6. STRESS (S, I)
Stress is the internal distribution of the
load measured as force per unit area i.e.,
For simple compression or tension the
stress is given by the expression,
F= force applied
A= cross-sectional areawww.indiandentalacademy.com
7. 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 1.145
x 10–3 psi, (1000 psi = 6.894 Mpa).
8. One test method commonly used for
dental materials is the THREE POINT
BENDING TEST or TRANSVERSE TEST.
When an external force is applied to the
mid point of the test beam, the stress can
be resolved. The numerical value of stress
is given by the expression,
9. Stress = 3FL
L = distance between the supports
b = width of the specimen
d = depth of the specimen
10. When a wire is compressed across the
diameter ,a tensile stress is set up in the
Stress = 2F
F = applied force
D = diameter of
T = length of the wire
This type of test is referred to as a Diametral
Compressive Tensile Test and is usually
used when conventional tensile testing is
difficult to carry out.www.indiandentalacademy.com
11. TYPES OF STRESS
TENSION OR TENSILE STRESS : It
tends to pull the material apart or tends to
stretch or elongate a body.
COMPRESSION OR COMPRESSIVE
STRESS : It is the direct opposite of
tension stress. If a body is placed under a
force, that tends to compress or shorten it,
the internal resistance to such a force is
called as compressive strain.
12. SHEAR STRESS
A stress that is applied by two forces
acting in opposite directions but not in the
These stresses tend to slide one part of
the material past another along planes
parallel to the applied force.
13. STRAIN (γ)
• Strain 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.
15. Hooke‟s Law
Within the elastic range, the material
deforms in direct proportion to the
stress applied, i.e.,
Stress = Modulus of elasticity x Strain
16. MODULUS OF ELASTICITY (Young‟s
It is defined as the ratio between a unit
stress and a unit strain, usually expressed
as pound/square inch (psi) or mega pascal
It is an index of stiffness or flexibility of a
material within the elastic range.
E = ---------------------
17. PROPORTIONAL LIMIT (IPL) or (P)
It is the point at which the first
deformation occurs. It is the
maximum stress at which the straight
line relationship between stress and
strain (Hooke‟s Law) is valid.
18. ELASTIC LIMIT (IEL) (E)
It corresponds to the stress beyond
which strains are not fully recovered.
It is the maximum stress that a
material can withstand without
19. YIELD STRENGTH (Ys) or (IYS)
It is the practical indicator at which the first
deformation is measured. It is measured
by pounds per square inch.
the point at which a plastic deformation of
0.1 % is measured and is called yield
21. ULTIMATE TENSILE STRENGTH
It is the maximum load carrying
capacity of the wire before it
It represents the maximum stress
required to fracture a material.
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.
It is the deformation as a result of tensile
It is usually expressed as percentage
elongation and is equal to
L increase in length
--------------- x 100 or --------------------- x 100
L0 original length
The ability of a material to withstand
permanent deformation without rupture
under compression as in hammering or
rolling into sheets.
25. Gold -Most ductile and most
Silver -Next to most ductile and
Platinum -Third most ductile
Copper -Third most malleablewww.indiandentalacademy.com
26. RESILIENCE ( stored or spring
Resilience represents the energy
storage capacity of a wire, when it is
stressed not to exceed its
It is the energy absorbed by a wire in
undergoing elastic deformation upto
the elastic limit.
27. The energy stored is released when the
wire springs back to its original shape after
removal of an applied stress.
Formability is the amount of
permanent deformation that a wire
will withstand before failing i.e. before
breaking or fracture.
It is the measure of the strain that a
wire can withstand without
undergoing plastic deformation.
A material is said to be flexible if it
withstands the strain or the load up to
its proportional limit without
31. LOAD DEFLECTION RATE
For a given load
observed within the
elastic limit is
known as load
32. SPRINGBACK (Range of action) AND
Springback ability of a wire is a
measure of its ability to undergo large
deflections without permanent
If a wire can be deflected over long
distances without permanent
deformation, it has a high spring back
33. 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.
