for the
sensitizing reaction.
◦ This is done by keeping the carbon content exceptionally low or by adding
other metals, like titanium, columbium and molybdenum having grater affinity
to carbon than chromium.
◦ Usually titanium six times more than the concentration of carbon is added to
the alloy for this purpose.

Stainless steel commercially available as:
◦ 3 M unitek
◦ TP orthodontics
◦ Ormco
◦ G and H wire company
◦ GAC
◦ Rocky mountain

DUPLEX STEEL
◦ Consists of an assembly of both austenite &ferrite grains. These steel contain
Mo, Cr, lower Ni, Fe.
◦ Properties:
Improved toughness &ductility
Yield strength is twice that of SS
Highly corrosion resistant

AUSTRALIAN ORTHODONTIC WIRES
◦ History:
1952;A J Wilcock introduced this in collaboration with Dr.P R Begg.
These wires are graded according to increasing order of resiliency, with
resiliency increasing from regular to supreme.
Wilcock AJ;Applied materials engineering for orthodontic wires; Aust
Orthod J,1989;11(1);22-29

Advantages:
◦ high tensile strength –thin wire and hence distribute force at optimum level for
tooth movement
◦ increased resiliency & toughness
Disadvantages:
• highly brittle &break easily when quick bent is given.
• relatively expensive than stainless steel
Orthod J,1989;11(1);22-29

◦ AJW wires are available according to the straightening
processes
◦ Spinner straightening : it is a mechanical process of
straightening resistant materials usually in the cold drawn
condition. The wire is pulled through rotating bronze rollers
which twist the wire into straight condition. The disadvantage of
this process are that this results in permanent deformation and
decreases yield strength value as the wires are strain softened
Orthod J,1989;11(1);22-29

Pulse straightening :
◦ Recent and more accepted method of wire straightening.
◦ Wire is pulled in a special machine, which permits lower
diameters of high tensile wires to be straightened.
◦ The surface has a smoother finish and therefore lower friction.
◦ Pulse straightened wires are better in terms of ultimate tensile
strength, high load deflection rate, significantly higher working
range, and lower frictional resistance
Orthod J,1989;11(1);22-29

Grades and wire dimensions of australian
wires
Wire grade Size (diameter) in inches
Regular 0.012” to 0.024”
Regular + 0.012” to 0.020”
Special 0.012” to 0.020”
Special+ 0.012” to 0.024”
Premium 0.012” to 0.020”
Premium+ 0.010” to 0.018”
Supreme 0.008” to 0.011”

◦ REGULAR GRADE(WHITE LABEL)
- lowest grade
- easiest to bend
- used for practice bending and forming auxillaries
◦ REGULAR PLUS GRADE(GREEN LABEL)
- relatively easy to form, yet more resilient than regular grade
- used for auxillaries and archwires when more pressure and resistance to
deformation are desired
◦ SPECIAL GRADE(BLACK LABEL)
- highly resilient yet can be formed into shape with little danger of breakage
Orthod J,1989;11(1);22-29

◦ SPECIAL PLUS GRADE(ORANGE LABEL)
- hardness and resiliency of 0.16 wire is excellent for supporting anchorage and
reducing deep bite
- must be bent with care
◦ EXTRA SPECIAL PLUS GRADE(BLUE LABEL-ESP)
- also referred to as premium plus in Australia
- good resiliency and hardness
- more difficult to bend and more subjected to fracture
- more ability to open bites and resist deformation
Orthod J,1989;11(1);22-29

◦ SUPREME GRADE(BLUE LABEL)
- further developed by Mr. A J Wilcock Jr in 1982 on request of Dr
Mollenhaeurf Australia
- it is an ultra light, tensile free round SS wire
- although supreme exceeds the yield strength of ESP, it is intended for use in
either short sections or full arch where sharp bends are not required
Orthod J,1989;11(1);22-29

CONTENTS-PART 2
◦ COBALT-CHROMIUM ARCHWIRES
◦ NICKEL TITANIUM ARCHWIRES
-Conventional Niti
-Japanese niti
-Chinese niti
-copper niti
◦ TMA WIRES
◦ ESTHETIC ARCHWIRE
◦ CONCLUSION

COBALT-CHROME WIRES
◦ In the 1950s the Elgin watch company developed an alloy
which had an unique property of excellent formability.
◦ Co-Cr-Ni alloys belongs to a group of alloys called satellite
alloys
◦ This alloy was later marketed by Rocky Mountain
orthodontics by Eligiloy
1997 Jun 1;67(3):197-207.

