Properties of
Orthodontic Wires
Part I
INDIAN DENTAL ACADEMY

Leader in continuing dental education
www.indiandentalacadem...
Introduction
Moving teeth and craniofacial harmony
Forces and moments

Wires
Light continuous forces

www.indiandentalacad...
History
1. Material Scarcity, Abundance of Ideas
(1750-1930)
noble metals
Gold, platinum, iridium and silver alloys
good c...
History
Angle (1887)  German silver (a type of
brass)
Opposition Farrar – discolored
Neusilber brass (Cu 65%, Ni 14%, Zn...
History
Wood, rubber, vulcanite, piano wire and
silk thread
No restrictions.

www.indiandentalacademy.com
History
Stainless steel (entered dentistry -1920)
Stahl and Eisen – Benno Strauss & Eduard
Maurer in 1914
By 1920 – Dr. F ...
History
2. Abundance of materials, Refinement
of Procedures (1930 – 1975)
 Improvement in metallurgy and organic
chemistr...
History
3. The beginning of Selectivity (1975 to
the present)
Orthodontic manufacturers
Beta titanium (1980)
CAD/CAM – lar...
Basic Properties of Materials
Elements –all particles identical
 Atoms-smallest
Electrons – orbits around nucleus
Floatin...
Basic Properties of Materials
Array of positive ions in a “sea of
electrons”
Electrons free to move
electrical and thermal...
Basic Properties of Materials
Molecules – 2 or more atoms
Amorphous – similar properties in all
directions – isotropy  Gl...
Basic Properties of Materials
CRYSTALS
Perfect crystals: anion – cation –anion –
cation
extremely strong
Thin wiskers rei...
Basic Properties of Materials
alloy crystals grow
anion – cation –anion – cation
Perfect crystals seldom exist
Crystals pe...
Basic Properties of Materials
Grains  microns to centimeters
Grain boundaries
Atoms are irregularly arranged, and this
le...
Basic Properties of Materials
Stages in the
formation of metallic
grains during the
solidification of a
molten metal

Poly...
Basic Properties of Materials
Vacancies – These are empty atom sites

www.indiandentalacademy.com
Interstitials – Smaller atoms that penetrate
the lattice Eg – Carbon, Hydrogen, Oxygen,
Boron. Often distort the metal str...
Basic Properties of Materials
Substitutial Element – another metal atom can
substitute one of the same or similar size. E....
Imperfections- although they lower the
cleavage strength of the metal , increase
its resistance to deformation

www.indian...
LATTICE
The three dimensional arrangement of
lines that can be visualized as connecting
the atoms in undisrupted crystals,...
Basic Properties of Materials

www.indiandentalacademy.com
Basic Properties of Materials
The atoms, which are
represented as points,
are not static. Instead,
they oscillate about th...
Lattice deformations:
various defects  slip planes-along which
dislocation occurs

www.indiandentalacademy.com
Basic Properties of Materials
shear stress  atoms of the crystals
can glide along these planes
more the slip planes easi...
Basic Properties of Materials
If the shearing force is:Small - atoms slip, and return back to their
original position (ela...
Basic Properties of Materials
During deformation - atomic bonds within
the crystal get stressed
 resistance to more defo...
Work hardening
Forced interlocking of grains and atoms of
metal.
Locked in and under pressure/tension
Carried at room temp...
Basic Properties of Materials
Strain hardening- principle
 Hard and strong, tensile strength
Brittle.
Annealing – heat b...
Basic Properties of Materials
ANNEALING:
Recovery
Recrystallization
Grain Growth

www.indiandentalacademy.com
Basic Properties of Materials

www.indiandentalacademy.com
Before Annealing
Recovery – Relief of stresses
Recrystallization – New grains
from severely cold worked areas
-original so...
Annealing
Smaller grains – harder and stronger
Larger grain boundaries to oppose the slip
planes.

www.indiandentalacademy...
Basic Properties of Materials
Various methods of obtaining smaller grain size
1. Enhancing crystal nucleation by adding fi...
Solution heat treatment
Heat below the solidus temp
Held for sometime, - random solid soln
Cool rapidly to room temp. reta...
Basic Properties of Materials
Twinning
Closed packed hexagonal type of crystals
Two symmetric halves
Fixed angle
NiTi - mu...
Basic Properties of Materials

www.indiandentalacademy.com
Basic Properties of Materials
Polymorphism
Metals and alloys exist as more than one
type of structure
Transition from one ...
Transition of Iron
Iron  FCC stable
(austenite), 912*c1394*c
Lattice spaces greater,
Carbon atom can easily be
incorporat...
Transition of Iron
On Cooling <912*c
FCC  BCC
Carbon diffuses
out as FeC
FeC adds strength
to ferrite and
austenite
TIME
...
Transition of Iron
Rapidly cooled
(quenched)


Carbon cannot escape

Highly strained,
distorted body
centered tetragonal
...
Basic Properties of Materials
Grain boundaries are more in number
Alloy is stronger and more brittlemartensitic change – v...
Basic Properties of Materials
Cooled slowly
Other crystal structures are formed at
intermediate temperatures Softer
Some ...
Basic Properties of Materials
Tempering –
Reheat the alloy to intermediate
temperature(1000*F/525*c)
Partial transformatio...
Basic Properties of Materials
Some alloys
FCC to BCC by rearrangement of atoms


Diagonal plane of the BCC unit becomes t...
Shape memory alloys – Easy switching
from one type of structure to another.
Bain distortion
Over a range of temperature {h...
Elastic Properties
Stress and strain
Stress- internal distribution of load.
F/A
Strain- internal distortion produced by lo...
Elastic Properties
Force applied to wire Deflection
Internal force---- (equal and opposite)
Internal force = Stress
Area...
Elastic Properties
Types of stress/strain
Tensile –stretch/pull
Compressive – compress/towards each other
Shear – 2 forces...
Elastic Properties

Stress

Wire returns back to original
dimension when stress is
removed

Elastic Portion

www.indianden...
Elastic Properties
Hooke’s law
Spring stretch in proportion to applied force
(proportional limit)
Modulus of elasticity – ...
Elastic Properties

Stress

Yield strength

0.1%

Proportional Limit
Elastic Limit

www.indiandentalacademy.com

Strain
Stress

Elastic Properties
Ultimate Tensile
Strength

www.indiandentalacademy.com

Fracture Point

Strain
Elastic Properties
ultimate tensile strength is higher than the
yield strength
important clinically  maximum force that
t...
Stress

Elastic Properties

Slope α Stiffness
Stiffness α

1

.

Springiness

www.indiandentalacademy.com

Strain
Elastic Properties

Stress

Point of arbitrary clinical loading
Yield point

Range

Springback
www.indiandentalacademy.com...
Elastic Properties
Clinically, ortho wires are deformed
beyond their elastic limit.
Springback properties are important
St...
Elastic Properties
Resiliency When a wire is stretched, the space between the
atoms increases. Within the elastic limit, t...
Stress

Elastic Properties

Yield strength
Proportional limit

Resilience

Formability

www.indiandentalacademy.com

Strai...
Elastic Properties
Formability - amount of permanent
deformation that the wire can withstand
without breaking
Indication o...
Elastic Properties
Flexibility
large deformation (or large strain) with
minimal force, within its elastic limit.
Maximal f...
Elastic Properties
Toughness –force required to fracture a
material. Total area under the stress –
strain graph.
Brittlene...
www.indiandentalacademy.com
Properties of
Orthodontic Wires
Part I

Dr. Vijaya Lakshmi
Elastic Properties

www.indiandentalacademy.com
Elastic Properties

www.indiandentalacademy.com
Stress

Elastic Properties

Yield strength
Proportional limit

Resilience

Formability

www.indiandentalacademy.com

Strai...
Requirements of an ideal archwire
(Kusy )
1. Esthetics

7. Resiliency

2. Stiffness

8. Coefficient of friction

3. Streng...
1. Esthetics
Desirable
No compromise on mechanical properties
White coloured wires discolour
Destroyed by oral enzymes
Def...
2. Stiffness / Load deflection Rate
Proffit: - slope of stress-strain curve
Thurow - force:distance ratio, measure of
resi...
Stiffness / Load deflection Rate
Magnitude of the force delivered by the appliance
for a particular amount of deflection.
...
3 point bending test

www.indiandentalacademy.com
3. Strength
Yield strength, proportional limit and ultimate
tensile/compressive strength
Kusy - force required to activate...
Strength
The shape and cross section of a wire
have an effect on the strength of the wire.
The effects of these will be co...
4. Range
Distance that the wire bends elastically,
before permanent deformation occurs
(Proffit).
Kusy – Distance to which...
5. Springback
Kusy -- The extent to which a wire
recovers its shape after deactivation
Ingram et al – a measure of how far...
5. Springback
Large springback
Activated to a large extent.
Hence it will mean fewer archwire
changes.
Ratio – yield stren...
6. Formability
Kusy – the ease in which a material may
be permanently deformed.
Ease of forming a spring or archwire
Proff...
7. Resiliency
Store/absorb more strain energy /unit
volume before they get permanently
deformed
Greater resistance to perm...
8. Coefficient of friction
Brackets (and teeth) must be able to slide
along the wire
High amounts of friction  anchor los...
9. Biohostability:- site for accumulation of
bacteria, spores or viruses. An ideal
archwire must have poor biohostability....
Properties of Wires
Before the titanium alloys were
introduced into orthodontics, the
practitioners used only steel wires....
Effects of Wire Cross Section
Wires of various dimensions and cross
sections.
Does the wire need to be move teeth over
lar...
Effects of Wire Cross Section
primary factor 
load deflection rate or stiffness
play of the wire
in the second order –
0....
Effects of Wire Cross Section
Based on stiffness/load deflection rate

Force delivered by a wire with high load deflection...
Effects of Wire Cross Section

Force delivered by a wire with low load deflection rate

Force delivered by a wire with low...
Load deflection rate
Shape

Moment Ratio to stiffness of
of Inertia round wire
Пd4
64
s4
12
b3h
12

1
1.7
1.7 b3h:d4
www.i...
Effects of Wire Cross Section
Dimension of wire increases- LDR
increases
Round and square wire of same
dimension-LDR of sq...
Effects of Wire Cross Section
Stiffness of different dimensions of wires
can be related to each other.
Relative stiffness
...
Effects of Wire Cross Section
Rectangular wires  bending perpendicular to
the larger dimension (ribbon mode)
easier than ...
Effects of Wire Cross Section
The larger dimension  correction is needed.
The smaller dimension  the plane in which
more...
Effects of Wire Cross Section
> 1st order correction in anterior segment
> 2nd order in the posterior segment,
wire can be...
Effects of Wire Cross Section
Cross-sectional shape:


On range and strength
 Diameter increases-strength third power
of...
Effects of Wire Cross Section
In torsion - absolute values of strength,
stiffness and range are different,
but the overall...
Effects of Length
Loops,
 the inter-bracket distance

1.
2.
3.

