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Page 1: Wrought metal alloys

WROUGHT METAL ALLOYS

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CONTENTS

DEFINITIONHOW WROUGHT METAL ALLOYS ARE MADE?USESPROPERTIESDEFORMATION OF METALSCARBON STEELGOLD ALLOYS

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STAINLESS STEELTITANIUM ALLOYSCHROMIUM – COBALT ALLOYSAJ WILCOCK WIRESCONCLUSION

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• Wrought: Beaten to shape.• Alloys: A metal made by combining two or

more metallic elements to give greater strength or resistance to corrosion

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• What are wrought metal alloys?

These are cold worked metals that are plastically deformed to bring about a change in shape of structure and their mechanical properties.

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How wrought alloys are made?

Mechanical work

Heat treatment

Wrought alloy

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How wrought metal alloys are made?

Cast alloys

Series of dies

Intermdiate heat treatment

Round wires

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Where all they are used?

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ORTHODONTIC WIRES

ORTHODONTIC BRACKETS

PRE-FABRICATED CROWNS

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PARTIAL DENTURE CLASP

ENDODONTIC FILES

SURGICAL INSTRUMENTS

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PROPERTIES• Strength• Stiffness• Springback• Resilience• Formability • Malleability • Ductility • Joinability• Biocompatibility

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STRE

SS

STRAIN

ELASTIC POINT

THE RATIO OF STRESS TO STRAIN N THE LINEAR PORTION OF THE CURVE IS CALLED YOUNG’S MODULUS

ELASTIC LIMIT

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STRE

SS

STRAIN

THE DEFORMATION MOST USED IS

0.2%

YIELD STRENGTH

YIELD POINT

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STRE

SS

STRAIN

ULTIMATE TENSILE SRENGTH

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STRE

SS

STRAIN

SPRING BACK

POINT OF ARBITARY CLINICAL LOADING

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STRE

SS

STRAIN

RESILENCE

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STRE

SS

STRAIN

FORMABILITY

YIELD POINT

FRACTURE POINT

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MALLEABILITY

• The material's ability to form a thin sheet by hammering or rolling.

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DUCTILITY

• The material's ability to be stretched into a wire.

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BIOCOMPATIBILITY

• Resistant to corrosion.

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JOINABILITY

Ease of auxillary attatchment soldering or welding

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Stress-strain curve

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DEFORMATION OF METALS

LATTICE IMPERFECTIONS

DISLOCATIONS

STRAIN HARDENING

FRACTURE

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CRYSTALIZATION OF METALS

RANDOM GROWTH

LATTICE POINTS ARE VACCANT OR OVER CROWDED

LATTICE IMPERFECTIONS

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Lattice imperfections are classified as:

POINT DEFECTS

LINE DEFECTS

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POINT DEFECTS

Vacancy – a vacant lattice site

Divacancy/ Trivacancy – two or more missing atoms

Interstitial – extra atom present in space lattice

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Vacancies are also known as “Equilibrium defects”.

This is necessary for the process of diffusion of metals

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DISLOCATIONS

Edge dislocation - lattice is regular except for the one plane of atoms that is discontinuous, forming “dislocation line” at the edge of the half plane.

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• Edge dislocation

• Continuous shear stress application

• Dislocation reaches edge of the crystal & disappears

• Leaves ONE UNIT of slip at the crystal surface

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SLIP PLANE

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Dislocationsare not equilibrium defectsit requires significant energy

Slip plane – plane along which a dislocation moves

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STRAIN HARDENING/ WORK HARDENING

• DEFORMATION AT ROOM TEMPERATURE

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Dislocations tend to buildup at grain

boundaries

Atomic slip occurs on other intersecting slip

planesPoint defects increase

& entire grain becomes distorted

Greater stress is required to produce

further slip

Metal becomes stronger, Harder and

less Ductile

Further increase in cold work metal FRACTURE

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• Consequences of strain hardening

• Surface hardness

• Yield Strength

• Ultimate tensile strength

•Ductility

• Resistance to corrosion of the metal

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ANNEALING

• Controlled heating and cooling process designed to produce desired properties in a metal.

