Orthodotnic wires /certified fixed orthodontic courses by Indian dental academy


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

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

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Orthodotnic wires /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Material Scarcity, Abundance of Ideas (1750-1930) • noble metals- Gold, platinum, iridium & silver alloys • good corrosion resistance • acceptable esthetics • lacked the flexibility and tensile strength www.indiandentalacademy.com
  3. 3. • Angle (1887)  German silver (a type of brass) • Opposition Farrar – discolored • Neusilber brass (Cu 65%, Ni 14%, Zn 21%) • various degrees of cold work (diff prop) – jack screws, – expansion arches, – Bands www.indiandentalacademy.com
  4. 4. • Wood, rubber, vulcanite, piano wire and silk thread • No restrictions. www.indiandentalacademy.com
  5. 5. • Stainless steel (entered dentistry -1920) • Stahl and Eisen – Benno Strauss & Eduard Maurer in 1914 • By 1920 – Dr. F Hauptmeyer. • Simon, schwarz, Korkhous, De Coster- orthodontic material • Replaced • Opposition  Emil Herbst  gold wire was stronger than stainless steel. (1934) Steel as ligature wire www.indiandentalacademy.com
  6. 6. Abundance of materials, Refinement of Procedures (1930 – 1975)  Improvement in metallurgy and organic chemistry – mass production(1960) • Cobalt chrome (1950s)-Elgin watch co • Rocky Mountain Orthodontics- Elgiloy • Nitinol (1970s)- Buehler, into orthodonticsAndreasen. Unitek www.indiandentalacademy.com
  7. 7. The beginning of Selectivity (1975 to the present) • Orthodontic manufacturers • Beta titanium (1980) • CAD/CAM – larger production runs • Composites and Ceramics • Iatrogenic damage  Nickel and bis-GMA New products- control of govt agencies, private organization www.indiandentalacademy.com
  8. 8. METHOD OF FORCE DELIVERY MATERIALS USED CONCEPT PHASE I Variation in archwire dimension Stainless steel, Gold VARIABLE CROSSSECTIONAL ORTHODONTICS PHASE II Variation in archwire material but same dimension Beta Titanium, Nickel Titanium, Stainless Steel, Cobalt Chromium VARIABLE MODULUS ORTHODONTICS PHASE III Variation in archwire properties (super elasticity) Superelastic Nickel Titanium PHASE IV Variation in structural composition of wire material Thermally activated Nickel Titanium PHASE V Variation in archwire material composition / structure Graded thermally active Nickel Titanium www.indiandentalacademy.com VARIABLE TRANSFORMATION TEMPERATURE ORTHODONTICS
  9. 9. • GOLD :Up until 1930’s the only orthodontic wires available were made of Gold and their alloys. 1887 – Angle tried replacing noble metals with German silver ,a Brass (65% Cu, 14% Ni, 21% Zn). Gold alloys- Esthetically pleasing Excellent Corrosion resistance Low proportional limit. 1940’s :With the substantial rise in the cost of gold, Austenitic stainless steel began to displace gold. www.indiandentalacademy.com
  10. 10. In early 1940 s Begg partnered with Wilcock to make resilient orthodontic wires – AUSTRALIAN STAINLESS STEEL. By 1960s gold was universally abandoned in favour of stainless steel. In 1960s :Cobalt –Chromium alloys were introduced. Their physical properties were very similar to stainless steel along with superior formability. Advantages- supplied in softer and more formable state that could be hardened by heat treatment www.indiandentalacademy.com
  11. 11. In 1962 :Buehler discovered Nitinol at Naval Ordinance laboratory. In 1970 :- Andreasen brought this intermetallic composition of 50% Ni and 50% Ti to orthodontics through University of Iowa. Unitek company licensed the patent (1974) and offered a stabilized martensitic alloy that doesn’t exhibit shape memory effect under the name NITINOL. www.indiandentalacademy.com
  12. 12. In 1977 : Beta titanium was introduced to orthodontic profession by C.J. Burstone and John Goldberg. This alloy had a modulus of elasticity closest to that of traditional gold along with good springback, formability and weldability. www.indiandentalacademy.com
  13. 13. In 1984 : A.J Wilcock Jr. as per request of Dr. Mallenhauer of Melbourne Australia, innovated in production of Ultra high tensile stainless steel round wires – The SUPREME GRADE. In 1985 :Burstone reported of an alloy, Chinese NiTi, developed by Dr. Tien Hua Cheng and associates at the General Research Institute for nonferrous metals in Beijing china. www.indiandentalacademy.com
  14. 14. In 1986 : Miura et al reported on Japanese NiTi, an alloy developed at Furukawa Electric Company Limited Japan in 1978. Both Chinese NiTi and Japanese NiTi are active austenitic alloys that form Stress Induced Martensite (SIM) www.indiandentalacademy.com
  15. 15. In 1988 : A.J Wilcock Jr. archwires. developed much harder Alpha Titanium In 1990 : Neo-Sentalloy is introduced as a true active martensitic alloy. In 1992 : Optiflex a new Orthodontic archwire – developed by M.F Talass. Combined unique mechanical properties with a highly esthetic appearance. www.indiandentalacademy.com
  16. 16. In 1994 :Copper NiTi, a new quaternary alloy containing Ni, Ti, Cu and Cr was invented by Dr. Rohit Sachdeva. Display phase transition at 27 C, 35 C, 40C. • In 2000 :Titanium Niobium – an innovative new arch wire designed for precision finishing, reported by Dalstra et al. www.indiandentalacademy.com
  17. 17. www.indiandentalacademy.com
  18. 18. Physical properties of materials can be considered as the ways that Materials respond to changes in their environment Physical properties : Descriptive of size, shape and appearance. Material properties : Those associated directly with the material www.indiandentalacademy.com
  19. 19. Tensile Strength Compressive Hardness Shear Elastic modulus Mechanical Properties Elasticity Resilience Ductility Physical Properties Plasticity Electrical & Electrochemical Electrode potential % elongation Yield strength Electrode resistivity Thermal Properties Thermal expansion Thermal conductivity Heat Flow www.indiandentalacademy.com Thermal Diffusivity
  20. 20. • ELASTIC (Reversible on force removal) • PLASTIC (Irreversible or nonelastic) www.indiandentalacademy.com
  21. 21. • Elastic or reversible deformation Proportional limit, Resilience, Modulus of Elasticity • Plastic or irreversible deformation Percent elongation. • Combination of Elastic and Plastic deformation Toughness and Yield strength www.indiandentalacademy.com
  22. 22. • When a force acts on a body tending to produce deformation ,a resistance is developed to this external force application. • The INTERNAL reaction is equal in intensity and opposite in direction to the applied external force and is called stress. • Stress= Force/Area. Denoted by S or  • Expressed as Pascal 1Pa = 1N/m2 or Megapascals (MPa) where 1 MPa = 106 Pa www.indiandentalacademy.com
  23. 23. www.indiandentalacademy.com
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  25. 25. • Strain is described as the change in length (Δ L = L – LO) per unit length of the body when it is subjected to a stress. • Change in length =L – Lo= ΔL • Strain () = ΔL / Original length(Lo) • Strain has no units of measurement. • It is a Dimensionless quantity. • Reported as an absolute value or as a percentage denoted by  (Epsilon) www.indiandentalacademy.com
  26. 26. Strain Elastic Plastic Each type of stress is capable of producing a corresponding deformation in a body  Tensile stress produces tensile strain.  Compressive stress produces compressive strain.  Shear stress produces shear strain. www.indiandentalacademy.com
  27. 27. A graph showing the relationship of stress and strain as a material is subjected to increasing loads • The curve produced in this diagram may also be called Elastic Curve • Represents energy storage capacity of the wire, so determines amount of work expected from a particular spring in moving a tooth. www.indiandentalacademy.com
  28. 28. • In the calculation of stress it is assumed that the cross sectional area of the specimen remains constant during the test. • Stresses are calculated based on original cross sectional area www.indiandentalacademy.com
  29. 29. A stress strain curve based on stresses calculated from a Non Constant Cross sectional area is called a true stress strain Curve. A true-stress strain curve may be quite different from an engineering stress-strain curve at high loads because significant changes in the area of specimen may occur. www.indiandentalacademy.com
  30. 30. Stress Wire returns back to original dimension when stress is removed Plastic Portion Elastic Portion www.indiandentalacademy.com Strain
  31. 31. Mechanical properties based on Elastic or reversible deformation are : ELASTIC MODULUS  FLEXIBILITY  RESILIENCE www.indiandentalacademy.com
  32. 32. Other properties that are determined from stresses at the end of elastic region of stress -strain plot and at beginning of plastic deformation region.  PROPORTIONAL LIMIT  YIELD STRENGTH www.indiandentalacademy.com
  33. 33. STIFFNESS :- It is a force / distance ratio that is a measure of resistance to deformation. It is a measure of the force required to bend or otherwise deform the material to a definite distance STRENGTH : - measure of the maximum possible load, the greatest force the wire can sustain ,if it is loaded to the limit of the material www.indiandentalacademy.com
  34. 34. It is defined as the distance that the wire elastically before permanent deformation. Relationship b/w three elastic properties :- will bend Strength = Stiffness x Range. Factors that influence Strength, Stiffness and Range : • Mechanical arrangement by which force is applied to teeth e.g :- bracket width, length of archwire, span and loops. • Form of wire itself – size and shape of cross section. • Material including the alloy formula, its hardness etc www.indiandentalacademy.com
  35. 35. • Strength is the stress that is necessary to cause fracture or a specified amount of plastic deformation. • Both types of deformational behaviour can be described by strength properties, but we must use proper strength terms to differentiate between maximum stress to produce permanent deformation and that required to produce fracture. www.indiandentalacademy.com
  36. 36. • Strength of a material can be described by one or more of the following properties • • • • Proportional Limit Elastic Limit Yield Strength. Ultimate Tensile Strength, Shear strength and compressive strength. www.indiandentalacademy.com
  37. 37. • It describes the relative STIFFNESS or rigidity of a material which is measured by the elastic region of stress – strain diagram.  It is denoted by letter E  determined from slope of linear portion of stress stain curve Elastic Modulus = Stress / Strain Modulus of Elasticity has same units as stress www.indiandentalacademy.com
  38. 38. Stress E www.indiandentalacademy.com Strain
  39. 39. • inherent property of a material and cannot be altered appreciably by heat treatment, work hardening or any other kind of conditioning – STRUCTURAL INSENSITIVITY www.indiandentalacademy.com
  40. 40. It is defined as the greatest stress that a material will sustain without a deviation from the linear proportionality of stress to strain. Hooke’s Law :- States that stress – strain ratio is constant upto the proportional limit, the constant in this linear stress-strain relationship is Modulus of Elasticity. www.indiandentalacademy.com
