Properties ofProperties of
OrthodonticOrthodontic WiresWires
Part I
INDIAN DENTAL ACADEMY
Leader in continuing dental educ...
IntroductionIntroduction
Moving teeth and craniofacial harmonyMoving teeth and craniofacial harmony
Forces and momentsForc...
HistoryHistory
1.1. Material Scarcity, Abundance of IdeasMaterial Scarcity, Abundance of Ideas
(1750-1930)(1750-1930)
nobl...
Angle (1887)Angle (1887)  German silver (a type ofGerman silver (a type of
brass)brass)
OppositionOpposition Farrar – ...
HistoryHistory
Wood, rubber, vulcanite, piano wire andWood, rubber, vulcanite, piano wire and
silk threadsilk thread
No re...
HistoryHistory
Stainless steel (entered dentistry -1920)Stainless steel (entered dentistry -1920)
Stahl and Eisen – Benno ...
HistoryHistory
2.2. Abundance of materials, RefinementAbundance of materials, Refinement
of Proceduresof Procedures (1930 ...
HistoryHistory
3.3. The beginning of SelectivityThe beginning of Selectivity (1975 to(1975 to
the present)the present)
Ort...
Basic Properties of MaterialsBasic Properties of Materials
Elements –all particles identicalElements –all particles identi...
Basic Properties of MaterialsBasic Properties of Materials
Array of positive ions in a “sea ofArray of positive ions in a ...
Basic Properties of MaterialsBasic Properties of Materials
Molecules – 2 or more atomsMolecules – 2 or more atoms
Amorphou...
Basic Properties of MaterialsBasic Properties of Materials
CRYSTALSCRYSTALS
Perfect crystals: anion – cation –anion –Perfe...
Basic Properties of MaterialsBasic Properties of Materials
alloy crystals growalloy crystals grow
anion – cation –anion – ...
Basic Properties of MaterialsBasic Properties of Materials
GrainsGrains  microns to centimetersmicrons to centimeters
Gr...
Basic Properties of MaterialsBasic Properties of Materials
Stages in the
formation of metallic
grains during the
solidific...
Basic Properties of MaterialsBasic Properties of Materials
VacanciesVacancies – These are empty atom sites– These are empt...
InterstitialsInterstitials –– Smaller atoms that penetrateSmaller atoms that penetrate
the lattice Eg – Carbon, Hydrogen, ...
Basic Properties of MaterialsBasic Properties of Materials
Substitutial Element – another metal atom can
substitute one of...
Imperfections- although they lower theImperfections- although they lower the
cleavage strength of the metal , increaseclea...
LATTICELATTICE
The three dimensional arrangement ofThe three dimensional arrangement of
lines that can be visualized as co...
Basic Properties of MaterialsBasic Properties of Materials
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Basic Properties of MaterialsBasic Properties of Materials
The atoms, which areThe atoms, which are
represented as points,...
Lattice deformations:Lattice deformations:
various defectsvarious defects  slipslip planesplanes--alongalong whichwhich
...
shear stressshear stress  atoms of the crystalsatoms of the crystals
can glide along these planescan glide along these p...
If the shearing force is:-If the shearing force is:-
SmallSmall - atoms slip, and return back to their- atoms slip, and re...
During deformation - atomic bonds withinDuring deformation - atomic bonds within
the crystal get stressedthe crystal get s...
Work hardeningWork hardening
Forced interlocking of grains and atoms ofForced interlocking of grains and atoms of
metal.me...
Strain hardening- principleStrain hardening- principle
 Hard and strong, tensile strengthHard and strong, tensile streng...
ANNEALING:ANNEALING:
RecoveryRecovery
RecrystallizationRecrystallization
Grain GrowthGrain Growth
Basic Properties of Mate...
Basic Properties of MaterialsBasic Properties of Materials
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Before Annealing
Recovery – Relief of stresses
Recrystallization – New grains
from severely cold worked areas
-original so...
AnnealingAnnealing
Smaller grains – harder and strongerSmaller grains – harder and stronger
Larger grain boundaries to opp...
Various methods of obtaining smaller grain sizeVarious methods of obtaining smaller grain size
1.1. Enhancing crystal nucl...
Solution heat treatmentSolution heat treatment
Heat below the solidus tempHeat below the solidus temp
Held for sometime, -...
TwinningTwinning
Closed packed hexagonal type of crystalsClosed packed hexagonal type of crystals
Two symmetric halvesTwo ...
Basic Properties of MaterialsBasic Properties of Materials
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PolymorphismPolymorphism
Metals and alloys exist as more than oneMetals and alloys exist as more than one
type of structur...
Transition of IronTransition of Iron
IronIron  FCC stableFCC stable
(austenite), 912*c-(austenite), 912*c-
1394*c1394*c
...
Transition of IronTransition of Iron
On Cooling <912*cOn Cooling <912*c
FCCFCC  BCCBCC
Carbon diffusesCarbon diffuses
ou...
Transition of IronTransition of Iron
Rapidly cooledRapidly cooled
(quenched)(quenched)

Carbon cannot escapeCarbon cannot...
Grain boundaries are more in numberGrain boundaries are more in number
Alloy is stronger and more brittle-Alloy is stronge...
Cooled slowlyCooled slowly
Other crystal structures are formed atOther crystal structures are formed at
intermediate tempe...
Tempering –Tempering –
Reheat the alloy to intermediateReheat the alloy to intermediate
temperature(1000*F/525*c)temperatu...
Some alloysSome alloys
FCC to BCC by rearrangement of atomsFCC to BCC by rearrangement of atoms

Diagonal plane of the BC...
Shape memory alloys – Easy switchingShape memory alloys – Easy switching
from one type of structure to another.from one ty...
Elastic PropertiesElastic Properties
Stress and strainStress and strain
Stress- internal distribution of load.Stress- inte...
Elastic PropertiesElastic Properties
Force applied to wireForce applied to wire DeflectionDeflection
Internal force---...
Elastic PropertiesElastic Properties
Types of stress/strainTypes of stress/strain
Tensile –Tensile –stretch/pullstretch/pu...
Elastic PropertiesElastic Properties
Strain
Stress
Elastic Portion
Wire returns back to original
dimension when stress is
...
Elastic PropertiesElastic Properties
Hooke’s lawHooke’s law
Spring stretch in proportion to applied forceSpring stretch in...
Elastic PropertiesElastic Properties
Strain
Stress
Elastic Limit
Proportional Limit
Yield strength
0.1%
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Elastic PropertiesElastic Properties
Strain
Stress
Ultimate Tensile
Strength Fracture Point
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Elastic PropertiesElastic Properties
ultimate tensile strengthultimate tensile strength is higher than theis higher than t...
Elastic PropertiesElastic Properties
Strain
Stress
Slope α Stiffness
Stiffness α 1 .
Springiness
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Elastic PropertiesElastic Properties
Strain
Stress
Range Springback
Point of arbitrary clinical loading
Yield point
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Elastic PropertiesElastic Properties
Clinically, ortho wires are deformed
beyond their elastic limit.
Springback propertie...
Elastic PropertiesElastic Properties
Resiliency -Resiliency -
When a wire is stretched, the space between theWhen a wire i...
Elastic PropertiesElastic Properties
Strain
Stress
Resilience Formability
Proportional limit
Yield strength
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Elastic PropertiesElastic Properties
FormabilityFormability - amount of permanent- amount of permanent
deformation that th...
Elastic PropertiesElastic Properties
FlexibilityFlexibility
large deformation (or large strain) withlarge deformation (or ...
Elastic PropertiesElastic Properties
ToughnessToughness ––force required to fracture aforce required to fracture a
materia...
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Properties ofProperties of
OrthodonticOrthodontic WiresWires
Part I
Dr. Vijaya Lakshmi www.indiandentalacademy.comwww.indi...
Elastic PropertiesElastic Properties
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Elastic PropertiesElastic Properties
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Elastic PropertiesElastic Properties
Strain
Stress
Resilience Formability
Proportional limit
Yield strength
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Requirements of an ideal archwireRequirements of an ideal archwire
(Kusy )(Kusy )
1.1. EstheticsEsthetics
2.2. StiffnessSt...
1. Esthetics1. Esthetics
DesirableDesirable
No compromise on mechanical propertiesNo compromise on mechanical properties
W...
2. Stiffness / Load deflection Rate2. Stiffness / Load deflection Rate
Proffit:Proffit: - slope of stress-strain curve- sl...
Stiffness / Load deflection RateStiffness / Load deflection Rate
Magnitude of the force delivered by the applianceMagnitud...
3 point bending test3 point bending test
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3. Strength3. Strength
Yield strength, proportional limit and ultimateYield strength, proportional limit and ultimate
tens...
StrengthStrength
TheThe shapeshape andand cross sectioncross section of a wireof a wire
have an effect on the strength of ...
4. Range4. Range
Distance that the wire bends elastically,Distance that the wire bends elastically,
before permanent defor...
5.5. SpringbackSpringback
KusyKusy -- The extent to which a wire-- The extent to which a wire
recovers its shape after dea...
5.5. SpringbackSpringback
Large springbackLarge springback
Activated to a large extent.Activated to a large extent.
Hence ...
6.6. FormabilityFormability
KusyKusy – the ease in which a material may– the ease in which a material may
be permanently d...
7.7. ResiliencyResiliency
Store/absorb more strain energy /unitStore/absorb more strain energy /unit
volume before they ge...
8.8. Coefficient of frictionCoefficient of friction
Brackets (and teeth) must be able to slideBrackets (and teeth) must be...
9.9. Biohostability:- site for accumulation ofBiohostability:- site for accumulation of
bacteria, spores or viruses. An id...
Properties of WiresProperties of Wires
Before the titanium alloys wereBefore the titanium alloys were
introduced into orth...
Effects of Wire Cross SectionEffects of Wire Cross Section
Wires of various dimensions and crossWires of various dimension...
Effects of Wire Cross SectionEffects of Wire Cross Section
primary factorprimary factor 
load deflection rate or stiffne...
Effects of Wire Cross SectionEffects of Wire Cross Section
Based on stiffness/load deflection rate
Force delivered by a wi...
Effects of Wire Cross SectionEffects of Wire Cross Section
Force delivered by a wire with low load deflection rate
Force d...
Load deflection rateLoad deflection rate
Shape Moment
of Inertia
Ratio to stiffness of
round wire
Пd4
64
1
s4
12
1.7
b3
h
...
Effects of Wire Cross SectionEffects of Wire Cross Section
Dimension of wire increases- LDRDimension of wire increases- LD...
Effects of Wire Cross SectionEffects of Wire Cross Section
Stiffness of different dimensions of wiresStiffness of differen...
Effects of Wire Cross SectionEffects of Wire Cross Section
Rectangular wiresRectangular wires  bending perpendicular tob...
Effects of Wire Cross SectionEffects of Wire Cross Section
The larger dimensionThe larger dimension  correction is neede...
Effects of Wire Cross SectionEffects of Wire Cross Section
> 1> 1stst
order correction in anterior segmentorder correction...
Effects of Wire Cross SectionEffects of Wire Cross Section
Cross-sectional shape:Cross-sectional shape:

On range and str...
Effects of Wire Cross SectionEffects of Wire Cross Section
In torsion - absolute values of strength,In torsion - absolute ...
Effects of LengthEffects of Length
Loops,Loops,
 the inter-bracket distancethe inter-bracket distance
For bendingFor ben...
Effects of LengthEffects of Length
In the case ofIn the case of torsiontorsion, the picture is, the picture is
slightly di...
Effects of LengthEffects of Length
Way the beam is attached also affects theWay the beam is attached also affects the
valu...
Effects of LengthEffects of Length
Cantilever Beam supported on both ends Fixed at both ends
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Effects of LengthEffects of Length
Stiffness is also affected by the method ofStiffness is also affected by the method of
...
Clinical ImplicationsClinical Implications
LIGHT CONTINUOUS FORCESLIGHT CONTINUOUS FORCES
Stiff wires should be taboo to t...
Clinical ImplicationsClinical Implications
Removable applianceRemovable appliance cantilever springcantilever spring
The...
Clinical ImplicationsClinical Implications
In archwires of stiffer materials the sameIn archwires of stiffer materials the...
Variable cross-section orthodontics.Variable cross-section orthodontics.
Variable modulus orthodontics.Variable modulus or...
Clinical ImplicationsClinical Implications
NiTi – high springbackNiTi – high springback
Initial stages – NiTi instead of s...
Clinical ImplicationsClinical Implications
variable modulus orthodontics –variable modulus orthodontics –
Advantage-Advant...
Clinical ImplicationsClinical Implications
Requirements of arch wires in different stages of
treatment www.indiandentalaca...
AppropriateAppropriate
wirewire
Take into account the amount of force that wireTake into account the amount of force that ...
NomogramsNomograms
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NomogramsNomograms
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AA rough idea can be obtained clinically as wellrough idea can be obtained clinically as well
Forming an arch wire with th...
CorrosionCorrosion
Nickel -Nickel -
1.1. Carcinogenic,Carcinogenic,
2.2. mutagenic,mutagenic,
3.3. cytotoxic andcytotoxic ...
CorrosionCorrosion
Placement in the oral cavityPlacement in the oral cavity

Greater peril than implantingGreater peril ...
CorrosionCorrosion
Stainless steel- Ni austenite stabilizer. NotStainless steel- Ni austenite stabilizer. Not
strongly bon...
CorrosionCorrosion
1.1. Uniform attack –Uniform attack –
the entire wire reacts with thethe entire wire reacts with the
en...
CorrosionCorrosion
Stainless Steel
NiTi
Pitting corrosion
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CorrosionCorrosion
3.3. Crevice corrosion or gasket corrosion -Crevice corrosion or gasket corrosion -
Parts of the wire e...
CorrosionCorrosion
4.4. GalvanicGalvanic //Electrochemical CorrosionElectrochemical Corrosion
two metals are joinedtwo met...
CorrosionCorrosion
AnodicAnodic

Looses ElectronsLooses Electrons

Soluble ionsSoluble ions

Leach outLeach out
Cath...
CorrosionCorrosion
5.5. Intergranular corrosionIntergranular corrosion
Sensitization - ppt of CrCSensitization - ppt of Cr...
CorrosionCorrosion
7.7. Microbiologically influenced corrosionMicrobiologically influenced corrosion
AdhesiveAdhesive
Crat...
Micro-0rganisms on various dentalMicro-0rganisms on various dental
materialsmaterials
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CorrosionCorrosion
8.8. Stress corrosionStress corrosion
Similar to galvanic corrosionSimilar to galvanic corrosion
Bendin...
CorrosionCorrosion
9.9. CorrosionCorrosion Fatigue:Fatigue:
Cyclic stressing of a wireCyclic stressing of a wire
Resistanc...
CorrosionCorrosion
Analysis of used wires also indicated that aAnalysis of used wires also indicated that a
biofilmbiofilm...
OrthOdOntic Arch Wire
MAteriAls
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Precious MetalsPrecious Metals
Upto about the 1950sUpto about the 1950s
Gold alloysGold alloys
Only wire which would toler...
Stainless SteelStainless Steel
1919 – Germany1919 – Germany  used to makeused to make
prostheses.prostheses.
Extremely c...
Stainless SteelStainless Steel
Variety of stainless steelsVariety of stainless steels
Varying the degree of coldVarying th...
Stainless SteelStainless Steel
stainless steel arch wires are cold workedstainless steel arch wires are cold worked
to var...
Stainless SteelStainless Steel
Structure and compositionStructure and composition
Chromium (11-26%)–Chromium (11-26%)–impr...
Stainless SteelStainless Steel
Carbon (0.08-1.2%)– provides strengthCarbon (0.08-1.2%)– provides strength
Reduces the corr...
Stainless SteelStainless Steel
Chromium carbidesChromium carbides
Amount of chromium decreasesAmount of chromium decreases...
Stabilization –

Element which precipitates carbide moreElement which precipitates carbide more
easily than Chromium.easi...
Stainless SteelStainless Steel
SiliconSilicon – (low concentrations) improves the– (low concentrations) improves the
resis...
Manufacture: AISI ,Manufacture: AISI ,specially for orthodontic purposesspecially for orthodontic purposes
Various steps –...
MeltingMelting

Various metals of the alloy are meltedVarious metals of the alloy are melted

Proportion influences the ...

