Orthodontic arch wires /certified fixed orthodontic courses by Indian dental academy

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


Contents

Ideal properties of orthodontic wires.
Evolution of orthodontic wires.
Stainless steel orthodontic wires.
Composite wires.
Optiflex arch wires.
 Multistranded wires.
Australian wires.


Strong
Resilient

Biocompatible

Formable

Good range
Esthetic
Criteria of an
ideal arch wire

Weldable

Poor biohost
Good
springback
Low friction


Springback:
This is a measure of how far a wire can be deflected

without causing permanent deformation.
Springback = YS/E


Stiffness or load deflection rate:
 This is amount of force required to produce a
specific deformation.
1
Stiffness= -----------Springiness


Formability:
High formability provides the ability to bend a wire into
desired configurations such as loops , coils without
fracturing.


Modulus of resilience or stored energy:
Resilience represents the energy storage capacity of a
wire which is a combination of strength & springiness.


Biocompatibility & Environmental stability:
Biocompatibility includes resistance to corrosion &
tissue tolerance to elements in the wire.
Environmental stability refers to maintainence of
desirable properties of the wire for extended periods of
time.


Joinability:
The ability to attach auxiliaries to orthodontic wires by
welding or soldering.
Friction:
The preferred wire material should produce least
friction at the wire/bracket interface.


Evolution of Orthodontic Wires
Noble Metal Alloys:
In 1860’s Pierre Fauchard introduced gold ,
platinum,iridium and silver alloys.
Esthetically pleasing and good corrosion resistant.
Lack flexibility & tensile strength.


Stainless Steel Wires:
In 1919, Hauptmeyer introduced stainless steel to
dentistry.
He first used it to make a prosthesis & called the
alloy WIE PLATIN; in German, “ like platinum”.
In 1930, Angle used stainless steel for the formation
of ligature wire.


In 1937, Stainless steel was considered to be used as

an orthodontic arch wire.
A.J.Wilcock introduced Australian wires which are

round high tensile stainless steel wires.


Advantages:
High stiffness
High yield strength
High resilience
Good formability
Good joinability
Adequate spring back
Biocompatible
Corrosion resistance
Economical

Disadvantages:
High modulus of elasticity
Frequent activations are required.


Cobalt chromium alloys:
In 1960’s originally developed for use in watch springs
by an Elgin watch company.
They were later marketed by Rocky mountain

orthodontics as Elgiloy.


Advantages:
Excellent corrosion resistance.
Relatively low cost.
Good Biocompatibility.
Out standing formability in as received condition.
Functionally remains active for longer duration if used
as a resilient spring.
Greater resistance to distortion.


Disadvantages:
Higher modulus of elasticity.
Lower spring back than stainless steel
Has to be heat treated.
Soldering is demanding.


Nickel Titanium Alloys:
In 1962, William Buchler first alloyed Nitinol at US
Naval Ordinance Laboratory , MaryLand .
Nitinol- Ni for Nickel, Ti for Titanium, Nol for Naval
Ordinance lab.
Andresen introduced NiTi containing equal % Nickel &
Titanium.


In 1986 two superelastic alloys (Japanese & Chinese)

which has active austenitic phase that forms stress
induced martensite.
In 1990 ’s a neo Sentalloy which is a true active
martensitic alloy having SME was introduced.
In 1994, copper
containing NiTi products
having SME were introduced.

Advantages:
Lowest force delivery of the four orthodontic wire
alloys.
Excellent springback in bendings, particularly for super
elastic and shape memory alloys.


Disadvantages:
Expensive particularly newer products.
Second highest arch wire-bracket friction after TMA.
Difficult to place permanent bends & cannot bend wire
over sharp edge or into complete loop.
Wires cannot be soldered & must be joined by
mechanical crimping process.


Beta Titanium alloys:
In 1980, beta titanium was introduced by Burstone
& Gold berg as wrought orthodontic wire. This alloy
is also known as titanium molybdenum aluminum.
Alpha Titanium:
Structurally it is the alpha phase with closely packed
hexagonal structure in contrast to beta titanium with
a body centered cubic structure.