34. THE PHYSICAL PROPERTIES
OF METALS AND ALLOYS
AND THEIR APPLICATION IN
WIRE FORM IN
35. Flexural rigidity (EI) ;
Resistance to distortion ;
Susceptibility to fracture
36. FLEXURAL RIGIDITY (EI)
Flexural rigidity of a wire is the product
of the Young‟s modulus (E) and a factor
(I) known as the second moment of
inertia of the cross-section of the wire.
I depends on the shape and dimensions
of the cross-section of a wire, and
determines how stiff a wire (with a given
Young‟s Modulus) will be.
37. For a circular cross-section,
I = π R4 / 4
Where, R is the radius of the cross-section.
The second moment of inertia of the
cross-section (I) increases greatly as the
radius of the wire is increased.
38. Doubling the radius (holding
everything else constant) therefore
increases the force applied by a
spring by (2)4, i.e., by 16 times.
For example, for a given deflection,
the use of 0.6 mm diameter wire
instead of 0.5 mm will double the
39. Flexural Rigidity may be determined
experimentally for a wire by mounting the
latter as a simple cantilever and
measuring the deflection for various loads
applied to the free end.
The value of Flexural Rigidity (EI) can be
deduced from the relationship between
force applied (p) and the deflection (y) of
the free end of the cantilever, i.e.
P/y = 3EI / l3
41. If a load is applied to the free end of a
simple cantilever, the upper layers of
the wire are extended and the lower
layers are compressed.
RESISTANCE OF WIRES TO
42. At any given cross-section of the wire
the variation in the magnitude and
direction of these internal stresses,
from the outer to the inner surfaces of
curvature, constitutes a series of
couples whose resultant, the moment
of resistance, is equal in magnitude
and opposite in sense to the Bending
Moment at the crosssection
43. The maximum fibre stress occurring in the
outermost layers of a bent wire at any point
may be calculated from the expression
σmax = GR/I where,
σmax is the maximum fibre stress,
G is the Bending Moment at that point,
R is the radius of the wire,
I is the second moment of inertia of the
44. Provided the maximum fibre stress,
σmax, is less than the effective yield
stress, σeff, the wire will behave
elastically and return to its rest
position when released.
If,σmax is greater than σeff at any
point along a wire, permanent plastic
deformation will take place.
45. The necessary condition for distortion
to occur may therefore be written
------------------- ≥ σeff
46. SUSCEPTIBILITY TO FRACTURE
It is usually assumed that appliances
occasionally fail because of metal fatigue
induced by the repeated stressing of the
A study of the fatigue life of 2-cm finger
springs by Bass and Stephens (1970)
showed that these springs were capable of
withstanding over 1,00,000 flexes when
the distance of flexure was 7.5 mm.www.indiandentalacademy.com
47. Harcourt and Munns (1967) have
investigated finger springs fractured in
use and conclude that fatigue failure is
less likely to occur than failure due to
surface defects produced by the pliers
during fabrication or by an abrasion
wheel when the appliance is being
trimmed, finished or fitted.
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
It is equivalent to the proportional limit
(PL) or approximately the yield strength
(YS) of the wire segment.
51. Considering the graphic
representation of the
stress – strain curve
three points can be
taken as representative
of the strength of a
- elastic limit
- yield point
-ultimate tensile strength
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.
53. 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
Springiness = 1 / stiffness.
54. Stiffness = Ed/L, higher the elastic
modulus, stiffer the wire.
55. According to the force
proportional to the
slope of the elastic
portion of the curve.
The more horizontal
the slope, the
springier the wire, the
more vertical the
slope the stiffer the
Range is defined as the maximum
amount of elastic activation before the
onset of a permanent or plastic
Range is usually determined from the
0.1% offset point on the force –
57. Strength,Stiffness and Range have
an important relationship,i.e.,
Strength = Stiffness x Range
58. FACTORS AFFECTING STIFFNESS,
STRENGTH AND RANGE
The mechanical arrangement by which
force is applied to the teeth, e.g. length of
The second factor is the form of the wire
itself – the size and shape of crossection.