Porosities due to dissolved gases (produced /Porosities due to dissolved gases (produced /
trapped)trapped)

Vacuum voi...
Rolling –Rolling –

First mechanical process.First mechanical process.

Ingot reduced to thinner barsIngot reduced to th...

Retain their property even after rollingRetain their property even after rolling

Shape & arrangement alteredShape & ar...
DrawingDrawing

More preciseMore precise

IngotIngot  final size.final size.

Wire pulled through small hole in a die...

Series of diesSeries of dies

Annealing at regular intervals.Annealing at regular intervals.

Exact number of drafts a...
Stress reliefStress relief
During manufacture, wire highly stressed.During manufacture, wire highly stressed.
Adverse effe...
Clinical implicationsClinical implications
Soldering attachments to arch wire:Soldering attachments to arch wire:

Raise ...
Stainless SteelStainless Steel
ClassificationClassification
American Iron and Steel Institute (AISI)American Iron and Stee...
Stainless SteelStainless Steel
The AISI numbers used for stainless steel rangeThe AISI numbers used for stainless steel ra...
Stainless SteelStainless Steel
Austenitic steels (the 300 series)Austenitic steels (the 300 series)
Better corrosion resis...
Stainless SteelStainless Steel
Martensitic steelMartensitic steel
FCCFCC  BCCBCC
BCC structure is highly stressed.BCC st...
Stainless SteelStainless Steel
Ferritic steelsFerritic steels – (the 400 series)– (the 400 series)
Good corrosion resistan...
Stainless SteelStainless Steel
Austenitic steels more preferableAustenitic steels more preferable :-:-
Greater ductility a...
Stainless SteelStainless Steel
Duplex steelsDuplex steels
Both austenite and ferrite grainsBoth austenite and ferrite grai...
Stainless steelStainless steel
Precipitation hardened steelsPrecipitation hardened steels
Certain elements added to themCe...
General properties of StainlessGeneral properties of Stainless
SteelSteel
Relatively stiff materialRelatively stiff materi...
Stainless SteelStainless Steel
Clinical terms:-Clinical terms:-
Loop - activated to a very small extent soLoop - activated...
Stainless SteelStainless Steel
Force required to engage a steel wire intoForce required to engage a steel wire into
a seve...
Stainless SteelStainless Steel
High stiffnessHigh stiffness 
Maintain the positions of teethMaintain the positions of te...
Stainless SteelStainless Steel
Lowest frictional resistanceLowest frictional resistance
Ideal choice of wire during space ...
High Tensile Australian WiresHigh Tensile Australian Wires
HistoryHistory
Early part of Dr. Begg’s careerEarly part of Dr....
High Tensile Australian WiresHigh Tensile Australian Wires
Beginners found it difficult to use theBeginners found it diffi...
High Tensile Australian WiresHigh Tensile Australian Wires
Newer grades were introduced after the 70s.Newer grades were in...
High Tensile Australian WiresHigh Tensile Australian Wires
Bauschinger effectBauschinger effect..
Described by Dr. Bauschi...
High Tensile Australian WiresHigh Tensile Australian Wires
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High Tensile Australian WiresHigh Tensile Australian Wires
1.1. Plastic prestrain increases the elastic limit ofPlastic pr...
High Tensile Australian WiresHigh Tensile Australian Wires
Straightening a wireStraightening a wire  pulling through apu...
Spinner straighteningSpinner straightening
It is mechanical process of straighteningIt is mechanical process of straighten...
Pulse straighteningPulse straightening
Special methodSpecial method
Placed in special machines that permitsPlaced in speci...
High Tensile Australian WiresHigh Tensile Australian Wires
Methods of increasing yield strength ofMethods of increasing yi...
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 WiresHigh Tensile Australian Wires
Higher yield strengthHigher yield strength 
more flexible.mor...
High Tensile Australian WiresHigh Tensile Australian Wires
MollenhauerMollenhauer 
Supreme grade wireSupreme grade wire ...
High Tensile Australian WiresHigh Tensile Australian Wires
Clinical significance of high yield strength
1. Increased worki...
High Tensile Australian WiresHigh Tensile Australian Wires
3. Zero Stress Relaxation3. Zero Stress Relaxation
If a wire is...
High Tensile Australian WiresHigh Tensile Australian Wires
external forcesexternal forces

particles slip over each othe...
High Tensile Australian WiresHigh Tensile Australian Wires
Zero stress relaxation in springs.Zero stress relaxation in spr...
High Tensile Australian WiresHigh Tensile Australian Wires
Twelftree, Cocks and Sims (AJO 1977)Twelftree, Cocks and Sims (...
Hazel, Rohan & West (1984)Hazel, Rohan & West (1984)

Stress relaxation of Special plus wires after 28Stress relaxation o...
Pulse straightened wires – SpinnerPulse straightened wires – Spinner
straightened wiresstraightened wires
(Skaria 1991)(Sk...
A study of the metallurgical properties of newlyA study of the metallurgical properties of newly
introduced high tensile w...
Highest yield strength and ultimate tensileHighest yield strength and ultimate tensile
strength as compared to the corresp...
Clinical implicationsClinical implications
Stage I:Stage I:
1.1. Wilcock (P) / S+ base wire(.014”)Wilcock (P) / S+ base wi...
High Tensile Australian WiresHigh Tensile Australian Wires
Dislocation lockingDislocation locking

High tensile wires ha...
High Tensile Australian WiresHigh Tensile Australian Wires
Small stress applied with the plier beaksSmall stress applied w...
High Tensile Australian WiresHigh Tensile Australian Wires
Ways of preventing fractureWays of preventing fracture
1.1. Ben...
High Tensile Australian WiresHigh Tensile Australian Wires
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High Tensile Australian WiresHigh Tensile Australian Wires
2.2. The wire should not be held tightly in theThe wire should ...
High Tensile Australian WiresHigh Tensile Australian Wires
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High Tensile Australian WiresHigh Tensile Australian Wires
3.3. The edges roundedThe edges rounded  reduce the stressred...
Multistranded WiresMultistranded Wires
2 or more wires of smaller diameter are2 or more wires of smaller diameter are
twis...
Multi stranded wiresMulti stranded wires
Co-axial
Twisted wire
Multi braided
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Multi stranded wiresMulti stranded wires
Strength – resist distortionStrength – resist distortion
Separate strands - .007”...
Multistranded WiresMultistranded Wires
As the diameter of a wire decreases –As the diameter of a wire decreases –
Stiffnes...
Multistranded WiresMultistranded Wires
Elastic properties of multistranded archwiresElastic properties of multistranded ar...
Multistranded WiresMultistranded Wires
Deflection ofDeflection of
multi stranded wire=multi stranded wire= KPLKPL33
kknEIn...
Multistranded WiresMultistranded Wires
Helical spring shape factorHelical spring shape factor
Coils resemble the shape of ...
Multistranded WiresMultistranded Wires
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Multistranded WiresMultistranded Wires
Kusy ( AJO-DO 1984)Kusy ( AJO-DO 1984)
Compared the elastic properties of tripleCom...
ResultsResults
ResultsResults
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ResultsResults
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ResultsResults
0.0175” S.Steel wire had stiffness equal to0.0175” S.Steel wire had stiffness equal to
0.016”NiTi & 40% of ...
Multistranded WiresMultistranded Wires
Ingram, Gipe and Smith (AJO 86)
Range of 4 diff wiresRange of 4 diff wires
Results:...
Multistranded WiresMultistranded Wires
Nanda et al (AO 97)Nanda et al (AO 97)
……. stiffness. stiffness
Increase in No. ofI...
Multistranded WiresMultistranded Wires
Kusy (AJO-DO 2002)Kusy (AJO-DO 2002)
Interaction between individual strands wasInte...
Multistranded WiresMultistranded Wires
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Welding of SteelWelding of Steel
3 useful properties3 useful properties ––
1.1. Comparatively low melting point,Comparativ...
Welding of SteelWelding of Steel
Sensitization - between 425 and 815Sensitization - between 425 and 815oo
CC
Chromium carb...
Welding of SteelWelding of Steel
Join twoJoin two thin sheetsthin sheets of metalof metal
Same thicknessSame thickness
Joi...
Cobalt ChromiumCobalt Chromium
1950s the Elgin Watch1950s the Elgin Watch
Rocky Mountain OrthodonticsRocky Mountain Orthod...
Cobalt ChromiumCobalt Chromium
Cobalt – 40-45%Cobalt – 40-45%
Chromium – 15-22%Chromium – 15-22%
Nickel – for strength and...
Cobalt ChromiumCobalt Chromium
Strength and formability modified by heatStrength and formability modified by heat
treatmen...
Cobalt ChromiumCobalt Chromium
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Cobalt ChromiumCobalt Chromium
Heat treated at 482Heat treated at 482oo
c for 7 to 12 minsc for 7 to 12 mins
Precipitation...
Cobalt ChromiumCobalt Chromium
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Cobalt ChromiumCobalt Chromium
BlueBlue – soft– soft
YellowYellow – ductile– ductile
GreenGreen – semiresilient– semiresil...
Cobalt ChromiumCobalt Chromium
After heat treatmentAfter heat treatment 
Strength:Strength:
BlueBlue andand yellowyellow...
Cobalt ChromiumCobalt Chromium
Heating above 650Heating above 650oo
CC

partial annealing, and softening of the wireparti...
Cobalt ChromiumCobalt Chromium
Properties of Co-Cr are very similar to thatProperties of Co-Cr are very similar to that
of...
Cobalt ChromiumCobalt Chromium
Ingram ,Gipe and Smith (AJO 86)Ingram ,Gipe and Smith (AJO 86)
Non heat treated Co-CrNon he...
Cobalt ChromiumCobalt Chromium
Frank and Nikolai ( AJO 1980)Frank and Nikolai ( AJO 1980)

Co-Cr alloysCo-Cr alloys ≡≡ st...
Cobalt ChromiumCobalt Chromium
Kusy et al (AJO
2001)
The elasticThe elastic
modulus did notmodulus did not
vary appreciabl...
Cobalt ChromiumCobalt Chromium
Round wiresRound wires 
higher ductility thanhigher ductility than
square orsquare or
rec...
Cobalt ChromiumCobalt Chromium
The modulus ofThe modulus of
elasticity 4 diffelasticity 4 diff
tempers of 0.016”tempers of...
Cobalt ChromiumCobalt Chromium
Elastic propertiesElastic properties (yield strength and(yield strength and
ultimate tensil...
Cobalt ChromiumCobalt Chromium
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Different tempers with different physicalDifferent tempers with different physical
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Orthodontic wires  properties/certified fixed orthodontic courses by Indian dental academy
Orthodontic wires  properties/certified fixed orthodontic courses by Indian dental academy
Orthodontic wires  properties/certified fixed orthodontic courses by Indian dental academy
Orthodontic wires  properties/certified fixed orthodontic courses by Indian dental academy
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Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

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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

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  • 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
  • Round as well as cross sectional wires
  • Writing system using picture symbols used in ancient egyt
  • The ability to absorb considerable energy before breaking: temper
  • Independent of the temper of the wire
  • They do not follow the regular order according to their temper in an expected manner but they are scattered hapazardly
  • Orthodontic wires properties/certified fixed orthodontic courses by Indian dental academy