  41. 41. Stress Yield strength Proportional limit Resilience Formability www.indiandentalacademy.com Strain
  42. 42. Below PL no permanent deformation occurs in a structure. Below PL – ELASTIC REGION Above Pl – PLASTIC REGION www.indiandentalacademy.com
  43. 43. • It is defined as the stress at which a material exhibits a specified limiting deviation from proportionality of stress to strain. • Amount of permanent strain is arbitrarily selected for material being examined and may be indicated as 0.1%, 0.2% or 0.5% (0.001, 0.002, 0.005) permanent strain • Amount of permanent strain may be referred to as PERCENT OFFSET. www.indiandentalacademy.com
  44. 44. Stress Yield strength Proportional Limit Elastic Limit 0.1% www.indiandentalacademy.com Strain
  45. 45. It is defined as maximum stress that a material can withstand before it undergoes permanent deformation.  For all practical purposes PL and EL represent same stress. But they differ in fundamental concept : PL deals with proportionality of strain to stress in structure.  EL describes elastic behavior of the material. www.indiandentalacademy.com
  46. 46. Stress Yield strength Proportional Limit Elastic Limit 0.1% www.indiandentalacademy.com Strain
  47. 47. BRITTLENESS :It is the relative inability of a material to sustain plastic deformation before fracture of a material occurs ULTIMATE STRENGTH :Ultimate tensile strength or stress is defined as the maximum stress that a material can withstand before failure in tension. www.indiandentalacademy.com
  48. 48. Stress Ultimate Tensile Strength www.indiandentalacademy.com Fracture Point Strain
  49. 49. The maximum flexibility is defined as the strain that occurs when the material is stressed to its proportional limit www.indiandentalacademy.com
  50. 50. Associated with “springiness” It is defined as the amount of energy absorbed by a structure when it is stressed to its proportional limit • Area bounded by the elastic region is measure of Resilience www.indiandentalacademy.com
  51. 51. Stress Yield strength Proportional limit Resilience Formability www.indiandentalacademy.com Strain
  52. 52. • Represents energy storage capacity of the wire, so determines amount of work expected from a particular spring or wire in moving a tooth. • High resilience- light forces for longer duration • Low resilience- high forces for shorter durationfrequent wire changes www.indiandentalacademy.com
  53. 53. Proportional to slope of elastic portion of stress-strain curve. More Horizontal the slope • Springier the wire having low stiffness • Springiness  1 Stiffness www.indiandentalacademy.com
  54. 54. Stress Slope α Stiffness Stiffness α 1 . Springiness www.indiandentalacademy.com Strain
  55. 55. The total area under the entire stress-strain curve is a measure of the energy required to fracture the material Higher the strength and higher the ductility (total plastic strain) greater the toughness. www.indiandentalacademy.com
  56. 56. Stress Yield strength Proportional limit TOUGHNESS Resilience Formability www.indiandentalacademy.com Strain
  57. 57. www.indiandentalacademy.com
  58. 58. www.indiandentalacademy.com
  59. 59. Ductility represents the ability of a material to sustain a large permanent deformation under tensile load without rupture. A material that may be drawn readily into a wire is said to be DUCTILE. Malleability :Ability of a material to sustain considerable permanent deformation without rupture under compression as in hammering or rolling into a sheet. www.indiandentalacademy.com
  60. 60. - Gold is most ductile and malleable pure metal - Silver is second. - Platinum ranks 3rd in ductility. - Copper ranks 3rd in malleability www.indiandentalacademy.com
  61. 61. • It is defined as the amount of permanent deformation that a wire can withstand before failing. • Represents the amount of permanent bending the wire will tolerate before it breaks. • Can be interpreted as area under plastic region of stress – strain curve. www.indiandentalacademy.com
  62. 62. Stress Yield strength Proportional limit Resilience Formability www.indiandentalacademy.com Strain
  63. 63. • It represents the elastic strain recovered on unloading from permanent deformation range. • Spring back is portion of load deflection curve between elastic limit and ultimate strength • Given by Expression :- YS/E. ( Yield strength / elastic modulus) • Value of YS/E represents the approximately amount of elastic strain released by archwire on unloading www.indiandentalacademy.com
  64. 64. www.indiandentalacademy.com
  65. 65. • For appliance to deliver relatively constant forces within optimal range it should have Low load deflection rate • Desirable for two important reasons : • Maintains a more desirable stress level in the periodontal ligament, since the force on a tooth will not radically change magnitude every time the tooth has been displaced. • Offers greater accuracy in control over force magnitude www.indiandentalacademy.com
  66. 66. Load Deflection α 1 / (Length of the wire)3 Rate α (Diameter of a round wire)4 α (Depth of rectangular wire)3 Wire Material Wire Configuration www.indiandentalacademy.com
  67. 67. – To control magnitude of forces • Active tooth movement (aligning) require a relatively constant force within an optimal range – Wire with high elastic property – Low load deflection rate – Sufficient stiffness to prevent deformation • Reactive unit (anchorage unit) requires a relatively – Rigid wire with high load deflection rate – Enhanced anchorage potential & minimization of undesirable side effects www.indiandentalacademy.com
  68. 68. When an archwire is bent the metal is stretched along the outside curvature and compressed along the inside curvature. • This combination of tension and compression that resists bending and actually accomplishes energy storage in the spring action of wire www.indiandentalacademy.com
  69. 69. The part of a beam that is neither elongated nor compressed in bending. • It is like a flat ribbon through the center of the wire, midway between outer and inner curved sides. www.indiandentalacademy.com
  70. 70. A measure of bending effort at any specified point in a beam, measured in units of force times distance (Ounce inches, grams-centimeters etc.) critical (dangerous) section :Maximum bending moment in a cantilever is at the supported end. In beam terminology the location of this maximum bending moment is called CRITICAL or DANGEROUS section www.indiandentalacademy.com
  71. 71. EFFECTS OF LENGTH AND CROSS SECTION ON ELASTIC PROPERTIES: EFFECTS OF LENGTH :IN BENDING :1 Stiffness Strength Range (Length)3 1 (Length) 1 (Length)2 www.indiandentalacademy.com
  72. 72. www.indiandentalacademy.com
  73. 73. www.indiandentalacademy.com
  74. 74. IN BENDING Round Wires 1. Range ‘C’ It is the distance b/w extreme fiber and neutral axis. ‘Index of working range of a bending wire 1 Range  C Therefore range is inversely proportional to diameter. www.indiandentalacademy.com
  75. 75. Stiffness of wires depends on value called the Moment of Inertia (I). Moment of Inertia Property of the cross section of a beam that is proportional to the effect of the cross section on resistance to bending or twisting (Stiffness). Stiffness  (diameter)4 www.indiandentalacademy.com
  76. 76. 3. Strength : Engineering term that defines strength in terms of wire’s cross section is SECTION MODULUS – Denoted by letter Z. Z = I/C. Strength  (Diameter)3 www.indiandentalacademy.com
  77. 77. Torsion is the actual twisting (strain) that takes place in the material as s result of the torque In case of rectangular wire ”C” is the distance from center of wire to an outer corner instead of to one of the sides. www.indiandentalacademy.com
  78. 78. There are no exponential effects of length in torsion. 1. Strength :- Length has absolutely no effect on strength. 2. Range :- Range in torsion is directly proportional to length 3. Stiffness :- Stiffness in torsion is inversely proportional to length. www.indiandentalacademy.com
  79. 79. • In round wires  width and thickness are always same . Both are called Diameter and treated as single dimension. www.indiandentalacademy.com
  80. 80. Rectangular wires: Width & Thickness  Vary independently of one another in rectangular wires. Width: Used to describe dimension perpendicular to direction of bending in plane of neutral axis. Thickness:  dimension in plane of bend www.indiandentalacademy.com
  81. 81. • Effect of width & thickness on range: Width has no effect on bending range of wire. • Range is inversely related to thickness. • Effect of width on stiffness and strength: Width is directly proportional to strength and stiffness in rectangular wires. www.indiandentalacademy.com
  82. 82. 3. Effect of thickness on stiffness and strength: Stiffness  (Thickness)3 Strength  (Thickness)2 www.indiandentalacademy.com
  83. 83. In 1977, ADA specification No. 32 was published. for orthodontic wires not containing precious metals contains directive on testing, packaging and marketing of orthodontic arch wires. Properties of orthodontic arch wires are commonly determined by means of various laboratory tests. Mechanical properties of orthodontic wires are determined from:- Tension test - Bending test - Torsion test. www.indiandentalacademy.com
  84. 84. Bending test: Considered more representative of clinical conditions than the tension test. Provides information on behaviour of wires when subjected to 1st and 2nd order bends. Torsion tests: Reflect wire characteristics in third order direction Graphic descriptions: -Stress against strain in tension -Bending moment against angular deflection. Torsional moment against torque angle. www.indiandentalacademy.com
  85. 85. Elastic Bending test: Bending couple is applied at one end of specimen where only rotation is permitted ; at the other end of test span wire is held against fixed knife edge stop. - Angular deformation measured is rotation of the shaft ( ). www.indiandentalacademy.com
  86. 86. Metallic orthodontic wires are manufactured by a series of proprietary steps, typically involving more than one company. Sources:- Stainless steel orthodontic wires are procured by suppliers from commercial sources of stainless steel. www.indiandentalacademy.com
  87. 87. Rolling Heat Treatment Ingot www.indiandentalacademy.com Drawing
  88. 88. Ingot:- Initially the wire alloy is cast in the form of an ingot which is subjected to successive deformation stages until cross section becomes sufficiently small for wire drawing. Rolling: the ingot is rolled into a long bar. • Done by series of rollers that gradually reduce the ingot to a relatively small diameter. www.indiandentalacademy.com
  89. 89. Considerable work hardening of the alloy occurs during rolling.  It may fracture if rolling is continued beyond this point.  TO PREVENT THIS: • Rolling process is interrupted Metal is ANNEALED by heating to a suitably high temperature www.indiandentalacademy.com
  90. 90. After ingot has been reduced to a fairly small diameter by rolling, it is further reduced to its final size by drawing. It is a forming process that is used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of tensile force applied to the exit side of 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. www.indiandentalacademy.com