For bending
Strength – decreases proportionately
Stiffnes...
Effects of Length
In the case of torsion, the picture is
slightly different. Increase in length: –
1. Stiffness decreases ...
Effects of Length
Way the beam is attached also affects the
values
cantilever, the stiffness of a wire is
obviously less
w...
Effects of Length

Cantilever

Beam supported on both ends

www.indiandentalacademy.com

Fixed at both ends
Effects of Length
Stiffness is also affected by the method of
ligation of the wire into the brackets.
Loosely ligated, so ...
Clinical Implications
LIGHT CONTINUOUS FORCES
Stiff wires should be taboo to the
orthodontist?
Springier wire, can be easi...
Clinical Implications
Removable appliance cantilever spring
The material of choice is usually steel. (Stiff
material)
Suf...
Clinical Implications
In archwires of stiffer materials the same
principle can be used.
The length of wire between bracket...
Variable cross-section orthodontics.

Variable modulus orthodontics.

www.indiandentalacademy.com
Clinical Implications
NiTi – high springback
Initial stages – NiTi instead of steel
Towards the end- stiff steel wire
TMA ...
Clinical Implications
variable modulus orthodontics –
Advantage


relatively constant dimension
important for the third ...
Clinical Implications

Requirements of arch wires in different stages of
www.indiandentalacademy.com
treatment
Appropriate
wire

Take into account the amount of force that wire
can deliver.
For example, a NiTi wire  efficient in tip...
Nomograms

www.indiandentalacademy.com
Nomograms

www.indiandentalacademy.com
A rough idea can be obtained clinically as well
Forming an arch wire with the thumb gives
an indication of the stiffness o...
Corrosion
Nickel 1. Carcinogenic,
2. mutagenic,
3. cytotoxic and
4. allergenic.
 Stainless steels, Co-Cr-Ni alloys and Ni...
Corrosion
Placement in the oral cavity

Greater peril than implanting

Implanted material gets surrounded by a
connectiv...
Corrosion
Stainless steel- Ni austenite stabilizer. Not
strongly bonded- slow release
Passivating film  traces of Fe ,Ni ...
Corrosion
1. Uniform attack –
the entire wire reacts with the
environment,
hydroxides or organometallic compounds
detectab...
Corrosion
Pitting corrosion

Stainless Steel

NiTi

www.indiandentalacademy.com
Corrosion
3. Crevice corrosion or gasket corrosion Parts of the wire exposed to corrosive
environment
Sites of tying to th...
Corrosion
4. Galvanic /Electrochemical Corrosion
two metals are joined
or even the same metal after different type of
trea...
Corrosion
Anodic

Looses Electrons

Soluble ions

Leach out

Cathodic (nobel)

Accepts electrons

Even less reactive
...
Corrosion
5. Intergranular corrosion
Sensitization - ppt of CrC
6. Fretting corrosion
Wire and brackets contact
Friction ...
Corrosion
7. Microbiologically influenced corrosion
Adhesive
Craters at the base of brackets
Or wires directly bonded on t...
Micro-0rganisms on various dental
materials

www.indiandentalacademy.com
Corrosion
8. Stress corrosion
Similar to galvanic corrosion
Bending of wires  different degress of
tension and compressio...
Corrosion
9. Corrosion Fatigue:
Cyclic stressing of a wire
Resistance to fracture decreases
Accelerated in a corrosive med...
Corrosion
Analysis of used wires also indicated that a
biofilm was formed on the wire.
Eliades et al
Calcification


Shie...
OrthOdOntic Arch Wire
MAteriAls

www.indiandentalacademy.com
Precious Metals
Upto about the 1950s
Gold alloys
Only wire which would tolerate the oral
environment
Crozat appliance – ac...
Stainless Steel
1919 – Germany  used to make
prostheses.
Extremely chemically stable
High resistance to corrosion.
Chromi...
Stainless Steel
Variety of stainless steels
Varying the degree of cold
work and annealing during
manufacture
Fully anneale...
Stainless Steel
stainless steel arch wires are cold worked
to varying extents,  yield strength
increases, at the cost of ...
Stainless Steel
Structure and composition
Chromium (11-26%)–improves the corrosion
resistance
Stabilizes BCC phase

Nickel...
Stainless Steel
Carbon (0.08-1.2%)– provides strength
Reduces the corrosion resistance
Sensitization.
During soldering or ...
Stainless Steel
Chromium carbides
Amount of chromium decreases
Chromium carbide is soluble, 
intergranular corrosion.
Sta...
Stainless Steel
Stabilization –







Element which precipitates carbide more
easily than Chromium.
Usu. Titanium.
T...
Stainless Steel
Silicon – (low concentrations) improves the
resistance to oxidation and carburization at high
temperatures...
MANUFACTURE
Manufacture: AISI ,specially for orthodontic purposes
Various steps –
1. Melting
2. Ingot Formation
3. Rolling...
steps
Melting



Various metals of the alloy are melted
Proportion influences the properties

Ingot formation





M...
Ingot formation


Porosities due to dissolved gases (produced /
trapped)



Vacuum voids due to shrinking of late coolin...
steps
Rolling –


First mechanical process.



Ingot reduced to thinner bars



Finally form a wire



Different wires...
Rolling


Retain their property even after rolling



Shape & arrangement altered



Grains get elongated, defects get ...
steps
Drawing


More precise



Ingot  final size.



Wire pulled through small hole in a die



Progressively smalle...
Drawing


Series of dies



Annealing at regular intervals.



Exact number of drafts and annealing cycles
depends on t...
Stress relief
During manufacture, wire highly stressed.
Adverse effects on mechanical properties
Annealing heat treatment
...
Clinical implications
Soldering attachments to arch wire:






Raise in temp----wire dead
Quick and well controlled.
...
Stainless Steel
Classification
American Iron and Steel Institute (AISI)
Unified Number System (UNS)
German Standards (DIN)...
Stainless Steel
The AISI numbers used for stainless steel range
from 300 to 502
Numbers beginning with 3 are all austeniti...
Stainless Steel
Austenitic steels (the 300 series)
Better corrosion resistance -attachments
FCC structure  non ferromagne...
Stainless Steel
Martensitic steel
FCC  BCC
BCC structure is highly stressed.
More grain boundaries,



Stronger
Less co...
Stainless Steel
Ferritic steels – (the 400 series)
Good corrosion resistance
Low strength.
Not hardenable by heat treatmen...
Stainless Steel
Austenitic steels more preferable :Greater ductility and ability to undergo more cold
work without breakin...
Stainless Steel
Duplex steels
Both austenite and ferrite grains
Increased toughness and ductility than
Ferritic steels
Twi...
Stainless steel
Precipitation hardened steels
Certain elements added to them 
precipitate and increase the hardness on
he...
General properties of Stainless
Steel
Relatively stiff material
Yield strength and stiffness can be varied


Altering the...
Stainless Steel
Clinical terms:Loop - activated to a very small extent so
as to achieve optimal force
Deactivated by only ...
Stainless Steel
Force required to engage a steel wire into
a severely mal-aligned tooth.


Either cause the bracket to po...
Stainless Steel
High stiffness 
Maintain the positions of teeth
Hold the corrections achieved
Begg treatment, stiff archw...
Stainless Steel
Lowest frictional resistance
Ideal choice of wire during space closure
with sliding mechanics
Teeth be hel...
High Tensile Australian Wires
History
Early part of Dr. Begg’s career
Arthur Wilcock Sr.


Lock pins, brackets, bands, wi...
High Tensile Australian Wires
Beginners found it difficult to use the
highest tensile wires
Grading system
Late 1950s, the...
High Tensile Australian Wires
Newer grades were introduced after the 70s.
Premium, premium +, supreme
Raw materials direct...
High Tensile Australian Wires
Bauschinger effect.
Described by Dr. Bauschinger in 1886.
Material strained beyond its yield...
High Tensile Australian Wires

www.indiandentalacademy.com
High Tensile Australian Wires
1. Plastic prestrain increases the elastic limit of
deformation in the same direction as the...
High Tensile Australian Wires
Straightening a wire  pulling through a
series of rollers
Prestrain in a particular directi...
Spinner straightening
It is mechanical process of straightening
resistant materials in the cold drawn
condition.
The wire ...
Pulse straightening
Special method
Placed in special machines that permits
high tensile wires to be straightened.
Advantag...
High Tensile Australian Wires
Methods of increasing yield strength of
Australian wires.