The third factor is the material, including
the alloy composition, its hardness.www.indiandentalacademy.com
59. EFFECTS OF SIZE AND SHAPE ON
A beam is any relatively slender
structure subjected to lateral (bending)
loads. An orthodontic archwire
functions mechanically as a beam.
60. Each of the major elastic properties –
strength , stiffness and range- is
substantially affected by a change in
geometry of the beam.
Both the cross-section and length of
beam are of great significance in
determining its properties.
61. Changes related to size and shape are
independent of the material. In other words,
decreasing the diameter of a steel beam by
50% would reduce its strength to a specific
percentage of what it had been previously.
Decreasing the diameter of the TMA beam
by 50% would reduce its strength by exactly
the same percentage.
62. Effects of diameter or cross section
63. When beams of any type made from
two sizes of wire are compared,
1. Strength changes as a cubic
function of the ratio of the two cross-
2. Springiness changes as the
fourth power of the ratios.
3. Range changes as a direct
64. Effects of length and attachment
65. Strength varies inversely with length.
Springiness varies as a cubic function
of the length ratios.
Range varies as a second power
Supporting a beam on both ends
makes it stronger but less springy.
66. If a beam is rigidly attached on both
ends, it is twice as strong but only
one-fourth as springy as a beam of
the same material and length.
67. The best balance of strength ,
springiness and range must be sought
among the almost innumerable
possible combinations of beam
materials, diameter and length.
68. GOLD ALLOY WIRES
The first wire introduced for
orthodontic purpose was made of
Gold arch wires were the ideal choice
of arch wires with good bio-
69. Composition of many gold alloy wires
corresponds to the type IV gold
They are also subjected to softening
and hardening heat treatments.
70. 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.
71. 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%.
72. Gold alloys used, can be called to a
large extent as binary alloys, as only
gold and copper are major metals
These binary alloys to a large extent
exhibit severe grain growth on heating
and have poor ductility in the hardened
73. Heat Treatment of Gold Alloys
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
74. 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.
75. 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
76. 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.
77. 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.
78. 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.
79. Properties of Gold wires
Yield strength of the gold wires range from
50,000 to 1,60,000 psi, depending on the
Modulus of elasticity of gold copper alloys
is approximately 15,000,000 psi.
The combination of these properties makes
gold very formable and capable of
delivering lower forces than stainless steel.
80. STAINLESS STEEL ALLOY
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
Chromium Nickel Carbon
Ferritic (BCC) 11.5-27 0 0.20 max
Austenitic(FCC) 16.0-26 7-22 0.25 max
Martensitic(BCT) 11.5-17 0-2.5 0.15-1.2 max
82. Silicon ,phosphorous ,sulphur,
manganese, tantalum, and niobium
may also be present in small amounts.
The balance is iron.
83. Ferritic Stainless Steel (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.
84. Ferritic Stainless Steel
Because temperature change induces no
phase change in the solid state , the alloy
is not hardenable by heat treatment.
This series of alloys finds little application
85. Martensitic Stainless Steel (FCC)
Martensitic stainless steel alloys share
the AISI 400 designation with the ferritic
They can be heat treated in the same
manner as plain carbon steels , with
Because of their higher strength and
hardness, martensitic stainless steels are
used for surgical and cutting instruments.
86. Austenitic Stainless Steel (BCT)
The austenitic stainless steel alloys are
the most corrosion resistant of the
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%).
87. Austenitic Stainless Steel
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
Type 316L (0.03% maximum carbon) is
the type ordinarily employed for implants.
88. The alloying elements Chromium and
Nickel maintains austenite at room
temperature and prevents conversion of
face centered cubic lattice structure of
austenite to a martensitic cubic lattice
89. 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,
90. Tarnish and corrosion are resisted by
stainless steel due to the passivating
effect of chromium.