  91. 91. V Rate of drawing. V Amount of cross section reduction per pass. V Nature of intermediate heat treatments. v Die material. www.indiandentalacademy.com
  92. 92. v Rectangular cross section wires are fabricated from round wires by a rolling process using TURK’S HEAD which contains series of rolls. v Rectangular or square cross section wires – have some degree of rounding at corners (EDGE BEVEL). www.indiandentalacademy.com
  93. 93. Hardness and spring properties of most orthodontic wires depend on effects of work hardening during manufacture. V If metal is almost in need of another annealing at its final size – it will have maximum work hardening and spring properties. www.indiandentalacademy.com
  94. 94. v If drawing is carried too far enough after last annealing – wire will be brittle. • If drawing is not carried far enough after last annealing – too much residual softness and very low working range and strength www.indiandentalacademy.com
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  96. 96. www.indiandentalacademy.com
  97. 97. ALLOY: A solid mixture of a metal with one or more other metals or with one or more non metals which are mutually soluble in molten state is called an alloy. e.g., Steel – Alloy of iron and carbon Stainless steel- alloy of iron, carbon and chromium. SOLID SOLUTION: An alloy phase in which one alloying elements enters space lattice of the other. www.indiandentalacademy.com
  98. 98. • Elements –all particles identical Atoms-smallest • Electrons – orbits around nucleus Floating in shells of diff energy levels Electrons form the basis of bonds Atoms interact via electrons • In metals, the energy levels are very closely spaced and the electrons tend to belong to the entire assembly rather than a single atom. www.indiandentalacademy.com
  99. 99. • Array of positive ions in a “sea of electrons” • Electrons free to move • electrical and thermal conductivity • Ductility and malleability • electrons adjust to deformation www.indiandentalacademy.com
  100. 100. • Molecules – 2 or more atoms • Amorphous – similar properties in all directions – isotropy  Glass • atoms organize themselves into specific lattices  geometry CRYSTAL  anisotropy www.indiandentalacademy.com
  101. 101. • Perfect crystals: anion – cation –anion – cation • extremely strong • Thin wiskers reinforce • If like ions are forced together, breakage results. Unlike metals, crystals cannot deform. www.indiandentalacademy.com
  102. 102. • alloy crystals grow • anion – cation –anion – cation Perfect crystals seldom exist Crystals penetrate each other such that the crystal shapes get deformed and cannot be discerned www.indiandentalacademy.com
  103. 103. GRAIN:- Metal is made up of thousands of tiny crystals. Such a metal is said to be polycrystalline and each crystal in a structure is called GRAIN. UNIT CELL:- The smallest division of the crystalline metal that defines the unique packing is called unit cell. • Eg., Iron – Body Centered Cubic (BCC) • Titanium – Hexagonal Close Packed (HCP). www.indiandentalacademy.com
  104. 104. • Grains  microns to centimeters • Grain boundaries • Atoms are irregularly arranged, and this leads to a weaker amorphous type structure. • Alloy  combination of crystalline (grains) and amorphous (grain boundaries) • Decreased mechanical strength and reduced corrosion resistance www.indiandentalacademy.com
  105. 105. Stages in the formation of metallic grains during the solidification of a molten metal www.indiandentalacademy.com
  106. 106. • Vacancies – These are empty atom sites www.indiandentalacademy.com
  107. 107. • Smaller atoms that penetrate the lattice Eg – Carbon, Hydrogen, Oxygen, Boron. Often distort the metal structure www.indiandentalacademy.com
  108. 108. another metal atom can substitute one of the same or similar size. E.g. - Nickel or Chromium substituting iron in stainless steel. www.indiandentalacademy.com
  109. 109. • Imperfections- although they lower the cleavage strength of the metal , increase its resistance to deformation www.indiandentalacademy.com
  110. 110. • The three dimensional arrangement of lines that can be visualized as connecting the atoms in undisrupted crystals, is called a lattice. • Unit cell • Crystal  combination of unit cells, in which each cell shares faces, edges or corners with the neighboring cells • 14 crystal lattices www.indiandentalacademy.com
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  113. 113. • The atoms, which are represented as points, are not static. • Instead, they oscillate about that point and are in dynamic equilibrium. www.indiandentalacademy.com
  114. 114. Elastic strain: v Atoms are shifted from their equilibrium positions by a fraction of their atomic spacing. v When stress is removed atoms return to equilibrium atomic spacing. Plastic Deformation: atoms are shifted to new atomic sites on lattice. Mechanism of plastic deformation is called “DISLOCATION MOTION”. – two types – line and point defects www.indiandentalacademy.com
  115. 115. • various defects  slip planes-along which dislocation occurs www.indiandentalacademy.com
  116. 116. www.indiandentalacademy.com
  117. 117. • shear stress  atoms of the crystals can glide along these planes • more the slip planes easier is it to deform • Slip planes intercepted at grain boundaries-increases the resistance to further deformation www.indiandentalacademy.com
  118. 118. If the shearing force is:- • Small - atoms slip, and return back to their original position (elastic deformation) • Beyond the elastic limit crystal suffers a slight deformation permanent (plastic deformation) • Greater stress - fracture www.indiandentalacademy.com
  119. 119. • During deformation - atomic bonds within the crystal get stressed  resistance to more deformation Number of atoms that get stressed also increases  resistance to more deformation www.indiandentalacademy.com
  120. 120. Process resulting from cold working (i.e., deformation at room temperature) Ultimate result of strain hardening with further increase in cold working is FRACTURE. RESULTS OF STRAIN HARDENING:v Increased surface hardness, strength and PL v Decreased ductility and resistance to corrosion www.indiandentalacademy.com
  121. 121. • Forced interlocking of grains and atoms of metal. • Locked in and under pressure/tension • Carried at room temperature. www.indiandentalacademy.com
  122. 122. A process characterized by the transfer of energy in the form of heat to a metallic material to alter its mechanical and / or thermal properties. www.indiandentalacademy.com
  123. 123. Stress relief heat treatment. Annealing heat treatment. Hardening heat treatment. www.indiandentalacademy.com
  124. 124. Releases the stresses incorporated in metal due to cold working procedures. Mechanism: Internal stresses are relieved by minute slippages and readjustments in intergranular relations without loss of hardening. e.g., - Recommended temperature for stress relieving of stainless steel is 750F (399C) for 11min. www.indiandentalacademy.com
  125. 125. System temperature is elevated by placing it in a high temperature environment. (e.g., furnance or a hot salt bath or by electric resistance/ induction heating). Upon reaching desired temperature the system is maintained there for a specific period of time. System is returned to its initial state temperature. www.indiandentalacademy.com
  126. 126. • Strain hardening  Hard and strong, tensile strength Brittle. • Annealing – heat below melting point. – More the cold work, more rapid the annealing – Higher melting point – higher annealing temp. – ½ the melting temperature (oK) www.indiandentalacademy.com
  127. 127. • Recovery • Recrystallization • Grain Growth www.indiandentalacademy.com
  128. 128. Before Annealing Recovery – Relief of stresses Recrystallization – New grains from severely cold worked areas -original soft and ductile condition Grain Growth – large crystal “eat up” small ones-ultimate coarse grain structure is produced www.indiandentalacademy.com
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  130. 130. • Smaller grains – harder and stronger • Larger grain boundaries to oppose the slip planes. www.indiandentalacademy.com
  131. 131. A heat treatment process employing a relatively high temperature that results in recrystallisation of microstructure and produces marked changes in mechanical properties. www.indiandentalacademy.com
  132. 132. Stages of annealing: Recovery Recrystallisation Grain growth. • Temperatures are substantially above that of stress relief – Annealing of stainless steel requires few minutes at 1800-2000F. www.indiandentalacademy.com
  133. 133. Process by which a metal alloy is hardened and strengthened by extremely small and uniformly dispersed particles that precipitate from a supersaturated solid solution. - Also called Age hardening. Long term process (of several hours). Carried out at temperature somewhat below that necessary to anneal followed by rapid quenching. e.g., heat treatment of Co-Cr alloy to increase their strength and resilience. www.indiandentalacademy.com
  134. 134. www.indiandentalacademy.com
  135. 135. • Oral cavity environment is inherently corrosive. • The oral fluids cause oxidation of metals. • CORROSION: A chemical or electrochemical process through which a metal is attacked by natural agents such as air and water, resulting in partial or complete dissolution, deterioration or weakening of any solid substance. • TARNISH: A process by which a metal surface is dulled in brightness or discolored through formation of chemical film such as sulfide and an oxide. – Tarnish is often forerunner of corrosion www.indiandentalacademy.com
  136. 136. Defined as “the process of interaction between a solid material and its chemical environment, which leads to loss of substance from the material, change in its structural characteristics, or loss of structural integrity” www.indiandentalacademy.com
  137. 137. Galvanic corrosion: An accelerated attack occurring on a less noble metal when electrochemically dissimilar metals are in electrical contact in presence of liquid corrosive environment. - Also known as Dissimilar metals corrosion. www.indiandentalacademy.com
  138. 138. Stress corrosion Cold working of an alloy by bending, burnishing etc localizes stresses in some parts of the structure.  A couple composed of stressed metal, saliva and unstressed metal is formed.  Stressed area is more readily dissolved by the electrolyte www.indiandentalacademy.com
  139. 139. Uniform Corrosion A uniform, regular removal of metal from the surface is the usually expected mode of corrosion Interaction of metals with the environment and the subsequent formation of hydroxides or organometallic compounds May not be detectable before large amounts of metal are dissolved www.indiandentalacademy.com
  140. 140. Pitting Corrosion localized, symmetrical corrosion in which pits form on the metal surface www.indiandentalacademy.com
  141. 141. Concentration cell corrosion: e.g., crevice corrosion. Accelerated corrosion in narrow spaces caused by localized electrochemical processes and chemistry changes such as acidification and depletion of O2 content. www.indiandentalacademy.com
