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Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
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Wires in orthodontics
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Wires in orthodontics
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Wires in orthodontics
Wires in orthodontics
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Wires in orthodontics
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Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
Wires in orthodontics
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Wires in orthodontics

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  • 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  • 2. CONTENTS :  Basic Properties of Wires  Composition, Heat treatment, manufacture and properties of:- 1.Gold Alloy wires 2.Stainless Steel wires 3.Chrome Cobalt wires 4.Nickel Titanium wires 5.Copper Nickel Titanium wires 6.Alpha-Titanium wires www.indiandentalacademy.com
  • 3. 7.Beta-Titanium wires 8.Tooth colored wires  Clinical importance of various wires  Choice of wires in the clinical situation  The Future  References www.indiandentalacademy.com
  • 4. PHYSICAL PROPERTIES OF ARCHWIRE MATERIALS www.indiandentalacademy.com
  • 5. VARIOUS PHYSICAL PROPERTIES  Stress  Strain  Modulus of elasticity  Proportional limit  Elastic limit  Yield strength  Ductility  Malleability  Elongation  Formability  Resilience  Flexibility  Springback www.indiandentalacademy.com
  • 6. STRESS (S, I)  Stress is the internal distribution of the load measured as force per unit area i.e., Force/Original area.  For simple compression or tension the stress is given by the expression, Stress =F/A Where, F= force applied A= cross-sectional areawww.indiandentalacademy.com
  • 7.  Stress is measured in common units of psi or Mpa (Mega Pascal).  1 Pascal – stress resulting from a force of 1 Newton (N) acting upon 1 sq. meter of surface and is equal to 1.145 x 10–3 psi, (1000 psi = 6.894 Mpa). www.indiandentalacademy.com
  • 8.  One test method commonly used for dental materials is the THREE POINT BENDING TEST or TRANSVERSE TEST.  When an external force is applied to the mid point of the test beam, the stress can be resolved. The numerical value of stress is given by the expression, www.indiandentalacademy.com
  • 9. Stress = 3FL 2bd where, L = distance between the supports b = width of the specimen d = depth of the specimen www.indiandentalacademy.com
  • 10.  When a wire is compressed across the diameter ,a tensile stress is set up in the specimen, Stress = 2F D²T F = applied force D = diameter of wire T = length of the wire This type of test is referred to as a Diametral Compressive Tensile Test and is usually used when conventional tensile testing is difficult to carry out.www.indiandentalacademy.com
  • 11. TYPES OF STRESS  TENSION OR TENSILE STRESS : It tends to pull the material apart or tends to stretch or elongate a body.  COMPRESSION OR COMPRESSIVE STRESS : It is the direct opposite of tension stress. If a body is placed under a force, that tends to compress or shorten it, the internal resistance to such a force is called as compressive strain. www.indiandentalacademy.com
  • 12. SHEAR STRESS  A stress that is applied by two forces acting in opposite directions but not in the same line.  These stresses tend to slide one part of the material past another along planes parallel to the applied force. www.indiandentalacademy.com
  • 13. STRAIN (γ) • Strain is the internal distortion produced by load or a stress, i.e., change in length per unit length when stress is applied. Strain = L‟ = change in length L original length • The common units of strain are inch per inch or centimeter per centimeter. www.indiandentalacademy.com
  • 14. www.indiandentalacademy.com
  • 15. Hooke‟s Law  Within the elastic range, the material deforms in direct proportion to the stress applied, i.e., Stress = Modulus of elasticity x Strain www.indiandentalacademy.com
  • 16. MODULUS OF ELASTICITY (Young‟s modulus) (E)  It is defined as the ratio between a unit stress and a unit strain, usually expressed as pound/square inch (psi) or mega pascal (Mpa). It is an index of stiffness or flexibility of a material within the elastic range. Stress (I) E = --------------------- Strain (γ) www.indiandentalacademy.com
  • 17. PROPORTIONAL LIMIT (IPL) or (P)  It is the point at which the first deformation occurs. It is the maximum stress at which the straight line relationship between stress and strain (Hooke‟s Law) is valid. www.indiandentalacademy.com
  • 18. ELASTIC LIMIT (IEL) (E)  It corresponds to the stress beyond which strains are not fully recovered. It is the maximum stress that a material can withstand without permanent deformations. www.indiandentalacademy.com
  • 19. YIELD STRENGTH (Ys) or (IYS)  It is the practical indicator at which the first deformation is measured. It is measured by pounds per square inch.  the point at which a plastic deformation of 0.1 % is measured and is called yield strength (YS). www.indiandentalacademy.com
  • 20. www.indiandentalacademy.com
  • 21. ULTIMATE TENSILE STRENGTH  It is the maximum load carrying capacity of the wire before it fractures.  It represents the maximum stress required to fracture a material. www.indiandentalacademy.com
  • 22. DUCTILITY  It is the ability of a material to be plastically strained in tension i.e., ability of a material to withstand permanent deformation under a tensile load without rupture. www.indiandentalacademy.com
  • 23. ELONGATION  It is the deformation as a result of tensile force application.  It is usually expressed as percentage elongation and is equal to L increase in length --------------- x 100 or --------------------- x 100 L0 original length www.indiandentalacademy.com
  • 24. MALLEABILITY  The ability of a material to withstand permanent deformation without rupture under compression as in hammering or rolling into sheets. www.indiandentalacademy.com
  • 25.  Gold -Most ductile and most malleable  Silver -Next to most ductile and malleable  Platinum -Third most ductile  Copper -Third most malleablewww.indiandentalacademy.com
  • 26. RESILIENCE ( stored or spring energy)  Resilience represents the energy storage capacity of a wire, when it is stressed not to exceed its proportional limit.  It is the energy absorbed by a wire in undergoing elastic deformation upto the elastic limit. www.indiandentalacademy.com
  • 27.  The energy stored is released when the wire springs back to its original shape after removal of an applied stress. www.indiandentalacademy.com
  • 28. FORMABILITY  Formability is the amount of permanent deformation that a wire will withstand before failing i.e. before breaking or fracture. www.indiandentalacademy.com
  • 29. www.indiandentalacademy.com
  • 30. FLEXIBILITY  It is the measure of the strain that a wire can withstand without undergoing plastic deformation.  A material is said to be flexible if it withstands the strain or the load up to its proportional limit without deforming permanently www.indiandentalacademy.com
