Nickel titanium in orthodontics /certified fixed orthodontic courses by Indian dental academy


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Nickel titanium in orthodontics /certified fixed orthodontic courses by Indian dental academy

  1. 1. Nickel Titanium in Orthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Ni Ti alloy was discovered in early 1960s by William F. Buehler, a research metallurgist at the Naval Ordnance Laboratory in Silver springs, Maryland. key discovery occurred in 1962, when a binary alloy composed of equi-atomic nickel and titanium was found to exhibit a shape recovery effect when heated after being mechanically deformed.
  3. 3. Although other reversible phase change materials were known at the time, the Ni-Ti alloys showed a large recoverable strain value when compared to other binary, ternary or quaternary shape memory alloy systems. Rumour has it that William Buehler, who was working with high nickel-bearing alloys for gas turbine components, left a small ingot of Ni-Ti alloy made in a vacuum melt furnace on a desk in direct sunlight.
  4. 4. When Buehler and his colleagues came back from lunch, they noticed the ingot’s shape had changed The physical performance of the Ni-Ti alloy made it a landmark discovery, and the range of commercially viable applications that have been found for the materials is proof of the importance of the nickel-titanium shape memory alloys. Buehler’s preliminary results led to development of the first Ni Ti orthodontic alloy 55% nickel and 45% titanium by pioneers such as Andreasen and his colleagues in 1972.
  5. 5. The Unitek Corporation licensed the patent [1974] and offered a stabilized martensitic alloy (M-NiTi) that does not exhibit any shape memory effect (SME) under the name, Nitinol. Nitinol – Ni Ti Naval ordnance laboratory. It is a stabilized form of the alloy in which work hardening has abolished the phase transformation
  6. 6. This alloy has low elastic modulus and high range The nickel-titanium wires contain approximately equiatomic proportions of nickel and titanium, and are based upon the intermetallic com-pound NiTi (sometimes written as TiNi). Examination of the binary phase diagram reveals that some deviation from stoichiometry is possible for NiTi.
  7. 7.
  8. 8. BASIC CONCEPTS ABOUT NICKEL TITANIUM ALLOYS 1. ACTIVE :- A term that is used to describe an alloy that is capable of undergoing its anticipated phase transformation. 2. PASSIVE :- An alloy that is incapable of undergoing its anticipated phase transformation because extensive plastic deformation has suppressed the transition.
  9. 9. AUSTENITE :High temperature phase of Nickel titanium alloys is called Austenite . Like many ferrous alloys this austenite can transform to Martensite. It has got Body centered cubic (BCC) structure. It is the stronger, higher temperature phase present in NiTi. MARTENSITIC TRASFORMATION :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 got distorted monoclinic, triclinic or HCP structure More deformable, lower temperature phase present in NiTi.
  10. 10. TWINNING :- In certain metals that crystallize in Hexagonal closed pack (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
  11. 11. The resulting structure is caused by a reversible Bain transformation [a rearrangement of atoms in the new phase], which is responsible for the alloy’s “Shape Memory” and Superelasticity, properties that derive from the twinning-detwinning mechanism.
  12. 12. When these alloys are subjected to higher temperature. ⇓ DETWINNING OCCURS ⇓ Alloy reverts to its original shape. (SHAPE MEMORY EFFECT).
  13. 13. Phase transformation terminologies Shape Memory: The ability of certain alloys to return to a predetermined shape upon heating via a phase transformation. Af Temperature: The temperature at which a shape memory alloy ( SMA ) finishes transforming to austenite upon heating. Ap Temperature: The temperature at which the SMA is about 50% transformed to Austenite upon heating.
  14. 14. As Temperature: The temperature at which the SMA starts transforming to Austenite upon heating. Mf Temperature: The temperature at which a SMA finishes transforming to Martensite upon cooling. Mp Temperature: The temperature, at which a SMA is about 50% transformed to Martensite upon cooling.
  15. 15. Ms Temperature: The temperature at which a SMA starts transforming to Martensite upon cooling. Hysteresis: The temperature difference between a phase transformation upon heating and cooling. In NiTi alloys, it is generally measured as the difference between Ap and Mp.
  16. 16.
  17. 17. Af temprature : Most important marker. To exploit super elasticity to its fullest potential, the working temperature of orthodontic appliances should be greater than Af temperature.
  18. 18. Phase Transformation: The change from one alloy phase to another with a change in temperature, pressure, stress, chemistry, and/or time. R-phase: A phase intermediate between Martensite and Austenite that can form in NiTi alloys under certain conditions.
  19. 19. Thermoelastic Martensitic Transformation : A diffusionless, thermally reversible phase transformation characterized by a crystal lattice distortion.
  20. 20. 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. Md: It is the highest temperature at which martensite formation can be induced by stress.
  21. 21. Typical Loading And Unloading Behavior Of Superelastic NiTi. Part of the unusual nature of a superelastic material like A-NITI is that its unloading curve differs from its loading curve (i.e.,the reversibility has an energy loss associated with it [hysteresis]).
  22. 22. Stress strain diagram of alloy with superelastic behaviour
  23. 23. This means the force that it delivers is not the same as the force applied to activate it.
  24. 24.
  25. 25. The different loading and unloading curves produce the even more remarkable effect that the force delivered by an ANITI wire can be changed during clinical use merely by releasing and retying it . Activation (to 80 degrees) and reactivation (to 40 degrees) curves for A-NiTi wire.