A thin , transparent but tough
impervious chromium oxide layer forms
on the surface of the alloy when it is
subjected to an oxidizing temperature as
mild as clean air or atmospheric room air.
91. 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
92. Chromium loss is called sensitization.
A procedure to introduce some element
that precipitates carbide in preference to
chromium preferably titanium is called
93. Heat Treatment of STAINLESS STEEL
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
By heat treatment residual stresses are
95. Arthur. J. Wilcock of Victoria, Australia,
produced the orthodontic archwire to
meet Dr. Begg‟s needs for use in Begg
The wire produced has certain unique
characteristics different from usual
stainless steel wires .
96. 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
97. REGULAR PLUS GRADE : Green
Relatively easy to form, yet more
resilient than regular grade. Used for
auxillaires and archwires when more
pressure and resistance to deformation
98. SPECIAL GRADE : Black Label.
Highly resilient, yet can be formed into
intricate shapes with little danger of
SPECIAL PLUS GRADE : Orange Label
Hardness and resiliency of the wire are
excellent for supporting anchorage and
reducing deep overbites.
99. EXTRA SPECIAL PLUS GRADE :Blue
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
100. 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 .
101. The new grades and sizes of wire makes
Premium : .020″
Premium Plus : .010″,.O12″,.014″,.016″,
Supreme : .008″, .009″, .010″, .011″.
102. Heat Treatment of AUSTRALIAN
The low and medium grade wires
exhibit better formability as they are
subjected to less work hardening and
hence are more ductile.
Till then the wires were straightened by
spinner straightening. The wire is
pulled through high speed rotating
bronze rollers which twist the wire into a
103. 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
104. 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
105. 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 .
106. Properties of AUSTRALIAN
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.
107. 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.
108. A cobalt-chromium-nickel orthodontic
wire alloy was developed during the
1950‟s by the Elgiloy Corporation (Elgin,
Initially it was manufactured for watch
springs by Elgin watch company, hence
the name Elgiloy.
CHROME COBALT ALLOY
109. 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 and 15.8%
110. Blue(soft) elgiloy : Can be bent easily
with finger pressure and pliers. Heat
treatment of blue elgiloy increases its
resistance to deformation.
Types of CHROME COBALT ALLOY
111. Yellow elgiloy : Relatively ductile and
more resilient than blue elgiloy. Further
increase in its resilience and spring
performance can be achieved by heat
112. 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.
113. The ideal temperature for heat
treatment is 900° F or 482°C for 7 to 12
minutes, in a dental furnace.
This causes precipitation hardening of
the alloy increasing the resistance of the
wire to deformation. This heat treatment
would increase the yield strength and
decrease the ductility.
Heat Treatment of COBALT-
114. Heat treatment(of Blue Elgiloy)
increases flexural yield strength(20-
30%), modulus of elasticity(10%),
reduces failure to corrosion in localized
areas where stresses can get
115. Properties of CHROME COBALT
Alloy Modulus of
184 1413 1682 8
Alloy Modulus of
184 1413 1682 8
AlloyAlloy Modulus of
184184 14131413 16821682 88
116. William F. Buehler in 1960‟s invented
Ni – Nickel
NICKEL TITANIUM ALLOY
117. Andreasen G.F. and co-workers
introduced the use of nickel-titanium
alloys for orthodontic use in the
118. 55% nickel, 45% titanium resulting in a
stoichiometric ratio of these elements.
1.6% cobalt is added to obtain
119. Transition Temperature Range : TTR
120. Transition Temperature Range :
Transition temperature range is a
specific temperature range when the
alloy nickel titanium on cooling
undergoes martensitic transformation
from cubic crystallographic lattice.
121. It is found to be in martensitic
crystallographic lattices consisting of
lesser symmetric lattices like
structures at lower temperatures.
In martensitic phase, the alloy cannot
be plastically deformed.
122. At higher temperatures the alloy is found
to be in cubic crystallographic lattice
consisting of body centered cubic
It is also known as Austenitic phase of
Plastic deformation can be induced, in
austenitic phase of the alloy.