1. Work hardening
2. Dislocation ...
By alternate sequence of
cold working and heat
treatment the yield point
of wire can be increased
to as much as
200tons/sq...
High Tensile Australian Wires
Higher yield strength 
more flexible.
Supreme grade
flexibility = βtitanium.
Higher resili...
High Tensile Australian Wires
Mollenhauer 
Supreme grade wire  faster and gentler
alignment of teeth.
Intrusion  simult...
High Tensile Australian Wires
Clinical significance of high yield strength
1. Increased working range:
Yield strength
modu...
High Tensile Australian Wires
3. Zero Stress Relaxation
If a wire is deformed and held in a fixed position, the
stress in ...
High Tensile Australian Wires
external forces

particles slip over each other

activation of the wire is lost
Overcome

...
High Tensile Australian Wires
Zero stress relaxation in springs.
To avoid relaxation in the wire’s working
stress
Diameter...
High Tensile Australian Wires
Twelftree, Cocks and Sims (AJO 1977)
Premium plus, Premium and Special plus
wires showed min...
High Tensile Australian Wires
Hazel, Rohan & West (1984)


Stress relaxation of Special plus wires after 28
days was less...
High Tensile Australian Wires
Pulse straightened wires – Spinner
straightened wires
(Skaria 1991)


Strength, stiffness a...
High Tensile Australian Wires
A study of the metallurgical properties of newly
introduced high tensile wires in comparison...
High Tensile Australian Wires
Highest yield strength and ultimate tensile
strength as compared to the corresponding
wires....
Clinical implications
Stage I:
1.
Wilcock (P) / S+
base wire(.014”)
2.
Ortho organizers (super +)

Wilcock (P) & S+; T.P....
High Tensile Australian Wires
Dislocation locking

High tensile wires have high density of
dislocations and crystal defec...
High Tensile Australian Wires
Small stress applied with the plier beaks

Crack propagation

Elastic energy is released
...
High Tensile Australian Wires
Ways of preventing fracture
1. Bending the wire around the flat beak of
the pliers.
Introduc...
High Tensile Australian Wires

www.indiandentalacademy.com
High Tensile Australian Wires
2. The wire should not be held tightly in the
beaks of the pliers.
Area of permanent deforma...
High Tensile Australian Wires

www.indiandentalacademy.com
High Tensile Australian Wires
3. The edges rounded  reduce the stress
concentration in the wire.
4. Ductile – brittle tra...
Multistranded Wires
2 or more wires of smaller diameter are
twisted together/coiled around a core wire.
Diameter - 0.0165 ...
Multi stranded wires
Co-axial

Twisted wire

www.indiandentalacademy.com

Multi braided
Multi stranded wires
Strength – resist distortion
Separate strands - .007” but final wire can
be either round / rectangula...
Multistranded Wires
As the diameter of a wire decreases –
Stiffness – decreases as a function of the 4 th
power
Range – in...
Multistranded Wires
Elastic properties of multistranded archwires
depend on –
1. Material parameters – Modulus of elastici...
Multistranded Wires
Deflection of
multi stranded wire= KPL3
knEI
K – load/support constant
P – applied force
L – length of...
Multistranded Wires
Helical spring shape factor
Coils resemble the shape of a helical spring.
The helical spring shape fac...
Multistranded Wires

www.indiandentalacademy.com
Multistranded Wires
Kusy ( AJO-DO 1984)
Compared the elastic properties of triple
stranded S.Steel wire with S.Steel, NiTi...
Results

Results

www.indiandentalacademy.com
Results

www.indiandentalacademy.com
Results
0.0175” S.Steel wire had stiffness equal to
0.016”NiTi & 40% of 0.016”TMA
Did not resemble the 0.018” SS wire exce...
Multistranded Wires
Ingram, Gipe and Smith (AJO 86)
Range of 4 diff wires
Results: NiTi>MS S.Steel>CoCr>Steel

www.indiand...
Multistranded Wires
Nanda et al (AO 97)
…. stiffness
Increase in No. of
strands  stiffness

www.indiandentalacademy.com
Multistranded Wires
Kusy (AJO-DO 2002)
Interaction between individual strands was
negligible.
Range and strength Triple s...
Multistranded Wires

www.indiandentalacademy.com
Welding of Steel
3 useful properties –
1. Comparatively low melting point,
2. High electrical resistance and
3. Low conduc...
Welding of Steel
Important to


minimize the time of passing the current



minimize the area of heating

Sensitization ...
Welding of Steel
Join two thin sheets of metal
Same thickness
Joining tubes, wires and springs, soldering
is generally rec...
Cobalt Chromium
1950s the Elgin Watch
Rocky Mountain Orthodontics
Elgiloy
CoCr alloys - stellite alloys


superior resist...
Cobalt Chromium
Cobalt – 40-45%
Chromium – 15-22%
Nickel – for strength and ductility
Iron, molybdenum, tungsten and titan...
Cobalt Chromium
Strength and formability modified by heat
treatment.
The alloy is highly formable, and can be
easily shape...
Cobalt Chromium

www.indiandentalacademy.com
Cobalt Chromium
Heat treated at 482oc for 7 to 12 mins
Precipitation hardening


 ultimate tensile strength of the alloy...
Cobalt Chromium

www.indiandentalacademy.com
Cobalt Chromium
Blue – soft
Yellow – ductile
Green – semiresilient
Red – resilient

www.indiandentalacademy.com
Cobalt Chromium
Blue considerable bending, soldering or
welding
Red  most resilient and best used for
springs



diffi...
Cobalt Chromium
After heat treatment 
Blue and yellow ≡ normal steel wire
Green and red tempers ≡ higher grade
steel

www...
Cobalt Chromium
Heating above 650oC


partial annealing, and softening of the wire

Optimum heat treatment  dark straw c...
Cobalt Chromium
Properties of Co-Cr are very similar to that
of stainless steel.
Force


2x of β titanium and



4 times...
Cobalt Chromium
Frank and Nikolai (1980)


Co-Cr alloys ≡ stainless steel.

Stannard et al (AJO 1986)


Co-Cr highest fr...
Cobalt Chromium
Ingram ,Gipe and Smith (AJO 86)
Non heat treated Co-Cr


Range < stainless steel of comparable sizes

But...
Cobalt Chromium
Kusy et al (AJO
2001)
The elastic
modulus did not
vary appreciably 
edgewise or
ribbon-wise
configuration...
Cobalt Chromium
Round wires 
higher ductility than
square or
rectangular wires.

www.indiandentalacademy.com
Cobalt Chromium
The modulus of
elasticity 4 diff
tempers of 0.016”
elgiloy is almost
similar

www.indiandentalacademy.com
Cobalt Chromium
Elastic properties (yield strength and ultimate
tensile strength and ductility) were quite
similar for dif...
Cobalt Chromium

www.indiandentalacademy.com
Cobalt Chromium
Different tempers with different physical
properties – attractive
More care taken during the manufacture
o...
References
A study of the metallurgical properties of newly
introduced high tensile wires in comparison to
the high tensil...
References
Stannard, Gau, Hanna. Comparative friction of
orthodontic wires under dry and wet conditions.
AJO 86;89:485-491...
References
Kusy and Dilley. Elastic property ratios of a triple
stranded stainless steel archwire. AJO
84;86:177-188
Arthu...
Thank you
For more details please visit
www.indiandentalacademy.com

www.indiandentalacademy.com
Upcoming SlideShare
Loading in …5
×

Properties of orthodontic wires /certified fixed orthodontic courses by Indian dental academy

500 views
422 views

Published on


The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
500
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
6
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide
  • Lattice- arrangements of points in a regular periodic pattern2D or 3D manner
  • Grain boundaries interfere with the movement of atoms found on slip planes, thereby increasing the strength
  • Monoclinic and closed hexagonal lattice
  • Secondary electron images of as-received wires. Excessively porous surfaces with a high susceptibility to pitting corrosion attributed to manufacturing defects.
  • Thurow emphasized on the need to understand the phy and mech behaviour of various wires in orthodontics-he has described the manufacturing process as follows:
  • Compare
  • Writing system using picture symbols used in ancient egyt
  • They do not follow the regular order according to their temper in an expected manner but they are scattered hapazardly
  • Properties of orthodontic wires /certified fixed orthodontic courses by Indian dental academy