  142. 142. Crevice Corrosion occurs between two close surfaces or in constricted places where oxygen exchange is not available www.indiandentalacademy.com
  143. 143. Fretting and Erosion-Corrosion The combination of a corrosive fluid and high flow velocity results in erosion-corrosion www.indiandentalacademy.com
  144. 144. Inter-granular Corrosion Reactive impurities may segregate, or passivating elements such as chromium may get depleted at the grain boundaries grain boundary and adjacent regions are often less corrosion resistant preferential corrosion at the grain boundary may be severe enough to drop grains out of the surface www.indiandentalacademy.com
  145. 145. Hydrogen damage reaction of the hydrogen with carbides in steel to form methane, resulting in decarburization voids, and surface blisters www.indiandentalacademy.com
  146. 146. Microbial Corrosion in Orthodontic Appliances microorganisms affect the corrosion of metal and alloys immersed in aqueous environment. Under similar conditions, the effect of bacteria in the oral environment on the corrosion of dental metallic materials remains unknown www.indiandentalacademy.com
  147. 147. www.indiandentalacademy.com
  148. 148. • Based upon material • Based on cross section www.indiandentalacademy.com
  149. 149. www.indiandentalacademy.com
  150. 150. • The orthodontist should consider a variety of factors• Strength , stiffness, flexibility of wire • The amount of force delivery that is desired • The elastic range , springback • Formability • The need for soldering and welding to assemble the appliance www.indiandentalacademy.com
  151. 151. www.indiandentalacademy.com
  152. 152. Two types of gold wires are recognized in ADA Sp. No. 7 Type I wire (75% gold) High noble Type II wire (65% gold) Noble Metal alloys www.indiandentalacademy.com
  153. 153. Pt and Pd Copper Nickel Zinc  increases the fusion temperature.  Contributes to ability of alloy to AGE HARDEN  Strengthens the alloy.  Scavenger agent. www.indiandentalacademy.com
  154. 154. Strengthened to variable stiffnesses with proper heat treatment, although they are typically used in the drawn condition. Accomplished by :Heating at 450 C (842 F) for 2 min. Cooling to 250 C (482 F) over a period of 30 min . Quenching to room temp. www.indiandentalacademy.com
  155. 155. • Good formability • Capable of delivering lower forces than stainless steel or low modulus of elasticity • Easily joined by soldering • Excellent corrosion resistance www.indiandentalacademy.com
  156. 156. DISADVANTAGES : High Cost.  Low proportional limit / yield strength. USES :Only the Crozat appliance is still occasionally made from gold following original design of early 1900s. www.indiandentalacademy.com
  157. 157. www.indiandentalacademy.com
  158. 158. The corrosion resisting steel was reported by Berno Strauss and Edward Maurer of Germany in 1914.  Stainless steel (SS) introduced to dentistry in 1919 Introduced at Krupp’s Dental Polyclinic in Germany by the company’s dentist Dr. F. Hauptmeyer He first used it to make a prosthesis and called it Wipla (Wieplatin ; In German- like platinum). By 1937 – widely accepted. www.indiandentalacademy.com
  159. 159. Steels – Iron based alloys that usually contain less that 1.2% carbon. Lattice arrangements of Iron Ferrite :- ( - iron)   •  Pure iron has BCC structure at room temp low temp phase- stable upto 912 C. Less amount of carbon Carbon has a very low solubility in ferrite (0.02 wt %) – because spaces between atoms in BCC structure are small www.indiandentalacademy.com
  160. 160.  Face centred Cubic (FCC) structure.  high temp phase- exists between 912 C 1394C. • Maximum carbon solubility of 2.1 weight %. www.indiandentalacademy.com
  161. 161. Austenite cooled rapidly (quenched) spontaneous DIFFUSIONLESS transformation to Body Centered tetragonal (BCT) structure.   Highly distorted and strained lattice. Hard, strong, brittle. www.indiandentalacademy.com
  162. 162. HeatTreatment (525 C) Martensite Ferrite Carbide This process results in -  The hardness  toughness www.indiandentalacademy.com +
  163. 163. Steel + 12-30% Chromium  STAINLESS STEEL  When at least 10-12% Chromium is present.   A Coherent oxide layer formed that passivates the surface rendering the alloy ‘STAINLESS’ www.indiandentalacademy.com
  164. 164. Steels are classified according to the American Iron and Steel Institute (AISI) system. Three types of stainless steel www.indiandentalacademy.com Ferritic Austenitic Martensitic
  165. 165. TYPE (Space lattice) Ferritic (BCC) Austenitic (FCC) Martensitic (BCT) CHROMIUM NICKEL CARBON 11.5 – 27 0 0.20 max. 16 –26 7 – 22 0.25 max. 11.5 – 17 0 – 2.5 0.15 – 1.20 BALANCE is Iron www.indiandentalacademy.com
  166. 166. Ferritic Stainless steels – AISI 400 series • good corrosion resistance • low cost • low strength • Not readily work hardenable. • Finds little application in dentistry. www.indiandentalacademy.com
  167. 167. Martensitic Stainless steels – AISI 400 Series • High strength, hardness and brittleness • Less corrosion resistant • less ductile. Used for surgical and cutting instruments www.indiandentalacademy.com
  168. 168. Most commonly used for orthodontic materials. Most corrosion resistant of the stainless steels. AISI 302 Three Types AISI 304 AISI 316 L 18% Chromium. AISI 302 8% Nickel. 0.15% Carbon. Balance- iron www.indiandentalacademy.com
  169. 169. Function of Nickel - Stabilizes Austenite phase at room temp so it is an “AUSTENIZING ELEMENT”. Other e.g :- Mn and N. Mechanism : Makes diffusion of carbon so low that Austenite cannot decompose and temperature is too low to allow formation of Martensite. www.indiandentalacademy.com
  170. 170. AISI 304 :- Similar Composition Chief difference  Carbon content (0.08%) Both 302 and 304 stainless steel are designated as 18-8 stainless steel Type 316 L – ‘L’  Low Carbon Content Carbon content  0.03% max. carbon Used for implants www.indiandentalacademy.com
  171. 171. Austenitic stainless steel is preferable to Ferritic SS because     Greater ductility. Substantial strengthening during cold working Greater ease of welding. Ability to overcome sensitization. www.indiandentalacademy.com
  172. 172. STAINLESS STEEL www.indiandentalacademy.com
  173. 173. High stiffness demonstrated by large values of Modulus of Elasticity.  Necessitate use of smaller wires for alignment of moderately or severely displaced teeth as it cannot be engaged easily due to its rigidity  Advantageous in resisting deformation caused by extra and intraoral tractional forces. 160-180 GPa www.indiandentalacademy.com
  174. 174. • SS has lower spring back than those of newer titanium based alloys.- .0060-.0094, therefore deforms easily without much recovery • Can’t be deflected to a greater extent www.indiandentalacademy.com
  175. 175. Represents work available to move teeth. substantially less than that of Beta titanium and Nitinol wires. Clinical Relevance : Implies that stainless steel wires produce higher forces that dissipate over shorter periods of time than either beta titanium or nitinol wires, thus requiring more frequent activation or archwire changes. www.indiandentalacademy.com
  176. 176. FORMABILITY :Excellent formability, yield strength- 11001500MPa JOINABILITY :SS wires can be soldered and welded. www.indiandentalacademy.com
  177. 177.  SS wire should not be heated to too high temp  To minimize Carbide precipitation.  To Prevent excessive softening of wire.  Use of low fusing sliver solders (620 C - 665 C).  Fluoride containing fluxes should be used because they dissolve the passivating film formed by chromium. Solder does not wet the metal when such a film is present. www.indiandentalacademy.com
  178. 178. CORROSION RESISTANCE :SS owes it corrosion resistance to Chromium – a highly reactive base metal . A thin transparent but tough and impervious oxide layer ( Cr2 O3 forms [PASSIVATION] is formed on surface of alloy when it is subjected to oxidizing atmosphere such as room air. O2 is necessary to form and maintain the film. Causes of Corrosion of Stainless Steel : Any surface roughness or unevenness.  Incorporation of bits of Carbon steel or similar metal in its surface. www.indiandentalacademy.com
  179. 179.  Stress Corrosion. Severe strain hardening may produce localized electric couples in presence of an electrolyte such as saliva.  Soldered joints. Attack by solutions containing chlorine www.indiandentalacademy.com
  180. 180. Classification Example Acetic acid Vinegar Copper chloride Certain appliance cleansers Fatty acids By-products of the micro-organism, Streptococcus mutans General foods Beet juice Hydrogen sulfide Effluent of mouth air Lactic acid Spoiled milk Phosphoric acid Colas Salt water Saliva Sodium hypochlorite Certain appliance cleansers Sulfite solution Wine Zinc chloride Certain mouth washes and certain appliance cleansers www.indiandentalacademy.com
  181. 181. 18–8 stainless steel may loose its resistance to corrosion if it is heated b/w 400 C-900C. The reason is :  Precipitation of Chromium Carbide (Cr3 C) at the grain boundaries.  Formation of Cr3C is most rapid at 650C.  When chromium combines with carbon its passivating qualities are lost  Chromium is depleted adjacent to grain boundaries.  Alloy becomes susceptible to INTERGRANULAR CORROSION. www.indiandentalacademy.com
  182. 182. 1. Keeping out of sensitizing temp range (425 - 650 C) 2. Controlling the Carbon. 1. Controlling temp to prevent intergranular corrosion :Speed in handling metal in sensitizing temp range – effective means of minimizing sensitization. e.g Quenching immediately after soldering. www.indiandentalacademy.com
  183. 183. by Titanium and Columbium.  Titanium is introduced in an amount approx 6 times the carbon content. Steel that has been treated to reduce the available Carbon is called STABILIZED STEEL www.indiandentalacademy.com
  184. 184. • Low levels of bracket / wire friction have been reported with experiments using stainless steel wires. • This signifies that stainless steel arch wires offer lower resistance to tooth movement than other orthodontic alloys www.indiandentalacademy.com
  185. 185. • Graner et al (1986) :• Compared frictional forces of Nitinol, Beta titanium and SS arch wires. • Larger forces are required during canine retraction using  Ti and Nitinol when compared to SS. • Kusy et al (1988) :• Investigated surface roughness of 6 Orthodontic archwire products. • Stainless steel appears the smoothest followed by Co-Cr,  Ti and Ni – Ti. www.indiandentalacademy.com
  186. 186. STRESS RELIEVING HEAT TREATMENT Only heat treatment used with stainless steel after bending wire into an arch, loops or coils. Purpose : Causes significant decrease in residual stress.  Enhances elastic properties of wire – slight  resilience. Temperature :- Recommended temperature time schedule is 750 F (399 C) for 11 min www.indiandentalacademy.com
  187. 187. • Funk (1951) :• Recommends use of color Index to determine when adequate heat treatment is achieved. • He suggests a straw colored wire indicates that optimum heat treatment has been attained. www.indiandentalacademy.com
  188. 188. 1. Oven is most reliable medium for heat Rx because of its relatively uniform temperature. 2. Heating the wire with special heat treating power source. Disadvantage: Lack of uniform temperature. www.indiandentalacademy.com