  • 31. LOAD DEFLECTION RATE  For a given load (force) the deflection observed within the elastic limit is known as load deflection rate. www.indiandentalacademy.com
  • 32. SPRINGBACK (Range of action) AND SPRINGINESS  Springback ability of a wire is a measure of its ability to undergo large deflections without permanent deformation.  If a wire can be deflected over long distances without permanent deformation, it has a high spring back value. www.indiandentalacademy.com
  • 33.  It is expressed as YS/E i.e., the ratio of yield strength to modulus of elasticity which represents the approximate amount of strain released by the wire on unloading. www.indiandentalacademy.com
  • 34. THE PHYSICAL PROPERTIES OF METALS AND ALLOYS AND THEIR APPLICATION IN WIRE FORM IN ORTHODONTICS www.indiandentalacademy.com
  • 35.  Flexural rigidity (EI) ;  Resistance to distortion ;  Susceptibility to fracture www.indiandentalacademy.com
  • 36. FLEXURAL RIGIDITY (EI)  Flexural rigidity of a wire is the product of the Young‟s modulus (E) and a factor (I) known as the second moment of inertia of the cross-section of the wire.  I depends on the shape and dimensions of the cross-section of a wire, and determines how stiff a wire (with a given Young‟s Modulus) will be. www.indiandentalacademy.com
  • 37.  For a circular cross-section, I = π R4 / 4 Where, R is the radius of the cross-section.  The second moment of inertia of the cross-section (I) increases greatly as the radius of the wire is increased. www.indiandentalacademy.com
  • 38.  Doubling the radius (holding everything else constant) therefore increases the force applied by a spring by (2)4, i.e., by 16 times.  For example, for a given deflection, the use of 0.6 mm diameter wire instead of 0.5 mm will double the force applied. www.indiandentalacademy.com
  • 39.  Flexural Rigidity may be determined experimentally for a wire by mounting the latter as a simple cantilever and measuring the deflection for various loads applied to the free end.  The value of Flexural Rigidity (EI) can be deduced from the relationship between force applied (p) and the deflection (y) of the free end of the cantilever, i.e. P/y = 3EI / l3 www.indiandentalacademy.com
  • 40. www.indiandentalacademy.com
  • 41.  If a load is applied to the free end of a simple cantilever, the upper layers of the wire are extended and the lower layers are compressed. RESISTANCE OF WIRES TO DISTORTION www.indiandentalacademy.com
  • 42.  At any given cross-section of the wire the variation in the magnitude and direction of these internal stresses, from the outer to the inner surfaces of curvature, constitutes a series of couples whose resultant, the moment of resistance, is equal in magnitude and opposite in sense to the Bending Moment at the crosssection considered.www.indiandentalacademy.com
  • 43.  The maximum fibre stress occurring in the outermost layers of a bent wire at any point may be calculated from the expression σmax = GR/I where, σmax is the maximum fibre stress, G is the Bending Moment at that point, R is the radius of the wire, I is the second moment of inertia of the cross-section. www.indiandentalacademy.com
  • 44.  Provided the maximum fibre stress, σmax, is less than the effective yield stress, σeff, the wire will behave elastically and return to its rest position when released.  If,σmax is greater than σeff at any point along a wire, permanent plastic deformation will take place. www.indiandentalacademy.com
  • 45.  The necessary condition for distortion to occur may therefore be written GR ------------------- ≥ σeff I www.indiandentalacademy.com
  • 46. SUSCEPTIBILITY TO FRACTURE  It is usually assumed that appliances occasionally fail because of metal fatigue induced by the repeated stressing of the wire.  A study of the fatigue life of 2-cm finger springs by Bass and Stephens (1970) showed that these springs were capable of withstanding over 1,00,000 flexes when the distance of flexure was 7.5 mm.www.indiandentalacademy.com
  • 47.  Harcourt and Munns (1967) have investigated finger springs fractured in use and conclude that fatigue failure is less likely to occur than failure due to surface defects produced by the pliers during fabrication or by an abrasion wheel when the appliance is being trimmed, finished or fitted. www.indiandentalacademy.com
  • 48. ELASTIC PROPERTIES www.indiandentalacademy.com
  • 49.  Strength  Stiffness  Range www.indiandentalacademy.com
  • 50. STRENGTH  It is a force value that is a measure of the maximum possible load,i.e., the greatest force that a wire can sustain or deliver, if it is loaded to the limit of the material.  It is equivalent to the proportional limit (PL) or approximately the yield strength (YS) of the wire segment. www.indiandentalacademy.com
  • 51.  Considering the graphic representation of the stress – strain curve three points can be taken as representative of the strength of a material - elastic limit - yield point -ultimate tensile strength www.indiandentalacademy.com
  • 52. STIFFNESS  It is the rate of force delivery required for a unit activation .  It is the measure of the force required to bend or otherwise deform the material to a definite distance. www.indiandentalacademy.com
  • 53.  Stiffness is proportional to the modulus of elasticity and cross-section of a given wire and is not appreciably influenced by any hardening treatment.  Stiffness and springiness are reciprocal properties. Springiness = 1 / stiffness. www.indiandentalacademy.com
  • 54.  Stiffness = Ed/L, higher the elastic modulus, stiffer the wire. www.indiandentalacademy.com
  • 55.  According to the force deflection curve, stiffness and springiness are proportional to the slope of the elastic portion of the curve.  The more horizontal the slope, the springier the wire, the more vertical the slope the stiffer the wire. www.indiandentalacademy.com
  • 56. RANGE  Range is defined as the maximum amount of elastic activation before the onset of a permanent or plastic deformation.  Range is usually determined from the 0.1% offset point on the force – deflection diagram.www.indiandentalacademy.com
  • 57.  Strength,Stiffness and Range have an important relationship,i.e., Strength = Stiffness x Range www.indiandentalacademy.com
  • 58. FACTORS AFFECTING STIFFNESS, STRENGTH AND RANGE  The mechanical arrangement by which force is applied to the teeth, e.g. length of archwire.  The second factor is the form of the wire itself – the size and shape of crossection.  The third factor is the material, including the alloy composition, its hardness.www.indiandentalacademy.com
  • 59. EFFECTS OF SIZE AND SHAPE ON ELASTIC PROPERTIES  A beam is any relatively slender structure subjected to lateral (bending) loads. An orthodontic archwire functions mechanically as a beam. www.indiandentalacademy.com