123. 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
Any plastic deformation below or in the
TTR is recoverable when the wire is
heated through RTTR.
124. TTR of nickel titanium alloy is between
482 - 510 C when the alloy is cooled
from higher temperature which is very
high for clinical usage.
Substitution of 1.6% cobalt results in
formation of TiNi and TiCo which have
transition temperature ranges of +164.6°
C for TiNi and –237.2° C for TiCo giving
a very wide transition temperature range.
125. It is the phenomenon, where in if a
plastic deformation incurred within or
below the TTR, it is recoverable within
certain strain limits of 8%, which is the
outer fibre strain limit of the wire.
126. Potential Applications of Certain
Nickel-Titanium (Nitinol) Alloys
SIMON CIVJAN, EUGENE F. HUGET, and
LASZLO B. DeSIMON
Journal of Dental Research, 1975
The nitinol wire should be plastically
deformed at a lower temperature and
casted. The casted wire should be
placed in the oven and heated between
482 C to 510 C.
Plastic deformation occurs and the wire
is then placed in the refrigerator.
129. 55-Niti can be “taught” to return to a
second or a low temperature shape.
The specimen is constrained in the
desired second configuration at a
temperature below the TTR and then
cycled, under constraint, a few times
131. The process forces the structure into a
preferred orientation that causes the
metal to assume alternately its first
memory (higher temperature) shape
when heated and to return to its second
(lower temperature) shape on cooling.
132. 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
133. Super elasticity
134. This property can be produced by stress
and not temperature difference.
Therefore it is called as stress induced
135. Chinese Niti Alloy
Another nickel titanium alloy
introduced by Burstone and
developed by Dr Tien Hua Cheng is
called as Chinese Niti alloy.
It has a springback that is 4.4 times
that of comparable stainless steel
wire and 1.6 times that of nitinol wire.
136. At 80° of activation the average
stiffness of Chinese NiTi wire is 73%
that of stainless steel wire and 36%
that of nitinol wire.
137. Japanese Niti Alloy
Another wire called the Japanese Niti
wire introduced by Fujio Miura is
manufactured by a different process and
demonstrates super elasticity.
138. Heat Treatment of the JAPANESE Niti
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.www.indiandentalacademy.com
139. 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.
140. 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
142. 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.
143. Manufacture of Niti Alloy wires
Nickel titanium are most commonly
manufactured into Nickel Titanium alloy
by the process of vacuum induction
Several re-melts are often needed to
improve homogeneity of nickel titanium
alloy. Powders are then made of the
144. The process of hot pressing is used by
the manufacturer to form the powders
into wires. Voids occur in the areas
where the powders are not completely
The wires obtain their final shape by the
process of drawing or rolling.
145. COPPER Ni Ti WIRES
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.
146. 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 0Cwww.indiandentalacademy.com
147. These variants would be useful for
different types of orthodontic patients.
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.
148. MULTI-STRANDED STAINLESS
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
149. 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.
150. According to studies conducted by Kusy
and Dilley, 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
151. D-RECT Wire
D-rect is an 8 stranded , interwoven
braided rectangular wire .
Its high flexibility , together with 3-
dimensional control and slot filling
capabilities make it ideally suitable
for multiple applications.
152. Initial torque control.
A finishing arch wire where torque
control is desired yet resilient to permit
interarch occlusal settling .
153. ALPHA TITANIUM WIRES
The alpha titanium alloy is attained by
adding 6% aluminium and 4% vanadium
Because of its hexagonal lattice, it
possesses fewer slip planes making it
less ductile from β- titanium.
The HCP structures of Alpha-Titanium
has only one active slip plane along its
base rendering it less ductile.www.indiandentalacademy.com
154. β – TITANIUM – TITANIUM
MOLYBDENUM ALLOY OR T.M.A.