    1. 1. Properties ofProperties of OrthodonticOrthodontic WiresWires Part I INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
    2. 2. IntroductionIntroduction Moving teeth and craniofacial harmonyMoving teeth and craniofacial harmony Forces and momentsForces and moments WiresWires Light continuous forcesLight continuous forces www.indiandentalacademy.comwww.indiandentalacademy.com
    3. 3. HistoryHistory 1.1. Material Scarcity, Abundance of IdeasMaterial Scarcity, Abundance of Ideas (1750-1930)(1750-1930) noble metalsnoble metals Gold, platinum, iridium and silver alloysGold, platinum, iridium and silver alloys good corrosion resistancegood corrosion resistance acceptable estheticsacceptable esthetics lacked the flexibility and tensile strengthlacked the flexibility and tensile strength www.indiandentalacademy.comwww.indiandentalacademy.com
    4. 4. Angle (1887)Angle (1887)  German silver (a type ofGerman silver (a type of brass)brass) OppositionOpposition Farrar – discoloredFarrar – discolored Neusilber brass (Cu 65%, Ni 14%, Zn 21%)Neusilber brass (Cu 65%, Ni 14%, Zn 21%) various degrees of cold work (diff prop)various degrees of cold work (diff prop)  jack screws,jack screws,  expansion arches,expansion arches,  BandsBands HistoryHistory www.indiandentalacademy.comwww.indiandentalacademy.com
    5. 5. HistoryHistory Wood, rubber, vulcanite, piano wire andWood, rubber, vulcanite, piano wire and silk threadsilk thread No restrictions.No restrictions. www.indiandentalacademy.comwww.indiandentalacademy.com
    6. 6. HistoryHistory Stainless steel (entered dentistry -1920)Stainless steel (entered dentistry -1920) Stahl and Eisen – Benno Strauss & EduardStahl and Eisen – Benno Strauss & Eduard Maurer in 1914Maurer in 1914 By 1920 – Dr. F Hauptmeyer.By 1920 – Dr. F Hauptmeyer. Simon, schwarz, Korkhous, De Coster-Simon, schwarz, Korkhous, De Coster- orthodontic materialorthodontic material ReplacedReplaced OppositionOpposition  Emil HerbstEmil Herbst  gold wire was stronger than stainless steel. (1934)gold wire was stronger than stainless steel. (1934) Steel as ligature wireSteel as ligature wire www.indiandentalacademy.comwww.indiandentalacademy.com
    7. 7. HistoryHistory 2.2. Abundance of materials, RefinementAbundance of materials, Refinement of Proceduresof Procedures (1930 – 1975)(1930 – 1975)  Improvement in metallurgy and organicImprovement in metallurgy and organic chemistry – mass production(1960)chemistry – mass production(1960)  Farrar’s dream(1878)Farrar’s dream(1878) Cobalt chrome (1950s)-Elgin watch coCobalt chrome (1950s)-Elgin watch co Rocky Mountain Orthodontics- ElgiloyRocky Mountain Orthodontics- Elgiloy Nitinol (1970s)- Buehler, intoNitinol (1970s)- Buehler, into orthodontics- Andreasen. Unitekorthodontics- Andreasen. Unitek www.indiandentalacademy.comwww.indiandentalacademy.com
    8. 8. HistoryHistory 3.3. The beginning of SelectivityThe beginning of Selectivity (1975 to(1975 to the present)the present) Orthodontic manufacturersOrthodontic manufacturers Beta titanium (1980)Beta titanium (1980) CAD/CAM – larger production runsCAD/CAM – larger production runs Composites and CeramicsComposites and Ceramics Iatrogenic damageIatrogenic damage  Nickel and bis-GMANickel and bis-GMA New products- control of govt agencies, priNew products- control of govt agencies, pri organizationorganization www.indiandentalacademy.comwww.indiandentalacademy.com
    9. 9. Basic Properties of MaterialsBasic Properties of Materials Elements –all particles identicalElements –all particles identical  Atoms-smallestAtoms-smallest Electrons – orbits around nucleusElectrons – orbits around nucleus Floating in shells of diff energy levelsFloating in shells of diff energy levels Electrons form the basis of bondsElectrons form the basis of bonds Atoms interact via electronsAtoms interact via electrons In metals, the energy levels are veryIn metals, the energy levels are very closely spaced and the electrons tend toclosely spaced and the electrons tend to belong to the entire assembly rather thanbelong to the entire assembly rather than a single atom.a single atom. www.indiandentalacademy.comwww.indiandentalacademy.com
    10. 10. Basic Properties of MaterialsBasic Properties of Materials Array of positive ions in a “sea ofArray of positive ions in a “sea of electrons”electrons” Electrons free to moveElectrons free to move electrical and thermal conductivityelectrical and thermal conductivity Ductility and malleabilityDuctility and malleability electrons adjust to deformationelectrons adjust to deformation www.indiandentalacademy.comwww.indiandentalacademy.com
    11. 11. Basic Properties of MaterialsBasic Properties of Materials Molecules – 2 or more atomsMolecules – 2 or more atoms Amorphous – similar properties in allAmorphous – similar properties in all directions – isotropydirections – isotropy  GlassGlass atoms organize themselves into specificatoms organize themselves into specific latticeslattices  geometrygeometry CRYSTALCRYSTAL  anisotropyanisotropy www.indiandentalacademy.comwww.indiandentalacademy.com
    12. 12. Basic Properties of MaterialsBasic Properties of Materials CRYSTALSCRYSTALS Perfect crystals: anion – cation –anion –Perfect crystals: anion – cation –anion – cationcation extremely strongextremely strong Thin wiskersThin wiskers reinforcereinforce If like ions are forced together, breakageIf like ions are forced together, breakage results. Unlike metals, crystals cannotresults. Unlike metals, crystals cannot deform.deform. www.indiandentalacademy.comwww.indiandentalacademy.com
    13. 13. Basic Properties of MaterialsBasic Properties of Materials alloy crystals growalloy crystals grow anion – cation –anion – cationanion – cation –anion – cation Perfect crystals seldom existPerfect crystals seldom exist Crystals penetrate each other such that theCrystals penetrate each other such that the crystal shapes get deformed and cannotcrystal shapes get deformed and cannot be discerned grainsbe discerned grains www.indiandentalacademy.comwww.indiandentalacademy.com
    14. 14. Basic Properties of MaterialsBasic Properties of Materials GrainsGrains  microns to centimetersmicrons to centimeters Grain boundariesGrain boundaries Atoms are irregularly arranged, and thisAtoms are irregularly arranged, and this leads to a weaker amorphous typeleads to a weaker amorphous type structure.structure. AlloyAlloy  combination of crystalline (grains)combination of crystalline (grains) and amorphous (grain boundaries)and amorphous (grain boundaries) Decreased mechanical strength andDecreased mechanical strength and reduced corrosion resistancereduced corrosion resistancewww.indiandentalacademy.comwww.indiandentalacademy.com
    15. 15. Basic Properties of MaterialsBasic Properties of Materials Stages in the formation of metallic grains during the solidification of a molten metal Polycrystalline- each crystal - grain www.indiandentalacademy.comwww.indiandentalacademy.com
    16. 16. Basic Properties of MaterialsBasic Properties of Materials VacanciesVacancies – These are empty atom sites– These are empty atom sites www.indiandentalacademy.comwww.indiandentalacademy.com
    17. 17. InterstitialsInterstitials –– Smaller atoms that penetrateSmaller atoms that penetrate the lattice Eg – Carbon, Hydrogen, Oxygen,the lattice Eg – Carbon, Hydrogen, Oxygen, Boron. Often distort the metal structureBoron. Often distort the metal structure www.indiandentalacademy.comwww.indiandentalacademy.com
    18. 18. Basic Properties of MaterialsBasic 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.comwww.indiandentalacademy.com
    19. 19. Imperfections- although they lower theImperfections- although they lower the cleavage strength of the metal , increasecleavage strength of the metal , increase its resistance to deformationits resistance to deformation www.indiandentalacademy.comwww.indiandentalacademy.com
    20. 20. LATTICELATTICE The three dimensional arrangement ofThe three dimensional arrangement of lines that can be visualized as connectinglines that can be visualized as connecting the atoms in undisrupted crystals, is calledthe atoms in undisrupted crystals, is called a lattice.a lattice. Unit cellUnit cell CrystalCrystal  combination of unit cells, incombination of unit cells, in which each cell shares faces, edges orwhich each cell shares faces, edges or corners with the neighboring cellscorners with the neighboring cells 14 crystal lattices14 crystal lattices www.indiandentalacademy.comwww.indiandentalacademy.com
    21. 21. Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    22. 22. Basic Properties of MaterialsBasic Properties of Materials The atoms, which areThe atoms, which are represented as points,represented as points, are not static. Instead,are not static. Instead, they oscillate about thatthey oscillate about that point and are in dynamicpoint and are in dynamic equilibrium.equilibrium. www.indiandentalacademy.comwww.indiandentalacademy.com
    23. 23. Lattice deformations:Lattice deformations: various defectsvarious defects  slipslip planesplanes--alongalong whichwhich dislocation occursdislocation occurs www.indiandentalacademy.comwww.indiandentalacademy.com
    24. 24. shear stressshear stress  atoms of the crystalsatoms of the crystals can glide along these planescan glide along these planes more the slip planesmore the slip planes easier is it toeasier is it to deformdeform Slip planes intercepted at grainSlip planes intercepted at grain boundaries-increases the resistance toboundaries-increases the resistance to further deformationfurther deformation Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    25. 25. If the shearing force is:-If the shearing force is:- SmallSmall - atoms slip, and return back to their- atoms slip, and return back to their original position (elastic deformation)original position (elastic deformation) Beyond the elastic limit -Beyond the elastic limit - crystal suffers a slight deformationcrystal suffers a slight deformation permanent (plastic deformation)permanent (plastic deformation) Greater stressGreater stress - fracture- fracture Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    26. 26. During deformation - atomic bonds withinDuring deformation - atomic bonds within the crystal get stressedthe crystal get stressed  resistance to more deformationresistance to more deformation Number of atoms that get stressed alsoNumber of atoms that get stressed also increasesincreases  resistance to moreresistance to more deformationdeformation Strain or work hardening or cold workStrain or work hardening or cold work Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    27. 27. Work hardeningWork hardening Forced interlocking of grains and atoms ofForced interlocking of grains and atoms of metal.metal. Locked in and under pressure/tensionLocked in and under pressure/tension Carried at room temperature.Carried at room temperature. www.indiandentalacademy.comwww.indiandentalacademy.com
    28. 28. Strain hardening- principleStrain hardening- principle  Hard and strong, tensile strengthHard and strong, tensile strength Brittle.Brittle. Annealing – heat below melting point.Annealing – heat below melting point.  More the cold work, more rapid the annealingMore the cold work, more rapid the annealing  Higher melting point – higher annealing temp.Higher melting point – higher annealing temp.  ½ the melting temperature (½ the melting temperature (oo K)K) Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    29. 29. ANNEALING:ANNEALING: RecoveryRecovery RecrystallizationRecrystallization Grain GrowthGrain Growth Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    30. 30. Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.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.comwww.indiandentalacademy.com
    32. 32. AnnealingAnnealing Smaller grains – harder and strongerSmaller grains – harder and stronger Larger grain boundaries to oppose the slipLarger grain boundaries to oppose the slip planes.planes. www.indiandentalacademy.comwww.indiandentalacademy.com
    33. 33. Various methods of obtaining smaller grain sizeVarious methods of obtaining smaller grain size 1.1. Enhancing crystal nucleation by adding fineEnhancing crystal nucleation by adding fine particles with a higher melting point, aroundparticles with a higher melting point, around which the atoms gather.which the atoms gather. 2.2. Preventing enlargement of existing grains.Preventing enlargement of existing grains. Abrupt cooling (quenching) of the metal.Abrupt cooling (quenching) of the metal. Dissolve specific elements at elevatedDissolve specific elements at elevated temperatures. Metal is cooledtemperatures. Metal is cooled Solute element precipitatesSolute element precipitates barriers to thebarriers to the slip planesslip planes.. Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    34. 34. Solution heat treatmentSolution heat treatment Heat below the solidus tempHeat below the solidus temp Held for sometime, - random solid solnHeld for sometime, - random solid soln Cool rapidly to room temp. retained.Cool rapidly to room temp. retained. Soft and ductileSoft and ductile AGE HARDENINGAGE HARDENING Below : ordered structureBelow : ordered structure Time periodTime period Stronger, harder but less ductile.Stronger, harder but less ductile. www.indiandentalacademy.comwww.indiandentalacademy.com
    35. 35. TwinningTwinning Closed packed hexagonal type of crystalsClosed packed hexagonal type of crystals Two symmetric halvesTwo symmetric halves Fixed angleFixed angle NiTi - multipleNiTi - multiple Subjected to a higher temperature,Subjected to a higher temperature, de - twinning occurs (shape memory)de - twinning occurs (shape memory) Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    36. 36. Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    37. 37. PolymorphismPolymorphism Metals and alloys exist as more than oneMetals and alloys exist as more than one type of structuretype of structure Transition from one to the otherTransition from one to the other Allotropy -Allotropy - reversiblereversible At higher temperature, ironAt higher temperature, iron FCC structureFCC structure (austenite)(austenite) lower temperatures,lower temperatures,  BCC structureBCC structure (ferrite)(ferrite) Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    38. 38. Transition of IronTransition of Iron IronIron  FCC stableFCC stable (austenite), 912*c-(austenite), 912*c- 1394*c1394*c Lattice spaces greater,Lattice spaces greater, Carbon atom can easily beCarbon atom can easily be incorporated into the unitincorporated into the unit cellcell www.indiandentalacademy.comwww.indiandentalacademy.com
    39. 39. Transition of IronTransition of Iron On Cooling <912*cOn Cooling <912*c FCCFCC  BCCBCC Carbon diffusesCarbon diffuses out as FeCout as FeC FeC adds strengthFeC adds strength to ferrite andto ferrite and austeniteaustenite TIMETIME www.indiandentalacademy.comwww.indiandentalacademy.com
    40. 40. Transition of IronTransition of Iron Rapidly cooledRapidly cooled (quenched)(quenched)  Carbon cannot escapeCarbon cannot escape Highly strained,Highly strained, distorted bodydistorted body centered tetragonalcentered tetragonal lattice calledlattice called martensitemartensite www.indiandentalacademy.comwww.indiandentalacademy.com