• Annealing takes place in 3 successive stages

RecoveryRecrystallization

Grain growth

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RECOVERY

• Cold worked properties begin to disappear.

• Slight decrease in tensile strength.

• No change in ductility.

• No changes in microscopic structure.

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• Recrystallization

The old grains are replaced by new set of

grains.

The material attains its original soft and ductile

condition.

The fibrous structure is transformed to small

grains.

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• Grain growth

Phenomenon occurs only in wrought metals

Grain size range from fine to coarse

Fine grain structure if annealed further, grains begin to grow

Large grains consume smaller grains

Grain growth process does not progress indefinitely to form single crystal

Rather, an ultimate coarse grain structure is formed

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CARBON STEELS

• Iron-based alloys usually containing 1.2% Carbon• Based on 3 possible lattice arrangements of iron,

different classes of steels are:

oFerriteoAusteniteoMartensite

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Ferrite

Body centered cubic (BCC) Pure iron at room temperature Phase is stable in temperature as high as 912C Carbon has very low solubility in ferrite

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Austenite

• Face centered cubic (FCC)• Stable form of iron at temperature between 912C &

1394C• Maximum carbon solubility is 2.1% by weight.

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Martensite

• Body centered tetragonal crystal structure.• Produced by quenching of austenite to undergo

spontaneous, diffusionless transformation.• This is a very strong brittle and hard alloy.• The formation of martensite is actually a

strengthening mechanism of carbon steel.

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• Lattice is highly distorted & strained resulting in an extremely hard, strong, brittle alloy-MARTENSITE

MARTENSITE decomposes to form FERRITE & CARBIDE

Accelerated by heat treatment process called TEMPERING

Reduces hardness but increases toughness

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WROUGHT GOLD ALLOYS

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HISTORY

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GOLD WIRES WRAPPED AROUND THE NECK OF ADJACENT TEETH.

The Use of Gold in Dentistry AN HISTORICAL OVERVIEW. PART IJ. A. Donaldson British Dental Association Museum, London, U.K.

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DENTAL APPLICATIONS OF GOLD ALLOYS

CONSTRUCTION OF REMOVABLE PARTIAL DENTURE CLASP.

FABRICATION OF ORTHODONTIC APPLIANCES.

AS RETENTION PINS FOR RESTORATION.

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• Type 5 and Type 10 dental gold alloys are used as orthodontic wires.

Gold in Dentistry: Alloys, Uses and PerformanceHelmut Knosp, Consultant, Pforzheim, Germany Richard J Holliday, World Gold Council, London, UK Christopher W. Corti, World Gold Council, London, UK

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PLATINUM-GOLD-PALLADIUM WIRES (P-G-P)

• Composition:– Platinum: 40%-50%– Gold: 25%-30%– Palladium: 25%-30%

• They possess,1) High fusion temperature & high recrystallization

temperature.2) Meet composition requirements for ADA type I

gold wire.

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PALLADIUM-SILVER-COPPER WIRES (P-S-C)

Composition:Palladium: 42%-44%Silver: 38%-41%Copper: 16%-17%Platinum: 0%-1%

P-S-C wires are neither Type I nor Type II gold wires, but their mechanical properties meet the requirements for ADA Type I or II gold wire

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EFFECT OF CONSTITUENTS OF GOLD ALLOYS

PLATINIUM –

• Bluish white metal.• Hardness similar to copper.• Higher melting point ( 1772°C) than porcelain.• Coefficient of thermal expansion close to porcelain.• Lighten the color of yellow gold based alloys• Common constituent in precision prosthetic

attachments.

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PALLADIUM

• White metal darker than platinum• Density little more than half that of Pt and Au• Absorbs hydrogen gas when heated• Not used in pure state in dentistry • Whitens yellow gold based alloys.

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SILVER(Ag)

• Malleable, ductile; white metal.• Stronger and harder than gold, softer than copper. • Absorbs oxygen in molten state and difficult to

cast• Forms series of solid solutions with palladium and

gold .• Neutralizes reddish color of alloys containing

copper

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COPPER:• Contributes the ability to

age harden.