In the 1960‟s an entirely different “high
temperature” form of titanium alloy
At temperature above 1625°F pure
titanium rearranges into a body centered
cubic lattice (B.C.C.), referred to as
155. With the addition of such elements as
molybdenum or columbium, a titanium
based alloy can maintain its beta
structure even when cooled to room
Such alloys are referred as beta
156. Goldberg and Burstone demonstrated
that with proper processing of an 11%
molybdenum, 6% Zirconium and 4% tin
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
71.7 931 1276 4
71.7 931 1276 4
71.771.7 931931 12761276 44
158. 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
159. 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.www.indiandentalacademy.com
160. Optiflex arch wire treatment
of a Skeletal Class III Open
JCO 1992, Vol 26, 245-252
161. TOOTH COLOURED
Optiflex is a new 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 fibre, it comprises
of three layers.
162. 1. A silicon dioxide core that provides the
force for moving teeth.
2. A silicon resin middle layer that protects
that core from moisture and adds
3. A strain resistant nylon outer layer that
prevents damage to the wire and further
increases its strength.
164. STAINLESS STEEL
Orthodontic stainless steel is the most
widely used alloy in orthodontics. It finds
its application as arch wires, auxiliaries,
removable appliances, bands, etc.
These wires are available both in round
as well as rectangular cross-sections.
165. The Australian stainless steel wires
described previously are used in the
Begg‟s technique as well as in the
preadjusted edgewise technique.
166. CHROME COBALT
The elgiloy blue alloy 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.
167. 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.
168. NICKEL TITANIUM
Because of its superior spring back,
superelasticity, shape memory, and its
ability to produce light force for longer
duration , NiTi is the ideal wire for initial
levelling and aligning.
Rectangular NiTi allows full
engagement of the bracket slot and
give better torque control in the initial
phase of treatment.www.indiandentalacademy.com
169. 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.
170. COPPER NiTi
Type I wire – Af 15 0C
Sachdeva does not recommend the
frequent use of this alloy because it
generates very heavy forces and clinical
indications are few.
171. Type II wire Af 270C
This wire generates the highest force of
the three ( Type I , III, IV) and is the best
In patients who have an average or
higher pain threshold.
In patients who have normal periodontal
172. Type II wire Af 270C
In patients where rapid tooth
movement is required ; the force
system generated by this orthodontic
arch wire is constant.
173. 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
2. In patients whose periodontium is
normal to slightly compromised.
3. When relatively low forces are desired.
174. 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
175. Type IV wire – Af 40 0C
Where tooth movement is deliberately
slowed down , i.e., when the patient
may not be able to visit the orthodontist
regularly or his/her cooperation is very
T.M.A appears to be well suited as a
utility arch for three primary reasons:
1. It is highly formable and utility arches
are easily formed.
2. With its enhanced resiliency a single
activation is all that is required to
achieve vertical corrections.
177. 3. With its reduced load/deflection rate the
incisor torque control can be obtained
while staying within accepted force
178. TOOTH COLORED WIRE
It is used in adult patients who wish that
their braces not be really visible for
reasons related to personal concerns or
It can be used as an initial wire in cases
with moderate amounts of crowding in
one or both arches.
179. It should be used in cases to be treated
without bicuspid extraction. Optiflex is
not the ideal arch wire for major cuspid
Optiflex can be used in presurgical
stage in cases which require
orthognathic intervention as part of the
180. IN SEARCH OF THE
IDEAL ARCH WIRE
181. No ideal arch wire exists.
This is not surprising because the
demands of the treatment plan require
different characteristic stiffness and
Nonetheless, several desirable
characteristics would be appropriate to
182. A Review of
Contemporary Arch Wires:
Their Properties and
Angle Orthod 1997;67(3);197-208
184. Wires should be esthetic.
When coated, white-colored wires have
routinely succumbed to the forces of
mastication and/or the enzyme activity
of the oral cavity.
When uncoated, transparent wires
have had such poor mechanical
properties that they function as a
Although esthetics are important to the
orthodontist, function is paramount.www.indiandentalacademy.com
185. Wires should have poor biohostability.
This characteristic goes beyond
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
186. Wires should possess low coefficients
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.