  26. 26. Superelastic compounds generally present a high stiffness in the initial segment of the slope of the stress-strain graph when the deflection of the wire is still minimum. The initial activation force required for autenitic NiTi can be 3 times greater than the force required to deflect a classic work hardened martensitic wire (nitinol).
  27. 27.
  28. 28. Stainless steel Nickel Titanium
  29. 29. INFLUENCE OF TREATMENT :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 b’ coz of their high elasticity
  30. 30. Hysteresis There is a difference in the transformation temperatures upon heating from martensite to austenite and cooling from austenite to martensite, resulting in a delay or “lag” in the transformation. This difference known as the transformation temperature hysteresis, is generally defined as the difference between the temperatures at which the material is 50% transformed to austenite upon heating and 50% transformed to martensite upon cooling.
  31. 31. For NiTi Alloys, the difference between Mp and Ap is 25-50°C. Thus Nitinol transformations exhibit thermal hysteresis, Ms ≠ Af and Mf ≠ As.
  32. 32.
  33. 33. In addition to the hysteresis, the overall span of the transformation may be important. Typical values for the overall transformation temperature span are about 4070°C. Both the hysteresis and the overall transformation temperature span are slightly different for different NiTi alloys. Further, alloying can greatly affect the transformation hysteresis. Copper additions have shown to reduce the hysteresis to about 10 to 15°C and Niobium additions can expand the hysteresis over 100°C. ( Santaro AJO 2001)
  34. 34. Austenite and Martensite have different crystal structure and mechanical properties the most notable mechanical properties of Nitinol wires i.e superelasticity and shape memory are result of reversible nature of Martensitic transformation
  35. 35. Martensitic transformations do not occur at a precise temperature but rather within a range known as temperature transition range(TTR). Range for most binary NiTi alloys → 40° - 60° C. Transformation from Austenite to Martensite can occur by. → Lowering the temperature. → Applying stress (Stress induced Martensite) SIM.
  36. 36. Specific TTR is a function of :→ 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 that temperature – Alloy is Austentic (Rigid). TTR below that temperature – Alloys is Martensitic (Superelastic)
  37. 37. EFFECTS OF ADDITIONS AND IMPURITIES ON TTR :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). For thermally activated purposes most common third metals are Cu and Co because. → Reduce the hysteresis → Bring TTR close to body temperature.
  38. 38. 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
  39. 39. Shape Memory is a Combination of Thermoelasticity and Pseudoelasticity
  40. 40. CLASSIFICATION OF NITI COMPOUNDS: I. Based on Transformation Temperature Ranges ( Waters,1992) Group 1: Alloys with TTRs between room temperature and body temperature [Active Martensite]. Group 2: Alloys with TTR below room temperature [Austenite active] Group 3: Alloys with TTR close to body temperature, “which by virtue of the shape memory effect spring back to their original shape when activated by body heat”.
  41. 41. Kusy ( 1991) classified NiTi into : Martensitic-stabilized alloys - do not possess shape memory or super elasticity, because the processing of the wire creates a stable martensitic structure. These are the non superelastic wire alloys such as originally developed Nitinol.
  42. 42. 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. The clinician can observe this thermoelastic shape memory if a deformed archwire segment is warmed in the hands. These are the shapememory wire alloys such as Neo Sentalloy and Copper Ni-Ti.
  43. 43. Austenitic-active alloys - undergo a stressinduced martensitic (SIM) transformation when activated. These alloys display superelastic behavior , which is the mechanical analogue of the thermoelastic shape-memory effect (SME). 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, such as Nitinol SE.
  44. 44. Nickel Titanium Wires CONVENTIONAL NITINOL - Original alloy - 55% Nickel, 45% Titanium ratio of elements. To modify mechanical properties and transition temp. 1.6% Cobalt was added to it
  45. 45. CRYSTAL STRUCTURE: -      Stabilized Martensitic form. -    No application of phase transition effects. The family of Stabilized Martensitic alloys now commercially available are referred to as M – NiTi.
  46. 46. PROPERTIES 1. Springback and Flexibility Most advantageous properties of Good Springback and Flexibility. Low force per unit of deactivation – stiffness. Nitinol are that is low Nitinol wires have greater springback and larger recoverable energy than Stainless Steel or β-Ti when activated to same extent. High spring back is useful in circumstances that require large deflections but low forces. Delivers 1/5th – 1/6th force per unit of deactivation
  47. 47. 2. Spring Rate / Load Deflection Rate: Load deflection rate of Stainless Steel is twice that of Nitinol. 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
  48. 48. 3. Formability : Nitinol has poor formability. Therefore best suited for preadjusted systems. -Bending also adversely effects springback property of this wire. -Bending of loops and stops in nitinol is not recommended. - Any 1st, 2nd and 3rd order bends have to be over prescribed to obtain desired permanent bend.
  49. 49. Cinch backs distal to molar tubes 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.
  50. 50. 4. Shape Memory: Andreasen and Morrow described the “shape memory” phenomenon as capability of wire to return to a previously manufactured shape when it is heated through TTR. Ironically the first 50 : 50 composition of Ni and Ti was shape memory alloy (SMA) in composition only. Nitinol alloy is passive. SME had been suppressed by cold working the wire during drawing to more than 8 – 10%.