  189. 189. • • • • • • • High strength High Stiffness Low resilience Low Spring back Low springiness Moderate range Good formability and joinability www.indiandentalacademy.com
  190. 190. • MECHANICAL PROPERTIES - High yield strength and high modulus of elasticity Yield strength Elastic Modulus Springback Goldberg + Burstone 275 x x 103 25,000 x x 103 11.0 Kusy et al 227 x x 103 28,000x 103 8.1 www.indiandentalacademy.com
  191. 191. Are available in :Various sizes and cross sections Round  0.012, 0.014, 0.016, 0.018, 0.020 etc. Rectangular  0.016x 0.022, 0.017x 0.025, 0.018x 0.025, 0.019x 0.025 etc. Square  0.016 x 0.016 , 0.017 x 0.017 www.indiandentalacademy.com
  192. 192. www.indiandentalacademy.com
  193. 193. • Various Grades :American Orthodontics Dentaurum Unitek RMO Available in Standard Gold tone Super Gold tone Super special spring hard Extra spring hard Spring hard Standard Resilient Resilient arch wire temper Retainer wire temper Clasp wire temper Ligature wire temper Spooled forms Straight lengths Preformed arches www.indiandentalacademy.com
  194. 194.  Tru – Arch, arch forms (A company)  Natural arches (American Orthodontics)  Preformed Anatomically Refined (Ormco)  Pentamorphic arches (RMO)  Standard and Proform (Ortho Organizers). www.indiandentalacademy.com arches
  195. 195. • Composed of specified numbers of thin wire sections coiled around each other to provide round or rectangular cross section. • Improved strength ,stiffness and Range www.indiandentalacademy.com
  196. 196. Kusy and Dilley (1984) :Investigated properties of Multistranded SS wires in a bending mode of stress. They noted that Stiffness of triple stranded 0.0175 inch (3 x 0.008 inch) SS arch wire was similar to that of 0.010 inch single stranded SS wire and 0.016 Nitinol  25 % stronger than 0.010 inch SS wire.  Nitinol tolerated more than 50% greater activation than multistranded wire. Triple stranded wire – half as stiff as 0.016 inch Beta titanium wire. www.indiandentalacademy.com
  197. 197. Ingram, Gipe and Smith (1986)  Titanium alloy wires and multistranded SS wires have low stiffness when compared with solid SS wires.  Multistranded wires – spring back similar to Nitinol but greater as compared to solid SS or Beta titanium wires. www.indiandentalacademy.com
  198. 198. - Provide a viable alternative to more expensive titanium wires for initial leveling - Braided rectangular steel wires are available in variety of stiffnesses and the stiffest of these is 0.021 x 0.025 – useful in 0.022 slot for finishing. www.indiandentalacademy.com
  199. 199. • Forms • Cross sections • No. of strands Braided Twisted Co-axial Round Rectangular Triple stranded Six stranded Eight stranded Nine stranded • Dimensions Round:- 0.015, 0.0175, 0.0195,0.0215 Rectangular : 0.016 x 0.022 to 0.021 x 0.025 www.indiandentalacademy.com
  200. 200. ORMCO Force 9 (braided) Respond (multistranded) D-Rect (braided) Triple flex(triple stranded) www.indiandentalacademy.com
  201. 201. GAC International Wildcat Tricat Pentacat Quadcat Multibraided Hexacat www.indiandentalacademy.com
  202. 202. American orthodontics – Twist (triple stranded) CO-Ax (five strand) Straight woven (eight- stranded rectangular wire) Dentaurum – Dentaflex Triple strand (round & rectangular) Six strand Co-axial Eight strand (braided, rectangular) www.indiandentalacademy.com
  203. 203. Leone - Twist (straight and preformed round & rectangular) Flex (straight and preformed round) Unitek - HI-T II Twist Flex (silver soldered) Unitek braided wire (8 strand) Unitek Coxial TP Orthodontics – CoAx, Pre-Cut CoAx (central core wire with 5 outer strands www.indiandentalacademy.com
  204. 204. Ormco Corporation :• Triple flex (Triple stranded twisted wire). • Respond (Coaxial – 6 stranded). • D-rect (Braided Rectangular – 8 stranded) • Force 9 (Braided Rectangular – 9 stranded). TP Orthodontics :- Co-Ax wire ( 5 strands) Unitek :- Twist flex (Triple stranded) RMO :- Triflex (3 strands, twisted) www.indiandentalacademy.com
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  207. 207. MAINSTAY OF BEGG TECHNIQUE In 1940 S :Dr. Begg met Mr. Arthur J. Wilicok Sr. of Whittlesea, Victoria who was directing metallurgical research projects at University of Melbourne. After many years of research and development Mr. Wilcock produced high tensile wires, cold drawn, heat treated wire that combined the balance between hardness and www.indiandentalacademy.com resiliency with unique property of zero stress relaxation.
  208. 208. – Hardness – Tensile strength – Springback – Resiliency – Zero stress relaxation – Yield strength www.indiandentalacademy.com
  209. 209. Regular Grade Lowest grade and easiest to bend. Used for practice bending. Regular plus Used for auxiliaries and archwires when more pressure and resistance to deformation is required. Special Grade 0.016 is often used for starting archwires in many techniques. www.indiandentalacademy.com
  210. 210. Special plus Routinely used by experienced operators Hardness and resiliency of 0.016 is excellent for supporting anchorage and reducing deep overbites. Must be bent with care. Extra Special plus grade (ESP) This grade is unequalled in resiliency and hardness Difficult to bend and is brittle www.indiandentalacademy.com
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  212. 212. www.indiandentalacademy.com
  213. 213. A.J Wilcock Scientific and Engineering Company announced new series of wire grades and sizes. Wires are straightened by use of 2 processes : 1. SPINNER STRAIGHTENING. 2. PULSE STRAIGHTENING. www.indiandentalacademy.com
  214. 214. • Mechanical process of straightening materials usually in cold drawn condition. • Wires are straightened by process of REVERSE STRAINING. • Flexing in a direction opposite to that of original bend • In conventional manufacturing wire is pulled through high speed rotating Bronze rollers which torsionally twist the wire into straight condition. www.indiandentalacademy.com
  215. 215. Disadvantage :-  Resultant deformation.  Decreased yield strength in tension and compression as compared to that of the “as drawn” material.  This phenomenon of strain softening/work softening due to reverse straining is known as “BAUSCHINGER EFFECT”. www.indiandentalacademy.com
  216. 216. This process was developed to overcome previous difficulties. Has several advantages over other straightening methods  Permits higher tensile wires to be straightened. • Less or no deformation  Material yield strength is not diminished • Wire has smoother surface and hence less bracket friction. www.indiandentalacademy.com
  217. 217. NEWER GRADES OF WILCOCK WIRES : Premium  Premium plus  Supreme PROPERTIES :Higher yield strength of newer grade wires influences following properties :- www.indiandentalacademy.com
  218. 218. SPRINGBACK - (YS/E) :– Newer grade wires have better springback than lower grade wires -can be deflected more without deformation RESILIENCY – (YS2/2E) :higher yield strength results in greater resiliency. This means that higher grade wires store or absorb more energy per unit volume before they get permanently deformed. www.indiandentalacademy.com
  219. 219. • Ability of wire to deliver over long periods a constant force when subjected to an external load. • Newer wires maintain their configuration over long periods against deforming forces (forces of occlusion) • higher yield strength prevents grain slippage www.indiandentalacademy.com
  220. 220. For the same material greater resiliency lesser the formability. Theses wires are more brittle than lower grade wires and need to be bent in specific way. Warm the wire by pulling through fingers before bending because these wires have a ductile brittle transition temp. slightly above room temp. Bend the wire around square beak of pliers. www.indiandentalacademy.com
  221. 221. 1.When relatively high load deflection rate is required :a) For generating relatively larger forces in stage I (for incisor intrusion and lateral contraction or expansion of post teeth).  0.016 or 0.018 Premium + or P wires are used. b) Large resistance to deformation is required e.g., Maintaining arch from  0.018 P or P + or 0.020 P wires are indicated. c) for overcoming undesired reactions of a torquing auxiliary or uprighting springs in IIIrd stage - 0.020 P wire is employed www.indiandentalacademy.com
  222. 222. 2. When a low load deflection rate is required. Supreme grade arch wires of sizes 0.008 – 0.011 are used for – Unravelling of crowded anterior teeth – MAA (Mollenhauer aligning auxiliary) – uprighting springs www.indiandentalacademy.com
  223. 223. 0.010 Supreme : Used to form Reciprocal torquing auxiliaries.  Best indicated for mouse trap auxiliary and Minisprings. 0.011 Supreme : Used for aligning second molars towards end of stage III. 0.012 Supreme – Torquing Auxiliary in Stage III because of its high resiliency and springback www.indiandentalacademy.com
  224. 224. The Mollenhauer bending plier is strongly recommended for bending Wilcock wire as it helps to minimise breakages. The tips are tungsten carbide inserted for durability, with rounded and highly polished edges. www.indiandentalacademy.com
  225. 225. • - TP ORTHODONTICS: Standard grade – white label Standard plus grade – green label Premier grade – black label Premier plus grade – orange label www.indiandentalacademy.com
  226. 226. • Reviewed in literature for past 10 years. • Nickel causes more allergic reactions then all other metals combined and also is cytotoxic • The typical symptoms of Ni allergy in an orthodontic pt. are – Widespread Erythema and swelling of Oral tissues developing 1-2 days after treatment is started. • Use of Ni – free alloys substitutes or Ni alternatives are recommended for Ni. Hypersensitive patients www.indiandentalacademy.com
  227. 227. NICKEL FREE STAINLESS STEEL :COMPOSITION :15 – 18% Chromium. 3 – 4% Molybdenum 10 - 14% Manganese. 0.9 % Nitrogen – To compensate for Ni. Nickel is no more an alloying element (but only an impurity) Orthodontic wires  Menzanium (Scheu Dental)  Nobinium (Dentaurum) www.indiandentalacademy.com
  228. 228.  SS is fabricated in a high pressure melting process where Manganese and Nitrogen replace allergic components of Ni.   Ideal for Ni sensitive patient. Corrosion resistant and durable. Availability :Supplied by Great lakes orthodontics. Grade :- Hard and spring Hard. Sizes :- 0.028, 0.032, 0.036. www.indiandentalacademy.com
  229. 229. • • • • • • • • C Cr Mn Mo Ni N Si Fe = 0,038% = 17,9% = 18,6% = 2,09% < 0.2% = 0,89% = 0,77% = Rest www.indiandentalacademy.com
  230. 230. • Duplex steels consist of an assembly of both austenite and ferrite grains. Besides iron these steels contain molybdenum and chromium and they have lower nickel content. – Improved toughness and ductility compared to ferritic steels. – Yield strength is twice that of Austenitic stainless steels. – Highly corrosion resistant. www.indiandentalacademy.com
  231. 231. www.indiandentalacademy.com
  232. 232. In 1950s Elgin watch company was developing a complex alloy whose primary ingredients were cobalt, chromium, Iron and Nickel. Cobalt chromium alloy was marketed as ELGILOY by Rocky Mountain Orthodontics. www.indiandentalacademy.com