Composition
Component percentage
Cobalt 40%
Chromium 20%
Nickel 15%
Molybdenum 7%
Manganese 2%
Carbon 0.16%
Beryllium 0.04%
Iron 15.8%
1997 Jun 1;67(3):197-207.

◦ Carbon forms carbide with many metallic constituents like cobalt, chromium,
molybdenum and strengthens the alloy on treatment
◦ The carbides that precipitates bring about the changes in the formability and
ductility of the alloys
1997 Jun 1;67(3):197-207.

General properties
◦ Best formability among all the wires and can tolerate complicated arch wire
designs
◦ Resiliency can be increased by the heat treatment
◦ Deliver low and constant forces for longer duration when used as resilient
springs and have greater fatigue and distortion than stainless steel
◦ High yield strength on heat treatment
◦ Good biocompatibility and corrosion resistance in the oral environment
◦ Good joinability and can be soldered and welded
◦ Low coefficient of friction
1997 Jun 1;67(3):197-207.

Commercially available as:
◦ Eligiloy (Rocky Mountain Orthodontics)
◦ Azura (Ormco Corporation)
◦ Multiphase (American Orthodontics Corporation)
1997 Jun 1;67(3):197-207.

Eligiloy wires are available in four
different tempers:
1. Blue (soft): This is the softest of the four wire tempers and can be easily
bent in to desired shapes. It is recommended for use when considerable wire
bending is needed such as multiple loop wires
2. Yellow (ductile):more resilient than blue Elgiloy, but can also be bent with
relative ease
3) Green (semi-resilient):more resilient than yellow
4) Red (resilient):hardest and more resilient Eligiloy and provides high spring
qualities. Heat treatment makes red Eligiloy extremely resilient but brittle
1997 Jun 1;67(3):197-207.

Advantages of cobalt chrome
wires
◦ Greater resistance to fatigue and distortion
◦ longer function as a resilient spring
◦ Better corrosion resistance
◦ Good formability before heat and better
springback after heat treatment
Disadvantages of cobalt
chrome wires
• Loss in yield strength and tensile
strength if annealed, so it is should
be welded or soldered with caution
1997 Jun 1;67(3):197-207.

NICKEL TITANIUM WIRES(NiTi)
◦ History :
First developed by William Buehler, a research metallurgist at Naval Ordnance
Laboratory in 1962
In 1971 introduced in orthodontics by ANDREASON et al
Andreasen GF& Marrow RE;Laboratory &clinical analysis of nitinol
wire;AMJ Orthod 1978;73;142-151

◦ Types of NiTi:
Martensitic alloy(M-NiTi)
Austenitic alloy(A-NiTi)
◦ Austenitic NiTi- has a complex ordered bcc structure
◦ Martensitic NiTi- has a distorted monoclinic, triclinic, or
hexagonal structure
◦ Transformation between austenitic and martensitic forms of NiTi
can be induced by both temperature and stress

◦ Austenitic NiTi is the high temperature , low stress form and
martensitic NiTi is the low temperature , high stress form
◦ Transformation occurs by twinning process, which is reversible
below the elastic limit.
◦ In addition, a third form of NiTi, called the R phase (because of
its rhombo-hedral crystal structure), appears as an intermediate
phase during the transformation between martensitic NiTi and
austenitic NiTi

Classification of NiTi wires
◦ Kusy has suggested that nickel titanium orthodontic wires can alternatively be
classified into three categories
1. Martensitic stabilized alloys
2. Martensitic active alloys
3. Austenitic active alloys

Martensitic stabilized alloys
◦ These alloys donot possess shape memory or super elasticity, because the cold
working of the wire creates a stable martensitic structure
◦ These are the non superelastic wire alloys such as ‘nitinol’

Martensitic active alloys
◦ Such alloys employ the thermoelastic effect to achieve shape memory.
◦ The oral environment raises the temperature of the deformed archwire with the
martensitic structure so that it transforms back to the austenitic structure and
returns to the starting shape
◦ Examples are neo Sentalloy and copper NiTi wires