  51. 51. 5. Joinability: Not joinable Since hooks cannot be bent or attached to Nitinol, crimpable hooks and stops are recommended for use. 6. Friction: 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 β-Ti, in 0.018 inch slot. In 0.022 inch slot – NiTi and β-Ti wires demonstrated similar levels of friction. Although NiTi has greater surface roughness Beta –Ti has greater frictional resistance
  52. 52. CLINICAL APPLICATIONS: Levelling and Aligning: Nitinol wire is much more difficult to deform during handling and seating into bracket slots is easier than Stainless Steel arch wires. - Reduces loops formerly needed to level dentition. - Can be used for longer periods of time without changing. -
  53. 53. Torque can be controlled early in treatment because successive arch wires fit with precision and case. The deactivation force released by superelastic NiTi for torque control is definitely lower than that released by an equivalent rectangular stainless steel wire, but the property is due more to the intrinsic elastic properties of NiTi compounds than to the presence of a phase transformation. - Rectangular Nitinol inserted early in Rx – accomplishes simultaneous leveling, torquing and correction of rotations.
  54. 54. Bite opening using RCS. (Reverse Curve of Spee)
  55. 55. ADVANTAGES : Fewer arch wire changes. Less chair side time. Less patient discomfort. Reduction in time to accomplish rotations.
  56. 56. LIMITATIONS: Poor formability. Poor joinability. 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. Such stability is often best maintained by using stiffer Stainless Steel wires tailored to the desired finished occlusion. Tendency for dentoalveolar expansion. Expensive.
  57. 57. Conventional Nitinol is available as Nitinol classic Unitek corporation. - Titanal Lancer pacific. Orthonol Rocky mountain orthodontics.
  58. 58. PSEUDOELASTIC NITINOL: 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. SUPERELASTICITY: Manifested by very large reversible strains and a non elastic stress strain or force deflection curve.
  59. 59. 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
  60. 60. MECHANISM OF SUPERELASTICITY: Stress Induced Martensitic Transformation : (SIM) Unique force deflection curve for A-NiTi occurs because of phase transition in grain structure from Austenite to Martensite, in response not to temperature change but applied force. 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.
  61. 61. It is possible for these materials as their TTR is close to room temperature. Md of A-NiTi group is above mouth temperature allowing formation of SIM at oral temperature.
  62. 62. 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
  63. 63. To exploit superelasticity to its fullest potential the working temperature of orthodontic appliances should be greater than the A f temperature. •    It is the differential between Af temperature and mouth temperature that determines the force generated by NiTi alloys. Af can be controlled over wide range by affecting composition, thermomechanical treatment and manufacturing process of alloy
  64. 64. A superelastic material will not be superelastic at all temperatures, but will exhibit good superelastic properties in a temperature window extending from the Active Af temperature upto a temperature which is about 50°C above active Af. A material with an Active Af of about 15°C will exhibit good superelasticity upto about 65 °C which means that the material will exhibit good superelasticity at both room temperature and body temperature
  65. 65. CHINESE NI TI 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.
  66. 66. Stiffness of Chinese NiTi is 36% that of Nitinol wire.   Temperature dependent effects are clinically insignificant. Chinese  NiTi  deformation  is  not  particularly  time  dependent  unlike  nitinol  wire,  will  not  continue  to  deform  a  significant  amount  in  mouth  between  adjustments. The initial activation force required for austenitic NiTi can be 3 times greater than the force required to deflect a classic work hardened martensitic wire (Nitinol).
  67. 67. JAPANESE NITI 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, not by temperature change and is called stress induced Martensitic transformation (SIM). Provides light continuous force for physiologic tooth movement
  68. 68. Japanese NiTi is marketed as Sentalloy. The relationship between the temperature and time of the heat treatment of the Japanese NiTi alloy wire was studied to optimize the superelastic properties of the alloy. When the heat application was raised to 500° C, the force level indicating the super-elastic property could be reduced.
  69. 69. Other Super Elastic NiTi wires 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
  70. 70. ADVANTAGES:  Constant force over wide range of deflection. Low stiffness. High springback. More effective in initial tooth alignment. Less patient discomfort.
  71. 71. LIMITATIONS OF SUPERELASTIC NiTi:   Cannot be soldered or welded. Poor formability. Tendency for dentoalveolar expansion. “Travels” around the arch. Expensive.
  72. 72. Thermoelastic nitinol 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.
  73. 73. CHARACTERISTICS OF AN IDEAL THERMODYNAMIC NITINOL WIRE: 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.
  74. 74. 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.
  75. 75. 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.
  76. 76. COPPER NiTi Invented by Dr. Rohit Sachdeva & Suchio Miyazaki . 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.
  77. 77. Chromium : to compensate for the above mentioned unwanted effect 0.5% chromium is added to return TTR close to oral temperature
  78. 78. TYPES OF CU-NITI: 1. Type I Af 15°C. 2. Type II Af 27°C 3. Type III Af 35°C 4. Type IV Af 40°C
  79. 79.
  80. 80.
  81. 81.
  82. 82. Chill Spray Facilitates adjustments or fitting of Ni Ti orthodontic archwires, springs,appliances, etc. Ideal for Niti Memory Expanders and Rotators such as the Tandem Loop Arndt Memory Expander and Arndt Memory Rotator. Chills to -620º F/-520 ºC.... puts Niti into its soft martensitic state
  83. 83. 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. Martensitic alloy has a greater working range than austenite, and it may therefore prove advantageous during the process of alignment and leveling.
  84. 84. The ability to vary transition temperatures in martensitic wires of identical dimensions, allows the clinician to apply appropriate levels of physiological force during alignment, whilst maintaining archwire size. 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
  85. 85. ADVANTAGES OF Cu-NiTi OVER OTHER NiTi Alloys: 1.     Cu – NiTi generates more constant force over long activation spans. 2. More resistant to permanent deformation. 3.  Exhibits better springback properties. 4. Exhibits smaller drop in unloading forces (reduced hysteresis). Provides precise TTRs at 4 different levels – Enables Clinician to select archwires on a case specific
  86. 86. Bioforce Sentalloy – A Graded Thermodynamic Wire The heat treatment of selected sections of the archwire by means of different electric current delivered by electric pliers modified the values of the deactivation forces by varying the amount of austenite present in the alloy. 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.