    41. 41. Grain boundaries are more in numberGrain boundaries are more in number Alloy is stronger and more brittle-Alloy is stronger and more brittle- martensitic change – various types of steelmartensitic change – various types of steel Interstitials are intentionally incorporatedInterstitials are intentionally incorporated into the alloy to make it hard when it isinto the alloy to make it hard when it is quenched.quenched. Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    42. 42. Cooled slowlyCooled slowly Other crystal structures are formed atOther crystal structures are formed at intermediate temperaturesintermediate temperatures SofterSofter Some are stable at room temperatureSome are stable at room temperature Ultimately, the final structure is softer andUltimately, the final structure is softer and more workablemore workable Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    43. 43. Tempering –Tempering – Reheat the alloy to intermediateReheat the alloy to intermediate temperature(1000*F/525*c)temperature(1000*F/525*c) Partial transformation into softer alloysPartial transformation into softer alloys Remedy brittle martensiteRemedy brittle martensite more workablemore workable Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    44. 44. Some alloysSome alloys FCC to BCC by rearrangement of atomsFCC to BCC by rearrangement of atoms  Diagonal plane of the BCC unit becomes theDiagonal plane of the BCC unit becomes the face of the FCC unitface of the FCC unit Basic Properties of MaterialsBasic Properties of Materials www.indiandentalacademy.comwww.indiandentalacademy.com
    45. 45. Shape memory alloys – Easy switchingShape memory alloys – Easy switching from one type of structure to another.from one type of structure to another. Bain distortionBain distortion Over a range of temperature {hysteresis}Over a range of temperature {hysteresis} unlike ironunlike iron www.indiandentalacademy.comwww.indiandentalacademy.com
    46. 46. Elastic PropertiesElastic Properties Stress and strainStress and strain Stress- internal distribution of load.Stress- internal distribution of load. F/AF/A Strain- internal distortion produced by loadStrain- internal distortion produced by load deflection/unit lengthdeflection/unit length www.indiandentalacademy.comwww.indiandentalacademy.com
    47. 47. Elastic PropertiesElastic Properties Force applied to wireForce applied to wire DeflectionDeflection Internal force----Internal force---- (equal and opposite)(equal and opposite) Internal forceInternal force = Stress= Stress Area of actionArea of action DeflectionDeflection change in lengthchange in length = Strain= Strain Original lengthOriginal length www.indiandentalacademy.comwww.indiandentalacademy.com
    48. 48. Elastic PropertiesElastic Properties Types of stress/strainTypes of stress/strain Tensile –Tensile –stretch/pullstretch/pull Compressive –Compressive – compress/towards each othercompress/towards each other Shear – 2 forcesShear – 2 forces opp direction, not in same line.opp direction, not in same line. sliding of one part over anothersliding of one part over another Complex force systemsComplex force systems www.indiandentalacademy.comwww.indiandentalacademy.com
    49. 49. Elastic PropertiesElastic Properties Strain Stress Elastic Portion Wire returns back to original dimension when stress is removed www.indiandentalacademy.comwww.indiandentalacademy.com
    50. 50. Elastic PropertiesElastic Properties Hooke’s lawHooke’s law Spring stretch in proportion to applied forceSpring stretch in proportion to applied force (proportional limit)(proportional limit) Modulus of elasticity – constant for a givenModulus of elasticity – constant for a given materialmaterial www.indiandentalacademy.comwww.indiandentalacademy.com
    51. 51. Elastic PropertiesElastic Properties Strain Stress Elastic Limit Proportional Limit Yield strength 0.1% www.indiandentalacademy.comwww.indiandentalacademy.com
    52. 52. Elastic PropertiesElastic Properties Strain Stress Ultimate Tensile Strength Fracture Point www.indiandentalacademy.comwww.indiandentalacademy.com
    53. 53. Elastic PropertiesElastic Properties ultimate tensile strengthultimate tensile strength is higher than theis higher than the yield strengthyield strength important clinicallyimportant clinically  maximum force thatmaximum force that the wire can deliverthe wire can deliver Ultimate tensile strength higher than theUltimate tensile strength higher than the stress at the point of fracturestress at the point of fracture  reduction in the diameter of the wirereduction in the diameter of the wire www.indiandentalacademy.comwww.indiandentalacademy.com
    54. 54. Elastic PropertiesElastic Properties Strain Stress Slope α Stiffness Stiffness α 1 . Springiness www.indiandentalacademy.comwww.indiandentalacademy.com
    55. 55. Elastic PropertiesElastic Properties Strain Stress Range Springback Point of arbitrary clinical loading Yield point www.indiandentalacademy.comwww.indiandentalacademy.com
    56. 56. Elastic PropertiesElastic Properties Clinically, ortho wires are deformed beyond their elastic limit. Springback properties are important Strength = Stiffness x Range www.indiandentalacademy.comwww.indiandentalacademy.com
    57. 57. Elastic PropertiesElastic Properties Resiliency -Resiliency - When a wire is stretched, the space between theWhen a wire is stretched, the space between the atoms increases. Within the elastic limit, there isatoms increases. Within the elastic limit, there is an attractive force between the atoms.an attractive force between the atoms. Energy stored within the wire.Energy stored within the wire. Strength + springinessStrength + springiness www.indiandentalacademy.comwww.indiandentalacademy.com
    58. 58. Elastic PropertiesElastic Properties Strain Stress Resilience Formability Proportional limit Yield strength www.indiandentalacademy.comwww.indiandentalacademy.com
    59. 59. Elastic PropertiesElastic Properties FormabilityFormability - amount of permanent- amount of permanent deformation that the wire can withstanddeformation that the wire can withstand without breakingwithout breaking Indication of the ability of the wire to takeIndication of the ability of the wire to take the shapethe shape Also an indication of the amount of coldAlso an indication of the amount of cold work that they can withstandwork that they can withstand www.indiandentalacademy.comwww.indiandentalacademy.com
    60. 60. Elastic PropertiesElastic Properties FlexibilityFlexibility large deformation (or large strain) withlarge deformation (or large strain) with minimal force, within its elastic limit.minimal force, within its elastic limit. Maximal flexibility is the strain that occursMaximal flexibility is the strain that occurs when a wire is stressed to its elastic limit.when a wire is stressed to its elastic limit. Max. flexibility =Max. flexibility = Proportional limitProportional limit Modulus of elasticity.Modulus of elasticity. www.indiandentalacademy.comwww.indiandentalacademy.com
    61. 61. Elastic PropertiesElastic Properties ToughnessToughness ––force required to fracture aforce required to fracture a material. Total area under the stress –material. Total area under the stress – strain graph.strain graph. BrittlenessBrittleness ––opposite of toughness. Aopposite of toughness. A brittle material, is elastic, butbrittle material, is elastic, but cannotcannot undergo plastic deformationundergo plastic deformation. eg: Glass. eg: Glass FatigueFatigue –– Repeated cyclic stress of aRepeated cyclic stress of a magnitude below the fracture point of amagnitude below the fracture point of a wire can result in fracture. This is calledwire can result in fracture. This is called fatigue.fatigue. www.indiandentalacademy.comwww.indiandentalacademy.com
    62. 62. www.indiandentalacademy.comwww.indiandentalacademy.com
    63. 63. Properties ofProperties of OrthodonticOrthodontic WiresWires Part I Dr. Vijaya Lakshmi www.indiandentalacademy.comwww.indiandentalacademy.com
    64. 64. Elastic PropertiesElastic Properties www.indiandentalacademy.comwww.indiandentalacademy.com
    65. 65. Elastic PropertiesElastic Properties www.indiandentalacademy.comwww.indiandentalacademy.com
    66. 66. Elastic PropertiesElastic Properties Strain Stress Resilience Formability Proportional limit Yield strength www.indiandentalacademy.comwww.indiandentalacademy.com
    67. 67. Requirements of an ideal archwireRequirements of an ideal archwire (Kusy )(Kusy ) 1.1. EstheticsEsthetics 2.2. StiffnessStiffness 3.3. StrengthStrength 4.4. RangeRange 5.5. SpringbackSpringback 6.6. FormabilityFormability 7.7. ResiliencyResiliency 8.8. Coefficient of frictionCoefficient of friction 9.9. BiohostabilityBiohostability 10.10. BiocompatibilityBiocompatibility 11.11. WeldabilityWeldability www.indiandentalacademy.comwww.indiandentalacademy.com
    68. 68. 1. Esthetics1. Esthetics DesirableDesirable No compromise on mechanical propertiesNo compromise on mechanical properties White coloured wires discolourWhite coloured wires discolour Destroyed by oral enzymesDestroyed by oral enzymes Deformed by masticatory loadsDeformed by masticatory loads Except the composite wiresExcept the composite wires www.indiandentalacademy.comwww.indiandentalacademy.com
    69. 69. 2. Stiffness / Load deflection Rate2. Stiffness / Load deflection Rate Proffit:Proffit: - slope of stress-strain curve- slope of stress-strain curve ThurowThurow - force:distance ratio, measure of- force:distance ratio, measure of resistance to deformation.resistance to deformation. BurstoneBurstone – Stiffness is related to – wire– Stiffness is related to – wire property & appliance designproperty & appliance design Wire property is related to – Material &Wire property is related to – Material & cross section.cross section. WilcockWilcock – Stiffness α– Stiffness α LoadLoad www.indiandentalacademy.comwww.indiandentalacademy.com
    70. 70. Stiffness / Load deflection RateStiffness / Load deflection Rate Magnitude of the force delivered by the applianceMagnitude of the force delivered by the appliance for a particular amount of deflection.for a particular amount of deflection. Low stiffness or Low LDR implies thatLow stiffness or Low LDR implies that:-:- 1) Low forces will be applied1) Low forces will be applied 2) The force will be more constant as the appliance2) The force will be more constant as the appliance deactivatesdeactivates 3) Greater ease and accuracy in applying a given3) Greater ease and accuracy in applying a given force.force. www.indiandentalacademy.comwww.indiandentalacademy.com
    71. 71. 3 point bending test3 point bending test www.indiandentalacademy.comwww.indiandentalacademy.com
    72. 72. 3. Strength3. Strength Yield strength, proportional limit and ultimateYield strength, proportional limit and ultimate tensile/compressive strengthtensile/compressive strength KusyKusy - force required to activate an archwire- force required to activate an archwire to a specific distance.to a specific distance. ProffitProffit - Strength = stiffness x range.- Strength = stiffness x range. Range limits the amount the wire can beRange limits the amount the wire can be bent, Stiffness is the indication of the forcebent, Stiffness is the indication of the force required to reach that limit.required to reach that limit.www.indiandentalacademy.comwww.indiandentalacademy.com
    73. 73. StrengthStrength TheThe shapeshape andand cross sectioncross section of a wireof a wire have an effect on the strength of the wire.have an effect on the strength of the wire. The effects of these will be consideredThe effects of these will be considered subsequently.subsequently. www.indiandentalacademy.comwww.indiandentalacademy.com
    74. 74. 4. Range4. Range Distance that the wire bends elastically,Distance that the wire bends elastically, before permanent deformation occursbefore permanent deformation occurs ((ProffitProffit).). KusyKusy – Distance to which an archwire can– Distance to which an archwire can be activated- working range.be activated- working range. ThurowThurow – A linear measure of how far a– A linear measure of how far a wire or material can be deformed withoutwire or material can be deformed without exceeding the limits of the material.exceeding the limits of the material.www.indiandentalacademy.comwww.indiandentalacademy.com
    75. 75. 5.5. SpringbackSpringback KusyKusy -- The extent to which a wire-- The extent to which a wire recovers its shape after deactivationrecovers its shape after deactivation Ingram et alIngram et al – a measure of how far a wire– a measure of how far a wire can be deflected without causingcan be deflected without causing permanent deformation. (Contrast topermanent deformation. (Contrast to ProffitProffit yield pointyield point).). www.indiandentalacademy.comwww.indiandentalacademy.com
    76. 76. 5.5. SpringbackSpringback Large springbackLarge springback Activated to a large extent.Activated to a large extent. Hence it will mean fewer archwireHence it will mean fewer archwire changes.changes. Ratio –Ratio – yield strengthyield strength Modulus of elasticityModulus of elasticity www.indiandentalacademy.comwww.indiandentalacademy.com
    77. 77. 6.6. FormabilityFormability KusyKusy – the ease in which a material may– the ease in which a material may be permanently deformed.be permanently deformed. Ease of forming a spring or archwireEase of forming a spring or archwire Proffit:Proffit: amount of permanent deformationamount of permanent deformation a wire can withstand without breakinga wire can withstand without breaking www.indiandentalacademy.comwww.indiandentalacademy.com
    78. 78. 7.7. ResiliencyResiliency Store/absorb more strain energy /unitStore/absorb more strain energy /unit volume before they get permanentlyvolume before they get permanently deformeddeformed Greater resistance to permanentGreater resistance to permanent deformationdeformation Release of greater amount of energy onRelease of greater amount of energy on deactivationdeactivation High work availability to move the teethHigh work availability to move the teeth www.indiandentalacademy.comwww.indiandentalacademy.com
    79. 79. 8.8. Coefficient of frictionCoefficient of friction Brackets (and teeth) must be able to slideBrackets (and teeth) must be able to slide along the wirealong the wire High amounts of frictionHigh amounts of friction  anchor loss.anchor loss. www.indiandentalacademy.comwww.indiandentalacademy.com
    80. 80. 9.9. Biohostability:- site for accumulation ofBiohostability:- site for accumulation of bacteria, spores or viruses. An idealbacteria, spores or viruses. An ideal archwire must have poor biohostability.archwire must have poor biohostability. 10.10.Biocompatibility:- Resistance ofBiocompatibility:- Resistance of corrosion, and tissue tolerance to the wire.corrosion, and tissue tolerance to the wire. 11. Weldability:- the ease by which the11. Weldability:- the ease by which the wire can be joined to other metals, bywire can be joined to other metals, by actually melting the 2 metals in the area ofactually melting the 2 metals in the area of the bond. (A filler metal may or may not bethe bond. (A filler metal may or may not be used.)used.) www.indiandentalacademy.comwww.indiandentalacademy.com