  233. 233. • • • • • • • • Cobalt Chromium Molybdenum Manganese Nickel Iron Carbon Beryllium -40% -20% -7% -2% -15% -15.8% -0.15% -0.04% www.indiandentalacademy.com
  234. 234. Manufactured in 4 tempers :1. SOFT (Blue) 2. DUCTILE (Yellow) 3. SEMIRESILIENT (Green) 4. RESILIENT (Red) www.indiandentalacademy.com
  235. 235. - Softest of the four wire types Bent easily with fingers or pliers. Used when considerable bending, soldering and welding is required . - Relatively ductile and more resilient than blue. - Bent with relative ease. - Further  in resilience can be achieved by heat treatment www.indiandentalacademy.com
  236. 236. - More resilient than yellow elgiloy. Can be shaped with pliers before heat treatment. - Most resilient and provides high spring qualities. - Careful manipulation with pliers is recommended because it withstands only minimal working. - Heat treatment makes it extremely resilient. www.indiandentalacademy.com
  237. 237. With exception of red temper elgiloy, springback is less than SS wires  But this property can be improved by adequate heat treatment. .0045-.0065-for , as received wire .0054-.0074 after heat treatment www.indiandentalacademy.com
  238. 238. High Modulus of elasticityDeliver twice force of  - Ti and 4 times force of Nitinol for equal amounts of activation. Less stiff than stainless steel 160-190GPa as received 180-210GPa heat treated www.indiandentalacademy.com
  239. 239. - Good formability. Modified by heat treatment.. -yield strength -830-100MPa as received -1100-1400MPa heat treated www.indiandentalacademy.com
  240. 240. JOINABILITY Can be soldered and welded. Precaution :- High temp (749C) causes Annealing. - Low fusing solder is recommended. BIOCOMPATIBILITY AND ENVIRONMENTAL STABILITY -Good www.indiandentalacademy.com
  241. 241. Although larger frictional forces have been noted previously between brackets and cobalt chromium wires but recent reports suggest that resistance to tooth movement along stainless steel and cobalt chromium wires may be comparable. www.indiandentalacademy.com
  242. 242. Temp and Time :900 F (482 C) for 7 – 12 min in a dental furnance. Temp above 1200 F (749C) results in partial annealing -  in resistance to deformation. Optimum levels of heat Rx are confirmed by : - Dark . - temperature indicating paste www.indiandentalacademy.com
  243. 243. Results in -  resistance of wire to deformation. - Increased resilience - Wire demonstrates properties similar to SS. www.indiandentalacademy.com
  244. 244. 1. Oven heat treatment. 2. Electrical heat treatment – using a heat treatment unit and temperature indicating paste to achieve proper temperature. Wet cotton is placed over bends in wire to prevent overheating the wire. 3. Flame heat treatment with match or brush flame. www.indiandentalacademy.com
  245. 245. Martin et al (1984) :- Investigated effect of heat treatment on various properties of Blue Elgiloy.  Heat treatment of blue Elgiloy  its yield strength and stiffness but  no. of 90 bends cycles to failure.  Significantly higher yield strength of electrically heat treated straight wire samples over oven heat treated samples was noted www.indiandentalacademy.com
  246. 246. www.indiandentalacademy.com
  247. 247. Elgiloy : Easier to bend than SS, NiTi and -Ti in its “as received state”. - Preferred in techniques in which loops are used. - ideal and economical finishing wire. www.indiandentalacademy.com
  248. 248. • Greater formability -resistance to fatigue and distortion. • Greater Resilience • Excellent corrosion resistance www.indiandentalacademy.com
  249. 249. • Lower spring back than stainless steel • High force delivery • Due to its soft feel during manipulation, operater can mistakenly believe that as received elgiloy blue wire has low force delivery • The value of modulus of elasticity is very similar for blue elgiloy and stainless steel www.indiandentalacademy.com
  250. 250. Available commercially as Elgiloy -Rocky Mountain orthodontics Azurloy -Ormco Corporation Flexiloy -Unitek Corporation www.indiandentalacademy.com
  251. 251. • Straight lengths – 14 inches • Preformed arches. Eg: Pentamorphic arches (RMO) www.indiandentalacademy.com
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  253. 253. • original work of Buehler for the Naval Ordinance Laboratory in the early 1960s. • First NiTi orthodontic alloy55% nickel and 45% titanium was developed by Andreasen and his colleagues www.indiandentalacademy.com
  254. 254. • The Unitek Corporation licensed the patent [1974] and offered a stabilized martensitic alloy (M-NiTi) that does not exhibit any shape memory effect under the name, Nitinol.. www.indiandentalacademy.com
  255. 255. COMPOSITION: Original alloy 55% Nickel 45% Titanium To modify mechanical properties and transition temp. 1.6% Cobalt was added to it www.indiandentalacademy.com
  256. 256. • It is a stabilized form of the alloy in which work hardening has abolished the phase transformation • This alloy has low elastic modulus OR stiffness and high range. www.indiandentalacademy.com
  257. 257. Titanium – a metal discovered by M.H. Klaproth in 1795. Titanium Light weight High strength Corrosion resistance www.indiandentalacademy.com
  258. 258. • Titanium is obtained in its pure form by heating the titanium ore in presence of carbon and chlorine. • The titanium tetrachloride (TiCl4) is then reduced with sodium to produce a titanium sponge. • This sponge is fused under vaccum or in an inert argon atmosphere and converted to ingots. www.indiandentalacademy.com
  259. 259.  Pure titanium exhibits ALLOTROPY – can crystallize into more than one structure.  At room temperature or below 885 C  Hexagonal close packed (HCP) - lattice is stable.  At higher temperatures i.e. above 885C -Rearranges into BCC or  phase. • Addition of Molybdenum / Columbium stabilize the  - phase at room temperature. www.indiandentalacademy.com
  260. 260. Phase Transformation: The change from one alloy phase to another with a change in temperature, pressure, stress, chemistry, and/or time. ACTIVE :A term that is used to describe an alloy that is capable of undergoing its anticipated phase transformation. PASSIVE :An alloy that is incapable of undergoing its anticipated phase transformation because extensive plastic deformation has suppressed the transition. www.indiandentalacademy.com
  261. 261. TWINNING :In certain metals that crystallize in HCP structure, deformation occurs by twinning. It refers to a movement that divides the lattice into two symmetric parts; these parts are no longer in the same plane but rather at a certain angle. e.g., :- NiTi alloys are characterized by multiple rather than single twining throughout the metal www.indiandentalacademy.com
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  263. 263. When these alloys are subjected temperature.  DETWINNING OCCURS  Alloy reverts to its original shape. (SHAPE MEMORY EFFECT). Eg.- conversion of martensite to austenite www.indiandentalacademy.com to higher
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  265. 265. • High temperature phase of Nickel titanium alloys is sometimes called Austenite because like many ferrous alloys this austenite can transform to Martensite • • • • BCC structure. Stronger Stiffer Higher temperature phase present in NiTi. www.indiandentalacademy.com
  266. 266. • Process of phase transformation which is DIFFUSIONLESS, occuring from within and without any chemical change which results in transformation of Austenite (parent phase) to Martensite following rapid cooling. • • • • It has HCP structure. More deformable Less Strong and Stiff Lower temperature phase www.indiandentalacademy.com
  267. 267. • Martensitic transformations do not occur at a precise temperature but rather within a range known as temperature transition range(TTR). • Transformation from Austenite to Marteniste and reverse do not take place at same temperature, this difference is known as HYSTERESIS. • Range for most binary NiTi alloys  40 - 60 C www.indiandentalacademy.com
  268. 268. • Transformation from Austenite to Martensite can occur by. – Lowering the temperature. – Applying stress (Stress induced Martensite) SIM. • Austenite and Martensite have different crystal structure and mechanical properties • superelasticity and shape memory are result of reversible nature of Martensitic transformation. www.indiandentalacademy.com
  269. 269.  With steels Martensitic transformation results in highly stressed structure called Martensite – Hard and brittle. • With NiTi alloys a similar martensitic transformation leads to soft structures • NiTi alloys - interstitial elements are carefully avoided even traces of O2, C and N in alloy lead to loss of elasticity and shape memory www.indiandentalacademy.com
  270. 270. R-phase: A phase intermediate between Martensite and Austenite that can form in NiTi alloys under certain conditions. Shape Memory: The ability of certain alloys to return to a predetermined shape upon heating via a phase transformation. www.indiandentalacademy.com
  271. 271. Superelasticity: The springy, “rubber like” behaviour present in NiTi shape Memory Alloys at temperatures above the Af temperature. The superelasticity arises from the formation and reversal of stress induced martensite. Thermoelastic Martensitic Transformation: A diffusionless, thermally reversible phase transformation characterized by a crystal lattice distortion www.indiandentalacademy.com
  272. 272. MARTENSITE AUSTENITE Low stiffness phase Elastic modulus of 31 – 35 GPa High stiffness phase Elastic modulus of 84 – 98 GPa www.indiandentalacademy.com
  273. 273. As Temperature: The temperature at which the SMA transforming to Austenite upon heating. starts Ap Temperature: The temperature at which the SMA is about 50% transformed to Austenite upon heating Af Temperature: The temperature at which a shape memory alloy finishes transforming to austenite upon heating. www.indiandentalacademy.com
  274. 274. Ms Temperature: The temperature at which a SMA starts transforming to Martensite upon cooling. Mp Temperature: The temperature, at which a SMA is about 50% transformed to Martensite upon cooling Mf Temperature: The temperature at which a SMA finishes transforming to Martensite upon cooling. Hysteresis: The temperature difference between a phase transformation upon heating and cooling. • Measured as the difference between Ap and Mp. www.indiandentalacademy.com
  275. 275. Above TTR alloy is fully austenitic www.indiandentalacademy.com
  276. 276. • Composition of the alloy. • Processing history. • TTRS can be obtained from below room temperature upto 275F or higher. • e.g . Considering body temperature as reference • TTR above this temperature – Alloy is Austentic (Rigid). • TTR below this temperature – Alloy is Martensitic (Soft) www.indiandentalacademy.com
  277. 277. Adding a third metal can lower the TTR  to as low as - 330 F ( - 200 C).  Narrow the difference b/w cooling and heating (Narrow Hysteresis). Most common third metals are Cu and Co because.  Reduce the hysteresis  Bring TTR close to body temperature. www.indiandentalacademy.com