Austenitic active alloys
◦ These undergo a stress induced martensitic tranformation when activated
◦ These alloys display superelastic behavior
◦ The reverse transformation from martensite back to austenite takes place
during unloading or deactivation
◦ Eg: Japanese NiTi wires

HYSTERESIS
◦ Transformation from Austenite to Martensite & reverse do not take place at
same temperature,this difference is known as hysteresis
◦ Range for NiTi are 40⁰ C -60⁰ C

Properties of NiTi wires
◦ Two important properties of NiTi wires are:
Shape memory
Super elasticity

Shape memory
◦ Shape memory refers to the ability of the material to “remember” its original
shape after being plastically deformed while in the martensitic form
◦ Related to phase transition b/w martensitic &austenitic forms within the alloy
◦ A certain shape is set while the alloy is maintained at an elevated temperature,
above the martensitic-austenitic transition temperature.
◦ When the alloy is cooled below the transition temperature, it can be plastically
deformed, but when it is heated again the original shape is restored

Superelasticity
◦ Ability of certain nickel titanium alloys to undergo extensive deformation
resulting from a stress assisted phase transformation, with the reverse
transformation occuring on unloading; called pseudoelasticity in engineering
materials science.

Stress-strain curve
• Section A-B represents purely
elastic deformation of the austenitic
phase.
• The stress corresponding to point B
is the maximum stress at which
transformation to the martensitic
phase starts to occur.
• At point C the transformation is
completed, the difference between the
slopes of A-B and B-C indicates the
ease with which transformation
occurs

◦ After the transformation is completed, the
martensite structure deforms elastically,
represented by section C-D (but orthodontic
wires are almost never stretched into this
region at point D the yield stress of the
martensitic phase is reached, and material
deforms plastically until failure occurs at E.
◦ If the stress is released before reaching point
D(as at point C' in the diagram) elastic
unloading of the martensite occurs along the
line C'-F

◦ Point F indicates the maximum stress on
which the stress induced martensite
structure can exist, and at that point the
reverse transformation to austenite
begins, continuing to point G, where the
austenite structure is completely
restored.
◦ G-H represents the elastic unloading of
the austenite phase.
◦ A small portion of the total strain may
not be recovered because of irreversible
changes during loading and unloading.

Other properties are:
◦ High spring back &flexibility
◦ Low stiffness
◦ Produces lower more constant &continous force on teeth.
◦ Poor formability (fractures rapidly when bent over a sharp edge)
◦ The shape memory wires have superior spring back to the superelastic and non
superelastic NiTi wires and are the most desirable NiTi orthodontic wires for
clinical use

Limitations of NiTi wires
◦ Poor formability
◦ Cannot be welded or soldered
◦ High frictional forces
◦ Nickel content is known to cause hypersensitivity reaction

CHINESE NITI
◦ History
-Developed by Dr Tein Hua Cheng & associates at General Research Institute
in Beijing ,China
-Reported by Dr Burstone in 1985(AmJOrthod 1985)
Marketed as Ni-Ti by Ormco
Charles J Burstone,Qin&Morton;Chinese Niti wire;A new orthodontic
alloy;AMJ Orthod 1985;87;445-451

Properties
◦ Springback:
-Chinese NiTi has 1.4 times the spring back of NiTi wire
-Chinese NiTi has 4.6 times the spring back of stainless steel
◦ Stiffness:
stiffness is 36% of nitinol wire
◦ Temperature dependant effects are clinically insignificant
◦ Highly suitable if low stiffness is required &large deflections are needed
Charles J Burstone,Qin&Morton;Chinese Niti wire;A new orthodontic
alloy;AMJ Orthod 1985;87;445-451

JAPANESE NITI
◦ History:
1978-Furukawa Electric Co.Ltd of Japan-produced a new type of alloy .
1986-Miura et al reported on this alloy(AmJO-1986)
◦ Marketed as Sentalloy
Miura F, Mogi M, Ohura Y, Hamanaka H. The super-elastic property of the Japanese NiTi alloy wire for use in
orthodontics. American Journal of Orthodontics and Dentofacial Orthopedics. 1986 Jul 1;90(1):1-0.