    1. 1. Properties of Orthodontic Wires Part I INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
    2. 2. Introduction Moving teeth and craniofacial harmony Forces and moments Wires Light continuous forces www.indiandentalacademy.com
    3. 3. History 1. Material Scarcity, Abundance of Ideas (1750-1930) noble metals Gold, platinum, iridium and silver alloys good corrosion resistance acceptable esthetics lacked the flexibility and tensile strength www.indiandentalacademy.com
    4. 4. History Angle (1887)  German silver (a type of brass) Opposition Farrar – discolored Neusilber brass (Cu 65%, Ni 14%, Zn 21%) various degrees of cold work (diff prop)    jack screws, expansion arches, Bands www.indiandentalacademy.com
    5. 5. History Wood, rubber, vulcanite, piano wire and silk thread No restrictions. www.indiandentalacademy.com
    6. 6. History Stainless steel (entered dentistry -1920) Stahl and Eisen – Benno Strauss & Eduard Maurer in 1914 By 1920 – Dr. F Hauptmeyer. Simon, schwarz, Korkhous, De Costerorthodontic material Replaced Opposition  Emil Herbst  gold wire was stronger than stainless steel. (1934) Steel as ligature wire www.indiandentalacademy.com
    7. 7. History 2. Abundance of materials, Refinement of Procedures (1930 – 1975)  Improvement in metallurgy and organic chemistry – mass production(1960)  Farrar’s dream(1878) Cobalt chrome (1950s)-Elgin watch co Rocky Mountain Orthodontics- Elgiloy Nitinol (1970s)- Buehler, into orthodontics- Andreasen. Unitek www.indiandentalacademy.com
    8. 8. History 3. The beginning of Selectivity (1975 to the present) Orthodontic manufacturers Beta titanium (1980) CAD/CAM – larger production runs Composites and Ceramics Iatrogenic damage  Nickel and bis-GMA New products- control of govt agencies, pri organization www.indiandentalacademy.com
    9. 9. Basic Properties of Materials Elements –all particles identical  Atoms-smallest Electrons – orbits around nucleus Floating in shells of diff energy levels Electrons form the basis of bonds Atoms interact via electrons In metals, the energy levels are very closely spaced and the electrons tend to belong to the entire assembly rather than a single atom. www.indiandentalacademy.com
    10. 10. Basic Properties of Materials Array of positive ions in a “sea of electrons” Electrons free to move electrical and thermal conductivity Ductility and malleability electrons adjust to deformation www.indiandentalacademy.com
    11. 11. Basic Properties of Materials Molecules – 2 or more atoms Amorphous – similar properties in all directions – isotropy  Glass atoms organize themselves into specific lattices  geometry CRYSTAL  anisotropy www.indiandentalacademy.com
    12. 12. Basic Properties of Materials CRYSTALS Perfect crystals: anion – cation –anion – cation extremely strong Thin wiskers reinforce If like ions are forced together, breakage results. Unlike metals, crystals cannot deform. www.indiandentalacademy.com
    13. 13. Basic Properties of Materials alloy crystals grow anion – cation –anion – cation Perfect crystals seldom exist Crystals penetrate each other such that the crystal shapes get deformed and cannot be discerned grains www.indiandentalacademy.com
    14. 14. Basic Properties of Materials Grains  microns to centimeters Grain boundaries Atoms are irregularly arranged, and this leads to a weaker amorphous type structure. Alloy  combination of crystalline (grains) and amorphous (grain boundaries) Decreased mechanical strength and reduced corrosion resistance www.indiandentalacademy.com
    15. 15. Basic Properties of Materials Stages in the formation of metallic grains during the solidification of a molten metal Polycrystalline- each crystal - grain www.indiandentalacademy.com
    16. 16. Basic Properties of Materials Vacancies – These are empty atom sites www.indiandentalacademy.com
    17. 17. Interstitials – Smaller atoms that penetrate the lattice Eg – Carbon, Hydrogen, Oxygen, Boron. Often distort the metal structure www.indiandentalacademy.com
    18. 18. Basic Properties of Materials Substitutial Element – another metal atom can substitute one of the same or similar size. E.g. Nickel or Chromium substituting iron in stainless steel. www.indiandentalacademy.com
    19. 19. Imperfections- although they lower the cleavage strength of the metal , increase its resistance to deformation www.indiandentalacademy.com
    20. 20. LATTICE The three dimensional arrangement of lines that can be visualized as connecting the atoms in undisrupted crystals, is called a lattice. Unit cell Crystal  combination of unit cells, in which each cell shares faces, edges or corners with the neighboring cells 14 crystal lattices www.indiandentalacademy.com
    21. 21. Basic Properties of Materials www.indiandentalacademy.com
    22. 22. Basic Properties of Materials The atoms, which are represented as points, are not static. Instead, they oscillate about that point and are in dynamic equilibrium. www.indiandentalacademy.com
    23. 23. Lattice deformations: various defects  slip planes-along which dislocation occurs www.indiandentalacademy.com
    24. 24. Basic Properties of Materials shear stress  atoms of the crystals can glide along these planes more the slip planes easier is it to deform Slip planes intercepted at grain boundaries-increases the resistance to further deformation www.indiandentalacademy.com
    25. 25. Basic Properties of Materials If the shearing force is:Small - atoms slip, and return back to their original position (elastic deformation) Beyond the elastic limit crystal suffers a slight deformation permanent (plastic deformation) Greater stress - fracture www.indiandentalacademy.com
    26. 26. Basic Properties of Materials During deformation - atomic bonds within the crystal get stressed  resistance to more deformation Number of atoms that get stressed also increases  resistance to more deformation Strain or work hardening or cold work www.indiandentalacademy.com
    27. 27. Work hardening Forced interlocking of grains and atoms of metal. Locked in and under pressure/tension Carried at room temperature. www.indiandentalacademy.com
    28. 28. Basic Properties of Materials Strain hardening- principle  Hard and strong, tensile strength Brittle. Annealing – heat below melting point.    More the cold work, more rapid the annealing Higher melting point – higher annealing temp. ½ the melting temperature (oK) www.indiandentalacademy.com
    29. 29. Basic Properties of Materials ANNEALING: Recovery Recrystallization Grain Growth www.indiandentalacademy.com
    30. 30. Basic Properties of Materials www.indiandentalacademy.com
    31. 31. 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 www.indiandentalacademy.com
    32. 32. Annealing Smaller grains – harder and stronger Larger grain boundaries to oppose the slip planes. www.indiandentalacademy.com
    33. 33. Basic Properties of Materials Various methods of obtaining smaller grain size 1. Enhancing crystal nucleation by adding fine particles with a higher melting point, around which the atoms gather. 2. Preventing enlargement of existing grains. Abrupt cooling (quenching) of the metal. Dissolve specific elements at elevated temperatures. Metal is cooled Solute element precipitates barriers to the slip planes. www.indiandentalacademy.com
    34. 34. Solution heat treatment Heat below the solidus temp Held for sometime, - random solid soln Cool rapidly to room temp. retained. Soft and ductile AGE HARDENING Below : ordered structure Time period Stronger, harder but less ductile. www.indiandentalacademy.com
    35. 35. Basic Properties of Materials Twinning Closed packed hexagonal type of crystals Two symmetric halves Fixed angle NiTi - multiple Subjected to a higher temperature, de - twinning occurs (shape memory) www.indiandentalacademy.com
    36. 36. Basic Properties of Materials www.indiandentalacademy.com
    37. 37. Basic Properties of Materials Polymorphism Metals and alloys exist as more than one type of structure Transition from one to the other Allotropy - reversible At higher temperature, iron FCC structure (austenite) lower temperatures,  BCC structure (ferrite) www.indiandentalacademy.com
    38. 38. Transition of Iron Iron  FCC stable (austenite), 912*c1394*c Lattice spaces greater, Carbon atom can easily be incorporated into the unit cell www.indiandentalacademy.com
    39. 39. Transition of Iron On Cooling <912*c FCC  BCC Carbon diffuses out as FeC FeC adds strength to ferrite and austenite TIME www.indiandentalacademy.com
    40. 40. Transition of Iron Rapidly cooled (quenched)  Carbon cannot escape Highly strained, distorted body centered tetragonal lattice called martensite www.indiandentalacademy.com
    41. 41. Basic Properties of Materials Grain boundaries are more in number Alloy is stronger and more brittlemartensitic change – various types of steel Interstitials are intentionally incorporated into the alloy to make it hard when it is quenched. www.indiandentalacademy.com
    42. 42. Basic Properties of Materials Cooled slowly Other crystal structures are formed at intermediate temperatures Softer Some are stable at room temperature Ultimately, the final structure is softer and more workable www.indiandentalacademy.com
    43. 43. Basic Properties of Materials Tempering – Reheat the alloy to intermediate temperature(1000*F/525*c) Partial transformation into softer alloys Remedy brittle martensite more workable www.indiandentalacademy.com
    44. 44. Basic Properties of Materials Some alloys FCC to BCC by rearrangement of atoms  Diagonal plane of the BCC unit becomes the face of the FCC unit www.indiandentalacademy.com
    45. 45. Shape memory alloys – Easy switching from one type of structure to another. Bain distortion Over a range of temperature {hysteresis} unlike iron www.indiandentalacademy.com
    46. 46. Elastic Properties Stress and strain Stress- internal distribution of load. F/A Strain- internal distortion produced by load deflection/unit length www.indiandentalacademy.com
    47. 47. Elastic Properties Force applied to wire Deflection Internal force---- (equal and opposite) Internal force = Stress Area of action Deflection change in length = Strain Original length www.indiandentalacademy.com
    48. 48. Elastic Properties Types of stress/strain Tensile –stretch/pull Compressive – compress/towards each other Shear – 2 forces opp direction, not in same line. sliding of one part over another Complex force systems www.indiandentalacademy.com