  278. 278. • Dissolved interstitial elements (small atoms such as O, N and C) disrupt the matrices which affects alloy shape memory and super elasticity • Thermally respondent wires – designed so that composition , Annealing and cold working match Ms to temperature of human body www.indiandentalacademy.com
  279. 279. MARTENSITIC ACTIVE ALLOYS  Those with transformation temperatures b/w room temperature and body temperature AUSTENITIC ACTIVE ALLOYS  Those with transformation temperature below room temperature www.indiandentalacademy.com
  280. 280. - Most important marker. - To exploit super elasticity to its fullest potential, the working temperature of orthodontic appliances should be greater than Af temperature. www.indiandentalacademy.com
  281. 281. Related to phase transitions within the NiTi alloy b/w Martensitic and Austenitic forms SHAPE MEMORY :It refers to the ability of the material to “remember” its original shape after being plastically deformed while in martensitic form. www.indiandentalacademy.com
  282. 282. To get wire to “Memorize” a certain form it must first be set into the desired shape and held tightly while undergoing a high temperature heat treatment. [heating wires in a mold for 10 min at 500F (280 C)]. After the wire is cooled to room temperature it can easily be deformed below the TTR because nitinol alloy is highly ductile. www.indiandentalacademy.com
  283. 283. • When the wire is heated above the TTR, the alloy will return to its original shape. • In the austenite phase, the memory metal “remembers” the shape it had before it was deformed www.indiandentalacademy.com
  284. 284. • THERMOELASTICITY :• The thermal analog of pseudoelasticity in which martensitic phase transformation occurs from austenite as temperature is decreased. www.indiandentalacademy.com
  285. 285. • Mechanical analog of thermoelasticity in which at constant temperature the austenitic to martensitic phase transformation occurs with increasing applied force. • As force is subsequently removed the reverse phase transformation occurs • Thermoelastic and pseudoelastic effects are complimentary i.e if one effect is small the other will be large and vice versa www.indiandentalacademy.com
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  287. 287. • Reversible stress induced martensitc transformation is exhibited when Af is less than oral temperature. www.indiandentalacademy.com
  288. 288. • This transformation is mechanical analogue of thermally induced shape memory effect. • The Austenitic alloy undergoes a transition in internal structure in response to stress without requiring a significant temperature change • It is possible for these materials as their TTR is close to room temperature www.indiandentalacademy.com
  289. 289. • Md: It is the highest temperature at which martensite formation can be induced by stress. • Md of A-NiTi group is above room temperature allowing formation of SIM at oral temperature www.indiandentalacademy.com
  290. 290. • Af (Austenitic finish) of these alloys is below mouth temperature.  • Formation of SIM is reversible when stress is reduced. • These alloys cannot be easily cooled down below their Ms.  • Do not display clinically useful shape memory. www.indiandentalacademy.com
  291. 291. • A – B :- Represents Elastic • C –D :- Elastic deformation of deformation of Austenitic phase. Martensite • Point B :- Martenstic phase • Point D :- Yield pt of martensite and transformation starts to occur. plastic deformation. • B – C :- Phase transition region from • Point E :- Failure point , Austenite to Martensite. • C – F :- Elastic unloading of • Stress Strain curve takes the shape of Martensite. plateau • F – G :- Phase transformation Constant load but large amount of strain Martensite – Austenite. (SUPERELASTIC REGION). • G – H :- Elastic unloading of • Point C :- Martensitic Austenite transformation completed. www.indiandentalacademy.com
  292. 292. • A – B :- Represents Elastic deformation of Austenitic phase. • Point B :- Martenstic phase transformation starts to occur. • B – C :- Phase transition region from Austenite to Martensite. • Stress Strain curve takes the shape of plateau Constant load but large amount of strain (SUPERELASTIC REGION). • Point C :- Martensitic transformation completed. • C –D :- Elastic deformation of Martensite • Point D :- Yield pt of martensite and plastic deformation. • Point E :- Failure point , • C – F :- Elastic unloading of Martensite. • F – G :- Phase transformation Martensite – Austenite. • G – H :- Elastic unloading of Austenite www.indiandentalacademy.com
  293. 293. A remarkable property of some alloys that exhibit a reversible elastic deformation characterized by a distinct non-linear relationship b/w load and deflection.  Seen as a characteristic plateau like appearance of the stress/strain curve during loading and unloading. www.indiandentalacademy.com
  294. 294. SUPERELASTIC BEHAVIOUR –:Martensitic crystal structure can be increasingly sheared with only gradually increasing force to approx 10 times the strain of normal alloys without exhibiting permanent deformation. www.indiandentalacademy.com
  295. 295. During detwinning - stress strain curve takes shape of plateau because even a minor increase in stress produces as much as 8% of deformation. Within the plateau the rearrangement of atoms is reversible. However if material is stressed beyond 2nd yield point permanent deformation results. In first stage Austenite deforms elastically from 0-2%. Above this level Martensitic superelastic transformation occurs that is completed at 8%-10% strain levels. The structure becomes detwinned Martensite. www.indiandentalacademy.com
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  297. 297. • Memory effects lasts only as long as twinning detwinning phenomenon can take place. • When atoms slide against each other with a full lattice unit – Irreversible transformation (permanent set) takes place. • Consequently cold worked wires do not transform www.indiandentalacademy.com
  298. 298. The martensitic-stabilized alloys do not possess shape memory or super elasticity, because the processing of the wire creates a stable martensitic structure. The martensitic-active alloys employ the thermoelastic effect to achieve shape memory; the oral environment raises the temperature of the deformed arch wire with the martensitic structure so that it transforms back to the austenitic structure and returns to the starting shape. ex- Neo Sentalloy www.indiandentalacademy.com
  299. 299. The austenitic-active alloys undergo a stress-induced martensitic (SIM) transformation when activated. These alloys display superelastic behavior (termed pseudoelastic ) • An austenitic-active alloy does not exhibit thermoelastic behavior when a deformed wire segment is warmed in the hands. • These alloys are the superelastic wires that do not possess thermoelastic shape memory at the temperature of the oral environment www.indiandentalacademy.com
  300. 300. • Reversible stress induced martensitc transformation is exhibited when Af is less than oral temperature. Ex- nitinol SE www.indiandentalacademy.com
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  302. 302. Springback and Flexibility-Good • Low stiffness. • Nitinol wires have greater springback and larger recoverable energy than SS or -Ti when activated to same extent. • High spring back is useful in circumstances that require large deflections but low forces. www.indiandentalacademy.com
  303. 303. • Load deflection rate of SS is twice that of Nitinol. i.e. increased load to produce more slight amount of deflection • Clinically this means that for any given malocclusion nitinol wire will produce a lower, more constant and continuous force on teeth than would a stainless steel wire of equivalent size www.indiandentalacademy.com
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  307. 307. • Nitinol has poor formability. • Fractures rapidly when bent over a sharp edge. • Bending also adversely effects springback property • Bending of loops and stops in nitinol is not recommended. • Any 1st, 2nd and 3rd order bends have to be overprescribed to obtain desired permanent bend. www.indiandentalacademy.com
  308. 308. • Can be obtained by flame annealing the end of wire. • This makes the wire dead soft and it can be bent into the preferred configuration. • A dark blue color indicates the desired annealing temperature. • Care should be taken not to overheat the wire because this makes it brittle. www.indiandentalacademy.com
  309. 309. Corrosion Resistance: Corrosion resistance feature of NiTi alloys is due to presence of large proportion of Titanium (48% 54%). Titanium alloys are covered with oxides (mainly TiO2) – forms a thin film that protects the metal. www.indiandentalacademy.com
  310. 310. Schwaninger, Sarkar and Foster (1982): noted that  Irregularities on surface of Nitinol wires – produced by manufacturing process predisposes wire to corrosive attack in mouth and not due to corrosion of alloy. www.indiandentalacademy.com
  311. 311. • Not joinable • Since hooks cannot be bent or attached to Nitinol, crimpable hooks and stops are recommended for use. www.indiandentalacademy.com
  312. 312. Garner, Allai and Moore (1986) and Kapila et al (1990): Noted that bracket wire frictional forces with nitinol wires are higher than those with SS wires and lower than those with -Ti, in 0.018 slot. In 0.022 slot – NiTi and -Ti wires demonstrated similar levels of friction. NiTi has greater surface roughness www.indiandentalacademy.com
  313. 313. Levelling and Aligning: Nitinol wire is much more difficult to deform during handling and seating into bracket slots than SS arch wires. - Reduces loops formerly needed to level dentition. - Can be used for longer periods of time without changing. - Torque can be controlled early in treatment because successive arch wires fit with precision and case. - Rectangular Nitinol inserted early in Rx – accomplishes simultaneous leveling, torquing and correction of rotations. - Bite opening using Reverse Curve of Spee www.indiandentalacademy.com
  314. 314. ADVANTAGES: • Fewer arch wire changes. • Less chair side time. • Less patient discomfort. • Reduction in time to correct rotations. www.indiandentalacademy.com
  315. 315. • By its very nature nitinol is not a stiff wire which means that it can easily be deflected. • Low stiffness of nitinol provides inadequate stability at completion of treatment. • • • • Tendency for dentoalveolar expansion. Expensive Poor formability. Poor joinability.. www.indiandentalacademy.com
  316. 316. Conventional Nitinol is available as - Nitinol classic - Titanal - Orthonol - 3M Unitek corporation. - Lancer pacific. - Rocky mountain orthodontics. www.indiandentalacademy.com
  317. 317. In the late 1980s, new Nickel titanium wires with an Active Austenitic grain structure appeared. These wires exhibited the remarkable property of NiTi alloys – SUPERELASTICITY. www.indiandentalacademy.com
  318. 318. This group is also referred to as A-NiTi. This group includes : Chinese NiTi. Japanese NiTi (Sentinol) 27C superelastic Cu-NiTi. In Austenitic active alloy both Martensite and Austenitic phases play an important role during its mechanical deformation www.indiandentalacademy.com