Advantages
◦ constant force over wide range of deflection
◦ low stiffness
◦ high springback
◦ more effective in initial tooth movement
◦ less patient discomfort
Miura F, Mogi M, Ohura Y, Hamanaka H. The super-elastic property of the Japanese NiTi alloy wire for use in
orthodontics. American Journal of Orthodontics and Dentofacial Orthopedics. 1986 Jul 1;90(1):1-0.

COPPER NITI
◦ 1994-introduced by Rohit Sachdeva &Suchio Miuasaki
◦ Composition:
Cu-5-6%
Cr-0.2-0.5%
Ni &Ti
Copper is added to enhance the thermal properties of nickel titanium alloy
Rohit sachdeva;Orthodontics for the next millenium;chapter-Biomechanical consideration in the selection of NiTi
alloys in orthodontics and variable transformation temperature orthodontics with copper-NiTi,1997;Ormco,227-247

Types of copper NiTi
1. Type 1(TTR OF 15 degrees)
◦ It generates very high forces
◦ Limited clinical implications
◦ Most popular and generates moderate to high forces
◦ Indicated in patients who have an average or higher pain threshold and in
patients where rapid tooth movement is required

◦ Generate forces in the mid range
◦ Indicated in the patients who have a low to normal pain
threshold, in patients whose periodontium is slightly
compromised and when lower forces are desired
◦ Generate very low forces
◦ Indicated in patients who are sensitive to pain, compromised
periodontal conditions

Advantages
◦ Loading force is 20% less for same degree of deformation of wire.
◦ Engages to severely mal-posed tooth with less patient discomfort
◦ More resistance to permanent deformation, so exhibits greater spring back
◦ Decreased hysteresis-more consistent force
◦ Patient can control deactivation of engaged wire by cold application, thereby
reducing discomfort

BETA TITANIUM WIRES(TMA)
◦ History:
◦ 1979-introduced by Burstone &Goldberg
◦ Composition:
Titanium -77.8%
Molybdenum -11.3%
Zirconium -6.6%
Tin -4.3%
Molybdenum stabilise the β phase at room temperature.
Zirconium contributes to increased strength and hardness
Burstone CJ, Goldberg AJ. Beta titanium: a new orthodontic alloy. American journal of
orthodontics. 1980 Feb 1;77(2):121-32.

◦ Pure titanium is normally found in a hexagonal close
packed(HCP)lattice form.
◦ If it is heated above 1625°F,the structure changes to a “Body
centered cubic” lattice referred to as “Beta phase”.
◦ If titanium was heated beyond 1625°F in the presence of
modifying elements such as
chromium,cobalt,columbium,copper,iron,manganese,molybdenu
m,nickel,tantalum or vanadium and then cooled –beta lattice
structure was maintained after cooling.

◦ Modulus of elasticity : less than half that of SS & approximately
twice that of nitinol. Ideal in situations where force less than SS is
required& where low modulus material such as NiTi is
inadequate.
◦ Springback: superior to that of Stainless Steel and can be
deflected twice as much as SS without permanent deformation.
greater torque control than SS
◦ Formability:
Good formability(due to their bcc structure)
Allows loops(T ,vertical , helix)to be bent
◦ Corrosion resistance:
High corrosion resistance (passivating surface layer of
titanium oxide)

◦ Weldability : beta titanium is the only orthodontic wire
possessing true weldability
◦ Absence of Ni --- so used in patients who are allergic to Ni
◦ High coefficient of friction: so use is restricted to frictionless
mechanics like loops & springs. Nitrogen ion implantation on
wire surface—causes surface hardening &decrease in frictional
force by 70%

Advantages:
◦ Elastic modulus below stainless steel and near to nickel-titanium alloy
◦ Excellent formability
◦ Weldability
◦ Low potential for hypersensitivity
Disadvantages:
◦ High surface roughness, which increases friction at the wire-bracket interface
during the wire sliding process
◦ Susceptibility to fracture during bending
◦ Expensive

ALPHA TITANIUM WIRES
◦History:
Developed by A.J Wilcock in 1988
◦Composition:
Ti-90% ,Al-6% ,Vn-4%
A comparative study of metallurgical & working properties of two new Titanium based alloy wires(TiMolium
&Beta III)with the earlier introduced titanium wires(TMA),and also Alpha Titanium wires. Dr. Jiku Abraham

◦ Advantages
-Quite resilient, hence used for torquing in finishing stages
-can be welded
◦ Disadvantages
-poor workability &formability
-brittle
-High cost