    49. 49. Elastic Properties Stress Wire returns back to original dimension when stress is removed Elastic Portion www.indiandentalacademy.com Strain
    50. 50. Elastic Properties Hooke’s law Spring stretch in proportion to applied force (proportional limit) Modulus of elasticity – constant for a given material www.indiandentalacademy.com
    51. 51. Elastic Properties Stress Yield strength 0.1% Proportional Limit Elastic Limit www.indiandentalacademy.com Strain
    52. 52. Stress Elastic Properties Ultimate Tensile Strength www.indiandentalacademy.com Fracture Point Strain
    53. 53. Elastic Properties ultimate tensile strength is higher than the yield strength important clinically  maximum force that the wire can deliver Ultimate tensile strength higher than the stress at the point of fracture  reduction in the diameter of the wire www.indiandentalacademy.com
    54. 54. Stress Elastic Properties Slope α Stiffness Stiffness α 1 . Springiness www.indiandentalacademy.com Strain
    55. 55. Elastic Properties Stress Point of arbitrary clinical loading Yield point Range Springback www.indiandentalacademy.com Strain
    56. 56. Elastic Properties Clinically, ortho wires are deformed beyond their elastic limit. Springback properties are important Strength = Stiffness x Range www.indiandentalacademy.com
    57. 57. Elastic Properties Resiliency When a wire is stretched, the space between the atoms increases. Within the elastic limit, there is an attractive force between the atoms. Energy stored within the wire. Strength + springiness www.indiandentalacademy.com
    58. 58. Stress Elastic Properties Yield strength Proportional limit Resilience Formability www.indiandentalacademy.com Strain
    59. 59. Elastic Properties Formability - amount of permanent deformation that the wire can withstand without breaking Indication of the ability of the wire to take the shape Also an indication of the amount of cold work that they can withstand www.indiandentalacademy.com
    60. 60. Elastic Properties Flexibility large deformation (or large strain) with minimal force, within its elastic limit. Maximal flexibility is the strain that occurs when a wire is stressed to its elastic limit. Max. flexibility = Proportional limit Modulus of elasticity. www.indiandentalacademy.com
    61. 61. Elastic 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. eg: Glass Fatigue – Repeated cyclic stress of a magnitude below the fracture point of a wire can result in fracture. This is called fatigue. www.indiandentalacademy.com
    62. 62. www.indiandentalacademy.com
    63. 63. Properties of Orthodontic Wires Part I Dr. Vijaya Lakshmi
    64. 64. Elastic Properties www.indiandentalacademy.com
    65. 65. Elastic Properties www.indiandentalacademy.com
    66. 66. Stress Elastic Properties Yield strength Proportional limit Resilience Formability www.indiandentalacademy.com Strain
    67. 67. Requirements of an ideal archwire (Kusy ) 1. Esthetics 7. Resiliency 2. Stiffness 8. Coefficient of friction 3. Strength 9. Biohostability 4. Range 10. Biocompatibility 5. Springback 11. Weldability 6. Formability www.indiandentalacademy.com
    68. 68. 1. Esthetics Desirable No compromise on mechanical properties White coloured wires discolour Destroyed by oral enzymes Deformed by masticatory loads Except the composite wires www.indiandentalacademy.com
    69. 69. 2. Stiffness / Load deflection Rate Proffit: - slope of stress-strain curve Thurow - force:distance ratio, measure of resistance to deformation. Burstone – Stiffness is related to – wire property & appliance design Wire property is related to – Material & cross section. Wilcock – Stiffness α Load www.indiandentalacademy.com
    70. 70. Stiffness / Load deflection Rate Magnitude of the force delivered by the appliance for a particular amount of deflection. Low stiffness or Low LDR implies that:1) Low forces will be applied 2) The force will be more constant as the appliance deactivates 3) Greater ease and accuracy in applying a given force. www.indiandentalacademy.com
    71. 71. 3 point bending test www.indiandentalacademy.com
    72. 72. 3. Strength Yield strength, proportional limit and ultimate tensile/compressive strength Kusy - force required to activate an archwire to a specific distance. Proffit - Strength = stiffness x range. Range limits the amount the wire can be bent, Stiffness is the indication of the force required to reach that limit. www.indiandentalacademy.com
    73. 73. Strength The shape and cross section of a wire have an effect on the strength of the wire. The effects of these will be considered subsequently. www.indiandentalacademy.com
    74. 74. 4. Range Distance that the wire bends elastically, before permanent deformation occurs (Proffit). Kusy – Distance to which an archwire can be activated- working range. Thurow – A linear measure of how far a wire or material can be deformed without exceeding the limits of the material. www.indiandentalacademy.com
    75. 75. 5. Springback Kusy -- The extent to which a wire recovers its shape after deactivation Ingram et al – a measure of how far a wire can be deflected without causing permanent deformation. (Contrast to Proffit yield point). www.indiandentalacademy.com
    76. 76. 5. Springback Large springback Activated to a large extent. Hence it will mean fewer archwire changes. Ratio – yield strength Modulus of elasticity www.indiandentalacademy.com
    77. 77. 6. Formability Kusy – the ease in which a material may be permanently deformed. Ease of forming a spring or archwire Proffit: amount of permanent deformation a wire can withstand without breaking www.indiandentalacademy.com
    78. 78. 7. Resiliency Store/absorb more strain energy /unit volume before they get permanently deformed Greater resistance to permanent deformation Release of greater amount of energy on deactivation High work availability to move the teeth www.indiandentalacademy.com
    79. 79. 8. Coefficient of friction Brackets (and teeth) must be able to slide along the wire High amounts of friction  anchor loss. www.indiandentalacademy.com
    80. 80. 9. Biohostability:- site for accumulation of bacteria, spores or viruses. An ideal archwire must have poor biohostability. 10.Biocompatibility:- Resistance of corrosion, and tissue tolerance to the wire. 11. Weldability:- the ease by which the wire can be joined to other metals, by actually melting the 2 metals in the area of the bond. (A filler metal may or may not be used.) www.indiandentalacademy.com
    81. 81. Properties of Wires Before the titanium alloys were introduced into orthodontics, the practitioners used only steel wires. So the way to control the stiffness of the wire was:1. Change the cross section of the wire 2. Increase the length of the wire (  inter bracket distance, incorporate loops.) www.indiandentalacademy.com
    82. 82. Effects of Wire Cross Section Wires of various dimensions and cross sections. Does the wire need to be move teeth over large distances, or does it need to correct the torque of the tooth? Is it primarily going to be used to correct first order irregularities, or second order? www.indiandentalacademy.com
    83. 83. Effects of Wire Cross Section primary factor  load deflection rate or stiffness play of the wire in the second order – 0.016” wire in 0.022” slot is only 1.15 times the play of a 0.018” wire. The play in the second order becomes significant if the wire dimensions are drastically different (0.010” and 0.020”) www.indiandentalacademy.com
    84. 84. Effects of Wire Cross Section Based on stiffness/load deflection rate Force delivered by a wire with high load deflection rate www.indiandentalacademy.com
    85. 85. Effects of Wire Cross Section Force delivered by a wire with low load deflection rate Force delivered by a wire with low load deflection rate www.indiandentalacademy.com
    86. 86. Load deflection rate Shape Moment Ratio to stiffness of of Inertia round wire Пd4 64 s4 12 b3h 12 1 1.7 1.7 b3h:d4 www.indiandentalacademy.com
    87. 87. Effects of Wire Cross Section Dimension of wire increases- LDR increases Round and square wire of same dimension-LDR of square wire is more. Rectangular wire – maximum stiffness www.indiandentalacademy.com
    88. 88. Effects of Wire Cross Section Stiffness of different dimensions of wires can be related to each other. Relative stiffness Stiffness number (Burstone) 3500 3000 2500 2000 1500 1000 500 0 14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 18x25 25x18 21x25 25x21 215x28 28x215 Wire dimension www.indiandentalacademy.com
    89. 89. Effects of Wire Cross Section Rectangular wires  bending perpendicular to the larger dimension (ribbon mode) easier than bending perpendicular to the smaller dimension (edgewise). Relative stiffness 3000 (Burstone ) Stiffne ss numbe r 3500 2500 2000 1500 1000 500 0 14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 Wire dime nsion www.indiandentalacademy.com 18x25 25x18 21x25 25x21 215x28 28x215
    90. 90. Effects of Wire Cross Section The larger dimension  correction is needed. The smaller dimension  the plane in which more stiffness is needed. > first order, < second order – RIBBON > Second order, < first order - EDGEWISE www.indiandentalacademy.com
    91. 91. Effects of Wire Cross Section > 1st order correction in anterior segment > 2nd order in the posterior segment, wire can be twisted 90o If both, 1st & 2nd order corrections are required to the same extent, then square or round wires. The square wires - advantage - simultaneously control torque better orientation into a rectangular slot. www.indiandentalacademy.com
    92. 92. Effects of Wire Cross Section Cross-sectional shape:  On range and strength  Diameter increases-strength third power of diameter  Range increases proportional to diameter www.indiandentalacademy.com
    93. 93. Effects of Wire Cross Section In torsion - absolute values of strength, stiffness and range are different, but the overall effect of changing the diameter of the wire is the same. 1. Strength – Increases with increase in diameter 2. Stiffness – increases 3. Range – decreases. www.indiandentalacademy.com
    94. 94. Effects of Length Loops,  the inter-bracket distance 1. 2. 3. For bending Strength – decreases proportionately Stiffness – decreases as a cubic function Range – increases as a square. www.indiandentalacademy.com
    95. 95. Effects of Length In the case of torsion, the picture is slightly different. Increase in length: – 1. Stiffness decreases proportionately 2. Range increases proportionately 3. Strength remains unchanged. www.indiandentalacademy.com