  • 60.  Each of the major elastic properties – strength , stiffness and range- is substantially affected by a change in geometry of the beam.  Both the cross-section and length of beam are of great significance in determining its properties. www.indiandentalacademy.com
  • 61.  Changes related to size and shape are independent of the material. In other words, decreasing the diameter of a steel beam by 50% would reduce its strength to a specific percentage of what it had been previously.  Decreasing the diameter of the TMA beam by 50% would reduce its strength by exactly the same percentage. www.indiandentalacademy.com
  • 62. Effects of diameter or cross section www.indiandentalacademy.com
  • 63.  When beams of any type made from two sizes of wire are compared, 1. Strength changes as a cubic function of the ratio of the two cross- sections. 2. Springiness changes as the fourth power of the ratios. 3. Range changes as a direct proportion.www.indiandentalacademy.com
  • 64. Effects of length and attachment www.indiandentalacademy.com
  • 65.  Strength varies inversely with length.  Springiness varies as a cubic function of the length ratios.  Range varies as a second power function.  Supporting a beam on both ends makes it stronger but less springy. www.indiandentalacademy.com
  • 66.  If a beam is rigidly attached on both ends, it is twice as strong but only one-fourth as springy as a beam of the same material and length. www.indiandentalacademy.com
  • 67.  The best balance of strength , springiness and range must be sought among the almost innumerable possible combinations of beam materials, diameter and length. www.indiandentalacademy.com
  • 68. GOLD ALLOY WIRES  The first wire introduced for orthodontic purpose was made of gold.  Gold arch wires were the ideal choice of arch wires with good bio- compatibility. www.indiandentalacademy.com
  • 69.  Composition of many gold alloy wires corresponds to the type IV gold casting alloys  They are also subjected to softening and hardening heat treatments. www.indiandentalacademy.com
  • 70.  Many wires appear to contain less than 60% gold with some containing less than 25 to 30% or even less.  The palladium content of the alloy is relatively high, which gives a composition closely resembling white gold casting alloys. www.indiandentalacademy.com
  • 71.  Palladium and platinum cause rise in the melting point, improve corrosion resistance and increase hardness and strength during heat treatment.  The copper content of most wires is well above 9%. www.indiandentalacademy.com
  • 72.  Gold alloys used, can be called to a large extent as binary alloys, as only gold and copper are major metals used.  These binary alloys to a large extent exhibit severe grain growth on heating and have poor ductility in the hardened state. www.indiandentalacademy.com
  • 73. Heat Treatment of Gold Alloys  The changes that are produced in the strength and ductility of a wrought gold alloy by heat treatment are due to the alterations in the gold copper compound present in the alloy.  Softening heat treatment is undertaken initially by heating the wire to 1300 F, for approximately ten minutes and then quenching it.www.indiandentalacademy.com
  • 74.  Softening of the alloys is produced as the gold copper alloy enters into solid solution at 1300 F.  All of the hardening elements are completely dissolved in each other in solid solution, the space lattice is free to move on the slip planes without interference. www.indiandentalacademy.com
  • 75.  Increased number of slip planes, causes increased ductility of the wire.  This wire left at room temperature for several days becomes harder.  Alternatively, after the wire is heated to 1300 F, it is reheated to 840 F and allowed to cool slowly. This allows the gold copper compound to come out of the solution. www.indiandentalacademy.com
  • 76.  This causes the formation of segregated molecules which produce a locking effect on the space lattice and causes resistance to slip.  The space lattice itself is also distorted to some degree, thus decreasing the number of planes on which slip can occur. In this way, the material becomes stronger and more resilient. www.indiandentalacademy.com
  • 77.  Besides (age) precipitation hardening, cold working of gold alloys increases strength of the wrought gold wires. The alloy hardens as the grain structure becomes broken up and the space lattice is distorted during cold working. www.indiandentalacademy.com
  • 78.  This type of hardening is easily relieved by heating the wire to recrystallization temperatures, recrystallization will take place and allow the atoms to return to normal position in the space lattice. www.indiandentalacademy.com
  • 79. Properties of Gold wires  Yield strength of the gold wires range from 50,000 to 1,60,000 psi, depending on the alloy.  Modulus of elasticity of gold copper alloys is approximately 15,000,000 psi.  The combination of these properties makes gold very formable and capable of delivering lower forces than stainless steel. www.indiandentalacademy.com
  • 80. STAINLESS STEEL ALLOY  Stainless steel wires began to replace gold wires in the 1930‟s .  Steels are iron – based alloys that usually contain less than 1.2% carbon.  When 12-30% chromium is added to steel the alloy is commonly called STAINLESS STEEL. www.indiandentalacademy.com
  • 81. Composition Type (Space Lattice) Chromium Nickel Carbon Ferritic (BCC) 11.5-27 0 0.20 max Austenitic(FCC) 16.0-26 7-22 0.25 max Martensitic(BCT) 11.5-17 0-2.5 0.15-1.2 max www.indiandentalacademy.com
  • 82.  Silicon ,phosphorous ,sulphur, manganese, tantalum, and niobium may also be present in small amounts. The balance is iron. www.indiandentalacademy.com
  • 83. Ferritic Stainless Steel (BCC)  These alloys are often designated as American Iron and Steel Institute(AISI) Series 400 stainless steels.  The ferritic alloys provide good corrosion resistance at a low cost , provided that high strength is not required. www.indiandentalacademy.com
  • 84. Ferritic Stainless Steel  Because temperature change induces no phase change in the solid state , the alloy is not hardenable by heat treatment.  This series of alloys finds little application in dentistry. www.indiandentalacademy.com
  • 85. Martensitic Stainless Steel (FCC)  Martensitic stainless steel alloys share the AISI 400 designation with the ferritic alloys.  They can be heat treated in the same manner as plain carbon steels , with similar results.  Because of their higher strength and hardness, martensitic stainless steels are used for surgical and cutting instruments. www.indiandentalacademy.com
  • 86. Austenitic Stainless Steel (BCT)  The austenitic stainless steel alloys are the most corrosion resistant of the stainless steels.  AISI 302 is the basic type , containing 18% chromium , 8% nickel , and 0.15% carbon. Type 304 has a similar composition , but the chief difference is its reduced carbon content (0.08%). www.indiandentalacademy.com