187. THE CHOICE OF ARCH
WIRE IN THE CLINICAL
188. The demands placed on the arch wire
depend upon the particular purpose for
which it is intended , and the purpose
will change at different stages of
190. For each arch wire ,
stiffness must be such that an
appropriate force magnitude is
strength must be sufficient to prevent
distortion by masticatory forces,
and range must make it possible to
apply the force over a sufficient
distance, so that frequent reactivation is
not required .
192. THE CHOICE OF ARCH
WIRES IN FIRST STAGE
193. 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.
194. 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
195. Initial arch wires should provide light,
continuous force of approximately 50
grams, to produce the most efficient
Arch wire should be able to move freely
within the brackets (2 mil clearance
In an 18-slot edgewise bracket, 16 mil
can be used.
196. Rectangular arch wires that tightly fit
within the bracket should be avoided as
the position of the root apex can be
Although a highly resilient 0.017” X
0.025” NiTi could be used, it will create
undesirable root movement at this
198. 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
199. 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
200. Arch wire materials appropriate for
initial alignment stage are round cross-
section wires as follows:
1. Nickel- titanium (preferably in its
2. Multistranded stainless steel
3. Australian premium and supreme
201. 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.
202. The very nature of initial alignment arch
wires means that they offer poor control
over unwanted tooth movements.
Their low stiffness means that it is
inadvisable to use them in combination
with elastic traction , because they will
allow too much tipping of (otherwise
unsupported) anchorage units.
203. In most cases, initial alignment is
complete within three months of
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.
205. 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.
206. In the early stages of mid-treatment
single strand , round, stainless steel
arch wires of small diameter are
Arch wires of 0.016” and then 0.018”
diameter are used.
207. Inter and intra-maxillary elastic forces
can be used safely with stainless steel
single strand round wires of 0.016”
diameter and above.
208. These wires are used for the purpose of
canine retraction using sliding
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.
209. 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.
210. In case of enmasse 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
Then 0.016” X 0.022” ss closing loop
arch wire is given for anterior retraction.
211. ARCH WIRES FOR
212. 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.
213. The arch wire requirements at this
stage are for high stiffness and low
When rectangular wire has been used at
the end of mid-treatment stage the
detailing arch wire should also be
rectangular ,of increased stiffness.
214. 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
These arch wires generate the
necessary root paralleling moments.
215. 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.
216. THE FUTURE
217. One promising approach toward
achieving an esthetic arch wire with
excellent overall properties involves the
use of composites.
Existing experimental prototypes are
tooth colored, can be as strong as the
strongest piano wire, and can vary in
stiffness from that of the most flaccid
multi-stranded archwire, to nearly that of
a beta-titanium archwire.www.indiandentalacademy.com
218. These characteristics can be varied
during manufacture without any change
in wire-slot engagement by pultrusion in
which the relative proportions of the fiber
and matrix materials are adjusted
appropriately and cured by
219. Mechanical tests show that such arch
wires are elastic until failure occurs.
When compared with NiTi, resilience
and springback are comparable.
When failure finally does occur, the wire
loses its stiffness, but it remains intact.
220. Enhanced biocompatibility should be
possible by modifying the surface
chemistry of the polymer.
The expectation is that the attractive
properties and characteristics of these
esthetic composites will capture a
significant share of the marketplace in
the near future.
Backofen W.A. & Gales G.F. : the low
temperature heat treatment of stainless
steel for orthodontics. A.O. 1951, vol 21,
Funk A.C. : heat Treatment of S. Steel .
A.O. 1951, vol 21, 129-136.
Burstone C.J. et al. Beta Titanium, A
new orthodontic alloy, AJO 1980, Vol.
77, 212 –132
222. Orthodontic materials –William Brantley
Refined Begg for modern times- V.P.
Orthodontic treatment with removable
appliances- Houston, Issacson
Ralph W. Philips Skinner‟s Science of
dental materials Ninth edition. 261-270,
223. Thank You!
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