IRIDIUM:• Grain refiners• Improves mechanical

properties and uniformity of properties within alloy

• Extremely high melting point of Ir - 2410°C and Ru - 2310°C – serve as nucleating centers

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NICKEL :• strengthener of alloy but

it reduces ductility.

• large quantity of Ni tends to reduce tarnish resistance & change alloy response to age hardening.

ZINC :• added as a scavenger agent

to obtain oxide-free ingots

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TREATMENT OF GOLD ALLOYS

• Softening heat treatment/homogenizing-Solution heat treatment.

• Hardening heat treatment-Age hardening.

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Softening Heat Treatment• Increases ductility .• reduces tensile strength ,proportional limit and

hardness.

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HARDENING HEAT TREATMENT

• Increases strength, proportional limit, and hardness, but decreases ductility.

• Copper present in gold alloy helps in this process.

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STAINLESS STEEL ALLOYS

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HISTORY

• First developed accidently by Harry Brearley in Sheffield, England.

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He tested this steel with nitric

acid ,lemon juice and tested

under microscope and found that

his alloys were highly resistant,

and immediately recognised the

potential for his steel within the

cutlery industry.

He named it as ‘Rustless Steel’,

but Stuart, dubbed it ‘Stainless

Steel’ after testing the material in

a vinegar solution, and the name

stuck

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• Stainless steel entered dentistry in 1919, introduced at Krupp’s dental poly clinic in Germany by F. Haupt Meyer.

• In 1930 Angle used it to make ligature wires.

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• Manufacturing of stainless steel

MELTING INGOT FORMATION ROLLING DRAWING

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MELTING The selection and melting of the components of alloys influence the physical properties of wire .

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Composition (as per AISI) TYPE Cr Ni C Mn Si P S

302 17-19 8-10 0.15 2 1 0.045 0.03

304 18-20 8-12 0.08 2 1 0.045 0.03

416 12-14 - 0.15 1.25 1 0.06 0.15

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• the molten metal is poured into the mold.

• A non uniform chunk of metal is produced.

• The mechanical properties of the ingot is controlled by its granular structure.

• When the ingot is cooled, grains forms at once.

• These growing crystals are surrounded each another.

Ingot formation

INGOT — colony of irregularly shaped grains of different materials.

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The pouring and cooling process affect porosity.

When ingot cools the inner mass hardens later, inside the outside hardened shell, which results in additional vacuum voids.

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• First mechanical step in process.• Ingot is rolled in series of rollers to reduce its diameter.

• . Now the wire is actually an "distorted ingot".• The squeezing and rolling of ingot alters the shape and

arrangement of the crystals

• The metal is annealed by heating into high temperature, which relives the internal stress formed by rolling.

• On cooling ,it resembles an original casting.

• Rolling will cause the elongation crystals into an finger like process, closely meshed with each other.

• Hardness/ brittleness increases as the grain positions and arrangements are altered

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DRAWING

The wire is reduced to its final size by drawing.

This is a more precise process in which the wire is pulled through a small

hole in a die.

Before it is reduced to orthodontic size a wire is drawn through many series of dies and

annealed several times along the way to relieve work

hardening.

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• The wires used in orthodontics are generally American Iron and Steel Institute {AISI} types 302 and 304 austenitic stainless steels. These alloys are known as “18-8” Stainless steels, so designated because of the percentages of chromium and nickel in the alloy.

IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 14, Issue 1 Ver. I (Jan. 2015), PP 47-50

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Properties of stainless steel

• When 12-30% chromium is added to steel it forms STAINLESS STEEL.

• Yield strength - 1100-15000Mpa.• The modulus of elasticity - 160 to 180 GPa. • PASSIVATION- property of SS to resist tarnish and

corrosion.

IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 14, Issue 1 Ver. I (Jan. 2015), PP 47-50

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• Sensitization

CORROSION RESISTANCE OF STAINLESS STEEL

18-8 STAINLESS STEEL LOSES ITS RESISTANCE TO

CORROSION.

DUE TO PRECIPITATION OF CHROMIUM CARBIDE AT GRAIN BOUNDARIES. (650C)

Reduce the carbon content.Precipitate carbide along slip planes.