    96. 96. Effects of Length Way the beam is attached also affects the values cantilever, the stiffness of a wire is obviously less wire is supported from both sides (as an archwire in brackets), again, the stiffness is affected www.indiandentalacademy.com
    97. 97. Effects of Length Cantilever Beam supported on both ends www.indiandentalacademy.com Fixed at both ends
    98. 98. Effects of Length Stiffness is also affected by the method of ligation of the wire into the brackets. Loosely ligated, so that it can slide through the brackets, it has ¼th the stiffness of a wire that is tightly ligated. www.indiandentalacademy.com
    99. 99. Clinical Implications LIGHT CONTINUOUS FORCES Stiff wires should be taboo to the orthodontist? Springier wire, can be easily distorted in the harsh oral environment. Aim at balance. www.indiandentalacademy.com
    100. 100. Clinical Implications Removable appliance cantilever spring The material of choice is usually steel. (Stiff material) Sufficiently thick steel wire Good strength to resist masticatory and other oral forces. Increase the length of the wire   Proportionate decrease in strength, but the stiffness will decrease as a cubic function  Length is increased by either bending the wire over itself, or by winding helicals or loops into www.indiandentalacademy.com the spring
    101. 101. Clinical Implications In archwires of stiffer materials the same principle can be used. The length of wire between brackets can be increased  loops, or smaller brackets, or special bracket designs. Also, the use of flexible wires Multistranded wires www.indiandentalacademy.com
    102. 102. Variable cross-section orthodontics. Variable modulus orthodontics. www.indiandentalacademy.com
    103. 103. Clinical Implications NiTi – high springback Initial stages – NiTi instead of steel Towards the end- stiff steel wire TMA - intermediate properties- transition wire www.indiandentalacademy.com
    104. 104. Clinical Implications variable modulus orthodontics – Advantage  relatively constant dimension important for the third order control variable stiffness approach,   compromise control for getting a wire with adequate stiffness, had to spend clinical time bending loops into stiffer archwires, which would offer less play. www.indiandentalacademy.com
    105. 105. Clinical Implications Requirements of arch wires in different stages of www.indiandentalacademy.com treatment
    106. 106. Appropriate wire Take into account the amount of force that wire can deliver. For example, a NiTi wire  efficient in tipping teeth to get them into alignment, but may not be able to achieve third order corrections. After using rectangular NiTi wires for alignment, rectangular steel wire must always be used to achieve the correct torque of the tooth. www.indiandentalacademy.com
    107. 107. Nomograms www.indiandentalacademy.com
    108. 108. Nomograms www.indiandentalacademy.com
    109. 109. A rough idea can be obtained clinically as well Forming an arch wire with the thumb gives an indication of the stiffness of the wire. Flexing the wires between the fingers, without deforming it, is a measure of flexibility Deflecting the ends of an archwire between the thumb and finger gives a measure of resiliency. www.indiandentalacademy.com
    110. 110. Corrosion Nickel 1. Carcinogenic, 2. mutagenic, 3. cytotoxic and 4. allergenic.  Stainless steels, Co-Cr-Ni alloys and NiTi are all rich in Ni www.indiandentalacademy.com
    111. 111. Corrosion Placement in the oral cavity  Greater peril than implanting  Implanted material gets surrounded by a connective tissue capsule  In the oral cavity, the alloy is free to react with the environment. www.indiandentalacademy.com
    112. 112. Corrosion Stainless steel- Ni austenite stabilizer. Not strongly bonded- slow release Passivating film  traces of Fe ,Ni and Mo. Aqueous environment   inner oxide layer outer hydroxide layer. CrO is not as efficient as TiO in resisting corrosion some Ni release Improper handling  sensitization www.indiandentalacademy.com
    113. 113. Corrosion 1. Uniform attack – the entire wire reacts with the environment, hydroxides or organometallic compounds detectable after a large amount of metal is dissolved. 2. Pitting Corrosion – manufacturing defects sites of easy attack www.indiandentalacademy.com
    114. 114. Corrosion Pitting corrosion Stainless Steel NiTi www.indiandentalacademy.com
    115. 115. Corrosion 3. Crevice corrosion or gasket corrosion Parts of the wire exposed to corrosive environment Sites of tying to the brackets Plaque build up  disturbs the regeneration of the passivating layer Reach upto 2-5 mm High amount of metals can be dissolved in the mouth. www.indiandentalacademy.com
    116. 116. Corrosion 4. Galvanic /Electrochemical Corrosion two metals are joined or even the same metal after different type of treatment (soldering etc) difference in the reactivity  Galvanic cell.  Less Reactive (Cathodic)  More Reactive (Anodic) less noble metal www.indiandentalacademy.com
    117. 117. Corrosion Anodic  Looses Electrons  Soluble ions  Leach out Cathodic (nobel)  Accepts electrons  Even less reactive S.Steel- active and passive areas : depletion & regeneration of passivating film www.indiandentalacademy.com
    118. 118. Corrosion 5. Intergranular corrosion Sensitization - ppt of CrC 6. Fretting corrosion Wire and brackets contact Friction  surface destruction Pressure  rupture of the oxide layer Debris get deposited at grain boundaries, grain structure is disturbed. www.indiandentalacademy.com
    119. 119. Corrosion 7. Microbiologically influenced corrosion Adhesive Craters at the base of brackets Or wires directly bonded on to teeth shown by Matasa. Certain bacteria dissolve metals directly form the wires. Others affect surface structure. www.indiandentalacademy.com
    120. 120. Micro-0rganisms on various dental materials www.indiandentalacademy.com
    121. 121. Corrosion 8. Stress corrosion Similar to galvanic corrosion Bending of wires  different degress of tension and compression. Alter the electrochemical behavior   anode cathode www.indiandentalacademy.com
    122. 122. Corrosion 9. Corrosion Fatigue: Cyclic stressing of a wire Resistance to fracture decreases Accelerated in a corrosive medium such as saliva www.indiandentalacademy.com
    123. 123. Corrosion Analysis of used wires also indicated that a biofilm was formed on the wire. Eliades et al Calcification  Shielding the wire  Protecting the patient from the alloy Stainless steel: Fe, Ni, Cr. www.indiandentalacademy.com Allergic potential
    124. 124. OrthOdOntic Arch Wire MAteriAls www.indiandentalacademy.com
    125. 125. Precious Metals Upto about the 1950s Gold alloys Only wire which would tolerate the oral environment Crozat appliance – according to original design www.indiandentalacademy.com
    126. 126. Stainless Steel 1919 – Germany  used to make prostheses. Extremely chemically stable High resistance to corrosion. Chromium content. The chromium gets oxidized,  Impermeable, corrosion resistant layer. www.indiandentalacademy.com
    127. 127. Stainless Steel Variety of stainless steels Varying the degree of cold work and annealing during manufacture Fully annealed stainless steel  extremely soft, and highly formable Ligature wire “Dead soft” www.indiandentalacademy.com
    128. 128. Stainless Steel stainless steel arch wires are cold worked to varying extents,  yield strength increases, at the cost of their formability The steel with the highest yield strength, the Supreme grade steels, are also very brittle, and break easily when bent sharply. www.indiandentalacademy.com
    129. 129. Stainless Steel Structure and composition Chromium (11-26%)–improves the corrosion resistance Stabilizes BCC phase Nickel(0-22%) – austenitic stabilizer copper, manganese and nitrogen - similar  amount of nickel added to the alloy  adversely affect the corrosion resistance. www.indiandentalacademy.com
    130. 130. Stainless Steel Carbon (0.08-1.2%)– provides strength Reduces the corrosion resistance Sensitization. During soldering or welding, 425-815 oc Chromium diffuses towards the carbon rich areas (usually the grain boundaries) www.indiandentalacademy.com
    131. 131. Stainless Steel Chromium carbides Amount of chromium decreases Chromium carbide is soluble,  intergranular corrosion. Stabilization www.indiandentalacademy.com
    132. 132. Stainless Steel Stabilization –      Element which precipitates carbide more easily than Chromium. Usu. Titanium. Ti 6x> Carbon No sensitization during soldering. Most steels used in orthodontics are not stabilized. www.indiandentalacademy.com
    133. 133. Stainless Steel Silicon – (low concentrations) improves the resistance to oxidation and carburization at high temperatures. Sulfur (0.015%) increases ease of machining Phosphorous – allows sintering at lower temperatures. But both sulfur and phosphorous reduce the corrosion resistance. www.indiandentalacademy.com
    134. 134. MANUFACTURE Manufacture: AISI ,specially for orthodontic purposes Various steps – 1. Melting 2. Ingot Formation 3. Rolling 4. Drawing www.indiandentalacademy.com
    135. 135. steps Melting   Various metals of the alloy are melted Proportion influences the properties Ingot formation     Molten alloy into mold. Non uniform chunk of metal Porosities and slag. Grains seen in the ingot – control of mechanical properties www.indiandentalacademy.com
    136. 136. Ingot formation  Porosities due to dissolved gases (produced / trapped)  Vacuum voids due to shrinking of late cooling interior.  Important to control microstructure at this stage – basis of its phy properties and mechanical performance www.indiandentalacademy.com
    137. 137. steps Rolling –  First mechanical process.  Ingot reduced to thinner bars  Finally form a wire  Different wires from the same batch, differ in properties www.indiandentalacademy.com
    138. 138. Rolling  Retain their property even after rolling  Shape & arrangement altered  Grains get elongated, defects get rearranged  Work hardening – structure locked up.  Wires start to crack if rolling continued  Annealing is done- mobile  Cooling – structure resembles original ingot, uniform www.indiandentalacademy.com
    139. 139. steps Drawing  More precise  Ingot  final size.  Wire pulled through small hole in a die  Progressively smaller diameter-uniform squeezing.  Same pressure all around, instead of from 2 opposite sides. www.indiandentalacademy.com