  • 87. Austenitic Stainless Steel  Both 302 and 304 stainless steel may be designated as 18-8 stainless steel ; they are the types most commonly used by the orthodontist in the form of band and wires .  Type 316L (0.03% maximum carbon) is the type ordinarily employed for implants. www.indiandentalacademy.com
  • 88.  The alloying elements Chromium and Nickel maintains austenite at room temperature and prevents conversion of face centered cubic lattice structure of austenite to a martensitic cubic lattice structure. www.indiandentalacademy.com
  • 89.  By nature austenite is malleable and ductile whereas martensite is hard and brittle. By maintaining austenite at room temperature, several uses of austenitic stainless steel are made use of in orthodontics, such as wires, bands, instruments etc. www.indiandentalacademy.com
  • 90.  Tarnish and corrosion are resisted by stainless steel due to the passivating effect of chromium.  A thin , transparent but tough impervious chromium oxide layer forms on the surface of the alloy when it is subjected to an oxidizing temperature as mild as clean air or atmospheric room air. www.indiandentalacademy.com
  • 91.  This protective oxide layer prevents tarnish and corrosion, but can be ruptured by mechanical or chemical means resulting in corrosion.  However ,the passivating oxide layer eventually forms again in an oxidizing environment. www.indiandentalacademy.com
  • 92.  Chromium loss is called sensitization.  A procedure to introduce some element that precipitates carbide in preference to chromium preferably titanium is called stabilization. www.indiandentalacademy.com
  • 93. Heat Treatment of STAINLESS STEEL Alloy  The physical properties of orthodontic stainless steel wires improve by heat treatment at low temperatures between 750° C to 820° C for ten minutes and at a lower temperature of 250° C for twenty minutes.  By heat treatment residual stresses are removed. www.indiandentalacademy.com
  • 94. Properties of STAINLESS STEEL Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Numb 90-de Cold witho fractu S. Steel 179 1579 2117 5 Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Numb 90-de Cold witho fractu S. Steel 179 1579 2117 5 AlloyAlloy Modulus of Elasticity (10³ MPa) Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Ultimate Tensile Strength (MPa) Numb 90-de Cold witho fractu Numb 90-de Cold witho fractu S. SteelS. Steel 179179 15791579 21172117 55 www.indiandentalacademy.com
  • 95.  Arthur. J. Wilcock of Victoria, Australia, produced the orthodontic archwire to meet Dr. Begg‟s needs for use in Begg technique.  The wire produced has certain unique characteristics different from usual stainless steel wires . AUSTRALIAN ORTHODONTIC ARCHWIRE www.indiandentalacademy.com
  • 96.  REGULAR GRADE : White label. Lowest grade and easiest to bend. Used for practice bending or forming auxillaries. It can be used for archwires when distortion and bite opening are not a problem. www.indiandentalacademy.com
  • 97.  REGULAR PLUS GRADE : Green Label Relatively easy to form, yet more resilient than regular grade. Used for auxillaires and archwires when more pressure and resistance to deformation is required. www.indiandentalacademy.com
  • 98. SPECIAL GRADE : Black Label. Highly resilient, yet can be formed into intricate shapes with little danger of breakage. SPECIAL PLUS GRADE : Orange Label Hardness and resiliency of the wire are excellent for supporting anchorage and reducing deep overbites. www.indiandentalacademy.com
  • 99.  EXTRA SPECIAL PLUS GRADE :Blue Label. Highly resilient and hard, difficult to bend and subjects to fracture.  Supreme Grade : Blue Label. Primarily used in early treatment for correction of rotations, alignment and levelling. Its yield strength exceeds that of E.S.P. www.indiandentalacademy.com
  • 100.  Each grade of wire is available in diameters of 0.010″, 0.012″, 0.014″, 0.016″, 0.018″, 0.020″, 0.022″. They are supplied in the form of spools or cut lengths of the wire.  With the demand for harder wires , even higher grades , premium and premium plus wires were developed . www.indiandentalacademy.com
  • 101.  The new grades and sizes of wire makes available are: Sizes Available Premium : .020″ Premium Plus : .010″,.O12″,.014″,.016″, .018″ Supreme : .008″, .009″, .010″, .011″. www.indiandentalacademy.com
  • 102. Heat Treatment of AUSTRALIAN WIRE  The low and medium grade wires exhibit better formability as they are subjected to less work hardening and hence are more ductile.  Till then the wires were straightened by spinner straightening. The wire is pulled through high speed rotating bronze rollers which twist the wire into a straightened condition. www.indiandentalacademy.com
  • 103.  Presently the premium and supreme wires are straightened by a process called pulse straightening .Though the exact procedure remains a trade secret , it enables to straighten these high yield strength wires , without structural deformation and altering the physical properties. www.indiandentalacademy.com
  • 104.  The properties of the wire are affected by the way the wire is straightened before bending it to form any component of the appliance .  If the wires are straightened by the process of reverse straining, meaning flexing in a direction opposite to that of the original bend, the yield point of the wire reduces.www.indiandentalacademy.com
  • 105.  The phenomenon is known as work softening due to reverse straining or the ‘Bauschinger Effect’ , named after the person who described it for the first time . www.indiandentalacademy.com
  • 106. Properties of AUSTRALIAN WIRES  These are ultra high tensile austenitic stainless steel arch wires.  The wires are resilient, certain bends when incorporated into the arch form and pinned to the teeth become activated by which stresses are produced within the wires which generates forces. www.indiandentalacademy.com
  • 107.  The wires must be sufficiently resilient to resist permanent deformation and maintain their activation, for maximum control of anchorage.  All these properties make these wires very hard and brittle. www.indiandentalacademy.com
  • 108.  A cobalt-chromium-nickel orthodontic wire alloy was developed during the 1950‟s by the Elgiloy Corporation (Elgin, IL,USA).  Initially it was manufactured for watch springs by Elgin watch company, hence the name Elgiloy. CHROME COBALT ALLOY www.indiandentalacademy.com
  • 109. Chrome cobalt alloy is a cobalt base alloy containing 40% cobalt, 20% chromium, 15% nickel, 7% Molybdenum, 2% manganese, 0.16% carbon, 0.04% beryllium and 15.8% iron. Composition www.indiandentalacademy.com
  • 110.  Blue(soft) elgiloy : Can be bent easily with finger pressure and pliers. Heat treatment of blue elgiloy increases its resistance to deformation. Types of CHROME COBALT ALLOY wires www.indiandentalacademy.com
  • 111.  Yellow elgiloy : Relatively ductile and more resilient than blue elgiloy. Further increase in its resilience and spring performance can be achieved by heat treatment. www.indiandentalacademy.com