METHODS TO REDUCE

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• STABILIZATION

A method employed where introduction of

some element that precipitates as carbide

in preference to chromium

TITANIUM is used approx 6 times Carbon content for stabilization

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Ferritic

Martensitic

Austensitic

STAINLESSSTEEL

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Ferritic stainless steel

• It has BCC structure• Composition:

Chromium - 11.5% to 27%Carbon – 0.2%Nickel – 0%

• Properties:– Provide good corrosion resistance.– Not hardenable by heat treatment because temperature

change induces no phase change in solid state.– Not readily work hardenable.– Little application in DENTISTRY.

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Martensitic stainless steel• BCT structure.• Composition:

Chromium – 11.5% to 17%Nickel – 0% to 2.5%Carbon – 0.15% to 1.2%

• Properties:– Can be heat treated– Has less corrosion resistance than other types of

stainless steels• Used for surgical and cutting instruments

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Austenitic stainless steel

• FCC structure.• AISI 302 series• Most corrosion resistant metal.• Used for orthodontic wires,endodontic instruments,

crowns in pediatric dentistry.

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Austenite18-8 stainless steel used in orthodontic

stainless steel wires and brackets

AISI 302(basic alloy)17-19% chromium

8-10%nickel0.15% carbon

AISI 30418-20%chromium

8-12%nickel0.08% carbon

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• AISI 316 LL – low carbon content, 0.03%10-14% Nickel2-3% molybdenum16-18% chromium - used to make implantsAISI-typeis currently used for bracket manufacturing

Variations in surface characteristics and corrosion behaviour of metal brackets and wires in different electrolyte solution.sChia-Tze Kao, Tsui-Hsien Huang,Europen jounal of orthodontics volume 33 issue 5,page 555-560

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Comparing Austenitic over Ferritic stainless steel

Austenitic stainless steel has:

• -Greater ductility & ability to undergo

more cold work without fracturing

• -Substantial strengthening during cold

working

• -Greater ease of welding

• -Ability to overcome sensitization

• -Comparative ease in forming

-Less critical grain growth

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Duplex steels SAF2205• Both austenite and ferrite grains

• Increased toughness and ductility

than Ferritic steels

• Twice the yield strength of austenitic

steels

• High corrosion resistance

• Lower nickel content

By Dr. Claude MatasaORTHODONTIC BIOMATERIALSProperties, risks and prevention

Due to its low content in nickel, the steel has been preferred for the manufacture of one-piece brackets by CEOSA, Madrid (Bioline® & Low nickel”®)

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Precipitation hardened steels [pH steels] [600 series] [630/17-4] [631/17-7]

Certain elements as chromium,copper,etc added

to steel tends to precipitate and increase the

hardness on heat treatment. –aging treatment-

decrease corrosion resistance.

The strength is very high.

Used to make mini-brackets.(due to high tensile

strength( PH17-4)

Edge lock brackets(17-7 ormco)

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Cobalt containing alloysUsed both for wires and brackets. Contain a large proportion of nickel.

Manganese containing steelsKnown as austenizing element, manganese acts by interstitially solubilizing the real austenizing element nitrogen thus replacing nickel Types [500 series]501 and 502 are low chromium [4-6%] steel not used for orthodontic appliance

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Tita

nium

allo

ysNickel titanium

(NiTi)

β- titanium

α- titanium

Titanium niobium

Timolium

Beta III

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NICKEL TITANIUM ALLOYS

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History • The term nitinol is derived from its composition and

its place of discovery (Nickel Titanium-Naval Ordnance Laboratory).

• William J. Buehler along with Frederick Wang, discovered its properties during research at the Naval Ordnance Laboratory in 1959.

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Composition:Nickel – 54%Titanium – 44%Cobalt- 2% or less

Nitinol alloy can exist in various crystallographic forms:Austenitic phase – BCC lattice, exists at high

temperatures & stable form

Martensitic phase – Close packed Hexagonal lattice, exists at room temperature

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Austenitic NiTi

Chinese NiTi(1985)

Japanese NiTi(1986)

Cu NiTi(1994)

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• A-NiTi is difficult to bend as they do not undergo plastic deformation easily

• Can be shaped if temperature

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• Superelastic properties of only a section of a wire can be changed by heat.