    81. 81. Properties of WiresProperties of Wires Before the titanium alloys wereBefore the titanium alloys were introduced into orthodontics, theintroduced into orthodontics, the practitioners used only steel wires. Sopractitioners used only steel wires. So the way to control the stiffness of the wirethe way to control the stiffness of the wire was:-was:- 1.1. Change the cross section of the wireChange the cross section of the wire 2.2. Increase the length of the wire (Increase the length of the wire ( interinter bracket distance, incorporate loops.)bracket distance, incorporate loops.) www.indiandentalacademy.comwww.indiandentalacademy.com
    82. 82. Effects of Wire Cross SectionEffects of Wire Cross Section Wires of various dimensions and crossWires of various dimensions and cross sections.sections. Does the wire need to be move teeth overDoes the wire need to be move teeth over large distances, or does it need to correctlarge distances, or does it need to correct the torque of the tooth?the torque of the tooth? Is it primarily going to be used to correctIs it primarily going to be used to correct first order irregularities, or second order?first order irregularities, or second order? www.indiandentalacademy.comwww.indiandentalacademy.com
    83. 83. Effects of Wire Cross SectionEffects of Wire Cross Section primary factorprimary factor  load deflection rate or stiffnessload deflection rate or stiffness play of the wireplay of the wire in the second order –in the second order – 0.016” wire in 0.022” slot is only 1.15 times the play of a0.016” wire in 0.022” slot is only 1.15 times the play of a 0.018” wire.0.018” wire. The play in the second order becomes significant if theThe play in the second order becomes significant if the wire dimensions are drastically different (0.010” andwire dimensions are drastically different (0.010” and 0.020”)0.020”) www.indiandentalacademy.comwww.indiandentalacademy.com
    84. 84. Effects of Wire Cross SectionEffects of Wire Cross Section Based on stiffness/load deflection rate Force delivered by a wire with high load deflection rate www.indiandentalacademy.comwww.indiandentalacademy.com
    85. 85. Effects of Wire Cross SectionEffects 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.comwww.indiandentalacademy.com
    86. 86. Load deflection rateLoad deflection rate Shape Moment of Inertia Ratio to stiffness of round wire Пd4 64 1 s4 12 1.7 b3 h 12 1.7 b3 h:d4 www.indiandentalacademy.comwww.indiandentalacademy.com
    87. 87. Effects of Wire Cross SectionEffects of Wire Cross Section Dimension of wire increases- LDRDimension of wire increases- LDR increasesincreases Round and square wire of sameRound and square wire of same dimension-LDR of square wire is more.dimension-LDR of square wire is more. Rectangular wire – maximum stiffnessRectangular wire – maximum stiffness www.indiandentalacademy.comwww.indiandentalacademy.com
    88. 88. Effects of Wire Cross SectionEffects of Wire Cross Section Stiffness of different dimensions of wiresStiffness of different dimensions of wires can be related to each other.can be related to each other. 0 500 1000 1500 2000 2500 3000 3500 Stiffnessnumber (Burstone) 14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 18x25 25x18 21x25 25x21 215x28 28x215 Wire dimension Relative stiffness www.indiandentalacademy.comwww.indiandentalacademy.com
    89. 89. Effects of Wire Cross SectionEffects of Wire Cross Section Rectangular wiresRectangular wires  bending perpendicular tobending perpendicular to the larger dimension (ribbon mode)the larger dimension (ribbon mode) easier than bending perpendicular to the smallereasier than bending perpendicular to the smaller dimension (edgewise).dimension (edgewise). 0 500 1000 1500 2000 2500 3000 3500 Stiffnessnumber (Burstone) 14 16 18 20 22 16x16 18x18 21x21 16x22 22x16 18x25 25x18 21x25 25x21 215x28 28x215 Wire dimension Relative stiffness www.indiandentalacademy.comwww.indiandentalacademy.com
    90. 90. Effects of Wire Cross SectionEffects of Wire Cross Section The larger dimensionThe larger dimension  correction is needed.correction is needed. The smaller dimensionThe smaller dimension  the plane in whichthe plane in which more stiffness is needed.more stiffness is needed. > first order, < second order – RIBBON> first order, < second order – RIBBON > Second order, < first order - EDGEWISE> Second order, < first order - EDGEWISE www.indiandentalacademy.comwww.indiandentalacademy.com
    91. 91. Effects of Wire Cross SectionEffects of Wire Cross Section > 1> 1stst order correction in anterior segmentorder correction in anterior segment > 2> 2ndnd order in the posterior segment,order in the posterior segment, wire can be twisted 90wire can be twisted 90oo If both, 1If both, 1stst & 2& 2ndnd order corrections are required toorder corrections are required to the same extent, thenthe same extent, then squaresquare oror round wires.round wires. The square wires - advantage -The square wires - advantage - simultaneouslysimultaneously control torquecontrol torque better orientation into a rectangular slot.better orientation into a rectangular slot. www.indiandentalacademy.comwww.indiandentalacademy.com
    92. 92. Effects of Wire Cross SectionEffects of Wire Cross Section Cross-sectional shape:Cross-sectional shape:  On range and strengthOn range and strength  Diameter increases-strengthDiameter increases-strength thirdthird powerpower of diameterof diameter  Range increases proportional toRange increases proportional to diameterdiameter www.indiandentalacademy.comwww.indiandentalacademy.com
    93. 93. Effects of Wire Cross SectionEffects of Wire Cross Section In torsion - absolute values of strength,In torsion - absolute values of strength, stiffness and range are different,stiffness and range are different, but the overall effect of changing thebut the overall effect of changing the diameter of the wire is the same.diameter of the wire is the same. 1.1. Strength – Increases with increase inStrength – Increases with increase in diameterdiameter 2.2. Stiffness – increasesStiffness – increases 3.3. Range –Range – decreases.decreases.www.indiandentalacademy.comwww.indiandentalacademy.com
    94. 94. Effects of LengthEffects of Length Loops,Loops,  the inter-bracket distancethe inter-bracket distance For bendingFor bending 1.1. Strength – decreases proportionatelyStrength – decreases proportionately 2.2. Stiffness – decreases as aStiffness – decreases as a cubiccubic functionfunction 3.3. Range – increases as aRange – increases as a squaresquare.. www.indiandentalacademy.comwww.indiandentalacademy.com
    95. 95. Effects of LengthEffects of Length In the case ofIn the case of torsiontorsion, the picture is, the picture is slightly different.slightly different. Increase in length:Increase in length: –– 1.1. Stiffness decreases proportionatelyStiffness decreases proportionately 2.2. Range increases proportionatelyRange increases proportionately 3.3. Strength remains unchanged.Strength remains unchanged. www.indiandentalacademy.comwww.indiandentalacademy.com
    96. 96. Effects of LengthEffects of Length Way the beam is attached also affects theWay the beam is attached also affects the valuesvalues cantilever, the stiffness of a wire iscantilever, the stiffness of a wire is obviously lessobviously less wire is supported from both sides (as anwire is supported from both sides (as an archwire in brackets), again, the stiffnessarchwire in brackets), again, the stiffness is affectedis affected www.indiandentalacademy.comwww.indiandentalacademy.com
    97. 97. Effects of LengthEffects of Length Cantilever Beam supported on both ends Fixed at both ends www.indiandentalacademy.comwww.indiandentalacademy.com
    98. 98. Effects of LengthEffects of Length Stiffness is also affected by the method ofStiffness is also affected by the method of ligation of the wire into the brackets.ligation of the wire into the brackets. Loosely ligated, so that it can slide throughLoosely ligated, so that it can slide through the brackets, it has ¼th the stiffness of athe brackets, it has ¼th the stiffness of a wire that is tightly ligated.wire that is tightly ligated. www.indiandentalacademy.comwww.indiandentalacademy.com
    99. 99. Clinical ImplicationsClinical Implications LIGHT CONTINUOUS FORCESLIGHT CONTINUOUS FORCES Stiff wires should be taboo to theStiff wires should be taboo to the orthodontist?orthodontist? Springier wire, can be easily distorted inSpringier wire, can be easily distorted in the harsh oral environment.the harsh oral environment. Aim atAim at balancebalance.. www.indiandentalacademy.comwww.indiandentalacademy.com
    100. 100. Clinical ImplicationsClinical Implications Removable applianceRemovable appliance cantilever springcantilever spring The material of choice is usually steel. (StiffThe material of choice is usually steel. (Stiff material)material) Sufficiently thick steel wireSufficiently thick steel wire Good strength to resist masticatory and otherGood strength to resist masticatory and other oral forces.oral forces. Increase the length of the wireIncrease the length of the wire   ProportionateProportionate decrease in strength, but thedecrease in strength, but the stiffness will decrease as astiffness will decrease as a cubiccubic functionfunction  Length is increased by eitherLength is increased by either bending the wirebending the wire over itselfover itself, or by winding, or by winding helicalshelicals oror loopsloops intointo the springthe spring www.indiandentalacademy.comwww.indiandentalacademy.com
    101. 101. Clinical ImplicationsClinical Implications In archwires of stiffer materials the sameIn archwires of stiffer materials the same principle can be used.principle can be used. The length of wire between brackets canThe length of wire between brackets can be increasedbe increased  loops, or smaller brackets, or special bracketloops, or smaller brackets, or special bracket designs.designs. Also, the use of flexible wiresAlso, the use of flexible wires Multistranded wiresMultistranded wires www.indiandentalacademy.comwww.indiandentalacademy.com
    102. 102. Variable cross-section orthodontics.Variable cross-section orthodontics. Variable modulus orthodontics.Variable modulus orthodontics. www.indiandentalacademy.comwww.indiandentalacademy.com
    103. 103. Clinical ImplicationsClinical Implications NiTi – high springbackNiTi – high springback Initial stages – NiTi instead of steelInitial stages – NiTi instead of steel Towards the end- stiff steel wireTowards the end- stiff steel wire TMA - intermediate properties- transitionTMA - intermediate properties- transition wirewire www.indiandentalacademy.comwww.indiandentalacademy.com
    104. 104. Clinical ImplicationsClinical Implications variable modulus orthodontics –variable modulus orthodontics – Advantage-Advantage-  relatively constant dimensionrelatively constant dimension  important for the third order controlimportant for the third order control variable stiffness approach,variable stiffness approach,  compromise control for getting a wire withcompromise control for getting a wire with adequate stiffness,adequate stiffness,  had to spend clinical time bending loops intohad to spend clinical time bending loops into stiffer archwires, which would offer less play.stiffer archwires, which would offer less play. www.indiandentalacademy.comwww.indiandentalacademy.com
    105. 105. Clinical ImplicationsClinical Implications Requirements of arch wires in different stages of treatment www.indiandentalacademy.comwww.indiandentalacademy.com
    106. 106. AppropriateAppropriate wirewire Take into account the amount of force that wireTake into account the amount of force that wire can deliver.can deliver. For example, a NiTi wireFor example, a NiTi wire  efficient in tippingefficient in tipping teeth to get them into alignment, but may not beteeth to get them into alignment, but may not be able to achieve third order corrections.able to achieve third order corrections. After using rectangular NiTi wires for alignment,After using rectangular NiTi wires for alignment, rectangular steel wire must always be used torectangular steel wire must always be used to achieve the correct torque of the tooth.achieve the correct torque of the tooth. www.indiandentalacademy.comwww.indiandentalacademy.com
    107. 107. NomogramsNomograms www.indiandentalacademy.comwww.indiandentalacademy.com
    108. 108. NomogramsNomograms www.indiandentalacademy.comwww.indiandentalacademy.com
    109. 109. AA rough idea can be obtained clinically as wellrough idea can be obtained clinically as well Forming an arch wire with the thumb givesForming an arch wire with the thumb gives an indication of thean indication of the stiffnessstiffness of the wire.of the wire. Flexing the wires between the fingers,Flexing the wires between the fingers, without deforming it, is a measure ofwithout deforming it, is a measure of flexibilityflexibility Deflecting the ends of an archwire betweenDeflecting the ends of an archwire between the thumb and finger gives a measure ofthe thumb and finger gives a measure of resiliency.resiliency. www.indiandentalacademy.comwww.indiandentalacademy.com
    110. 110. CorrosionCorrosion Nickel -Nickel - 1.1. Carcinogenic,Carcinogenic, 2.2. mutagenic,mutagenic, 3.3. cytotoxic andcytotoxic and 4.4. allergenic.allergenic.  Stainless steels, Co-Cr-Ni alloys and NiTiStainless steels, Co-Cr-Ni alloys and NiTi are all rich in Niare all rich in Ni www.indiandentalacademy.comwww.indiandentalacademy.com
    111. 111. CorrosionCorrosion Placement in the oral cavityPlacement in the oral cavity  Greater peril than implantingGreater peril than implanting  Implanted material gets surrounded by aImplanted material gets surrounded by a connective tissue capsuleconnective tissue capsule  In the oral cavity, the alloy is free to reactIn the oral cavity, the alloy is free to react with the environment.with the environment.www.indiandentalacademy.comwww.indiandentalacademy.com
    112. 112. CorrosionCorrosion Stainless steel- Ni austenite stabilizer. NotStainless steel- Ni austenite stabilizer. Not strongly bonded- slow releasestrongly bonded- slow release Passivating filmPassivating film  traces of Fe ,Ni and Mo.traces of Fe ,Ni and Mo. Aqueous environmentAqueous environment  inner oxide layerinner oxide layer  outer hydroxide layer.outer hydroxide layer. CrO is not as efficient as TiO in resistingCrO is not as efficient as TiO in resisting corrosioncorrosion some Ni releasesome Ni release Improper handlingImproper handling  sensitizationsensitization www.indiandentalacademy.comwww.indiandentalacademy.com
    113. 113. CorrosionCorrosion 1.1. Uniform attack –Uniform attack – the entire wire reacts with thethe entire wire reacts with the environment,environment, hydroxides or organometallic compoundshydroxides or organometallic compounds detectable after a large amount of metaldetectable after a large amount of metal is dissolved.is dissolved. 2.2. Pitting CorrosionPitting Corrosion –– manufacturing defectsmanufacturing defects sites of easy attacksites of easy attack www.indiandentalacademy.comwww.indiandentalacademy.com
    114. 114. CorrosionCorrosion Stainless Steel NiTi Pitting corrosion www.indiandentalacademy.comwww.indiandentalacademy.com
    115. 115. CorrosionCorrosion 3.3. Crevice corrosion or gasket corrosion -Crevice corrosion or gasket corrosion - Parts of the wire exposed to corrosiveParts of the wire exposed to corrosive environmentenvironment Sites of tying to the bracketsSites of tying to the brackets Plaque build upPlaque build up  disturbs the regeneration ofdisturbs the regeneration of the passivating layerthe passivating layer Reach upto 2-5 mmReach upto 2-5 mm High amount of metals can be dissolved in theHigh amount of metals can be dissolved in the mouth.mouth. www.indiandentalacademy.comwww.indiandentalacademy.com