  • 112.  Green elgiloy : More resilient than yellow elgiloy and can be shaped with pliers before heat treatment.  Red elgiloy : Most resilient of elgiloy wires, with high spring qualities. Heat treatment makes it extremely resilient. www.indiandentalacademy.com
  • 113.  The ideal temperature for heat treatment is 900° F or 482°C for 7 to 12 minutes, in a dental furnace.  This causes precipitation hardening of the alloy increasing the resistance of the wire to deformation. This heat treatment would increase the yield strength and decrease the ductility. Heat Treatment of COBALT- CHROME ALLOY www.indiandentalacademy.com
  • 114.  Heat treatment(of Blue Elgiloy) increases flexural yield strength(20- 30%), modulus of elasticity(10%), reduces failure to corrosion in localized areas where stresses can get concentrated. www.indiandentalacademy.com
  • 115. Properties of CHROME COBALT ALLOY Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Nu 90 Co Be wit fra Chrome Cobalt 184 1413 1682 8 Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Nu 90 Co Be wit fra Chrome Cobalt 184 1413 1682 8 AlloyAlloy Modulus of Elasticity (10³ MPa) Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength (MPa) 0.2% Offset Yield Strength (MPa) Ultimate Tensile Strength (MPa) Ultimate Tensile Strength (MPa) Nu 90 Co Be wit fra Nu 90 Co Be wit fra Chrome Cobalt Chrome Cobalt 184184 14131413 16821682 88 www.indiandentalacademy.com
  • 116.  William F. Buehler in 1960‟s invented Nitinol Ni – Nickel ti-titanium Nol-Naval Ordinance Laboratory,U.S.A. NICKEL TITANIUM ALLOY www.indiandentalacademy.com
  • 117. Andreasen G.F. and co-workers introduced the use of nickel-titanium alloys for orthodontic use in the 1970‟s. www.indiandentalacademy.com
  • 118.  55% nickel, 45% titanium resulting in a stoichiometric ratio of these elements.  1.6% cobalt is added to obtain desirable properties. Composition www.indiandentalacademy.com
  • 119.  Transition Temperature Range : TTR  Shape Memory  Super elasticity Properties www.indiandentalacademy.com
  • 120. Transition Temperature Range : TTR  Transition temperature range is a specific temperature range when the alloy nickel titanium on cooling undergoes martensitic transformation from cubic crystallographic lattice. www.indiandentalacademy.com
  • 121.  It is found to be in martensitic crystallographic lattices consisting of lesser symmetric lattices like orthorhombic,tetragonal crystallographic structures at lower temperatures.  In martensitic phase, the alloy cannot be plastically deformed. www.indiandentalacademy.com
  • 122.  At higher temperatures the alloy is found to be in cubic crystallographic lattice consisting of body centered cubic crystallographic structures.  It is also known as Austenitic phase of the alloy.  Plastic deformation can be induced, in austenitic phase of the alloy. www.indiandentalacademy.com
  • 123.  The same plastic deformation induced at the higher temperature returns back when the alloy is heated through a temperature range known as reverse transformation (transition) temperature range, RTTR.  Any plastic deformation below or in the TTR is recoverable when the wire is heated through RTTR. www.indiandentalacademy.com
  • 124.  TTR of nickel titanium alloy is between 482 - 510 C when the alloy is cooled from higher temperature which is very high for clinical usage.  Substitution of 1.6% cobalt results in formation of TiNi and TiCo which have transition temperature ranges of +164.6° C for TiNi and –237.2° C for TiCo giving a very wide transition temperature range. www.indiandentalacademy.com
  • 125. It is the phenomenon, where in if a plastic deformation incurred within or below the TTR, it is recoverable within certain strain limits of 8%, which is the outer fibre strain limit of the wire. Shape Memory www.indiandentalacademy.com
  • 126. Potential Applications of Certain Nickel-Titanium (Nitinol) Alloys SIMON CIVJAN, EUGENE F. HUGET, and LASZLO B. DeSIMON Journal of Dental Research, 1975 www.indiandentalacademy.com
  • 127. Manufacture  The nitinol wire should be plastically deformed at a lower temperature and casted. The casted wire should be placed in the oven and heated between 482 C to 510 C.  Plastic deformation occurs and the wire is then placed in the refrigerator. www.indiandentalacademy.com
  • 128. www.indiandentalacademy.com
  • 129.  55-Niti can be “taught” to return to a second or a low temperature shape.  The specimen is constrained in the desired second configuration at a temperature below the TTR and then cycled, under constraint, a few times over. www.indiandentalacademy.com
  • 130. www.indiandentalacademy.com
  • 131.  The process forces the structure into a preferred orientation that causes the metal to assume alternately its first memory (higher temperature) shape when heated and to return to its second (lower temperature) shape on cooling. www.indiandentalacademy.com
  • 132. It is the property of the wire explained as even when the strain is added, the rate of stress increase levels off due to the progressive deformation produced by the stress induced martinsitic transformation. Super elasticity www.indiandentalacademy.com
  • 133. Super elasticity www.indiandentalacademy.com
  • 134.  This property can be produced by stress and not temperature difference. Therefore it is called as stress induced martensitic transformation. www.indiandentalacademy.com
  • 135. Chinese Niti Alloy  Another nickel titanium alloy introduced by Burstone and developed by Dr Tien Hua Cheng is called as Chinese Niti alloy.  It has a springback that is 4.4 times that of comparable stainless steel wire and 1.6 times that of nitinol wire. www.indiandentalacademy.com
  • 136.  At 80° of activation the average stiffness of Chinese NiTi wire is 73% that of stainless steel wire and 36% that of nitinol wire. www.indiandentalacademy.com
  • 137. Japanese Niti Alloy  Another wire called the Japanese Niti wire introduced by Fujio Miura is manufactured by a different process and demonstrates super elasticity. www.indiandentalacademy.com
  • 138. Heat Treatment of the JAPANESE Niti wire  A new type of heat treatment was reported by Fujio Miura and associates which is known as Direct Electric Resistance Heat Treatment (DERHT).  An electric current is directly passed through the wire, thus generating enough heat to make it possible to bend it as well as impart change in the super elastic property of the wire.www.indiandentalacademy.com
  • 139.  Heat treating equipment consists of an electric power supply, a pair of electric pliers, an electric arch holder.  The amount of heat can be controlled by amperage and the heating time.  The DERHT method utilizes the electric resistance of the wire to generate heat. www.indiandentalacademy.com
  • 140.  In spite of resulting molecular re- arrangement, the mechanical properties of the wire are unchanged.  On testing it was found that the heat treated segments demonstrated better super elastic properties in relation to time. www.indiandentalacademy.com