• Properties of A-NiTi have quickly made it the preferred material for orthodontic appliances.

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MARTENSITIC NiTi

Dr GEORGE ANDERSON (1971)

SHAPE MEMORY COULD NOT BE EXPLOITED

• STIFFNESS• FORCE PER DEACTIVATION• FORMABILITY

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The cooling/heating cycle shows thermal hyteresis

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The relative concentration of two phases in the alloy will determine the relative stiffness of the wire and the amount of force delivered.

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• In metals that crystalize in HCP , deformation occurs by Twinning.

This twinning is responsible for Shape memory and super elastic properties of metals.

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Shape memory effect

Superelasticity – phenomenon where austenite to martensite transition is induced by stress .

Achieved by 1st establishing a shape at temp erature near 482°C

cooled & formed into a 2nd shape and heat treated through a low transition temperature

wire will return to its original shape

COBALT content is used to control the lower transition temperature (approx 37°C mouth temperature)

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SHAPE MEMORY

THERMALLY INDUCED AT ORAL TEMPERATURE

SUPER ELASTICITY

MECHANICAL OR STRESS INDUCED

MARTENSITIC PHASE TRANSFORMATION

AUSTENITIC MARTENSITIC AUSTENITIC

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Key properties of Nitinol alloys include:• Large forces that can be generated.• Excellent damping properties below the transition

temperature.• Excellent corrosion resistance.• Nonmagnetic.• High fatigue strength.• Moderate impact resistance.• Moderate heat resistance.• Biocompatible.

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Advantages

I. Fewer arch wire changesII. Less chair side timeIII. Less patient discomfort

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Uses of NITINOL

DENTISTRY:

ORTHODONTIC WIRES

ENDODONTIC FILES

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• MEDICAL APPLICATION:

ANCHORS FOR TENDON FIXATION.

STENTS FOR CARDIOVASCULAR APPLICATION

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• AEROSPACE AND NAVAL APPLICATION:

• ACTUATOR TO CONTROL WATER:

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Miura F, Mogi M, Ohura Y, Hamanaka H.: The super- property of the Japanese NiTi alloy wire for use in orthodontics. Am J Orthod Dentofac Orthop 1986; 90: 1-10.

Recent advances in NiTi wires

• Bioforce sentalloy• Nitrogen coated archwires• Nitinol total control

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Nitinol Total Control• Developed by TODD A.THAYER.• Superelastic nickel titanium alloy to deliver light,

continuous forces over a desired treatment range with bend ability required to account for variations in tooth morphology,archform and bracket prescriptions.

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COPPER NiTiIntroduced in 1994 by Dr. Rohit Sachdeva.Quartenary alloy• Nickel• Titanium• Copper• ChromiumHas both superelastic and shape memory properties.

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• Advantages of Cu-NiTi over traditional NiTi alloys:

More resistant to permanent deformation and better springback

Smaller loading force for same degree of deformation

More consistent forces which are active longer within the optimal tooth moving range

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• Presence of copper helps to:

• Stress required to deform martensitic phase

• Hysteresis

Thermal reactive properties of NiTi

Creates a consistent unloading force which closely approximates loading forces.

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MARTENSITIC TRANSFORMATION

STRESS INDUCED TEMPERATURE DEPENDENT

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• To exploit superelasticity to its fullest potential the working temperature of the orthodontic appliance > austensitic finish temperature.

• Difference between austensitic and mouth temperature determines the force generated.

• Austensitic temperature

1.COMPOSITION 2.THERMOMECHANICAL TREATMENT 3.MANUFACTURING PROCESS

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AUSTENSITIC FINISH

TEMPERATURE

TYPE I TYPE II TYPE III TYPE IV

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• TYPE I:

NOT FREQUENTLY USED AS IT GENERATES VERY HIGH FORCES.

Af 15C

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• TYPE II:

• > FORCES WHEN COMPARED TO TYPE III AND TYPE IV.

• AVERAGE OR HIGHER PAIN THRESHOLD PATIENTS.