  87. 87. 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 BioForce (GAC) offers 80 grams of force for anteriors and up to 320 grams for molars
  88. 88. NITROGEN COATED ARCHWIRES: Implanting Nitrogen on surface of NiTi alloys by Ion implantation process – NITRIDING. Advantages: -    Make Titanium more esthetically pleasing giving it gold like aspect. -      Hardens surface. -      Reduces friction. -      Reduces Nickel release into mouth. e.g : Bioforce Ionguard - 3µm Nitrogen coating.
  89. 89. The IONGUARD process actually alters the wire’s surface to provide a dramatically reduced coefficient of friction for sliding mechanics that are better than the same size stainless steel wire and half the friction of competitive NiTi wire. It also seals the occlusal surface of the wire to eliminate breakage and reduce nickel leaching. While the IONGUARD process alters the surface of the wire, none of the wire’s unique properties is changed.
  90. 90. Nitinol Total Control .A new Orthodontic alloy. TODD A. THAYER, KARL FOX,ERIC MEYER ( JCO1999) developed a new pseudo-superelastic nickel titanium,alloy, Nitinol Total Control, Accepts specific 1st-, 2nd-, and 3rd-order bends while maintaining its desirable superelastic properties.
  91. 91. Combines the ability of superelastic nickel titanium to deliver light, continuous forces over a desired treatment range with the bend ability required to account for variations in tooth morphology, archform, and bracket prescriptions. Frictional and bending tests verify that the force levels produced by them are within accepted ranges for optimal tooth movement. Furthermore,wire properties are not temperaturedependent.
  92. 92. Because of relatively low stiffness, it should not be used for space closure. It can avoid the need to change archwires, , int he following situations: Repositioning due to improper bracket placement • Repositioning brackets to maintain torque control •
  93. 93. Placement of extrusion, intrusion, or utilityarches •Functional finishing with detailing bends thataddress variations in tooth morphology and interarch occlusal relationships • Filling the bracket slot with controlled, lightforce (torque without shearing the bracket) Reduces archwire inventory without compromising treatment mechanics. Lower forces are generally associated with less patient discomfort. In addition, by reducing the number of archwire changes required, allows the clinician to treat more patients effectively and efficiently.
  94. 94.
  95. 95. NiTi wire bending pliers. In 1988, Miura, Mogi, and Ohura demonstrated the use of electrical-resistance heat treatment to introduce permanent bends in their nickel titanium wires. The technique requires special pliers attached to an electric power supply. Although the authors claimed that the superelastic force of the wire was not affected by the treatment, heating the wire does alter the crystalline structure of the nickel titanium lattice .
  96. 96. Masel offers two “V” Notch Stop pliers that place precise “V” bends in NiTi wire. The newly designed Extraoral “V” Notch Stop Plier #649 forms a precise 1-mm “V” stop that prevents wire from disengaging from the buccal tube. Bends round wire from 0.012 to 0.020 inches, and rectangular wire up to 0.017 x 0.022 inches.
  97. 97. The Intraoral “V” Notch Stop Plier makes “V” stops right in the mouth with one squeeze. It bends round wire up to 0.016 inches and rectangular wire up to 0.016 x 0.022 inches.
  98. 98. HU-FRIEDY’S Hammerhead NiTi Tie Back Plier Reduce a multi-step process down to one, simple squeeze — no heat required Bends NiTi wire intraorally with no heat treating Designed to tie back NiTi distal to the buccal tube, gabel bends, omega loops
  99. 99. Bendistal Pliers Allow orthodontists to NiTi wires intraorally using a V-bend technique that corrects many challenging orthodontic problems with singlesqueeze adjustments. The pliers’ tiny tips fit between brackets to allow placement of intraoral activating bends on tied archwires without breaking the wire or the brackets.
  100. 100. The pliers are available in a set of two, featuring a long and thin design to reach behind the molar tube for easier cinch-back purposes and wire activations in the four mouth quadrants.
  101. 101.
  102. 102.
  103. 103.
  104. 104. Recycling & Sterilization of Nickel Titanium Archwires Recycling of nitinol wires is often practiced because of their favorable physical properties and the high cost of the wire. The ability to recycle these archwire relies on effective sterilization of the wire prior to re-use without resulting in deterioration of clinical properties.
  105. 105. For effective sterilization, steam autoclaving (ideally at 134ºC, 32 psi for 3 minutes) is the method recommended. For instruments unable to withstand autoclaving, an effective cold disinfection solution such as 2% glutaraldehyde is an alternative.
  106. 106. Mayhew and Kusy (1988) and Buckthal and Kusy(1986) have demonstrated no appreciable loss in properties of nitinol wires after as many as three cycles of various forms of heat sterilization or chemical disinfection . In a recent in vitro investigation on the effects of a simulated oral environment on 0.016” nickel titanium wires, Harris et al(1988) noted a significant decrease in yield strength of these wires over a period of four months.
  107. 107. The testing procedure involved a static environment in which thermal changes were not taken into account and in which the dynamic changes in forces, such as those of mastication and occlusion, were nonexistent.
  108. 108. Burstone et al (1985) and Miura et al (1986) noted that temperatures greater than 60ºC increased the susceptibility of these austenitic nickel titanium wires to plastic deformation and decreased their springback.