  • 141. www.indiandentalacademy.com
  • 142.  Hence it is possible to heat treat any desired section of the archwire by DERHT method and utilize optimally the super elastic property of the wire.  For smaller diameter wires lesser current is required. For eg : 0.022” wire requires 8.0A for 2.0 seconds, 0.014” wire requires 3.5A for 2.0 seconds. www.indiandentalacademy.com
  • 143. Manufacture of Niti Alloy wires  Nickel titanium are most commonly manufactured into Nickel Titanium alloy by the process of vacuum induction melting.  Several re-melts are often needed to improve homogeneity of nickel titanium alloy. Powders are then made of the alloy. www.indiandentalacademy.com
  • 144.  The process of hot pressing is used by the manufacturer to form the powders into wires. Voids occur in the areas where the powders are not completely pressed together.  The wires obtain their final shape by the process of drawing or rolling. www.indiandentalacademy.com
  • 145. COPPER Ni Ti WIRES  In 1994 Ormco Corporation introduced a new orthodontic wire alloy, Copper NiTi.  Copper Ni Ti is a new quaternary ( nickel, Titanium copper and chromium ) alloy. www.indiandentalacademy.com
  • 146.  Orthodontic archwires fabricated from this alloy have been developed for specific clinical situations and are classified as follows: Type I Af 15 0C Type II Af 27 0C Type III Af 35 0C Type IV Af 40 0Cwww.indiandentalacademy.com
  • 147.  These variants would be useful for different types of orthodontic patients.  For example, the 27oC variant would be useful for mouth breathers; the 35oC variant is activated at normal body temperature; and the 40 o C variant would provide activation only after consuming hot food and beverages. www.indiandentalacademy.com
  • 148. MULTI-STRANDED STAINLESS STEEL WIRES  Flexibility of stainless steel wire can be increased by building up a strand of stainless steel wire around a core of 0.0065” wire along with 0.0055” wires used as wrap wires.  This produces an overall diameter of approximately 0.165”. www.indiandentalacademy.com
  • 149.  The strand of stainless steel wire is more flexible due to the contact slip between adjacent wrap wires and the core wire of the strand.  When the strand is deflected the wrap wires will slip with respect to the core wire and each other. If there is no elastic deformation each wire returns to its normal position, giving elasticity to the strand of the wire. www.indiandentalacademy.com
  • 150.  According to studies conducted by Kusy and Dilley, multi-stranded wires have elastic properties similar to nickel- titanium arch wires. Hence they can be used as a substitute to the newer alloy wires considering the cost of the nickel titanium wires .  The 0.0175” triple stranded wire and 0.016” Nitinol demonstrated a similar stiffness. www.indiandentalacademy.com
  • 151. D-RECT Wire  D-rect is an 8 stranded , interwoven braided rectangular wire .  Its high flexibility , together with 3- dimensional control and slot filling capabilities make it ideally suitable for multiple applications. www.indiandentalacademy.com
  • 152.  Initial torque control.  A finishing arch wire where torque control is desired yet resilient to permit interarch occlusal settling . www.indiandentalacademy.com
  • 153. ALPHA TITANIUM WIRES  The alpha titanium alloy is attained by adding 6% aluminium and 4% vanadium to titanium  Because of its hexagonal lattice, it possesses fewer slip planes making it less ductile from β- titanium.  The HCP structures of Alpha-Titanium has only one active slip plane along its base rendering it less ductile.www.indiandentalacademy.com
  • 154. β – TITANIUM – TITANIUM MOLYBDENUM ALLOY OR T.M.A.  In the 1960‟s an entirely different “high temperature” form of titanium alloy became available.  At temperature above 1625°F pure titanium rearranges into a body centered cubic lattice (B.C.C.), referred to as „Beta‟ phase. www.indiandentalacademy.com
  • 155.  With the addition of such elements as molybdenum or columbium, a titanium based alloy can maintain its beta structure even when cooled to room temperature.  Such alloys are referred as beta stabilized titaniums. www.indiandentalacademy.com
  • 156.  Goldberg and Burstone demonstrated that with proper processing of an 11% molybdenum, 6% Zirconium and 4% tin beta titanium alloy, it is possible to develop an orthodontic wire with a modulus of elasticity of 9.4 x 10 6 psi and yield strength of 17 x 10 4 psi.  The resulting YS/E ratio (springback) of 1.8 x 10 -2 is superior to 1.1 x 10 -2 for stainless steel. www.indiandentalacademy.com
  • 157. Properties Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength(MP a) Ultimate Tensile Strength (MPa) Num 90-d Cold with fract β- Titanium 71.7 931 1276 4 Alloy Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength(MP a) Ultimate Tensile Strength (MPa) Num 90-d Cold with fract β- Titanium 71.7 931 1276 4 AlloyAlloy Modulus of Elasticity (10³ MPa) Modulus of Elasticity (10³ MPa) 0.2% Offset Yield Strength(MP a) 0.2% Offset Yield Strength(MP a) Ultimate Tensile Strength (MPa) Ultimate Tensile Strength (MPa) Num 90-d Cold with fract Num 90-d Cold with fract β- Titanium β- Titanium 71.771.7 931931 12761276 44 www.indiandentalacademy.com
  • 158.  The low elastic modulus yields large deflections for low forces.  The high ratio of yield strength to elastic modulus produces orthodontic appliances that can sustain large elastic activations when compared with stainless steel devices of the same geometry. www.indiandentalacademy.com
  • 159.  β- titanium can be highly cold worked . The wrought wire can be bent into various orthodontic configurations and has formability comparable to that of austenitic stainless steel .  Clinically satisfactory joints can be made by electrical resistance welding of β- titanium (light-capacitance weld). Such joints need not be reinforced with solder.www.indiandentalacademy.com
  • 160. Optiflex arch wire treatment of a Skeletal Class III Open bite Talass M.F. JCO 1992, Vol 26, 245-252 www.indiandentalacademy.com
  • 161. TOOTH COLOURED ORTHODONTIC WIRES  Optiflex is a new orthodontic arch wire designed by Dr. Talass and manufactured by ORMCO.  It has got unique mechanical properties with a highly aesthetic appearance. Made of clear optical fibre, it comprises of three layers. www.indiandentalacademy.com
  • 162. 1. A silicon dioxide core that provides the force for moving teeth. 2. A silicon resin middle layer that protects that core from moisture and adds strength. 3. A strain resistant nylon outer layer that prevents damage to the wire and further increases its strength. www.indiandentalacademy.com
  • 163. CLINICAL IMPORTANCE OF VARIOUS WIRES www.indiandentalacademy.com
  • 164. STAINLESS STEEL  Orthodontic stainless steel is the most widely used alloy in orthodontics. It finds its application as arch wires, auxiliaries, removable appliances, bands, etc.  These wires are available both in round as well as rectangular cross-sections. www.indiandentalacademy.com