• NORMAL PERIODONTAL HEALTH• RAPID TOOTH MOVEMENT.• FORCE GENERATED IS CONSTANY

Af 27C

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• TYPE III:

• GENERATES FORCES IN MILD RANGE.• LOW TO NORMAL THRESHOLD PATIENTS.• NORMAL TO SLIGHTLY COMPROMISED

PERIODONTIUM.

Af 35C

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• TYPE IV:

• GENERATE TOOTH MOVING FORCES ONLY WHEN MOUTH TEMP ERATURE>40 DEG C

• FOR PATIENTS WHO ARE VERY SENSITIVE TO PAIN

• COMPROMISED PERIODONTAL HEALTH • FOR PATIENTS WHO HAVE LONG

INTERVALS BETWEEN APPOINTMENTS OR POOR CO-OPERATION

Af 40C

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• ADVANTAGES:

• Constant and sustained unloading forces.

• hysteresis – equal actvation and deactivation forces.

• Provides prescise transformation temperature.

• Easier to engage in a slot

• Decrease of force is less than NiTi hence it continues to work as teeth near their intended positions.

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β-TITANIUM

• Termed as Titanium-Molybdenum Alloys (TMA)

Dr. CHARLES BURSTONE AND JON GOLDBERG

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• Composition:– Titanium – 77.8%– Molybdenum – 11.3%– Zirconium – 6.6%– Tin – 4.3%

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• Mechanical properties of beta-titanium alloys

ELASTIC MODULUS • SPRINGBACK.• YIELD STRENGTH TO

ELASTIC MODULUS RATIO.• COLD WORKED.• DUCTILITY

GOOD FORMABILITY COMPARED TO AUSTENSITIC STAINLESS STEEL

• CORROSION RESISTANCE.• ENVIRONMENTAL STABILITY.

HEAT TREATMENT

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ONLY ORTHODONTIC WIRE POSSESSING TRUE WELDABILITY

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Welding properties of beta-titanium alloys

Clinically satisfactory joints can be made by welding. Weld made with insufficient heat fails at the interface between the wires. Overheating may cause a failure adjacent to the welded joint.

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Advantages of Beta-titanium over Stainless steel

• Beta-titanium replaced stainless steel for certain uses, as stainless steel had dominated orthodontics since the 1960s.

• It has strength/modulus of elasticity ratios almost twice those of 18-8 austenitic stainless steel, larger elastic deflections in springs, and reduced force per unit displacement, 2.2 times below those of stainless steel appliances.

JON GOLDBERG* and CHARLES J. BURSTONE+ Department of Restorative Dentistry,* Department of Orthodontics+, The University of Connecticut Health Center, Farmington, Connecticut 06032, and Institute of Materials Science,*+ Storrs, Connecticut 06268

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INITIAL TOOTH ALIGNMENT

• CLINICAL USE

FINISHING ARCHES

K-SIR ARCH

PENDULUM APPLIANCE

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TITANIUM-NIOBIUM

• Composition : Titanium- 82% Molybdenum-15% Niobium- 3%

Nickel free alloy.

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PROPERTIES• Easy to bend.• Formability < TMA Load deflection• Yield strength < SS.• Stiffness ¼ of SS.• Indicated when lower forces than those

exerted by TMA are needed.

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ADVANTAGES• No leaching of Nickel.• Biocompatible.

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CLINICAL IMPLICATIONS

• Finishing wire with multiple bends• Fixed retainers

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TIMOLIUM TITANIUM WIRE

Timolium archwires combine

• Flexibility • Continuous force NICKEL TITANIUM• Springback

• High stiffness • Bendability STAINLESS STEEL

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• Easier to bend and shape• Can be welded. • Loops and bends can be made without breakage.

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CLINICAL IMPLICATIONS

During initial treatment it is excellent for:• space closure• tooth alignment• levelling and bite opening.

Total control during detailing makes Timolium the wire of choice during the final treatment phase.

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β-III WIRES

Introduced by Dr.RAVINDRA NANDA Bendable High force Low deflection rate Co-efficient of friction is more

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• Nickel free titanium wire with memory• Ideal for multilooping, cantilever, utility arches• First choice of wire for finishing stages where tip &

torque corrections fully accomplished during initial stages

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ΑLPHA- TITANIUM

The composition of α-titanium include• 88.9% titanium, • 7.86% Aluminum • 4.05% Vanadium.