  109. 109. Corrosion Susceptibility Corrosion in wire alloys becomes a factor in the quality of the wire performance in Orthodontics. Corrosion phenomena are increased by internal stresses in the metal appliances, by the inhomogeneous structure of the alloy, and by different metals coming into contact.
  110. 110. When the in vivo and in vitro corrosion behaviour of stainless steel, Elgiloy, nitinol and TMA wires were compared, It was found that the stainless steel, Elgiloy and TMA exhibited no appreciable corrosion damage, but the pitting due to corrosion was observed on the surface of nitinol.( Clinard , JDR 1981)
  111. 111. A study by Kim and Johnson(1999) determined if there is a significant difference in the corrosive potential of stainless steel, nickel titanium, nitride-coated nickel titanium, epoxy-coated nickel titanium, and titanium orthodontic wires. SEM photographs revealed that some nickel titanium and stainless steel wires were susceptible to pitting and localized corrosion. The nitrides coating did not affect the corrosion of the alloy, but epoxy coating decreased corrosion. Titanium wires and epoxy-coated nickel titanium wires exhibited the least corrosive potential.
  112. 112. Study by Eliades et al (2000) evaluating the structure and morphological condition of retrieved NiTi orthodontic arch wires reported that intra-oral exposure of NiTi wires alters the topography and structure of the alloy surface through surface attack in the form of pitting or crevice corrosion or formation of integuments. NiTi wires were coated by intra-orally formed proteinaceous integuments that masked the alloy surface topography to an extent dependent on the individual patient’s oral environmental conditions and the intra-oral exposure period.
  113. 113. Clinical Performance Evans et al (1998) clinically evaluated three commonly used orthodontic tooth aligning arch wires: 0.016 x 0.022 inch active martensitic medium force nickel titanium, 0.016 x 0.022 inch graded force active martensitic nickel titanium , and 0.015 inch multistrand stainless steel. It was a prospective randomized clinical trial Heat activated nickel titanium arch wires failed to demonstrate a better performance than the cheaper multistrand stainless steel wires in this randomized clinical trial.
  114. 114. The failure to demonstrate in vivo superiority at the clinical level may be due to the confounding effects of large variations in individual metabolic response. Alternatively, it may be that in routine clinical practice NiTi-type wires are not sufficiently deformed to allow their full superelastic properties to come in to play during initial alignment.
  115. 115. According to data, under conditions of minimum crowding there is no special reason to use a superelastic alloy wire rather than an established multistranded stainless steel wire, because the range of force delivered by the multistranded stainless steel is considered acceptable. Superelastic NiTi may represent the elective choice when moderate crowding is present and when arch form and torque control are required in the initial stages of treatment because an equivalent rectangular multistranded stainless steel wire presents rather higher stiffness and is subject to permanent deformation.
  116. 116. NiTi Coil Springs Compression & tension springs made of Ni Ti have been recommendeda) Minimum of permanent deformation. b) More constant force during unloading. Closed coil springs – used for space closure. Open coil springs- Mainly for opening space to unravel the teeth for distalization of molars.
  117. 117. The superelastic coil springs were designed and manufactured to produce a specific force throughout the working range of the spring. Like the adjustable force springs, our superelastic coil springs will not take a permanent set. They return to their original length after normal deflection.
  118. 118. Coil Springs With Eyelets Adjustable force and superelastic closed coil springs are available with eyelets. These stainless steel eyelets attach to each end of adjustable force or superelastic closing (closed coil) springs. This allows to easily engage a bracket hook, sliding hook, buccal tube hook and/or posted arch wire hooks
  119. 119. Place one eyelet over the distal hook and gripping the leading edge of the front eyelet with pliers, pull gently forward to engage your anterior hook.
  120. 120. A study was designed by Heinz et al ( AJO 1999) to determine whether relatively constant forces can be delivered and whether the force magnitudes approach the manufacturer’s targeted force values. Heavy, medium, and light springs were activated 15 mm at temperatures that ranged from 15°C to 60°C. The forces were measured during deactivation with a specially constructed force transducer temperature chamber.
  121. 121. Relatively constant forces can be achieved with an over-activation procedure that allows relaxation to the desired activation. The light springs delivered forces that were near the targeted force; no difference was found between the heavy and medium springs in the constant force range. The force magnitudes varied markedly depending on mouth temperature.
  122. 122. Angolkar, RS Nanda (AJO1992) designed a in vitro study to determine the force degradation of closed coil springs made of stainless steel (SS), cobalt-chromium-nickel (Co-Cr-Ni) and nickeltitanium (Niti) alloys, when they were extended to generate an initial force value in the range of 150 to 160 gm. The specimens were divided into two groups. Group I included SS, Co-Cr-Ni, and two nickeltitanium spring types (Niti 1 and Niti 2), 0.010 ´ 0.030 inch with an initial length of 12 mm.
  123. 123. Group ll was comprised of SS, Co-Cr-Ni, and Ni Ti 3 0.010 ´ 0.036-inch springs, with an initial length of 6 mm. A universal testing machine was used to measure force. Initial force was recorded, and then the springs were extended to the respective distances at 4 hours, 24 hours, 3 days, 7 days, 14 days, 21 days, and 28 days resulting in a total of eight time periods. Between the time intervals, all springs were extended to the same initial extension on specially designed racks and stored in a salivary substitute at 37° C.