  • 165.  The Australian stainless steel wires described previously are used in the Begg‟s technique as well as in the preadjusted edgewise technique. www.indiandentalacademy.com
  • 166. CHROME COBALT  The elgiloy blue alloy is very popular because it can be easily manipulated into desired shapes and then heat treated to achieve considerable increases in strength and resilience.  This heat treatment can be performed easily with the aid of an electrical resistance welding apparatus. www.indiandentalacademy.com
  • 167.  The other three tempers of Elgiloy have mechanical properties that are similar to tempers that are available with the less expensive stainless steel wire alloys. www.indiandentalacademy.com
  • 168. NICKEL TITANIUM  Because of its superior spring back, superelasticity, shape memory, and its ability to produce light force for longer duration , NiTi is the ideal wire for initial levelling and aligning.  Rectangular NiTi allows full engagement of the bracket slot and give better torque control in the initial phase of treatment.www.indiandentalacademy.com
  • 169.  NiTi is also available in the form of coil springs. These NiTi coil springs greatly enhance efficiency in both space closure and space opening.  NiTi coil springs are also used for distalization of molars. www.indiandentalacademy.com
  • 170. COPPER NiTi  Type I wire – Af 15 0C Sachdeva does not recommend the frequent use of this alloy because it generates very heavy forces and clinical indications are few. www.indiandentalacademy.com
  • 171.  Type II wire Af 270C This wire generates the highest force of the three ( Type I , III, IV) and is the best used :  In patients who have an average or higher pain threshold.  In patients who have normal periodontal health. www.indiandentalacademy.com
  • 172. Type II wire Af 270C  In patients where rapid tooth movement is required ; the force system generated by this orthodontic arch wire is constant. www.indiandentalacademy.com
  • 173.  Type III wire – Af 350C This wire generates force in the midrange and is best used : 1. In patients who have a low to normal pain threshold. 2. In patients whose periodontium is normal to slightly compromised. 3. When relatively low forces are desired. www.indiandentalacademy.com
  • 174.  Type IV wire – Af 40 0C These wires generate forces when the mouth temperature exceeds 400C. These forces are intermittent in nature. Used in :-  Patients who are sensitive to pain.  Patients who have compromised periodontal conditions. www.indiandentalacademy.com
  • 175.  Type IV wire – Af 40 0C  Where tooth movement is deliberately slowed down , i.e., when the patient may not be able to visit the orthodontist regularly or his/her cooperation is very poor. www.indiandentalacademy.com
  • 176. BETA-TITANIUM  T.M.A appears to be well suited as a utility arch for three primary reasons: 1. It is highly formable and utility arches are easily formed. 2. With its enhanced resiliency a single activation is all that is required to achieve vertical corrections. www.indiandentalacademy.com
  • 177. 3. With its reduced load/deflection rate the incisor torque control can be obtained while staying within accepted force ranges. www.indiandentalacademy.com
  • 178. TOOTH COLORED WIRE (OPTIFLEX)  It is used in adult patients who wish that their braces not be really visible for reasons related to personal concerns or professional considerations.  It can be used as an initial wire in cases with moderate amounts of crowding in one or both arches. www.indiandentalacademy.com
  • 179.  It should be used in cases to be treated without bicuspid extraction. Optiflex is not the ideal arch wire for major cuspid retraction.  Optiflex can be used in presurgical stage in cases which require orthognathic intervention as part of the treatment. www.indiandentalacademy.com
  • 180. IN SEARCH OF THE IDEAL ARCH WIRE www.indiandentalacademy.com
  • 181.  No ideal arch wire exists.  This is not surprising because the demands of the treatment plan require different characteristic stiffness and ranges.  Nonetheless, several desirable characteristics would be appropriate to list. www.indiandentalacademy.com
  • 182. A Review of Contemporary Arch Wires: Their Properties and Characteristics Robert P.Kusy Angle Orthod 1997;67(3);197-208 www.indiandentalacademy.com
  • 183. www.indiandentalacademy.com
  • 184.  Wires should be esthetic.  When coated, white-colored wires have routinely succumbed to the forces of mastication and/or the enzyme activity of the oral cavity.  When uncoated, transparent wires have had such poor mechanical properties that they function as a placebo.  Although esthetics are important to the orthodontist, function is paramount.www.indiandentalacademy.com
  • 185.  Wires should have poor biohostability. This characteristic goes beyond biocompatibility.  As a poor biohost, the ideal archwire should neither actively nurture nor passively act as a substrate for micro- organisms that will smell foul, cause color changes that detract from esthetics, or remove and/or build up material that compromise mechanical properties. www.indiandentalacademy.com
  • 186.  Wires should possess low coefficients of friction.  Finally, wires should have formability, weldability, resilience, and springback so that they may be deformed into loops or bends, fused onto a clasp, employed to maximize their stored elastic energy, and ultimately return to their initial shape. www.indiandentalacademy.com
  • 187. THE CHOICE OF ARCH WIRE IN THE CLINICAL SITUATION www.indiandentalacademy.com
  • 188.  The demands placed on the arch wire depend upon the particular purpose for which it is intended , and the purpose will change at different stages of treatment. www.indiandentalacademy.com
  • 189. www.indiandentalacademy.com
  • 190.  For each arch wire , stiffness must be such that an appropriate force magnitude is delivered, strength must be sufficient to prevent distortion by masticatory forces, and range must make it possible to apply the force over a sufficient distance, so that frequent reactivation is not required . www.indiandentalacademy.com
  • 191. www.indiandentalacademy.com
  • 192. THE CHOICE OF ARCH WIRES IN FIRST STAGE www.indiandentalacademy.com
  • 193.  In nearly every patient with malaligned teeth, the root apices are closer to the normal position than the crowns.  This is so as malalignment almost always develops as the eruption paths of teeth are deflected. www.indiandentalacademy.com
  • 194.  To bring teeth into alignment, a combination of labiolingual and mesiodistal tipping guided by an archwire is needed, but root movement is usually not.  Several important consequences for orthodontic mechanotherapy follow from this. www.indiandentalacademy.com