The elastic modulus and yield strength • 110 GPa and 40 MPa respectively Aluminum, carbon, oxygen and nitrogen, stabilize the a-titanium structure. That is, they raise the temperature for transformation to β-titanium.

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• Hexagonal lattice possesses fewer slip planes making it less ductile than ß-titanium.

• The wires are soft enough for initial gentle action on teeth in spite of large wire dimension .

• They seem to harden and become brittle with passage of time in the mouth, possibly due to the absorption of hydrogen and formation of titanium hydrides.

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COBALT-CHROMIUM NICKEL ALLOY

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• Cobalt – 40%• Chromium – 20%• Nickel – 15%• Molybdenum – 7%• Manganese – 2%• Carbon – 0.016%• Beryllium – 0.04%• Iron – 15.8%

Composition:

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• Also known as ELGILOY.• It is manufactured in four tempers:

SOFT DUCTILE SEMIRESILIENT

RESILIENT

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• Heat treatment of elgiloy

Softening heat treatment temperature:1100°C to 1200°C followed by rapid quench

Age hardening temperature range:260°C to 650°C

According to the manufacturer, alloy for ELGILOY is held at 482°C for 5 hours

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• ELGILOY wire is heat treated at 482°C for 7 to 12 minutes - mainly to increase the yield strength & decrease the ductility.

ELGILOY wires should not be ANNEALED.

• Because the resulting softening effect cannot be reversed by subsequent heat treatment.

• If only a portion of wire is annealed, severe embrittlement of adjacent sections may occur

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The advantages of Co-Cr wires over stainless steel wires include greater resistance to fatigue and distortion, and

longer function as a resilient spring.

Kapila S, Sachdeva R. Mechanical properties and clinical applications of orthodontic wires. Am J Orthod Dentofacial Orthop. 1989;96:100–9

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Recovery heat treatment of ELGILOY

• Stress-relief heat treatment :

ELGILOY wires are heat treated at comparatively low temperatures (370°C to 480°C) after it has been cold worked.

Stress-relief treatment:1)Removes residual stresses during recovery

without pronounced alteration in mechanical properties.

2)Improves working elastic properties.3)Reduce failure caused by corrosion.

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A J WILCOCK WIRES

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Wilcock archwire have been the main stay of Begg's tech.

Developed by the late Mr. Arthur J. Wilcock senior of Whittlesea, Victoria Australia that enabled Dr. Begg to develop his light wire tech.

They are available in spools and straight lengths

Until recently the grade of wire routinely used was special plus and for those cases resistant to bite opening extra special plus was used. The new grades and sizes of wires are now available.

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• Properties of AJ Wilcock wires:

TENSILE STRENGTH

STIFFNESS

RESILIENCE

ZERO STRESS RELAXATIONRESISTANT TO DEFORMATION

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• A J Wilcock wires are graded into:

REGULAR

REGULAR PLUS

SPECIAL

SPECIAL PLUS

PREMIUM

PREMIUM PLUS

SUPREME

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Regular grade

LOWEST GRADE

EASY TO BEND

USED FOR AUXILIARIES

USED WHEN ARCHFORM DISTORTION IS NOT A PROBLEM OR BITE OPENING IS NOT REQUIRED

DIAMETER-0.012-0.024

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Regular plus

Relatively easy to form.More resilient than regular.Used for making auxiliaries. Used for making an archform when more pressure and resistance to deformation are desired.

DIAMETER- 0.012-0.020

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Special grade

HIGHLY RESILIENT

LESS BREAKAGE

USED MOSTLY AS ARCHWIRES

DIAMETER-0.012-0.020

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Special plus

HARDNESS AND RESILIENCY IS EXCELLENT FOR MAINTAINING ANCHORAGE AND REDUCING OVERBITE

CHANCES OF FRACTURE MORE

SHOULD BE BENT WITH CAUTION

DIAMETER-0.012-0.024

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Premium

High resilience

• IDEAL FOR OPEN BITE.