  319. 319. Developed by Dr. Tien Hua Cheng and associates for orthodontic applications at the General Research Institute for Non ferrous metals in Beijing, China. Reported by Burstone in 1985. Spring Back : At 80 of activation. Chinese NiTi wire has : 1.4 times the springback of Nitinol wire. 4.6 times the springback of SS wire. www.indiandentalacademy.com
  320. 320. Activation (original 80°) and reactivation (to 40°) curves for NiTi wire. The moment decreases to 383 gm-mm after 40° of deactivation. If the wire is untied and retied into a bracket (reactivation), the moment increases to 700 gm-mm. www.indiandentalacademy.com
  321. 321. • Stiffness of Chinese NiTi is 36% that of Nitinol wire • Unusual non linear unloading curve for Chinese NiTi is potentially significant factor for constant force application www.indiandentalacademy.com
  322. 322. • Small activations produce higher stiffness. • Significance: • Magnitude of a force increases if a wire is retied into the bracket. • If the tooth moved toward the archwire and the clinician then untied the wire and retied it, the force would be same after retying. www.indiandentalacademy.com
  323. 323. • clinically insignificant • exhibits some small differences at varying temperatures because material components have lower transition temperatures www.indiandentalacademy.com
  324. 324. • Chinese NiTi deformation is not particularly time dependent unlike nitinol wire, will not continue to deform a significant amount in mouth between adjustments. • Clinical Significance: • Because of its high range of action or Springback, Chinese NiTi wire is applicable in situations where large deflections are required. www.indiandentalacademy.com
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  326. 326. • Straight wire procedures where teeth are badly malaligned. • In appliances designed to deliver constant forces during major stages of tooth movement. • Chinese NiTi higher stiffness at small activations make it more effective than wires of traditional alloys whose force levels may be too low. (as teeth approach passive shape) www.indiandentalacademy.com
  327. 327. In 1978 : Furukawa Electric Co. Ltd. of Japan produced a new type of Japanese NiTi alloy. In 1986 : Miura et al reported on Japanese NiTi Superelasticity is produced by stress, and is called stress induced Martensitic transformation (SIM). Provides light continuous force for physiologic tooth movement www.indiandentalacademy.com
  328. 328. • The relationship between the temperature and time of the heat treatment of the Japanese NiTi alloy wire was studied to optimize the super-elastic properties of the alloy. When the heat application was raised to 500° C, the force level indicating the super-elastic property could be reduced. www.indiandentalacademy.com
  329. 329. • arch wires providing a different magnitude of force can be fabricated from the wires of the same diameter. • In addition, in the preformed arch wire, different magnitudes of force can be produced by controlling the temperature and time in the desired section of the arch wire www.indiandentalacademy.com
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  331. 331. • 3M Unitek: Nitinol Super Elastic • American Orthodontics: – Titanium Memory Wire:Available in two force levels : • Force I – low force • Force II – high force • Ortho Organizers:Nitanium • Masel Orthodontics Elastinol www.indiandentalacademy.com
  332. 332. • ADVANTAGES: • Constant force over wide range of deflection.  Low stiffness.  High springback.  More effective in initial tooth alignment.  Less patient discomfort. LIMITATIONS OF SUPERELASTIC NiTi: 1. Cannot be soldered or welded. 2. Poor formability. 3. Tendency for dentoalveolar expansion. 4. “Travels” around the arch. 5. Expensive. www.indiandentalacademy.com
  333. 333. Thermal analog of pseudoelasticity in which martensitic phase transformation occurs from Austenite as temperature is decreased. This phase transformation can be reversed by increasing the temperature to its original value. www.indiandentalacademy.com
  334. 334. 1. Dead soft at room temperature so that it can be tied easily. 2. Instantaneously activated by heat of mouth. 3. Able to apply clinically acceptable orthodontic forces. 4. Once fully activated would not be affected further by increased heat in the mouth. 5. A fairly narrow TTR i.e., it should be completely active at mouth temperature yet completely passive at lower temperature. This property would allow the clinician sufficient time to tie archwire into the bracket slots before heat of mouth activates the wire. www.indiandentalacademy.com
  335. 335.  Thermoelastic Nitinol – formable at ice water temperatures.   Ice water is below Ms of thermoelastic wires   Martensite while engaging  When warmed above Af by mouth temp.   Transformation is reversed to from Austenite   Wire returns to its original shape thus displaying shape memory. www.indiandentalacademy.com
  336. 336. • Active Martensite Thermodynamic Wire: • Included in the active martensitic group are wires with an Af set at a temperature at or above 37C [CuNiTi 37C and CuNiTi 40C], which is almost complete, transformed into martensite during clinical application. www.indiandentalacademy.com
  337. 337. • Martensitic alloy has a greater working range than austenite, and it may therefore prove advantageous during the process of alignment and leveling. • The ability to vary transition temperatures in martensitic wires of identical dimensions, allows the clinician to apply appropriate levels of physiological force during alignment, while maintaining archwire size.. www.indiandentalacademy.com
  338. 338. This wire combines greater heat sensitivity, high shape memory, and extremely low, constant forces to provide a full-size wire that can be inserted early in treatment www.indiandentalacademy.com
  339. 339. Invented by Dr. Rohit Sachdeva – 1994. COMPOSITION : Quaternary alloy containing. * Nickel * Copper (5 – 6%) * Titanium * Chromium (0.2 – 0.5%) Copper: - Increases strength - Reduces hysteresis - these benefits occur at expense of increasing TTR above that of oral cavity. To compensate for the above mentioned unwanted effect 0.5% chromium is added to return TTR close to oral temperature www.indiandentalacademy.com
  340. 340. TYPES OF CU-NITI: 1. Type I Af 2. Type II Af 3. Type III Af 4. Type IV Af 15C. 27C 35C 40C www.indiandentalacademy.com
  341. 341. • These 4 alloys form the basis for “Variable Transformation Temperature Orthodontics Type I – Af - 15C Not frequently used Generates very heavy forces. Type II – Af - 27C Generates highest forces of 3 types (II, III and IV) Indications:  In patients who have an average or higher pain threshold. In patients who have normal periodontal health. In patients where rapid tooth movement is required and force system generated by archwire is constant www.indiandentalacademy.com
  342. 342. Type III Af 35C Generates forces in mid range. Indications:  Patients who have a low to normal pain threshold. In patients whose periodontium is normal to slightly compromised. Where relatively low forces are desired. Type IV Af - 40C  These wires generate forces only when mouth temperature exceeds 40C. Intermittent forces. www.indiandentalacademy.com
  343. 343. • Patients who are sensitive to pain. • Patients who have compromised PDL conditions. • Where tooth movement is deliberately slowed down i.e when the patient may not be able to visit the orthodontist regularly or poor patient cooperation www.indiandentalacademy.com
  344. 344. • • • • • Cu – NiTi generates more constant force over long activation spans. More resistant to permanent deformation. Exhibits better springback properties. Exhibits smaller drop in unloading forces (reduced hysteresis). Provides precise TTRs at 4 different levels – Enables Clinician to select archwires on a case specific www.indiandentalacademy.com
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  346. 346. ALIGNMENT: Principles of choice for alignment arches: 1. Arch wires for alignment should provide light, continuous force of approx. 50 gms. 2. Arch wires should be able to move freely within the brackets. 3. Rectangular arch wires which fit tight within bracket slots so that position of root apices could be affected – should be avoided. www.indiandentalacademy.com
  347. 347. In Finishing Stage: Appropriate stiffness at relatively small deflections rather than range is primary consideration. If rectangular A-NiTi is used in finishing stage – Torsional stiffness must be considered in choice of wire. M-NiTi usually is better choice (21 x 25 M-NiTi for 0.022 slot) for rectangular NiTi wires www.indiandentalacademy.com
  348. 348. • True thermoelastic alloys may therefore be indicated for early torque control during the alignment phase of treatment and in periodontally compromised patients. www.indiandentalacademy.com
  349. 349. 1. DUAL FLEX ARCHWIRES Invented by James L Cannon. Consists of anterior and posterior segments of different stiffnesses. a. Dual flex Archwire # 1 - Anterior segment – 0.016 Titanal (Nickel titanium) - Posterior segment – 0.016 Stainless steel. www.indiandentalacademy.com
  350. 350.   Anterior segment flexible – Easy Bracket engagement in crowded anterior teeth.  Posterior segment rigid – 1. controls rotation 2. prevents tipping from elastic traction 3. Permits bite opening bends to be made easily. www.indiandentalacademy.com
  351. 351. Dual Flex Archwire # 2: • Anterior segment – 0.016 x 0.022 Titanal. • Posterior segment – 0.018 stainless steel • For use with combination bracket when retraction of anterior teeth in upright positions which doesn’t utilize all of the extraction sites www.indiandentalacademy.com
  352. 352. • By Ortho Organizers • Nitanium Total Control Archwire • Superelastic bendable Nickel Titanium archwire • Accepts 1st, 2nd and 3rd order bends permanently • Low friction wire. www.indiandentalacademy.com
  353. 353. • By introducing variable TTR within same archwire. • This takes the form of graded force delivery within the same aligning archwire • The heat treatment of selected sections of the archwire by means of different electric current delivered by electric pliers modify the values of the deactivation forces by varying the amount of austenite present in the alloy. www.indiandentalacademy.com
  354. 354. • A Graded Thermodynamic Wire • After heating the anterior segment for 60 minutes, the linear plateau of the deactivation force dropped to 80 g in a 3-point bending test at room temperature. • Similar manufacturing procedures have been perfected to produce wires such as Bioforce Sentalloy (GAC) that are able to deliver selective forces according to the needs of the individual dental arch segments www.indiandentalacademy.com
  355. 355. BioForce (GAC) offers 80 grams of force for anteriors and up to 320 grams for molars www.indiandentalacademy.com
  356. 356. Speed system –developed by H.G. Hanson. Two Types of Archwires are used in Speed System: -“Speed” super cable archwires- Superelastic NiTi coaxial wire – 7 stranded - “Speed” D archwires- for full 3-D control while sliding. www.indiandentalacademy.com
  357. 357. Appearance of Titanium alloys is not esthetic ,several methods of surface hardening as well as several coatings have been developed. Implanting Nitrogen on surface of NiTi alloys by Ion implantation process – NITRIDING. www.indiandentalacademy.com