Advantages:
Intermediate force delivery between stainless steel,
Elgiloy & Nickel-titanium.
Excellent formability
Excellent spring back characteristics.
Excellent biocompatibility from high titanium
content.
Disadvantages:
Expensive
Higher arch wire bracket friction.

Titanium-Niobium wires:
In 1995, an esthetic arch wire known as titanium –
niobium wire was introduced by Dr.Rohith Sachdeva.
Advantages:
Ideal finishing wires
Less stiff than TMA, formability.
Able to maintain low force levels.


Composite wires:
Goldberg et al reported the fabrication of fibre
reinforced composites.
In 1999, Kusy et al patented a method for pultrusion of
fibre reinforced composite wire.
Composition:
In organic fibre
+
Thermoplastic resin.


Advantages:
High elastic recovery.
High tensile strength.
Excellent formability.
Excellent esthetics.
Ability to directly bond attachments to these wires.


Optiflex arch wires:
 These are esthetic arch wires composed of
Silicon di oxide core
-provides force or
resiliency.
Silicon resin middle layer -Adds strength.
Nylon outer layer


--

Strain resistant.

These wires provide light forces & are used during

initial aligning phase.
To prevent permanent deformation sharp bends should

be avoided.


Stainless steel wires in orthodontics
Introduction:
Steel is an iron based alloy which contains less than
1.2% of carbon.
Chromium (12-30%) - added to steel, the alloy is
called stainless steel.


Composition:
Iron
- 71%
Chromium
- 18%
Nickel
- 0.8%
Carbon
< 1.2%
Others
Manganese, Nitrogen, Molybdenum


Additions/impurities:
Carbon
silicon
sulphur
phosphorus
chromium: Resistant to corrosion.


Passivating effect of chromium:
When exposed to air , a thin transparent oxide layer
formed on the surface protects it against tarnish &
corrosion.
Nickel:
It helps to stabilize at low temperature.
Manganese, Nitrogen:
Stabilizes the structure.


Molybdenum:
Increases corrosion resistance.
Pitting resistance equivalent (PRE), evaluate the
resistance of the alloy to pitting corrosion based on the
content of Cr, Mo, N
The higher the PRE value ,the less susceptible the alloy
is to pitting corrosion.


Carbon content:
Low carbon content corrosion resistance.
Silicon:
Silicon at low concentration improves resistance to
oxidation.


Advantages:
High stiffness
High yield strength.
High resilience.
Good formability
Good joinability.
Adequate springback
Bio compatible.
Corrosion resistance
Economical.

Disadvantages:
Soldering is demanding.
Lower spring back than Nickel titanium alloys.
High modulus of elasticity.
More frequent activations are required to maintain the
same force levels.


Classification of stainless steel:


1.
2.
3.
4.
5.
6.

Classified according to American iron & steel institute
system(AISI).
Parallels the unified number system (UNS) & the German
standards. (DIN).
Austenitic steels.
Martensitic steels.
Ferritic steels.
Duplex steels.
Precipitation hardenable steels.
Manganese containing steels.


Austenitic stainless steel:
At temperatures between 9120C & 13940C, a stable

form of iron is a face centered cubic structure ((FCC)
called Austenite.
 18-8 stainless steel
Composition:
Chromium
18%
Nickel
8%
Carbon
0.08-0.15%


Most corrosion resistant of all stainless steels.
 Austenite has FCC structure which is unstable at
room temperature & turns to BCC structure.
 If austenizing elements(Ni ,Mn &N) are added, then
stability can be maintained.
 They are not attached by magnet.



Advantages of Austenite
1. Greater ductility & ability to undergo more cold work
with out breaking.
2. Substantial strengthening during cold working.
3. Greater ease of welding.
4. Increased formability.
5. Ability to readily overcome sensitization.


Applications of Austenite:
1. In orthodontics --- wires, bands, ribbons, hooks
bows & springs.
1. In prosthodontics --- partial denture clasps, bars.
2. Generally
--- instruments, burs, pliers
sterilizers , trays.
space maintainers


Sensitization:
Loss of corrosion resistance of 18-8 stainless steel,
when heated b/n 4000C-9000C(temperature used during
soldering & welding ) is called sensitization.
This due to precipitation of chromium carbide at grain
boundaries.