    140. 140. Drawing  Series of dies  Annealing at regular intervals.  Exact number of drafts and annealing cycles depends on the alloy (gold <carbon steel<stainless steel) www.indiandentalacademy.com
    141. 141. Stress relief During manufacture, wire highly stressed. Adverse effects on mechanical properties Annealing heat treatment By minute slippages & readjustments in intergranular relations without the loss of hardening higher temp of annealing Alternate sequence of cold working & heat treatment—improve strength www.indiandentalacademy.com
    142. 142. Clinical implications Soldering attachments to arch wire:     Raise in temp----wire dead Quick and well controlled. Cinch back, heat Wire # www.indiandentalacademy.com
    143. 143. Stainless Steel Classification American Iron and Steel Institute (AISI) Unified Number System (UNS) German Standards (DIN). www.indiandentalacademy.com
    144. 144. Stainless Steel The AISI numbers used for stainless steel range from 300 to 502 Numbers beginning with 3 are all austenitic Higher the number   More the iron content  More expensive the alloy  Numbers having a letter L signify a low carbon content www.indiandentalacademy.com
    145. 145. Stainless Steel Austenitic steels (the 300 series) Better corrosion resistance -attachments FCC structure  non ferromagnetic Not stable at room temperature, Austenite stabilizers Ni, Mn and N Known as the 18-8 stainless steels . www.indiandentalacademy.com
    146. 146. Stainless Steel Martensitic steel FCC  BCC BCC structure is highly stressed. More grain boundaries,   Stronger Less corrosion resistant Making instrument edges which need to be sharp and wear resistant. www.indiandentalacademy.com
    147. 147. Stainless Steel Ferritic steels – (the 400 series) Good corrosion resistance Low strength. Not hardenable by heat treatment. Not readily cold worked. www.indiandentalacademy.com
    148. 148. Stainless Steel Austenitic steels more preferable :Greater ductility and ability to undergo more cold work without breaking. Substantial strengthening during cold work. (Cannot be strengthened by heat treatment). Strengthening effect is due partial conversion to martensite. Easy to weld Easily overcome sensitization Ease in forming. www.indiandentalacademy.com
    149. 149. Stainless Steel Duplex steels Both austenite and ferrite grains Increased toughness and ductility than Ferritic steels Twice the yield strength of austenitic steels Lower nickel content Manufacturing low nickel attachments www.indiandentalacademy.com
    150. 150. Stainless steel Precipitation hardened steels Certain elements added to them  precipitate and increase the hardness on heat treatment. The strength is very high Resistance to corrosion is low. Used to make mini-brackets. www.indiandentalacademy.com
    151. 151. General properties of Stainless Steel Relatively stiff material Yield strength and stiffness can be varied  Altering the carbon content and  Cold working and  Annealing High forces - dissipate over a very short amount of deactivation (high load deflection rate). www.indiandentalacademy.com
    152. 152. Stainless Steel Clinical terms:Loop - activated to a very small extent so as to achieve optimal force Deactivated by only a small amount (0.1 mm) Force level will drop tremendously Not physiologic More activations www.indiandentalacademy.com
    153. 153. Stainless Steel Force required to engage a steel wire into a severely mal-aligned tooth.  Either cause the bracket to pop out,  Or the patient to experience pain. Overcome by using thinner wires, which have a lower stiffness. Fit poorly loss of control on the teeth. www.indiandentalacademy.com
    154. 154. Stainless Steel High stiffness  Maintain the positions of teeth Hold the corrections achieved Begg treatment, stiff archwire, to dissipate the adverse effects of third stage auxiliaries www.indiandentalacademy.com
    155. 155. Stainless Steel Lowest frictional resistance Ideal choice of wire during space closure with sliding mechanics Teeth be held in their corrected relation Minimum resistance to sliding www.indiandentalacademy.com
    156. 156. High Tensile Australian Wires History Early part of Dr. Begg’s career Arthur Wilcock Sr.  Lock pins, brackets, bands, wires, etc Wires which would remain active for long No frequent visits This lead Wilcock to develop steel wires of high tensile strength. www.indiandentalacademy.com
    157. 157. High Tensile Australian Wires Beginners found it difficult to use the highest tensile wires Grading system Late 1950s, the grades available were –  Regular  Regular plus  Special  Special plus www.indiandentalacademy.com
    158. 158. High Tensile Australian Wires Newer grades were introduced after the 70s. Premium, premium +, supreme Raw materials directly from the suppliers from out of Australia More specific ordering and obtaining better raw materials Premium grade-high tensile strength Brittle. Softening , loss of high tensile properties www.indiandentalacademy.com
    159. 159. High Tensile Australian Wires Bauschinger effect. Described by Dr. Bauschinger in 1886. Material strained beyond its yield point in one direction, then strained in the reverse direction , its yield strength in the reverse direction is reduced. www.indiandentalacademy.com
    160. 160. High Tensile Australian Wires www.indiandentalacademy.com
    161. 161. High Tensile Australian Wires 1. Plastic prestrain increases the elastic limit of deformation in the same direction as the prestrain. 2. Decreases in opposite If the magnitude of the prestrain is increased, the elastic limit in the reverse direction can reduce to zero. www.indiandentalacademy.com
    162. 162. High Tensile Australian Wires Straightening a wire  pulling through a series of rollers Prestrain in a particular direction. Yield strength for bending in the opposite direction will decrease. Premium wire  special plus or special wire www.indiandentalacademy.com
    163. 163. Spinner straightening It is mechanical process of straightening resistant materials in the cold drawn condition. The wire is pulled through rotating bronze rollers that torsionally twist it into straight condition. Disadv: Decreases yield strength Creates rougher surface www.indiandentalacademy.com
    164. 164. Pulse straightening Special method Placed in special machines that permits high tensile wires to be straightened. Advantages: 1. 2. 3. Permits the straightening of high tensile wires Does not reduce the yield strength of the wire Results in a smoother wire, hence less wire – bracket friction. www.indiandentalacademy.com
    165. 165. High Tensile Australian Wires Methods of increasing yield strength of Australian wires. 1. Work hardening 2. Dislocation locking 3. Solid solution strengthening 4. Grain refinement and orientation www.indiandentalacademy.com
    166. 166. By alternate sequence of cold working and heat treatment the yield point of wire can be increased to as much as 200tons/sq inch as shown in this graph. www.indiandentalacademy.com
    167. 167. High Tensile Australian Wires Higher yield strength  more flexible. Supreme grade flexibility = βtitanium. Higher resiliency  nearly three times. NiTi  higher flexibility but it lacks formability www.indiandentalacademy.com
    168. 168. High Tensile Australian Wires Mollenhauer  Supreme grade wire  faster and gentler alignment of teeth. Intrusion  simultaneously with the base wires Gingival health seemed better Originally in lingual orthodontics Equally good for labial orthodontics as well. www.indiandentalacademy.com
    169. 169. High Tensile Australian Wires Clinical significance of high yield strength 1. Increased working range: Yield strength modulus of elasticity 2. Increased resiliency: ( yield strength)2 elastic modulus Stiffness remains the same www.indiandentalacademy.com
    170. 170. High Tensile Australian Wires 3. Zero Stress Relaxation If a wire is deformed and held in a fixed position, the stress in the wire may diminish with time, but the strain remains constant. Engineering terms, implies that a form of slip by dislocation movement takes place at the atomic level Property of a wire to give constant light force, when subjected to external forces (like occlusal forces). www.indiandentalacademy.com
    171. 171. High Tensile Australian Wires external forces  particles slip over each other  activation of the wire is lost Overcome   Internal friction Between particles  yield strength www.indiandentalacademy.com
    172. 172. High Tensile Australian Wires Zero stress relaxation in springs. To avoid relaxation in the wire’s working stress Diameter of coil : Diameter of wire = 4 smaller diameter of wires  smaller diameter springs (like the mini springs) Midi springs www.indiandentalacademy.com
    173. 173. High Tensile Australian Wires Twelftree, Cocks and Sims (AJO 1977) Premium plus, Premium and Special plus wires showed minimal stress relaxation. Special, Remanit, Yellow Elgiloy, Unisil. www.indiandentalacademy.com
    174. 174. High Tensile Australian Wires Hazel, Rohan & West (1984)  Stress relaxation of Special plus wires after 28 days was less than Dentaurum SS and Elgiloy wires. Barrowes (1982) & Jyothindra Kumar (1989)  Higher working range among steel wires. www.indiandentalacademy.com
    175. 175. High Tensile Australian Wires Pulse straightened wires – Spinner straightened wires (Skaria 1991)  Strength, stiffness and Range higher  Coeff. of friction higher  Similar surface topography, stress relaxation and Elemental makeup. www.indiandentalacademy.com
    176. 176. High Tensile Australian Wires A study of the metallurgical properties of newly introduced high tensile wires in comparison to the high tensile Australian wires for various applications in orthodontic treatment Dr. Anuradha Acharya (2000)  Super Plus (Ortho Organizers) – between Special plus and Premium  Premier (TP) – Comparable to Special  Premier Plus – Special Plus  Bowflex – Premium www.indiandentalacademy.com
    177. 177. High Tensile Australian Wires Highest yield strength and ultimate tensile strength as compared to the corresponding wires. Higher range Lesser coefficient of friction  Surface area seems to be rougher than that of the other manufacturers’ wires. Lowest stress relaxation. www.indiandentalacademy.com