Mechanical properties of cobalt-chromium wires
compared to stainless steel and -titanium wires
β
Ahmad Alobeid, Malak Hasan,1
Mahmoud Al-Suleiman,2
and Tarek El-Bialy
◦ AIM: to evaluate the mechanical properties of BE wires compared to stainless
steel (SS) and titanium Molybdenum alloy (TMA) also known as titanium
β
as provided by two companies.
◦ MATERIALS AND METHOD: Six 0.016 x 0.022-14mm-samples of each wire
were fixed individually to Instron machine and were tested in loading and
unloading for three times. The initial load was set for 500 Kg at a speed of
1mm/min and displacement was adjusted for (0.5, 1mm in loading and 0.5
mm unloading at 25°C).
◦ STATISTICS ANALYSIS: Variables were compared between groups by ANOVA
test using SPSS statistical software.
Alobeid A, Hasan M, Al-Suleiman M, El-Bialy T. Mechanical properties of cobalt-chromium wires compared
to stainless steel and β-titanium wires. journal of orthodontic science. 2014 Oct;3(4):137.

• RESULTS:BE without heat treatment shows comparable forces to SS when loaded 0.5 and showed decreased forces in 1 mm loading over
the three tests compared to SS, and higher than TMA in the first two 1 mm loading experiments. However in the third 1 mm loading, BE
showed lowest forces
• TMA alloy showed the lowest forces in loading and unloading and the least deformation compared to BE or SS alloys
• There were insignificant differences in loading and unloading forces between SS and BE alloys
• After repeating the tests, wire deformation was the highest for BE then SS then TMA alloy
• SS and TMA wires showed differences in forces to deformation and resilience between companies. However, there were no differences in
BE mechanical properties between companies
• Increased deformation of BE after loading may limit its clinical use.
Alobeid A, Hasan M, Al-Suleiman M, El-Bialy T. Mechanical properties of cobalt-chromium wires compared to stainless steel and β-titanium
wires. journal of orthodontic science. 2014 Oct;3(4):137.

TITANIUM –NIOBIUM
WIRES
◦ A new ‘finishing wire’ made from a nickel free Titanium – Niobium alloy (Ti-
Nb) was introduced by Rohit Sachdeva in 1996
◦ Possess resiliency equal to that of SS
◦ Designed for tooth finishing.
◦ Stiffness is 20% lower than TMA &70% lower than SS.
◦ Lower springback &larger plastic range.
◦ Bends can be made & hence avoid excessive force levels of steel wire.

TIMOLIUM TITANIUM WIRE
◦ Timolium archwires combine the flexibility, continuous force and springback
of nickel titanium with the high stiffness and bendability of stainless steel wire.
◦ When compared to Nickel Titanium or Beta Titanium wire, Timolium
outperforms in the following:
More resistant to breakage,
Smoother for reduced friction,
Brightly polished and aesthetically pleasing,
Nickel free for sensitive patients,
Easier to bend and shape,
Can be welded.

ESTHETIC ARCHWIRES
COMPOSITE
PLASTICS
OPTIFLEX
ARCHWIRES
COATED
ARCHWIRES

Singh DP. Esthetic archwires in orthodontics-A review. J Oral Hyg Health.
2016;4(194):2332-0702.

COMPOSITE PLASTICS
◦ Composed of glass fibers & acrylic resin .
Properties:
◦ Esthetically pleasing because of their translucent quality. Tends to transmit
color of host teeth
◦ Stiffness range from that of NiTi to β-titanium without changing cross-sectional
dimension
◦ When fiber & resin content are equal, spring back is greater than 95% & total
water sorption is only 1.5% by weight so that dimensional stability is good
2016;4(194):2332-0702.