    116. 116. CorrosionCorrosion 4.4. GalvanicGalvanic //Electrochemical CorrosionElectrochemical Corrosion two metals are joinedtwo metals are joined or even the same metal after different type ofor even the same metal after different type of treatment (soldering etc)treatment (soldering etc) difference in the reactivitydifference in the reactivity  Galvanic cell.Galvanic cell.   Less ReactiveLess Reactive More ReactiveMore Reactive (Cathodic)(Cathodic) (Anodic(Anodic) less) less noble metalnoble metal www.indiandentalacademy.comwww.indiandentalacademy.com
    117. 117. CorrosionCorrosion AnodicAnodic  Looses ElectronsLooses Electrons  Soluble ionsSoluble ions  Leach outLeach out Cathodic (nobel)Cathodic (nobel)  Accepts electronsAccepts electrons  Even less reactiveEven less reactive S.Steel- active and passive areas : depletion & regeneration of passivating film www.indiandentalacademy.comwww.indiandentalacademy.com
    118. 118. CorrosionCorrosion 5.5. Intergranular corrosionIntergranular corrosion Sensitization - ppt of CrCSensitization - ppt of CrC 6.6. Fretting corrosionFretting corrosion Wire and brackets contactWire and brackets contact FrictionFriction  surface destructionsurface destruction PressurePressure  rupture of the oxide layerrupture of the oxide layer Debris get deposited at grain boundaries, grainDebris get deposited at grain boundaries, grain structure is disturbed.structure is disturbed. www.indiandentalacademy.comwww.indiandentalacademy.com
    119. 119. CorrosionCorrosion 7.7. Microbiologically influenced corrosionMicrobiologically influenced corrosion AdhesiveAdhesive Craters at the base of bracketsCraters at the base of brackets Or wires directly bonded on to teethOr wires directly bonded on to teeth shown by Matasa.shown by Matasa. Certain bacteria dissolve metals directlyCertain bacteria dissolve metals directly form the wires.form the wires. Others affect surface structure.Others affect surface structure. www.indiandentalacademy.comwww.indiandentalacademy.com
    120. 120. Micro-0rganisms on various dentalMicro-0rganisms on various dental materialsmaterials www.indiandentalacademy.comwww.indiandentalacademy.com
    121. 121. CorrosionCorrosion 8.8. Stress corrosionStress corrosion Similar to galvanic corrosionSimilar to galvanic corrosion Bending of wiresBending of wires  different degress ofdifferent degress of tension and compression.tension and compression. Alter theAlter the electrochemical behaviorelectrochemical behavior   anode cathodeanode cathode www.indiandentalacademy.comwww.indiandentalacademy.com
    122. 122. CorrosionCorrosion 9.9. CorrosionCorrosion Fatigue:Fatigue: Cyclic stressing of a wireCyclic stressing of a wire Resistance to fracture decreasesResistance to fracture decreases Accelerated in a corrosive medium suchAccelerated in a corrosive medium such as salivaas saliva www.indiandentalacademy.comwww.indiandentalacademy.com
    123. 123. CorrosionCorrosion Analysis of used wires also indicated that aAnalysis of used wires also indicated that a biofilmbiofilm was formed on the wire.was formed on the wire. Eliades et alEliades et al CalcificationCalcification  Shielding the wireShielding the wire  Protecting the patient from the alloyProtecting the patient from the alloy Stainless steel: Fe, Ni, Cr. Allergic potentialStainless steel: Fe, Ni, Cr. Allergic potential www.indiandentalacademy.comwww.indiandentalacademy.com
    124. 124. OrthOdOntic Arch Wire MAteriAls www.indiandentalacademy.comwww.indiandentalacademy.com
    125. 125. Precious MetalsPrecious Metals Upto about the 1950sUpto about the 1950s Gold alloysGold alloys Only wire which would tolerate the oralOnly wire which would tolerate the oral environmentenvironment Crozat appliance – according to originalCrozat appliance – according to original designdesign www.indiandentalacademy.comwww.indiandentalacademy.com
    126. 126. Stainless SteelStainless Steel 1919 – Germany1919 – Germany  used to makeused to make prostheses.prostheses. Extremely chemically stableExtremely chemically stable High resistance to corrosion.High resistance to corrosion. Chromium content.Chromium content. The chromium gets oxidized,The chromium gets oxidized,  Impermeable, corrosion resistant layer.Impermeable, corrosion resistant layer. www.indiandentalacademy.comwww.indiandentalacademy.com
    127. 127. Stainless SteelStainless Steel Variety of stainless steelsVariety of stainless steels Varying the degree of coldVarying the degree of cold work and annealing duringwork and annealing during manufacturemanufacture Fully annealed stainlessFully annealed stainless steelsteel  extremely soft, andextremely soft, and highly formablehighly formable Ligature wireLigature wire ““Dead soft”Dead soft” www.indiandentalacademy.comwww.indiandentalacademy.com
    128. 128. Stainless SteelStainless Steel stainless steel arch wires are cold workedstainless steel arch wires are cold worked to varying extents,to varying extents,  yield strengthyield strength increases, at the cost of their formabilityincreases, at the cost of their formability The steel with the highest yield strength,The steel with the highest yield strength, the Supreme grade steels, are also verythe Supreme grade steels, are also very brittle, and break easily when bentbrittle, and break easily when bent sharply.sharply. www.indiandentalacademy.comwww.indiandentalacademy.com
    129. 129. Stainless SteelStainless Steel Structure and compositionStructure and composition Chromium (11-26%)–Chromium (11-26%)–improves the corrosionimproves the corrosion resistanceresistance Stabilizes BCC phaseStabilizes BCC phase Nickel(0-22%) – austenitic stabilizerNickel(0-22%) – austenitic stabilizer copper, manganese and nitrogen - similarcopper, manganese and nitrogen - similar  amount of nickel added to the alloyamount of nickel added to the alloy  adversely affect the corrosion resistance.adversely affect the corrosion resistance. www.indiandentalacademy.comwww.indiandentalacademy.com
    130. 130. Stainless SteelStainless Steel Carbon (0.08-1.2%)– provides strengthCarbon (0.08-1.2%)– provides strength Reduces the corrosion resistanceReduces the corrosion resistance SensitizationSensitization.. During soldering or welding, 425-815During soldering or welding, 425-815oo cc Chromium diffuses towards the carbonChromium diffuses towards the carbon rich areas (usually the grain boundaries)rich areas (usually the grain boundaries) www.indiandentalacademy.comwww.indiandentalacademy.com
    131. 131. Stainless SteelStainless Steel Chromium carbidesChromium carbides Amount of chromium decreasesAmount of chromium decreases Chromium carbide is soluble,Chromium carbide is soluble,  intergranular corrosion.intergranular corrosion. StabilizationStabilization www.indiandentalacademy.comwww.indiandentalacademy.com
    132. 132. Stabilization –  Element which precipitates carbide moreElement which precipitates carbide more easily than Chromium.easily than Chromium.  Usu. Titanium.Usu. Titanium.  Ti 6x> CarbonTi 6x> Carbon  No sensitization during soldering.No sensitization during soldering.  Most steels used in orthodontics are notMost steels used in orthodontics are not stabilized.stabilized. Stainless SteelStainless Steel www.indiandentalacademy.comwww.indiandentalacademy.com
    133. 133. Stainless SteelStainless Steel SiliconSilicon – (low concentrations) improves the– (low concentrations) improves the resistance to oxidation and carburization at highresistance to oxidation and carburization at high temperatures.temperatures. SulfurSulfur (0.015%) increases ease of machining(0.015%) increases ease of machining Phosphorous – allows sintering at lower– allows sintering at lower temperatures.temperatures. But both sulfur and phosphorousBut both sulfur and phosphorous reduce thereduce the corrosion resistance.corrosion resistance. www.indiandentalacademy.comwww.indiandentalacademy.com
    134. 134. Manufacture: AISI ,Manufacture: AISI ,specially for orthodontic purposesspecially for orthodontic purposes Various steps –Various steps – 1.1. MeltingMelting 2.2. Ingot FormationIngot Formation 3.3. RollingRolling 4.4. DrawingDrawing MANUFACTUREMANUFACTURE www.indiandentalacademy.comwww.indiandentalacademy.com
    135. 135. MeltingMelting  Various metals of the alloy are meltedVarious metals of the alloy are melted  Proportion influences the propertiesProportion influences the properties Ingot formationIngot formation  Molten alloy into mold.Molten alloy into mold.  Non uniform chunk of metalNon uniform chunk of metal  Porosities and slag.Porosities and slag.  Grains seen in the ingot – control ofGrains seen in the ingot – control of mechanical propertiesmechanical properties stepssteps www.indiandentalacademy.comwww.indiandentalacademy.com
    136. 136.  Porosities due to dissolved gases (produced /Porosities due to dissolved gases (produced / trapped)trapped)  Vacuum voids due to shrinking of late coolingVacuum voids due to shrinking of late cooling interior.interior.  Important to control microstructure at thisImportant to control microstructure at this stage – basis of its phy properties andstage – basis of its phy properties and mechanical performancemechanical performance Ingot formationIngot formation www.indiandentalacademy.comwww.indiandentalacademy.com
    137. 137. Rolling –Rolling –  First mechanical process.First mechanical process.  Ingot reduced to thinner barsIngot reduced to thinner bars  Finally form a wireFinally form a wire  Different wires from the same batch, differ inDifferent wires from the same batch, differ in propertiesproperties stepssteps www.indiandentalacademy.comwww.indiandentalacademy.com
    138. 138.  Retain their property even after rollingRetain their property even after rolling  Shape & arrangement alteredShape & arrangement altered  Grains get elongated, defects get rearrangedGrains get elongated, defects get rearranged  Work hardening – structure locked up.Work hardening – structure locked up.  Wires start to crack if rolling continuedWires start to crack if rolling continued  AnnealingAnnealing is done- mobileis done- mobile  Cooling – structure resembles original ingot, uniformCooling – structure resembles original ingot, uniform RollingRolling www.indiandentalacademy.comwww.indiandentalacademy.com
    139. 139. DrawingDrawing  More preciseMore precise  IngotIngot  final size.final size.  Wire pulled through small hole in a dieWire pulled through small hole in a die  Progressively smaller diameter-uniform squeezing.Progressively smaller diameter-uniform squeezing.  Same pressure all around, instead of from 2 oppositeSame pressure all around, instead of from 2 opposite sides.sides. stepssteps www.indiandentalacademy.comwww.indiandentalacademy.com
    140. 140.  Series of diesSeries of dies  Annealing at regular intervals.Annealing at regular intervals.  Exact number of drafts and annealing cyclesExact number of drafts and annealing cycles depends on the alloy (gold <carbondepends on the alloy (gold <carbon steel<stainless steel)steel<stainless steel) DrawingDrawing www.indiandentalacademy.comwww.indiandentalacademy.com
    141. 141. Stress reliefStress relief During manufacture, wire highly stressed.During manufacture, wire highly stressed. Adverse effects on mechanical propertiesAdverse effects on mechanical properties Annealing heat treatmentAnnealing heat treatment By minute slippages & readjustments inBy minute slippages & readjustments in intergranular relations without the loss ofintergranular relations without the loss of hardening higher temp of annealinghardening higher temp of annealing Alternate sequence of cold working & heatAlternate sequence of cold working & heat treatment—improve strengthtreatment—improve strength www.indiandentalacademy.comwww.indiandentalacademy.com
    142. 142. Clinical implicationsClinical implications Soldering attachments to arch wire:Soldering attachments to arch wire:  Raise in temp----wire deadRaise in temp----wire dead  Quick and well controlled.Quick and well controlled.  Cinch back, heatCinch back, heat  Wire #Wire # www.indiandentalacademy.comwww.indiandentalacademy.com
    143. 143. Stainless SteelStainless Steel ClassificationClassification American Iron and Steel Institute (AISI)American Iron and Steel Institute (AISI) Unified Number System (UNS)Unified Number System (UNS) German Standards (DIN).German Standards (DIN). www.indiandentalacademy.comwww.indiandentalacademy.com
    144. 144. Stainless SteelStainless Steel The AISI numbers used for stainless steel rangeThe AISI numbers used for stainless steel range from 300 to 502from 300 to 502 Numbers beginning withNumbers beginning with 33 are all austeniticare all austenitic Higher the numberHigher the number   More the iron contentMore the iron content  More expensive the alloyMore expensive the alloy  Numbers having a letter L signify a low carbonNumbers having a letter L signify a low carbon contentcontent www.indiandentalacademy.comwww.indiandentalacademy.com
    145. 145. Stainless SteelStainless Steel Austenitic steels (the 300 series)Austenitic steels (the 300 series) Better corrosion resistance -attachmentsBetter corrosion resistance -attachments FCC structureFCC structure  non ferromagneticnon ferromagnetic Not stable at room temperature,Not stable at room temperature, Austenite stabilizersAustenite stabilizers Ni, Mn and NNi, Mn and N Known as the 18-8 stainless steelsKnown as the 18-8 stainless steels.. www.indiandentalacademy.comwww.indiandentalacademy.com
    146. 146. Stainless SteelStainless Steel Martensitic steelMartensitic steel FCCFCC  BCCBCC BCC structure is highly stressed.BCC structure is highly stressed. More grain boundaries,More grain boundaries,  StrongerStronger  Less corrosion resistantLess corrosion resistant Making instrument edges which need toMaking instrument edges which need to be sharp and wear resistant.be sharp and wear resistant. www.indiandentalacademy.comwww.indiandentalacademy.com
    147. 147. Stainless SteelStainless Steel Ferritic steelsFerritic steels – (the 400 series)– (the 400 series) Good corrosion resistanceGood corrosion resistance Low strength.Low strength. Not hardenable by heat treatment.Not hardenable by heat treatment. Not readily cold worked.Not readily cold worked. www.indiandentalacademy.comwww.indiandentalacademy.com
    148. 148. Stainless SteelStainless Steel Austenitic steels more preferableAustenitic steels more preferable :-:- Greater ductility and ability to undergo more coldGreater ductility and ability to undergo more cold work without breaking.work without breaking. Substantial strengthening during cold work.Substantial strengthening during cold work. (Cannot be strengthened by heat treatment).(Cannot be strengthened by heat treatment). Strengthening effect is due partial conversion toStrengthening effect is due partial conversion to martensite.martensite. Easy to weldEasy to weld Easily overcome sensitizationEasily overcome sensitization Ease in forming.Ease in forming. www.indiandentalacademy.comwww.indiandentalacademy.com