    178. 178. Clinical implications Stage I: 1. Wilcock (P) / S+ base wire(.014”) 2. Ortho organizers (super +)  Wilcock (P) & S+; T.P. Bowflex .016”  Ortho organizers ( super +) T.P P+  Latter part of Stage I and most of Stage II 1. T.P (Premier), Wilcock P ,S+ .018” dia 2. Ortho Organizers (super +) T.P Bowflex  Base wires in Stage III , torquing auxiliaries, uprighting springs 1. Wilcock S+ / P .020” base wire  Wilcock P and Supreme in .012”, .010” dia respectively www.indiandentalacademy.com
    179. 179. High Tensile Australian Wires Dislocation locking  High tensile wires have high density of dislocations and crystal defects  Pile up, and form a minute crack  Stress concentration www.indiandentalacademy.com
    180. 180. High Tensile Australian Wires Small stress applied with the plier beaks  Crack propagation  Elastic energy is released  Propagation accelerates to the nearest grain boundary www.indiandentalacademy.com
    181. 181. High Tensile Australian Wires Ways of preventing fracture 1. Bending the wire around the flat beak of the pliers. Introduces a moment about the thumb and wire gripping point, which reduces the applied stress on the wire. www.indiandentalacademy.com
    182. 182. High Tensile Australian Wires www.indiandentalacademy.com
    183. 183. High Tensile Australian Wires 2. The wire should not be held tightly in the beaks of the pliers. Area of permanent deformation to be slightly enlarged, Nicking and scarring avoided. The tips of the pliers should not be of tungsten carbide. www.indiandentalacademy.com
    184. 184. High Tensile Australian Wires www.indiandentalacademy.com
    185. 185. High Tensile Australian Wires 3. The edges rounded  reduce the stress concentration in the wire. 4. Ductile – brittle transition temperature slightly above room temperature. Wire should be warmed. Spools kept in oven at about 40o, so that the wire remains slightly warm. www.indiandentalacademy.com
    186. 186. Multistranded Wires 2 or more wires of smaller diameter are twisted together/coiled around a core wire. Diameter - 0.0165 or 0.0175, but the stiffness is much less. On bending  individual strands slip over each other and the core wire, making bending easy. (elastic limit) www.indiandentalacademy.com
    187. 187. Multi stranded wires Co-axial Twisted wire www.indiandentalacademy.com Multi braided
    188. 188. Multi stranded wires Strength – resist distortion Separate strands - .007” but final wire can be either round / rectangular Sustain large elastic deflection in bending Thurow: rough idea – multiply www.indiandentalacademy.com
    189. 189. Multistranded Wires As the diameter of a wire decreases – Stiffness – decreases as a function of the 4 th power Range – increases proportionately Strength – decreases as a function of the 3 rd power Multistranded wires  Small diameter wires, High strength Gentler force www.indiandentalacademy.com
    190. 190. Multistranded Wires Elastic properties of multistranded archwires depend on – 1. Material parameters – Modulus of elasticity 2. Geometric factors – wire dimension 3. Constants:  Number of strands coiled  The distance from the neutral axis to the outer most fiber of a strand  Plane of bending  Poisson’s ratio www.indiandentalacademy.com
    191. 191. Multistranded Wires Deflection of multi stranded wire= KPL3 knEI K – load/support constant P – applied force L – length of the beam K – helical spring shape factor n- no of strands E – modulus of elasticity I – moment of inertia www.indiandentalacademy.com
    192. 192. Multistranded Wires Helical spring shape factor Coils resemble the shape of a helical spring. The helical spring shape factor is given as – 2sin α 2+ v cos2 α α - helix angle and v - Poisson’s ratio (lateral strain/axial strain) Angle α can be seen in the following diagram :www.indiandentalacademy.com
    193. 193. Multistranded Wires www.indiandentalacademy.com
    194. 194. Multistranded Wires Kusy ( AJO-DO 1984) Compared the elastic properties of triple stranded S.Steel wire with S.Steel, NiTi & B-TMA www.indiandentalacademy.com
    195. 195. Results Results www.indiandentalacademy.com
    196. 196. Results www.indiandentalacademy.com
    197. 197. Results 0.0175” S.Steel wire had stiffness equal to 0.016”NiTi & 40% of 0.016”TMA Did not resemble the 0.018” SS wire except : Size Wire-bracket relation. www.indiandentalacademy.com
    198. 198. Multistranded Wires Ingram, Gipe and Smith (AJO 86) Range of 4 diff wires Results: NiTi>MS S.Steel>CoCr>Steel www.indiandentalacademy.com
    199. 199. Multistranded Wires Nanda et al (AO 97) …. stiffness Increase in No. of strands  stiffness www.indiandentalacademy.com
    200. 200. Multistranded Wires Kusy (AJO-DO 2002) Interaction between individual strands was negligible. Range and strength Triple stranded Ξ Coaxial (six stranded) Stiffness  Coaxial < Triple stranded Range of single stranded SS wire, triple stranded and co-axial were similar. www.indiandentalacademy.com
    201. 201. Multistranded Wires www.indiandentalacademy.com
    202. 202. Welding of Steel 3 useful properties – 1. Comparatively low melting point, 2. High electrical resistance and 3. Low conductivity of heat. www.indiandentalacademy.com
    203. 203. Welding of Steel Important to  minimize the time of passing the current  minimize the area of heating Sensitization - between 425 and 815 oC Chromium carbides need time for their formation. www.indiandentalacademy.com
    204. 204. Welding of Steel Join two thin sheets of metal Same thickness Joining tubes, wires and springs, soldering is generally recommended. Electrodes - small tips, not exceeding 1 mm in diameter. www.indiandentalacademy.com
    205. 205. Cobalt Chromium 1950s the Elgin Watch Rocky Mountain Orthodontics Elgiloy CoCr alloys - stellite alloys  superior resistance to corrosion, comparable to that of gold alloys. www.indiandentalacademy.com
    206. 206. Cobalt Chromium Cobalt – 40-45% Chromium – 15-22% Nickel – for strength and ductility Iron, molybdenum, tungsten and titanium to form stable carbides and enhance hardenability. www.indiandentalacademy.com
    207. 207. Cobalt Chromium Strength and formability modified by heat treatment. The alloy is highly formable, and can be easily shaped. Heat treated.   Strength  Formability  www.indiandentalacademy.com
    208. 208. Cobalt Chromium www.indiandentalacademy.com
    209. 209. Cobalt Chromium Heat treated at 482oc for 7 to 12 mins Precipitation hardening   ultimate tensile strength of the alloy, without hampering the resilience. After heat treatment, elgiloy had elastic properties similar to steel. www.indiandentalacademy.com
    210. 210. Cobalt Chromium www.indiandentalacademy.com
    211. 211. Cobalt Chromium Blue – soft Yellow – ductile Green – semiresilient Red – resilient www.indiandentalacademy.com
    212. 212. Cobalt Chromium Blue considerable bending, soldering or welding Red  most resilient and best used for springs   difficult to form, (brittle) After heat treatment , no adjustments can be made to the wire, and it becomes extremely resilient. www.indiandentalacademy.com
    213. 213. Cobalt Chromium After heat treatment  Blue and yellow ≡ normal steel wire Green and red tempers ≡ higher grade steel www.indiandentalacademy.com
    214. 214. Cobalt Chromium Heating above 650oC  partial annealing, and softening of the wire Optimum heat treatment  dark straw color of the wire advantage of Co-Cr over SS is –  Greater resistance to fatigue and distortion  longer function as a resilient spring www.indiandentalacademy.com
    215. 215. Cobalt Chromium Properties of Co-Cr are very similar to that of stainless steel. Force  2x of β titanium and  4 times of NiTi. www.indiandentalacademy.com
    216. 216. Cobalt Chromium Frank and Nikolai (1980)  Co-Cr alloys ≡ stainless steel. Stannard et al (AJO 1986)  Co-Cr highest frictional resistance in wet and dry conditions. www.indiandentalacademy.com
    217. 217. Cobalt Chromium Ingram ,Gipe and Smith (AJO 86) Non heat treated Co-Cr  Range < stainless steel of comparable sizes But after heat treatment, the range was considerably increased. www.indiandentalacademy.com
    218. 218. Cobalt Chromium Kusy et al (AJO 2001) The elastic modulus did not vary appreciably  edgewise or ribbon-wise configurations. www.indiandentalacademy.com
    219. 219. Cobalt Chromium Round wires  higher ductility than square or rectangular wires. www.indiandentalacademy.com
    220. 220. Cobalt Chromium The modulus of elasticity 4 diff tempers of 0.016” elgiloy is almost similar www.indiandentalacademy.com
    221. 221. Cobalt Chromium Elastic properties (yield strength and ultimate tensile strength and ductility) were quite similar for different cross sectional areas and tempers. This does not seem to agree with what is expected of the wires. www.indiandentalacademy.com
    222. 222. Cobalt Chromium www.indiandentalacademy.com
    223. 223. Cobalt Chromium Different tempers with different physical properties – attractive More care taken during the manufacture of the wires. www.indiandentalacademy.com
    224. 224. References A study of the metallurgical properties of newly introduced high tensile wires in comparison to the high tensile Australian wires for various applications in orthodontic treatment. – Anuradha Acharya, MDS Dissertation September 2000. Kusy & Greenberg. Effects of composition and cress section on the elastic properties of orthodontic wires. Angle Orthod 1981;51:325341 Kapila & Sachdeva. Mechanical properties and clinical applications of orthodontic wires . AJO 89;96:100-109. www.indiandentalacademy.com
    225. 225. References Stannard, Gau, Hanna. Comparative friction of orthodontic wires under dry and wet conditions. AJO 86;89:485-491 Burstone. Variable modulus orthodontics. AJO 81; 80:1-16 Kusy. A review of contemporary archwires: Their properties and characteristics. Angle orthodontist 97;67:197-208 Ingram, Gipe, Smith. Comparative range of orthodontic wires AJO 1986;90:296-307 Tidy. Frictional forces in fixed appliances. AJO 89; 96:249-54 Twelftree, Cocks, Sims. Tensile properties of Orthodontic wires. AJO 89;72:682-687 www.indiandentalacademy.com
    226. 226. References Kusy and Dilley. Elastic property ratios of a triple stranded stainless steel archwire. AJO 84;86:177-188 Arthur J Wilcock. JCO interviews. JCO 1988;22:484-489 Frank and Nikolai. A comparative study of frictional resistance between orthodontic brackets and archwires. AJO 80;78:593-609 Arthur Wilcock. Applied materials engineering for orthodontic wires. Aust. Orthod J. 1989;11:2229. www.indiandentalacademy.com
    227. 227. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

    ×