Stabilization:
Introduction of one or two elements that form carbide
precipitates in preference to chromium such as niobium.
Stainless steels stabilized in this manner are said to be
stabilized steels.


Martensitic stainles steel:
When austenite (FCC) is cooled very rapidly
(quenched) , it will undergo transformation to a body
centered tetragonal structure called Martensite.


Corrosion resistance of martensitic stainless steels is

less than other types.
High strength & hardness.
These are used as surgical & cutting instruments
because of its high strength & hardness.


Ferritic stainless steel:
Pure iron at room temperature has body centered cubic
(BCC) structure called ferrite, stable at 9120C.
Super ferrites contain 19-30% chromium.


Duplex steels:
Consist of combination of austenite & ferrite .
Not attracted by magnets.
When improperly heat treated, they have a tendency to

form a brittle phase (sigma) that diminishes their
corrosion resistance.


Precipitation-Hardenable steels:
Hardened by heat treatment unlike other stainless steels.
Because of its high tensile strength ,used for mini
brackets.


Manganese containing steels:
Manganese – used as replacement for nickel.
Manganese acts by dissolving the really austenizing
element , nitrogen.


Multistranded wires
These are small diameter stainless steel wires twisted or

braided to form large diameter wires.
They may be
Round
based on cross section
Rectangular
}
3 strands
based on no.of strands
6 strands
}
Braided
based on mode of joining strands
Twisted
}

Large elastic deflections & apply low forces compared

to stainless steel wires
Spring back similar to NiTi, but larger compared to

stainless steel & beta titanium.


Australian wires

These are round high tensile stainless steel wires &

were introduced by A.J.Wilcock.
These are used during initial aligning phase.


Grades of australian wires:

1.
2.
3.
4.
5.
6.
7.

Regular.
Regular plus.
Special.
Special plus.
Premium.
Premium plus.
Supreme.


Higher yield strength of the newer grade wires
influence the following properties:
Working range, also called as maximum flexibility,
spring back of elastic strain:

Range ~


YS
--------EM

Resiliency:
Modulus of resiliency


(YS)2
~ ---------EM

Zero stress relaxation:
Ability of the wire to deliver a constant force over long
periods when subjected to an external load.
Formability:
For the same material, greater the resiliency lesser is
the formability.


Banding
Banding involves the use of thin stainless steel strips
called bands that are pinched tightly around the teeth and
then cemented to the teeth.
It is preferable to band a tooth that
requires buccal as well as lingual
attachments.
Bands are better likely to resist heavy
forces as in the case of extraoral
devices such as head gears.

Steps in banding:
Separation of teeth.

Selection of band material.
Pinching of the band.
Fixing the attachments.
Cementation of the band.


Bonding
The method of fixing attachments directly over the enamel
using adhesive resins is called bonding.
The most accepted method is the pretreatment by
acid etching technique.
This technique was introduced in 1955 by
Buonocore.
The pretreatment of enamel by acid etch technique
helps in the following ways:

Enhances the surface energy .
Enhances the surface area and porosity.


Advantages of bonding:
It is esthetically superior.
It is faster to bond than to pinch bands
around the teeth.
It enables maintenance of better oral
hygiene.
It is possible to bond on teeth that have
aberrant shapes or forms. It might be
impossible to band such teeth.
Disadvantages of bonding:
•Bonded attachments are weaker than banded attachments
and hence are more prone to bond failure.
• Bonding involves etching of the enamel with an acid which
may lead to enamel loss and an increased risk of
demineralization.
• Enamel fracture can occur during debonding.

Brackets
Brackets act as handles to transmit the
force from the active components to the
teeth.

Edgewise type of bracket.
Ribbon arch brackets.
Weldable and bondable
brackets.


Metallic brackets


ceramic brackets

Buccal tubes


Lingual attachments


Ligature wires


lock pins

Elastics and Elastomerics


Elastic chain


E –Thread

Springs


Separators


References

Orthodontics –the art and science – S.I.bhalajhi.
Orthodontic materials -William A.Brantley.
Refined Begg for modern times – Dr.Vijay P Jayade.
Anusavice,Philip’s ,Science of Dental materials.


Thank you


Orthodontic arch wires /certified fixed orthodontic courses by Indian dental academy

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