  124. 124. All springs showed a force loss over time. Of the total, the major force loss for most springs was found to occur in the first 24 hours. The SS and Co-Cr-Ni springs showed relatively higher force decay in group I (0.010 ´ 0.030 inch) compared with Niti 1 and Niti 2. The Niti 3 springs of group II (0.010 ´ 0.036 inch) showed higher force degradation than the SS and Co-Cr-Ni springs of this group.
  125. 125. The least force decay was found in the Niti 1 springs. In general, the total force loss after 28 days was in the range of 8% to 20% for all springs tested. This was considered to be relatively less compared with force loss shown by latex elastics and synthetic elastic modules as reported in the literature.
  126. 126. Jebby Jacob, K.Sadashiva Shetty (JIOS 2002) conducted a study to evaluate the force characteristics of NiTi open & closed coil springs of different length, diameter, lumen size to determine the effect of static simulated oral environment on spring properties . Results showedIncrease in size of lumen : decreased force. Increasing wire diameter : increases force. Increasing open coil spring length : range of superelaticity increased significantly.
  127. 127. Closed coil springs with shorter length & smaller diameter showed good super elastic range. Spring properties showed very minor changes over a period of 4 weeks in static stimulated oral enviornment.
  128. 128. Nattrass (EJO1998) conducted a study on 9mm closed coil spring & found that increase in temprature increased the force level. In same study elastomeric chains were also tested & it was found that they were effected both by temprature & oral environment. Increase in temprature & exposure to soft drink & turmeric solution lead to a more force loss in elastomeric chains.
  129. 129. Han et al (Angle 1993) conducted a study of Ni Ti closed coil springs, Stainless steel springs,& polyurethane elastics in a simulated oral environment for 4 weeks. Results showed degradation of physical properties of stainless steel springs & elastics, but Ni Ti remained relatively stable.
  130. 130. In a in vivo study by Sonis AL ( JCO 1994) Ni Ti closed coil springs produced nearly twice as rapid a rate of tooth movement as conventional elastic at same force level. Miura et al ( 1988) compared mechanical properties of Japanese Ni Ti & stainless steel coil springs in both closed & open types.
  131. 131. Japanese Ni Ti coil springs exhibited superior spring back, super elastic properties. Most important characteristic of Ni Ti coil spring was the ability to exert a very long range of constant ,light & continuous force.
  132. 132. Ni Ti Palatal expander Conventional rapid palatal expanders are uncomfortable, require patient cooperation, and rely on labor-intensive laboratory production. They are inefficient because of the intermittent nature of their force application. Also, they are often soldered to maxillary first molars with pre-existing mesiolingual rotations that the devices are unable to correct. These rotations can distort the appliances into ineffective shapes, and until the rotations are corrected, much of the potential expansion time can be wasted.
  133. 133. To overcome the limitations of conventional expansion appliances, William Arndt ( JCO 1993) developed a tandem-loop, nickel titanium, temperature-activated palatal expander with the ability to produce light, continuous pressure on the midpalatal suture while simultaneously uprighting, rotating, and distalizing the maxillary first molars. The action of the appliance is a consequence of nickel titanium's shape memory and transition temperature effects. Nickel titanium can be processed into a set shape to which it constantly tends to return after deformation
  134. 134.
  135. 135. In addition, it can be alloyed to produce a metal with a specific transition temperature. At temperatures below the transition temperature, the interatomic forces weaken, making the metal much more flexible. Above the transition temperature, the interatomic forces bind the atoms tighter and the metal stiffens.
  136. 136. The nickel titanium expander has a transition temperature of 94°F. When it is chilled before insertion, it becomes flexible and can easily be bent to facilitate placement . As the mouth begins to warm the appliance, the metal stiffens, the shape memory is restored, and the expander begins to exert a light, continuous force on the teeth and the midpalatal suture .
  137. 137. Nickel titanium expanders come in eight different intermolar widths, ranging from 26mm to 47mm, that generate forces of 180-300g. The 26-32mm sizes have softer wires that produce lower force levels for younger patients. The clinician determines the appropriate size by measuring the amount of expansion needed, then adding 3mm for overcorrection.
  138. 138. Freeze-gel packs, provided in the expander kits, can be placed around the expander assembly while the band cement is being prepared. This will cool the appliance enough to allow easy insertion into the lingual sheaths. The expander should be handled by the molar attachments during placement to avoid warming the nickel titanium.
  139. 139. When the appliance begins to stiffen in the mouth, it may cause some discomfort at first. The patient can alleviate this by sipping a cold liquid, which will temporarily make the nickel titanium slightly more flexible. Many of my patients have delighted in showing this effect to their friends.
  140. 140. Maurice Corbett (JCO 1997) Described a modification called the Nickel palatal expander 2, that delivers a uniform, slow continuous force for maxillary expansion, molar distalization and rotation. Puneet Batra,Ritu Duggal, Hari Prakash (JIOS 2003): studied the efficacy of nitinol expander in cleft and non cleft patients and they concluded that it would be effective in both type of patients requiring transverse expansion of the maxilla.
  141. 141. Donohue V, Marshman, WinchesterL EJO 2004 compared maxillary expansion using either a quadhelix appliance or a nickel titanium expander in 28 patients. There was no significant difference in the efficacy or rate of expansion between the two appliances. The quad helix however appeared to exert a more controlled rate of expansion.
  142. 142. Molar distalization Superelastic NiTi wire: Locatelli et al (1992) used a 100 gm NeoSentalloy wire (superelastic Nickel-titanium wire) with shape memory for molar distalization . Crimp stops just distal to first premolar bracket are placed 5 – 7 mm distal to anterior opening of molar tube and hooks between lateral incisors and canines. Excess wire is deflected gingivally into buccal fold. As wire returns to original shape, it exerts 100 gm distal force against molars.