◦ Esthetic as the connecting bar is clear or
translucent
◦ Biocompatible and less hypersensitivity
reported as compared to stainless steel and other
metals.
◦ High modulus of elasticity in flexure, six times
greater yield strength and 2 times greater
resilience.
◦ Option to join pieces together with an adhesive
to make a string structural unit.
◦ Attachments can be added for inter-maxillary
tooth movement without bands or brackets
◦ Vertical elastics can be applied directly to FRC
bars, either on full arches or on segments for
closure of an open-bite
◦ FRC bars are strong and rigid in
tension but less in bending mode and
areweakest in shear and torsion
◦ Unlike metals, they are not
homogenous materials so shear loads
need to be minimized.
◦ Sound bonding technique is required.
ADVANTAGES DISADVANTAGES

OPTIFLEX WIRES
◦ Optiflex is a non metallic orthodontic arch wire
designed by Dr. Talass and manufactured by
Ormco.
◦ It has got unique mechanical properties with a
highly aesthetic appearance made of clear optical
fiber. It comprises of 3 layers.
1) A silicon dioxide core: that provides the force
for moving tooth.
2) A silicon resin cladding: middle layer that
protects the core form moisture and adds strength.
3) Nylon Coating: outer layer that prevents
damage to the wire and further increases strength.

Advantages:
1) It the most aesthetic orthodontic archwire.
2) It is completely stain resistant, and will not stain or loose its clear look even
after several weeks in mouth.
3) Its effective in moving teeth using light continuous force
4) Optiflex is very flexible , it has an extremely wide range of actions, when
indicated it can be tied with electrometric ligatures to severely malaligned teeth
without fear of fracturing the arch wire.
5) Due to superior properties optiflex can be used with any bracket system
2016;4(194):2332-0702.

COATED ARCHWIRES
TEFLON COATED
EPOXY COATED
NITANIUM TOOTH TONED ARCHWIRE
2016;4(194):2332-0702.

TEFLON COATED
◦ Coating on an archwire material has been introduced to enhance esthetics and
decrease friction
◦ These wires are designed to be more acceptable by the patients
◦ Normally the coating is 0.002” thick TEFLON
◦ TEFLON coating is applied two coats by conventional airspray or electrostatic
techniques
2016;4(194):2332-0702.

EPOXY COATED
◦ Epoxy coated archwire is tooth coloured and has superior wear resistance and
colour stability of 6-8 weeks
◦ Available in NiTi and SS in preformed arches of different sizes
◦ Available in various brand names like Filaflex and Orthocosmetic Elastinol
2016;4(194):2332-0702.

NITANIUM TOOTH TONED
ARCHWIRE
◦ It is superelastic NiTi wire with special plastic and friction reducing tooth
coloured coatings which blend with natural dentition, ceramic, plastic and
composite brackets and maintains its original colour
◦ Marketed as ortho organizers
◦ They deliver gentle forces
2016;4(194):2332-0702.

CONCLUSION
◦ In the last few decades, a variety of new wires has been introduced into
orthodontics. These wires demonstrate a wide spectrum of mechanical
properties & have added to the versatility of orthodontic treatment.
◦ Future lies in finding newer materials which gives more physiologic tooth
moving forces.
◦ The quest for newer orthodontic wire still continues.

REFERENCES
◦ Proffit W R; Contemporary Orthodontics,Ed.2,Mosby
◦ Current Principles & Techniques. Graber T M & Vanarsdall R
◦ Orthodontic Materials- scientific and clinical aspects William Brantley, Theodore Eliades
◦ Charles J Burstone&AJ Goldberg;Beta Titanium;A new orthodontic alloy;AMJ Orthod
1980;77:121-132.
◦ Wilcock AJ;Applied materials engineering for orthodontic wires; Aust Orthod
J,1989;11(1);22-29
◦ Andreasen GF& Marrow RE;Laboratory &clinical analysis of nitinol wire;AMJ Orthod
1978;73;142-151
◦ Charles J Burstone,Qin&Morton;Chinese Niti wire;A new orthodontic alloy;AMJ Orthod
1985;87;445-451

◦ Fujio Miura,Mogi,Ohura&Hamanaka;The super-elastic property of the Japanese
NiTi alloy wire for use in orthodontics;AMJ Orthod Dentofac
Orthop,1986;90;1-10
◦ Rohit sachdeva;Orthodontics for the next millenium;chapter-Biomechanical
consideration in the selection of NiTi alloys in orthodontics and variable
transformation temperature orthodontics with copper-NiTi,1997;Ormco,227-247
◦ A comparative study of metallurgical & working properties of two new
Titanium based alloy wires(TiMolium &Beta III)with the earlier introduced
titanium wires(TMA),and also Alpha Titanium wires. Dr. Jiku Abraham
◦ Singh DP. Esthetic archwires in orthodontics-A review. J Oral Hyg Health.
2016;4(194):2332-0702.

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