    149. 149. Stainless SteelStainless Steel Duplex steelsDuplex steels Both austenite and ferrite grainsBoth austenite and ferrite grains Increased toughness and ductility thanIncreased toughness and ductility than Ferritic steelsFerritic steels Twice the yield strength of austeniticTwice the yield strength of austenitic steelssteels Lower nickel contentLower nickel content Manufacturing low nickel attachmentsManufacturing low nickel attachmentswww.indiandentalacademy.comwww.indiandentalacademy.com
    150. 150. Stainless steelStainless steel Precipitation hardened steelsPrecipitation hardened steels Certain elements added to themCertain elements added to them  precipitate and increase the hardness onprecipitate and increase the hardness on heat treatment.heat treatment. The strength is very highThe strength is very high Resistance to corrosion is low.Resistance to corrosion is low. Used to make mini-brackets.Used to make mini-brackets. www.indiandentalacademy.comwww.indiandentalacademy.com
    151. 151. General properties of StainlessGeneral properties of Stainless SteelSteel Relatively stiff materialRelatively stiff material Yield strength and stiffness can be variedYield strength and stiffness can be varied  Altering the carbon content andAltering the carbon content and  Cold working andCold working and  AnnealingAnnealing High forces - dissipate over a very shortHigh forces - dissipate over a very short amount of deactivation (amount of deactivation (high loadhigh load deflection ratedeflection rate).).www.indiandentalacademy.comwww.indiandentalacademy.com
    152. 152. Stainless SteelStainless Steel Clinical terms:-Clinical terms:- Loop - activated to a very small extent soLoop - activated to a very small extent so as to achieve optimal forceas to achieve optimal force Deactivated by only a small amount (0.1Deactivated by only a small amount (0.1 mm)mm) Force level will drop tremendouslyForce level will drop tremendously Not physiologicNot physiologic More activationsMore activationswww.indiandentalacademy.comwww.indiandentalacademy.com
    153. 153. Stainless SteelStainless Steel Force required to engage a steel wire intoForce required to engage a steel wire into a severely mal-aligned tooth.a severely mal-aligned tooth.  Either cause the bracket to pop out,Either cause the bracket to pop out,  Or the patient to experience pain.Or the patient to experience pain. Overcome by using thinner wires, whichOvercome by using thinner wires, which have a lower stiffness.have a lower stiffness. Fit poorlyFit poorly loss of control on the teeth.loss of control on the teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
    154. 154. Stainless SteelStainless Steel High stiffnessHigh stiffness  Maintain the positions of teethMaintain the positions of teeth Hold the corrections achievedHold the corrections achieved Begg treatment, stiff archwire, to dissipateBegg treatment, stiff archwire, to dissipate the adverse effects of third stagethe adverse effects of third stage auxiliariesauxiliaries www.indiandentalacademy.comwww.indiandentalacademy.com
    155. 155. Stainless SteelStainless Steel Lowest frictional resistanceLowest frictional resistance Ideal choice of wire during space closureIdeal choice of wire during space closure with sliding mechanicswith sliding mechanics Teeth be held in their corrected relationTeeth be held in their corrected relation Minimum resistance to slidingMinimum resistance to sliding www.indiandentalacademy.comwww.indiandentalacademy.com
    156. 156. High Tensile Australian WiresHigh Tensile Australian Wires HistoryHistory Early part of Dr. Begg’s careerEarly part of Dr. Begg’s career Arthur Wilcock Sr.Arthur Wilcock Sr.  Lock pins, brackets, bands, wires, etcLock pins, brackets, bands, wires, etc Wires which would remain active for longWires which would remain active for long No frequent visitsNo frequent visits This lead Wilcock to develop steel wires of highThis lead Wilcock to develop steel wires of high tensile strength.tensile strength. www.indiandentalacademy.comwww.indiandentalacademy.com
    157. 157. High Tensile Australian WiresHigh Tensile Australian Wires Beginners found it difficult to use theBeginners found it difficult to use the highest tensile wireshighest tensile wires Grading systemGrading system Late 1950s, the grades available were –Late 1950s, the grades available were –  RegularRegular  Regular plusRegular plus  SpecialSpecial  Special plusSpecial plus www.indiandentalacademy.comwww.indiandentalacademy.com
    158. 158. High Tensile Australian WiresHigh Tensile Australian Wires Newer grades were introduced after the 70s.Newer grades were introduced after the 70s. Premium, premium +, supremePremium, premium +, supreme Raw materials directly from the suppliers from out ofRaw materials directly from the suppliers from out of AustraliaAustralia More specific ordering and obtaining better raw materialsMore specific ordering and obtaining better raw materials Premium grade-high tensile strengthPremium grade-high tensile strength Brittle.Brittle. Softening , loss of high tensile propertiesSoftening , loss of high tensile properties www.indiandentalacademy.comwww.indiandentalacademy.com
    159. 159. High Tensile Australian WiresHigh Tensile Australian Wires Bauschinger effectBauschinger effect.. Described by Dr. Bauschinger in 1886.Described by Dr. Bauschinger in 1886. Material strained beyond its yield point inMaterial strained beyond its yield point in one direction,one direction, then strained in the reverse directionthen strained in the reverse direction,, its yield strength in the reverse direction isits yield strength in the reverse direction is reducedreduced.. www.indiandentalacademy.comwww.indiandentalacademy.com
    160. 160. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    161. 161. High Tensile Australian WiresHigh Tensile Australian Wires 1.1. Plastic prestrain increases the elastic limit ofPlastic prestrain increases the elastic limit of deformation in the same direction as thedeformation in the same direction as the prestrain.prestrain. 2.2. Decreases in oppositeDecreases in opposite If the magnitude of the prestrain is increased,If the magnitude of the prestrain is increased, the elastic limit in the reverse direction canthe elastic limit in the reverse direction can reduce to zero.reduce to zero. www.indiandentalacademy.comwww.indiandentalacademy.com
    162. 162. High Tensile Australian WiresHigh Tensile Australian Wires Straightening a wireStraightening a wire  pulling through apulling through a series of rollersseries of rollers Prestrain in a particular direction.Prestrain in a particular direction. Yield strength for bending in the oppositeYield strength for bending in the opposite direction will decrease.direction will decrease. Premium wirePremium wire  special plus or specialspecial plus or special wirewire www.indiandentalacademy.comwww.indiandentalacademy.com
    163. 163. Spinner straighteningSpinner straightening It is mechanical process of straighteningIt is mechanical process of straightening resistant materials in the cold drawnresistant materials in the cold drawn condition.condition. The wire is pulled through rotating bronzeThe wire is pulled through rotating bronze rollers that torsionally twist it into straightrollers that torsionally twist it into straight condition.condition. Disadv:Disadv: Decreases yield strengthDecreases yield strength Creates rougher surfaceCreates rougher surface www.indiandentalacademy.comwww.indiandentalacademy.com
    164. 164. Pulse straighteningPulse straightening Special methodSpecial method Placed in special machines that permitsPlaced in special machines that permits high tensile wires to be straightened.high tensile wires to be straightened. Advantages:Advantages: 1.1. Permits the straightening of high tensile wiresPermits the straightening of high tensile wires 2.2. Does not reduce the yield strength of the wireDoes not reduce the yield strength of the wire 3.3. Results in a smoother wire, hence less wire –Results in a smoother wire, hence less wire – bracket friction.bracket friction. www.indiandentalacademy.comwww.indiandentalacademy.com
    165. 165. High Tensile Australian WiresHigh Tensile Australian Wires Methods of increasing yield strength ofMethods of increasing yield strength of Australian wires.Australian wires. 1.1. Work hardeningWork hardening 2.2. Dislocation lockingDislocation locking 3.3. Solid solution strengtheningSolid solution strengthening 4.4. Grain refinement and orientationGrain refinement and orientation www.indiandentalacademy.comwww.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.comwww.indiandentalacademy.com
    167. 167. High Tensile Australian WiresHigh Tensile Australian Wires Higher yield strengthHigher yield strength  more flexible.more flexible. Supreme gradeSupreme grade flexibility = β-flexibility = β- titanium.titanium. Higher resiliencyHigher resiliency  nearly three times.nearly three times. NiTiNiTi  higher flexibilityhigher flexibility but it lacks formabilitybut it lacks formability www.indiandentalacademy.comwww.indiandentalacademy.com
    168. 168. High Tensile Australian WiresHigh Tensile Australian Wires MollenhauerMollenhauer  Supreme grade wireSupreme grade wire  faster and gentlerfaster and gentler alignment of teeth.alignment of teeth. IntrusionIntrusion  simultaneously with the basesimultaneously with the base wireswires Gingival health seemed betterGingival health seemed better Originally in lingual orthodonticsOriginally in lingual orthodontics Equally good for labial orthodontics asEqually good for labial orthodontics as well.well. www.indiandentalacademy.comwww.indiandentalacademy.com
    169. 169. High Tensile Australian WiresHigh Tensile Australian Wires Clinical significance of high yield strength 1. Increased working range:1. Increased working range: Yield strengthYield strength modulus of elasticitymodulus of elasticity 2.2. Increased resiliency:Increased resiliency: (( yield strength)2yield strength)2 elastic moduluselastic modulus Stiffness remains the sameStiffness remains the same www.indiandentalacademy.comwww.indiandentalacademy.com
    170. 170. High Tensile Australian WiresHigh Tensile Australian Wires 3. Zero Stress Relaxation3. Zero Stress Relaxation If a wire isIf a wire is deformeddeformed and held in aand held in a fixed positionfixed position, the, the stressstress in the wire mayin the wire may diminishdiminish with time, but thewith time, but the strainstrain remains constantremains constant.. Engineering terms, implies that a form of slip by dislocationEngineering terms, implies that a form of slip by dislocation movement takes place at the atomic levelmovement takes place at the atomic level Property of a wire to giveProperty of a wire to give constant light forceconstant light force, when, when subjected to external forces (like occlusal forces).subjected to external forces (like occlusal forces). www.indiandentalacademy.comwww.indiandentalacademy.com
    171. 171. High Tensile Australian WiresHigh Tensile Australian Wires external forcesexternal forces  particles slip over each otherparticles slip over each other  activation of the wire is lostactivation of the wire is lost OvercomeOvercome   Internal frictionInternal friction Between particlesBetween particles  yield strength www.indiandentalacademy.comwww.indiandentalacademy.com
    172. 172. High Tensile Australian WiresHigh Tensile Australian Wires Zero stress relaxation in springs.Zero stress relaxation in springs. To avoid relaxation in the wire’s workingTo avoid relaxation in the wire’s working stressstress Diameter of coil : Diameter of wire = 4Diameter of coil : Diameter of wire = 4 smaller diameter of wiressmaller diameter of wires  smallersmaller diameter springs (like the mini springs)diameter springs (like the mini springs) Midi springsMidi springs www.indiandentalacademy.comwww.indiandentalacademy.com
    173. 173. High Tensile Australian WiresHigh Tensile Australian Wires Twelftree, Cocks and Sims (AJO 1977)Twelftree, Cocks and Sims (AJO 1977) Premium plus, Premium and Special plusPremium plus, Premium and Special plus wires showed minimal stress relaxation.wires showed minimal stress relaxation. Special,Special, Remanit,Remanit, Yellow Elgiloy,Yellow Elgiloy, Unisil.Unisil. www.indiandentalacademy.comwww.indiandentalacademy.com
    174. 174. Hazel, Rohan & West (1984)Hazel, Rohan & West (1984)  Stress relaxation of Special plus wires after 28Stress relaxation of Special plus wires after 28 days was less than Dentaurum SS and Elgiloydays was less than Dentaurum SS and Elgiloy wires.wires. Barrowes (1982) & Jyothindra KumarBarrowes (1982) & Jyothindra Kumar (1989)(1989)  Higher working range among steel wires.Higher working range among steel wires. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    175. 175. Pulse straightened wires – SpinnerPulse straightened wires – Spinner straightened wiresstraightened wires (Skaria 1991)(Skaria 1991)  Strength, stiffness and Range higherStrength, stiffness and Range higher  Coeff. of friction higherCoeff. of friction higher  Similar surface topography, stress relaxation andSimilar surface topography, stress relaxation and Elemental makeup.Elemental makeup. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    176. 176. A study of the metallurgical properties of newlyA study of the metallurgical properties of newly introduced high tensile wires in comparison to theintroduced high tensile wires in comparison to the high tensile Australian wires for various applicationshigh tensile Australian wires for various applications in orthodontic treatmentin orthodontic treatment Dr.Dr. Anuradha Acharya (2000)Anuradha Acharya (2000)  Super Plus (Ortho Organizers) – between SpecialSuper Plus (Ortho Organizers) – between Special plus and Premiumplus and Premium  Premier (TP) – Comparable to SpecialPremier (TP) – Comparable to Special  Premier Plus – Special PlusPremier Plus – Special Plus  Bowflex – PremiumBowflex – Premium High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    177. 177. Highest yield strength and ultimate tensileHighest yield strength and ultimate tensile strength as compared to the correspondingstrength as compared to the corresponding wires.wires. Higher rangeHigher range Lesser coefficient of frictionLesser coefficient of friction  Surface area seems to be rougher than that of theSurface area seems to be rougher than that of the other manufacturers’ wires.other manufacturers’ wires. Lowest stress relaxation.Lowest stress relaxation. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    178. 178. Clinical implicationsClinical implications Stage I:Stage I: 1.1. Wilcock (P) / S+ base wire(.014”)Wilcock (P) / S+ base wire(.014”) 2.2. Ortho organizers (super +)Ortho organizers (super +)  Wilcock (P) & S+; T.P. Bowflex .016”Wilcock (P) & S+; T.P. Bowflex .016”  Ortho organizers ( super +) T.P P+Ortho organizers ( super +) T.P P+  Latter part of Stage I and most of Stage IILatter part of Stage I and most of Stage II 1.1. T.P (Premier), Wilcock P ,S+ .018” diaT.P (Premier), Wilcock P ,S+ .018” dia 2.2. Ortho Organizers (super +) T.P BowflexOrtho Organizers (super +) T.P Bowflex  Base wires in Stage III , torquing auxiliaries,Base wires in Stage III , torquing auxiliaries, uprighting springsuprighting springs 1.1. Wilcock S+ / P .020” base wireWilcock S+ / P .020” base wire  Wilcock P and Supreme in .012”, .010” diaWilcock P and Supreme in .012”, .010” dia respectivelyrespectively www.indiandentalacademy.comwww.indiandentalacademy.com