  143. 143.
  144. 144. Super elastic nickel titanium wires have been found as effective as other means in producing distal movement of the maxillary first molars. When the distalization is carried out before the second molars have erupted, it can reliably produce 1-2mm of space.
  145. 145. The concept of using coil springs for distalization was introduced by Miura (1988) who used 100 gms superelastic coils. Gianelly ( AJO1991) used Japanese NiTi coil springs exerting 100 gms of force to move maxillary molars distally.
  146. 146. Movement achieved is 1-1.5 mm per month. NiTi molar distalizing springs are also a part of appliances like Jones jig, Distal jet etc.
  147. 147. Erverdi et al ( BJO 1997) compared Ni Ti coil springs & repelling magnets as 2 methods of intra oral molar distalizers for a period of 3 months. Although upper molar distalization was achieved with ease in both techniques, Ni Ti coil springs were found to be more effective in terms of movement achieved.
  148. 148. Neet Separating Springs The Neet Separating Springs are manufactured from Nickel Titanium. These innovative separators provide light continous forces that will separate stubborn molars while maintaining patient comfort. Inserting the separator into any contact is easy and will provide generous space for banding. The clinician no longer has to struggle trying to "saw" through the contact with an elastomeric separator.
  149. 149.
  150. 150. Nickel allergy Nickel is the most common metal to cause contact dermatitis in orthodontics. Nickel-titanium alloys may have nickel content in excess of 50 per cent and can thus potentially release enough nickel in the oral environment to elicit manifestations of an allergic reaction. Nickel elicits contact dermatitis, which is a Type IV delayed hypersensitivity immune response.
  151. 151. It has been shown that the level of nickel in saliva and serum increases significantly after the insertion of fixed orthodontic appliances. ( Agaoglu,2001). It has been suggested that a threshold concentration of approximately 30 ppm of nickel may be sufficient to elicit a cytotoxic response. (Bour ,1994).
  152. 152. Barrett et al ( AJO,1993) reported that the release rate for nickel from stainless steel or nickel titanium wires are not significantly different Possible risks associated with nickel toxicity : Risk of nephrotoxicity, Carcinogenicity, risk of immune changes & alveolar bone loss.
  153. 153. : Flexile nickel-titanium wires release increased amounts of nickel and are thought to induct nickel sensitivity; there may be up to 20 per cent conversion rate. (Jia ,1999) These high nickel content wires should be avoided in nickel sensitive patients. Alternatives include twistflex stainless steel, fibre-reinforced composite archwires. Wires such as TMA, pure titanium, and gold-plated wires may also be used without risk.
  154. 154. Altered nickel-titanium archwires also exist and include plastic/resin-coated nickeltitanium archwires.
  155. 155. Ion-implanted nickel-titanium archwires have their surface bombarded with nitrogen ions, which forms an amorphous surface layer, conferring corrosion resistance and displacing nickel atoms. Manufacturers claim that these altered nickeltitanium archwires exhibit less corrosion than stainless steel or non-coated nickel-titanium wires, which results in a reduction of the release of nickel and decrease the risk of an allergic response.
  156. 156. Diagnosis of nickel allergy It is important to make a correct diagnosis of nickel allergy, symptoms of which may occur either within or remote to the oral environment. The following patient history would suggest a diagnosis of nickel allergy: previous allergic response after wearing earrings or a metal watchstrap;
  157. 157. appearance of allergy symptoms shortly after the initial insertion of orthodontic components containing nickel; confined extra-oral rash adjacent to headgear studs.
  158. 158. Intra oral aging For brackets & archwires, issue of interest is the in vivo alteration of material due to the expected long period of performance, with possible effects on mechanical properties. Main focus of the alterations induced on orthodontic wires is on Ni Ti archwires because stainless steel & Co-Cr-Ni archwires are usually replaced in an escalating stepwise process as treatment progresses.
  159. 159. Generally it has been shown that intra oral exposure of Ni Ti wires alter the topography & structure of the alloy surface through surface attack in form of pitting, crevice corrosion, or formation of integuments. Retrieved Ni Ti wires demonstrated signs of corrosion after more than 2 months of in vivo placement. Signs of pitting corrosion have been detected in retrieved wires after at least 6months exposure.
  160. 160. Adsorption of intraoral integuments might greatly reduce the coefficient of friction ( salivary protein adsorption, plaque accumulation) . Alternatively calcified integuments might increase surface resistance & resistance to shear forces. Also intraorally exposed Ni Ti wires do break more frequently than expected : Variations in intra oral temprature might affect their properties & fracture resistance.
  161. 161. Also the force delivery of superelastic coil springs can be substantially affected by small changes in temprature.
  162. 162. CONCLUSION Properties of Nickel Titanium alloy have made them preferred material in Orthodontic treatment. However their use should be done keeping all treatment goals in mind.
  163. 163. References Denny JP, Valiathan Ashima, Surendra Shetty V : Wires in orthodontics. JIOS : 1993;24:6065. Kapila Sunil, Sachdeva Rohit: Mechanical properties and clinical application of orthodontic wires. AJODO 1989; 96:100-109. Miura, F.; Mogi, M.; and Ohura, Y.: Japanese NiTi alloy wire:Use of the direct electric resistance heat treatment method, Eur.J. Orthod. 10:187-191, 1988.