DIAMETER-0.012-0.020

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Premium plus

• In early treatment – alignment and levelling.• Preferred in high angle and undue molar extrusion.

DIAMETER- 0.011-0.018

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Supreme

• Unravelling crowded anerior teeth• Mini uprighting springs.

DIAMETER-0.008-0.011

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Process of manufacturing

SPINNER STRAIGHTENINGPULSE STRAIGHTENING

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SPINNER STRAIGHTENING

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• Deformation • Decreased yield stress value makes it strain

softened

DISADVANTAGES

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PULSE STRAIGHTENING • The wire is pulsed in special machines the

permit high tensile wires to be straightened. • The advantages

• —It permits highest tensile wire to be straightened.

• —Tensile yield stress is not altered. • —Smoother surface of wire hence less

friction.

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• Greater flexibility of spring fabricated.• Greater resiliency • Permits the usage of small diameter wire resulting in

a continuous force with minimal relaxation.

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• BAUSCHINGER EFFECT

If the wires are straightened by the process of reverse straining, meaning flexing in a direction opposite to that of original bend, the yield point of the wire reduces.

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Clinical tips and facts • The higher grade wires especially pulse

straightened are excellent for applying constant force for a longer time without undergoing softening.

• For a careless patient and patients with occlusal interference, chance of wire fracture is more. So low grade wire is preferred.

• The wire used for making arches is selected according to the load deflection, we required.

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Clinical tips and facts

• The higher grade wires especially pulse straightened are excellent for applying constant force for a longer time without undergoing softening.

• For a careless patient and patients with occlusal interference, chance of wire fracture is more. So low grade wire is preferred.

• The wire used for making arches is selected according to the load deflection, we required

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CONCLUSION• In the last few decades, a variety of new alloys has been

introduced into orthodontics.• Appropriate use of all the available wire types may enhance

patient comfort and reduce chairside time and the duration of treatment.

• The restricted use of only stainless steel wires to treat an entire case from start to finish therefore may be indicated only in a few patients.

• It may be beneficial instead to exploit the desirable qualities of a particular wire type that is specifically selected to satisfy the demands of the presenting clinical situation.

• This, in turn, would provide the most optimal and efficient treatment results.

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REFERENCES• Phillips' Science of Dental Materials By Kenneth J. Anusavice• Krishnan V, Kumar KJ. Mechanical properties and surface

characteristics of three archwire alloys. Angle Orthod. 2004;74:825–31.

• The Use of Gold in Dentistry AN HISTORICAL OVERVIEW. PART I J. A. Donaldson British Dental Association Museum, London, U.K

• Gold in Dentistry: Alloys, Uses and Performance Helmut Knosp, Consultant, Pforzheim, Germany Richard J Holliday, World Gold Council, London, UK Christopher W. Corti, World Gold Council, London, UK• A non-rusting steel". New York Times. 31 January 1915

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• IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 14, Issue 1 Ver. I (Jan. 2015), PP 47-50

• Variations in surface characteristics and corrosion behaviour of metal brackets and wires in different electrolyte solution.sChia-Tze Kao, Tsui-Hsien Huang,Europen jounal of orthodontics volume 33 issue 5,page 555-560

By Dr. Claude Matasa• ORTHODONTIC BIOMATERIALSProperties, risks and prevention

• Miura F, Mogi M, Ohura Y, Hamanaka H.: The super- property of the Japanese NiTi alloy wire for use in orthodontics. Am J Orthod Dentofac Orthop 1986; 90: 1-10.

• An Evaluation of Beta Titanium Alloys for Use in Orthodontic Appliances JON GOLDBERG* and CHARLES J. BURSTONE+ Department of Restorative Dentistry,* Department of Orthodontics+, The University of Connecticut Health Center, Farmington, Connecticut 06032, and Institute of Materials Science,*+ Storrs, Connecticut 06268• Structure, Composition, and Mechanical Properties of Australian Orthodontic Wires Brian M. Pelsuea; Spiros Zinelisb; T. Gerard Bradleyc; David W. Berzinsd; Theodore Eliadese; George Eliadesf

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