    179. 179. High Tensile Australian WiresHigh Tensile Australian Wires Dislocation lockingDislocation locking  High tensile wires have high density ofHigh tensile wires have high density of dislocations and crystal defectsdislocations and crystal defects  Pile up, and form a minute crackPile up, and form a minute crack  Stress concentrationStress concentration www.indiandentalacademy.comwww.indiandentalacademy.com
    180. 180. High Tensile Australian WiresHigh Tensile Australian Wires Small stress applied with the plier beaksSmall stress applied with the plier beaks  Crack propagationCrack propagation  Elastic energy is releasedElastic energy is released  Propagation accelerates to the nearest grainPropagation accelerates to the nearest grain boundaryboundary www.indiandentalacademy.comwww.indiandentalacademy.com
    181. 181. High Tensile Australian WiresHigh Tensile Australian Wires Ways of preventing fractureWays of preventing fracture 1.1. Bending the wire around theBending the wire around the flat beakflat beak ofof the pliers.the pliers. Introduces aIntroduces a momentmoment about the thumbabout the thumb and wire gripping point, which reducesand wire gripping point, which reduces the applied stress on the wire.the applied stress on the wire. www.indiandentalacademy.comwww.indiandentalacademy.com
    182. 182. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    183. 183. High Tensile Australian WiresHigh Tensile Australian Wires 2.2. The wire should not be held tightly in theThe wire should not be held tightly in the beaks of the pliers.beaks of the pliers. Area of permanent deformation to beArea of permanent deformation to be slightly enlarged,slightly enlarged, Nicking and scarring avoided.Nicking and scarring avoided. The tips of the pliers shouldThe tips of the pliers should notnot be ofbe of tungsten carbide.tungsten carbide. www.indiandentalacademy.comwww.indiandentalacademy.com
    184. 184. High Tensile Australian WiresHigh Tensile Australian Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    185. 185. High Tensile Australian WiresHigh Tensile Australian Wires 3.3. The edges roundedThe edges rounded  reduce the stressreduce the stress concentration in the wire.concentration in the wire. 4.4. Ductile – brittle transition temperatureDuctile – brittle transition temperature slightly above room temperature.slightly above room temperature. Wire should be warmed.Wire should be warmed. Spools kept in oven at about 40Spools kept in oven at about 40oo , so that, so that the wire remains slightly warm.the wire remains slightly warm. www.indiandentalacademy.comwww.indiandentalacademy.com
    186. 186. Multistranded WiresMultistranded Wires 2 or more wires of smaller diameter are2 or more wires of smaller diameter are twisted together/coiled around a core wire.twisted together/coiled around a core wire. Diameter - 0.0165 or 0.0175, but theDiameter - 0.0165 or 0.0175, but the stiffness is much less.stiffness is much less. On bendingOn bending  individual strands slip overindividual strands slip over each other and the core wire, makingeach other and the core wire, making bending easy. (yield point)bending easy. (yield point)www.indiandentalacademy.comwww.indiandentalacademy.com
    187. 187. Multi stranded wiresMulti stranded wires Co-axial Twisted wire Multi braided www.indiandentalacademy.comwww.indiandentalacademy.com
    188. 188. Multi stranded wiresMulti stranded wires Strength – resist distortionStrength – resist distortion Separate strands - .007” but final wire canSeparate strands - .007” but final wire can be either round / rectangularbe either round / rectangular Sustain large elastic deflection in bendingSustain large elastic deflection in bending Thurow: rough idea – multiplyThurow: rough idea – multiply www.indiandentalacademy.comwww.indiandentalacademy.com
    189. 189. Multistranded WiresMultistranded Wires As the diameter of a wire decreases –As the diameter of a wire decreases – Stiffness – decreases as a function of the 4Stiffness – decreases as a function of the 4thth powerpower Range – increases proportionatelyRange – increases proportionately Strength – decreases as a function of the 3Strength – decreases as a function of the 3rdrd powerpower Multistranded wiresMultistranded wires  Small diameter wires,Small diameter wires, High strengthHigh strength Gentler forceGentler force www.indiandentalacademy.comwww.indiandentalacademy.com
    190. 190. Multistranded WiresMultistranded Wires Elastic properties of multistranded archwiresElastic properties of multistranded archwires depend on –depend on – 1.1. Material parametersMaterial parameters – Modulus of elasticity– Modulus of elasticity 2.2. Geometric factorsGeometric factors – wire dimension– wire dimension 3.3. Constants:Constants:  Number of strands coiledNumber of strands coiled  The distance from the neutral axis to theThe distance from the neutral axis to the outer most fiber of a strandouter most fiber of a strand  Plane of bendingPlane of bending  Poisson’s ratioPoisson’s ratio www.indiandentalacademy.comwww.indiandentalacademy.com
    191. 191. Multistranded WiresMultistranded Wires Deflection ofDeflection of multi stranded wire=multi stranded wire= KPLKPL33 kknEInEI K – load/support constantK – load/support constant P – applied forceP – applied force L – length of the beamL – length of the beam K –K – helical spring shape factorhelical spring shape factor n- no of strandsn- no of strands E – modulus of elasticityE – modulus of elasticity I – moment of inertiaI – moment of inertia www.indiandentalacademy.comwww.indiandentalacademy.com
    192. 192. Multistranded WiresMultistranded Wires Helical spring shape factorHelical spring shape factor Coils resemble the shape of a helical spring.Coils resemble the shape of a helical spring. The helical spring shape factor is given as –The helical spring shape factor is given as – 2sin α2sin α 2+ v cos2+ v cos22 αα α - helix angle andα - helix angle and v - Poisson’s ratio (lateral strain/axial strain)v - Poisson’s ratio (lateral strain/axial strain) Angle α can be seen in the following diagram :-Angle α can be seen in the following diagram :- www.indiandentalacademy.comwww.indiandentalacademy.com
    193. 193. Multistranded WiresMultistranded Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    194. 194. Multistranded WiresMultistranded Wires Kusy ( AJO-DO 1984)Kusy ( AJO-DO 1984) Compared the elastic properties of tripleCompared the elastic properties of triple stranded S.Steel wire with S.Steel, NiTi &stranded S.Steel wire with S.Steel, NiTi & BB-TMA-TMA www.indiandentalacademy.comwww.indiandentalacademy.com
    195. 195. ResultsResults ResultsResults www.indiandentalacademy.comwww.indiandentalacademy.com
    196. 196. ResultsResults www.indiandentalacademy.comwww.indiandentalacademy.com
    197. 197. ResultsResults 0.0175” S.Steel wire had stiffness equal to0.0175” S.Steel wire had stiffness equal to 0.016”NiTi & 40% of 0.016”TMA0.016”NiTi & 40% of 0.016”TMA Did not resemble the 0.018” SS wire except :Did not resemble the 0.018” SS wire except : SizeSize Wire-bracket relation.Wire-bracket relation. www.indiandentalacademy.comwww.indiandentalacademy.com
    198. 198. Multistranded WiresMultistranded Wires Ingram, Gipe and Smith (AJO 86) Range of 4 diff wiresRange of 4 diff wires Results: NiTi>MS S.Steel>CoCr>SteelResults: NiTi>MS S.Steel>CoCr>Steel www.indiandentalacademy.comwww.indiandentalacademy.com
    199. 199. Multistranded WiresMultistranded Wires Nanda et al (AO 97)Nanda et al (AO 97) ……. stiffness. stiffness Increase in No. ofIncrease in No. of strandsstrands  stiffnessstiffness Varies as the amountVaries as the amount of deflectionof deflection www.indiandentalacademy.comwww.indiandentalacademy.com
    200. 200. Multistranded WiresMultistranded Wires Kusy (AJO-DO 2002)Kusy (AJO-DO 2002) Interaction between individual strands wasInteraction between individual strands was negligible.negligible. Range and strengthRange and strength Triple strandedTriple stranded ΞΞ Co-Co- axial (six stranded)axial (six stranded) StiffnessStiffness  Coaxial < Triple strandedCoaxial < Triple stranded Range of single stranded SS wire, tripleRange of single stranded SS wire, triple stranded and co-axial were similar.stranded and co-axial were similar. www.indiandentalacademy.comwww.indiandentalacademy.com
    201. 201. Multistranded WiresMultistranded Wires www.indiandentalacademy.comwww.indiandentalacademy.com
    202. 202. Welding of SteelWelding of Steel 3 useful properties3 useful properties –– 1.1. Comparatively low melting point,Comparatively low melting point, 2.2. High electrical resistance andHigh electrical resistance and 3.3. Low conductivity of heat.Low conductivity of heat. www.indiandentalacademy.comwww.indiandentalacademy.com
    203. 203. Welding of SteelWelding of Steel Sensitization - between 425 and 815Sensitization - between 425 and 815oo CC Chromium carbides need time for theirChromium carbides need time for their formation.formation. Important toImportant to  minimize the time of passing the currentminimize the time of passing the current  minimize the area of heatingminimize the area of heating www.indiandentalacademy.comwww.indiandentalacademy.com
    204. 204. Welding of SteelWelding of Steel Join twoJoin two thin sheetsthin sheets of metalof metal Same thicknessSame thickness Joining tubes, wires and springs, solderingJoining tubes, wires and springs, soldering is generally recommended.is generally recommended. Electrodes - small tips, not exceedingElectrodes - small tips, not exceeding 1mm in diameter.1mm in diameter. www.indiandentalacademy.comwww.indiandentalacademy.com
    205. 205. Cobalt ChromiumCobalt Chromium 1950s the Elgin Watch1950s the Elgin Watch Rocky Mountain OrthodonticsRocky Mountain Orthodontics ElgiloyElgiloy CoCr alloys - stellite alloysCoCr alloys - stellite alloys  superior resistance to corrosion, comparablesuperior resistance to corrosion, comparable to that of gold alloys.to that of gold alloys. www.indiandentalacademy.comwww.indiandentalacademy.com
    206. 206. Cobalt ChromiumCobalt Chromium Cobalt – 40-45%Cobalt – 40-45% Chromium – 15-22%Chromium – 15-22% Nickel – for strength and ductilityNickel – for strength and ductility Iron, molybdenum, tungsten and titaniumIron, molybdenum, tungsten and titanium to form stable carbides and enhanceto form stable carbides and enhance hardenability.hardenability. www.indiandentalacademy.comwww.indiandentalacademy.com
    207. 207. Cobalt ChromiumCobalt Chromium Strength and formability modified by heatStrength and formability modified by heat treatment.treatment. The alloy is highly formable, and can beThe alloy is highly formable, and can be easily shaped.easily shaped. Heat treated.Heat treated.  StrengthStrength   FormabilityFormability  www.indiandentalacademy.comwww.indiandentalacademy.com
    208. 208. Cobalt ChromiumCobalt Chromium www.indiandentalacademy.comwww.indiandentalacademy.com
    209. 209. Cobalt ChromiumCobalt Chromium Heat treated at 482Heat treated at 482oo c for 7 to 12 minsc for 7 to 12 mins Precipitation hardeningPrecipitation hardening   ultimate tensile strength of the alloy,ultimate tensile strength of the alloy, without hampering the resilience.without hampering the resilience. After heat treatment, elgiloy had elasticAfter heat treatment, elgiloy had elastic properties similar to steel.properties similar to steel. www.indiandentalacademy.comwww.indiandentalacademy.com
    210. 210. Cobalt ChromiumCobalt Chromium www.indiandentalacademy.comwww.indiandentalacademy.com
    211. 211. Cobalt ChromiumCobalt Chromium BlueBlue – soft– soft YellowYellow – ductile– ductile GreenGreen – semiresilient– semiresilient RedRed – resilient– resilient No adjustmentsNo adjustments www.indiandentalacademy.comwww.indiandentalacademy.com
    212. 212. Cobalt ChromiumCobalt Chromium After heat treatmentAfter heat treatment  Strength:Strength: BlueBlue andand yellowyellow ≡≡ normal steel wirenormal steel wire GreenGreen andand redred temperstempers ≡≡ higher gradehigher grade steelsteel www.indiandentalacademy.comwww.indiandentalacademy.com
    213. 213. Cobalt ChromiumCobalt Chromium Heating above 650Heating above 650oo CC  partial annealing, and softening of the wirepartial annealing, and softening of the wire Optimum heat treatmentOptimum heat treatment  dark straw colordark straw color of the wireof the wire Advantage of Co-Cr over SS is –Advantage of Co-Cr over SS is –  Greater resistance to fatigue and distortionGreater resistance to fatigue and distortion  longer function as a resilient springlonger function as a resilient spring www.indiandentalacademy.comwww.indiandentalacademy.com
    214. 214. Cobalt ChromiumCobalt Chromium Properties of Co-Cr are very similar to thatProperties of Co-Cr are very similar to that of stainless steel.of stainless steel. ForceForce  2x2x of β titanium andof β titanium and  44 times of NiTi.times of NiTi. www.indiandentalacademy.comwww.indiandentalacademy.com
    215. 215. Cobalt ChromiumCobalt Chromium Ingram ,Gipe and Smith (AJO 86)Ingram ,Gipe and Smith (AJO 86) Non heat treated Co-CrNon heat treated Co-Cr  Range < stainless steel of comparable sizesRange < stainless steel of comparable sizes But after heat treatment, the range wasBut after heat treatment, the range was considerably increased.considerably increased. www.indiandentalacademy.comwww.indiandentalacademy.com
    216. 216. Cobalt ChromiumCobalt Chromium Frank and Nikolai ( AJO 1980)Frank and Nikolai ( AJO 1980)  Co-Cr alloysCo-Cr alloys ≡≡ stainless steel.stainless steel. Stannard et al (AJO 1986)Stannard et al (AJO 1986)  Co-Cr highest frictional resistance in wet andCo-Cr highest frictional resistance in wet and dry conditions.dry conditions. www.indiandentalacademy.comwww.indiandentalacademy.com
    217. 217. Cobalt ChromiumCobalt Chromium Kusy et al (AJO 2001) The elasticThe elastic modulus did notmodulus did not vary appreciablyvary appreciably  edgewise oredgewise or ribbon-wiseribbon-wise configurations.configurations. www.indiandentalacademy.comwww.indiandentalacademy.com
    218. 218. Cobalt ChromiumCobalt Chromium Round wiresRound wires  higher ductility thanhigher ductility than square orsquare or rectangular wires.rectangular wires. www.indiandentalacademy.comwww.indiandentalacademy.com
    219. 219. Cobalt ChromiumCobalt Chromium The modulus ofThe modulus of elasticity 4 diffelasticity 4 diff tempers of 0.016”tempers of 0.016” elgiloy is almostelgiloy is almost similarsimilar www.indiandentalacademy.comwww.indiandentalacademy.com
    220. 220. Cobalt ChromiumCobalt Chromium Elastic propertiesElastic properties (yield strength and(yield strength and ultimate tensile strength and ductility) wereultimate tensile strength and ductility) were quite similar for different cross sectional areasquite similar for different cross sectional areas and tempers.and tempers. This does not seem to agree with what isThis does not seem to agree with what is expected of the wires.expected of the wires. www.indiandentalacademy.comwww.indiandentalacademy.com
    221. 221. Cobalt ChromiumCobalt Chromium www.indiandentalacademy.comwww.indiandentalacademy.com
    222. 222. Cobalt ChromiumCobalt Chromium Different tempers with different physicalDifferent tempers with different physical properties – attractiveproperties – attractive More care taken during the manufactureMore care taken during the manufacture of the wires.of the wires. www.indiandentalacademy.comwww.indiandentalacademy.com

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