  164. 164. Theodore Eliades, Christopher Bourauel : Intra oral aging of Orthodontic materials: the picture we miss & its clinical relevance. AJODO 2005,127 ; 403-412. Brantley WA, Eliades T.: Orthodontic materials-scientific and clinical aspects. New York: Thieme;2001. Page – 80 - 103 Andreasen GF, Brady PR: A use hypothesis for 55-nitinol wires for orthodontics. Angle Orthod 1972; 42: 172-177.
  165. 165. Burstone CJ, Qin B, Morton JY : Chinese NiTi wire – a new orthodontic alloy. AJO 1985; 87: 445-452. Miura F, Mogi M, Ohura Y, Hamanaka H.: The super-elastic property of the Japanese NiTi alloy wire for use in orthodontics. Am J Orthod Dentofac Orthop 1986; 90: 1-10. TODD A. THAYER, KARL FOX,ERIC MEYER: Nitinol Total Control .A new Orthodontic alloy.JCO1999; 27 (10), 563-567.
  166. 166. Andreasen GF, Hilleman TB: An evaluation of 55 cobalt substituted nitinol wire for use in orthodontics. JADA 1971; 82: 1373-1375. Andreasen GF, Morrow RE.: Laboratory and clinical analyses of nitinol wire. AJO 1978; 73:142-151. JIOS interviews Dr.Rohit Sachdeva on diagnosis, anterior esthetic finishing and newer wires. JIOS 1996; 27: 74-80.
  167. 167. Waters NE: Orthodontic products update. Superelastic nickel titanium wires. BJO; 1992;19:319-322. Kusy RP : Nitinol alloys: so, who’s on first? AJO 1991 ; 100: 25A-26A. Hurst CL, Duncanson MG Jr, Nanda RS, Angolkar PV.: An evaluation of the shapememory phenomenon of nickel-titanium orthodontic wires. AJO 1990; 98: 72-76.
  168. 168. Santoro M, Nicolay OF, Cangialosi TJ.: Pseudoelasticity and thermoelasticity of nickel titanium alloys: A clinically oriented review. Part I: Temperature transitional ranges. AJODO 2001; 119:587-593. Segner D, Ibe D.: Properties of superelastic wires and their relevance to orthodontic treatment. EJO 1995; 17:395-402 Angolkar, RS Nanda : Force degradation of closed coil spring. AJODO 1992, 102 (2); 127133.
  169. 169. West AE, Jones Ml, Newcombe RG. : Multiflex versus superelastic: a randomized clinical trial of the tooth aligning ability of initial archwires. AJODO 1995; 108:464-471. O’Brien KD, Lewis D, Shaw W, Combe E: A clinical trial of aligning archwires. EJO 1990; 12:380-384. Rucker KB, Kusy RP: Elastic flexural properties of multistranded stainless steel verses conventional nickel titanium archwires. Angle Orthod 2002; 72:302309.
  170. 170. Agaoglu G, Arun T, Izagu B, Yarat A: Nickel and chromium levels in the saliva and serum of patients with fixed orthodontic appliances. Angle Orthod 2001; 71: 375-79. Bass JK, Fine H, Cisneros GJ : Nickel hypersensitivity in the orthodontic patient. AJODO 1993; 103: 280-5.
  171. 171. Barrett RD, Bishara SE, Quinn JK : Biodegradation of orthodontic appliances: part I, biodegradation of nickel and chromium in vitro. AJODO; 1993;103:8-14. Krishna Prasad K, Valiathan A: Nickel Toxicity. Biomedicine. 1993 ;13(1) :1-7. Rahilly G, Price N: Nickel allergy and orthodontics. J Orthod 2003;30:171-174
  172. 172. Kim H, Johnson J: Corrosion of stainless steel, nickel-titanium, coated nickel-titanium, and titanium orthodontic wire. Angle Orthod 1999; 69: 39-44. Eliades T, Eliades G, Athanasiou AE, Bradley TG: Surface characterization of retrieved NiTi orthodontic arch wires. EJO; 22: 317-326. Buckthal, J.E. Mayhew, M.J. Kusy, R.P. Crawford J: Survey of sterilization and disinfection procedures. JCO 1986;20:759765.
  173. 173. Buckthal, J.E. and Kusy, R.P: Effects of cold disinfectants on the mechanical properties and the surface topography of nickel-titanium archwires. AJO 1988; 94: 117-112. Kapila S, Reichhold GW, Anderson RS, WatanakeL G: Effects of clinical recycling on mechanical properties of nickel titanium alloy wires. AJODO 1991; 100:428-435. Puneet Batra,Ritu Duggal, Hari Prakash: Efficacy of Nitinol Expander in cleft and non cleft patients, JIOS 2003;36:130-34.
  174. 174. Arndt WV: Nickel Titanium Palatal expander. JCO 1993, 27; 129-137. Donohue V, Marshman, WinchesterL: Clinical comparison of the quadhelix appliance and the NiTi palatal expander: A preliminary prospective investigation. EJO 2004;26;411-20. Locatelli R, Bednar J, Gianelly A : Molar distalization with super elastic NiTi wire. JCO 1992,26, 5;277-279.
  175. 175. Gianelly A , Bednar J, Dietz V.S.: Japanese Ni Ti coils used to move molars distally. AJODO 1991,99;564-566. Jebby Jacob, H.S. Divakar Karanth, K.Sadashiva Shetty : Force characteristics of NiTi open & closed coil springs in a simulated oral environment. JIOS,2002;35;76 -88. Han , Quick DC: Ni Ti spring properties in a simulated oral environment. Angle Orthod 1993,63: 67-71.
  176. 176. Thank you For more details please visit