  • 195.  Initial arch wires should provide light, continuous force of approximately 50 grams, to produce the most efficient tooth tipping.  Arch wire should be able to move freely within the brackets (2 mil clearance required).  In an 18-slot edgewise bracket, 16 mil can be used. www.indiandentalacademy.com
  • 196.  Rectangular arch wires that tightly fit within the bracket should be avoided as the position of the root apex can be affected.  Although a highly resilient 0.017” X 0.025” NiTi could be used, it will create undesirable root movement at this stage. www.indiandentalacademy.com
  • 197. www.indiandentalacademy.com
  • 198.  The springier the arch wire, more important it is that the crowding should be at least reasonably symmetric.  Otherwise, there is a danger that archform will be lost as asymmetrically irregular teeth are brought into alignment. www.indiandentalacademy.com
  • 199.  If only one tooth is crowded and out of line, a rigid wire is needed that maintains the arch form, and an auxillary wire should be used to correct the malaligned tooth. www.indiandentalacademy.com
  • 200.  Arch wire materials appropriate for initial alignment stage are round cross- section wires as follows: 1. Nickel- titanium (preferably in its superelastic form) 2. Multistranded stainless steel 3. Australian premium and supreme grade wires. www.indiandentalacademy.com
  • 201.  Where tooth displacements are marked , the first arch wire should be particularly low in stiffness and high in range .  „Superelastic‟ nickel titanium wire of 0.014” to 0.016” diameter or six- strand multistranded stainless steel wire of 0.0175” diameter may be chosen. www.indiandentalacademy.com
  • 202.  The very nature of initial alignment arch wires means that they offer poor control over unwanted tooth movements.  Their low stiffness means that it is inadvisable to use them in combination with elastic traction , because they will allow too much tipping of (otherwise unsupported) anchorage units. www.indiandentalacademy.com
  • 203.  In most cases, initial alignment is complete within three months of commencing treatment.  Considering the poor control offered and the dangers of producing unwanted tooth movement , initial archwires should be exchanged for the archwires of mid-treatment as soon as possible. www.indiandentalacademy.com
  • 204. MID-TREATMENT ARCH WIRES www.indiandentalacademy.com
  • 205.  The highly flexible arch wires used for initial alignment are replaced by a series of arch wires of increasing stiffness, offering progressively greater control over tooth position. www.indiandentalacademy.com
  • 206.  In the early stages of mid-treatment single strand , round, stainless steel arch wires of small diameter are appropriate .  Arch wires of 0.016” and then 0.018” diameter are used. www.indiandentalacademy.com
  • 207.  Inter and intra-maxillary elastic forces can be used safely with stainless steel single strand round wires of 0.016” diameter and above. www.indiandentalacademy.com
  • 208.  These wires are used for the purpose of canine retraction using sliding mechanics.  Australian ss arch wires are sufficiently stiff to enable the molars to resist unwanted movement, and they therefore play an important part both in molar control and in anchorage management. www.indiandentalacademy.com
  • 209.  After canine retraction, 0.016” X 0.022” NiTi progressing to 0.017” X 0.025” NiTi or 0.017” X 0.025” NiTi is directly given for levelling and alignment.  Then 0.016” X 0.022” ss closing loop arch wire is given for anterior retraction. www.indiandentalacademy.com
  • 210.  In case of enmasse retraction, after the first stage, 0.016” X 0.022” NiTi progressing to 0.017” X 0.025” NiTi is given for completing the levelling and alignment.  Then 0.016” X 0.022” ss closing loop arch wire is given for anterior retraction. www.indiandentalacademy.com
  • 211. ARCH WIRES FOR FINISHING STAGE www.indiandentalacademy.com
  • 212.  If preadjusted edgewise brackets have been used then theoretically the detailing stage will be unnecessary because of the activation programmed into the brackets.  However, minor errors in bracket positioning will become obvious in these final stages of treatment , and arch wire modification may still be required. www.indiandentalacademy.com
  • 213.  The arch wire requirements at this stage are for high stiffness and low range.  When rectangular wire has been used at the end of mid-treatment stage the detailing arch wire should also be rectangular ,of increased stiffness. www.indiandentalacademy.com
  • 214.  With the 18-slot appliance, the finishing arch wire is either 0.017” X 0.022” or 0.017” X 0.025” ss.  They are flexible enough to engage brackets even if mild tipping has occurred.  These arch wires generate the necessary root paralleling moments. www.indiandentalacademy.com
  • 215.  If greater tipping has occurred, a more flexible full-dimension rectangular arch wire is required.  In such cases, a β-Ti or M-NiTi 0.017” X 0.025” wire may be needed initially. www.indiandentalacademy.com
  • 216. THE FUTURE www.indiandentalacademy.com
  • 217.  One promising approach toward achieving an esthetic arch wire with excellent overall properties involves the use of composites.  Existing experimental prototypes are tooth colored, can be as strong as the strongest piano wire, and can vary in stiffness from that of the most flaccid multi-stranded archwire, to nearly that of a beta-titanium archwire.www.indiandentalacademy.com
  • 218.  These characteristics can be varied during manufacture without any change in wire-slot engagement by pultrusion in which the relative proportions of the fiber and matrix materials are adjusted appropriately and cured by electromagnetic radiation. www.indiandentalacademy.com
  • 219.  Mechanical tests show that such arch wires are elastic until failure occurs.  When compared with NiTi, resilience and springback are comparable.  When failure finally does occur, the wire loses its stiffness, but it remains intact. www.indiandentalacademy.com
  • 220.  Enhanced biocompatibility should be possible by modifying the surface chemistry of the polymer.  The expectation is that the attractive properties and characteristics of these esthetic composites will capture a significant share of the marketplace in the near future. www.indiandentalacademy.com
  • 221. REFERENCES  Backofen W.A. & Gales G.F. : the low temperature heat treatment of stainless steel for orthodontics. A.O. 1951, vol 21, 117 –124  Funk A.C. : heat Treatment of S. Steel . A.O. 1951, vol 21, 129-136.  Burstone C.J. et al. Beta Titanium, A new orthodontic alloy, AJO 1980, Vol. 77, 212 –132 www.indiandentalacademy.com
  • 222.  Orthodontic materials –William Brantley  Refined Begg for modern times- V.P. Jayade  Orthodontic treatment with removable appliances- Houston, Issacson  Ralph W. Philips Skinner‟s Science of dental materials Ninth edition. 261-270, 537-551. www.indiandentalacademy.com
  • 223. Thank You! www.indiandentalacademy.com For more details please visit www.indiandentalacademy.com

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