Titanium and its alloy /certified fixed orthodontic courses by Indian dental academy


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Titanium and its alloy /certified fixed orthodontic courses by Indian dental academy

  1. 1. Titanium and its alloy used in orthodontics INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. INTRODUCTION • Titanium was discovered by GREGOR • ( England 1790 ) • Bothe et al implanted titanium in lab. animals • (1940) • A light weight metal • Atomic weight – 47.9 • Non magnetic www.indiandentalacademy.com
  3. 3. • SUPERIOR CORROSION RESISTANCE • A thin complex film Tio2 gives Ti affinity, a self adherence that may cause friction. • • • Titanium is not esthetic Laser aided depositions Implantation of nitrogen ( IONGUARD ) www.indiandentalacademy.com
  4. 4. • Alpha phase – Hexagonal unit cells • At room temperature • Beta phase – Body centered cubic cells • At temperatures above 1620F or 882C www.indiandentalacademy.com
  5. 5.  Alpha type – ALPHA TITANIUM (A.J. Wilcock)  Beta type – Beta II or ORMCO‘ TMA Titanium-Niobium wires TiMolium Beta III wires. Alloy that have both phases alpha and beta such as Ti-5Al-2.5Fe or the widely used Ti-6Al-4V are difficult to draw and bend but can be machined easily to make implants and expansion screws. www.indiandentalacademy.com
  6. 6. Different forms used in orthodontics Titanium Implants brackets Nonnickel alloys Beta type – Beta II or ORMCO‘ TMA TitaniumNiobium wires TiMolium Beta III wires. Alpha Ti wires www.indiandentalacademy.com Nickel titanium Orthodontic arch wires auxiliaries
  7. 7. Titanium as implant material www.indiandentalacademy.com
  8. 8. • Implant materials. • requirements • The material must be nontoxic and biocompatible, possess excellent mechanical properties, and provide resistance to stress, strain, and corrosion. • Commonly used materials can be divided into 3 categories: • biotolerant (stainless steel, chromium-cobalt alloy), • bioinert (titanium, carbon), and • bioactive (hydroxylapatite, ceramic oxidized aluminum). www.indiandentalacademy.com
  9. 9. • Commercially pure titanium is the material most often used in implantology. It consists of 99.5% titanium, and the remaining 0.5% is other elements, such as carbon, oxygen, nitrogen, and hydrogen. • . www.indiandentalacademy.com
  10. 10. • Because of titanium‘s characteristics (no allergic and immunological reactions and no neoplasm formation), it is considered an ideal material and is widely used. • Its mechanical characteristics, moreover, are well suited to implant requirements: it is very lightweight, and it has excellent resistance to traction and breaking, enabling it to withstand both masticatory loads and the stresses of orthodontic forces. www.indiandentalacademy.com
  11. 11. • Bone grows along the titanium oxide surface, which is formed after contact with air or tissue fluid. • Biocompatibility is attributed to the stable oxide layer primarily TiO2 that spontaneously forms when Ti is exposed to oxygen. • This reaction converts the base metal into a ceramic material that electrically and chemically passivates the implant www.indiandentalacademy.com
  12. 12. • This biomaterial surface interacts with water, ions and numerous biomolecules after implantation the nature of these reactions will determine how cells and tissue respond to the implant. • Manufactures immerse these implants in acidic solution to enhance the formation of passivating oxide film.(2-6nm) • However, pure titanium has less fatigue strength than titanium alloys. A titanium alloy—titanium-6 aluminum-4 vanadium—is used to overcome this disadvantage. www.indiandentalacademy.com
  13. 13. Surface design of Ti implants • Machined finished • Smooth surface (Branemark System <0.2µm Nobel Biocare) • Poor interaction with • 0.5-1µm tissue • Poor mechanical retention • Allow epithelial downward growth deep per-iimplant www.indiandentalacademy.com pockets
  14. 14. • Implants with different surface characteristics continue to be developed in attempts to increase the degree and rate of Osseo integration to allow early and immediate loading and to promote integration in anatomic sites with poor/insufficient bone quality for conventional implants. • uncoated implants might be preferred to prevent excessive Osseo integration and complicated later surgical removal. www.indiandentalacademy.com
  15. 15. • Ti implants with intermediate surface have higher bone –implant contact. Furthermore increase in roughness can lead to increase plaque accumulation, peri-implantitis, and failure. www.indiandentalacademy.com
  16. 16. Methods for altering surface texture David et al DCNA,2006 • Ablative ( removal of material from the surface) • Grit blasting • Acid etching • Grit blasting followed by acid etching • Additive (deposit material on implant surface) • Plasma spraying ;TPS ( one of the roughest dental implant surface) • coating Ti implants with hydroxy apatite– surface chemistry dramatically changes from Ti02 to a bone like ceramic with potential for chemically bonding to bone www.indiandentalacademy.com
  17. 17. Bone implant interface interaction Osseo integration Osseo coalescence Direct structural and functional connection between implant and load carrying implant Refer specifically to chemical integration of implants in bone tissue by surface reactive materials. Largely refers to physical integration or mechanical fixation of an implant into bone Calcium phosphate, bioactive glasses. Exhibit resistance to both shear and tension loads Good resistance to shear load but poor resistance to tension www.indiandentalacademy.com
  18. 18. i m p l a n t t i s s u e www.indiandentalacademy.com
  19. 19. • Osseo integrated implants can be used as a firm osseous anchor for orthodontic treatment because they are able to resist continuous horizontal forces of at least 5 N (about 510 gm) during a period of several months. • The implant must have a certain surface area available for Osseo integration to support the forces of orthodontic traction. If the length is decreased, the diameter must be increased. www.indiandentalacademy.com
  20. 20. • However practical consideration for the orthodontist is whether some critical degree of implant stability is required for functional efficiency? • There are substantial differences between conventional implants and temporary skeletal anchorage devices(TSADs) • conventional prosthodontic implants, generally loaded after Osseo integration, are intended to be permanent, whereas implants for orthodontic anchorage are usually loaded long before osseointegration is achieved and are intended to be removed relatively soon. www.indiandentalacademy.com
  21. 21. Difference in nature of force • Conventional implants are subject to high intermittent forces of mastication, but forces acting on orthodontic anchors are light and continuous. • The direction of loading and the size of the implants also vary between the 2 systems www.indiandentalacademy.com
  22. 22. • Implant stability depends not only on Osseo integration, but also on the mechanical stability achieved at placement. • Osseous contact with an implant as low as 5% was shown to resist orthodontic loads. Ohmae et al reported that an integration index of 25% would provide reliable anchorage. www.indiandentalacademy.com
  23. 23. • Complete Osseo integration would clearly be undesirable for a TSAD, and it is apparent that implants can be functional, even with a very low integration index. • Clinical stability sufficient for orthodontic anchorage can be achieved even with levels of Osseo integration as low as 5%. Under 25% of Osseo integration, screws remain easy to remove • Osseo integration rates appeared lower around miniimplants, ranging from 10% to 58%, in contrast to the reported Osseo integration index of 75.5% around orthodontically loaded palatal implants in humans. • For the clinician, a decrease in implant diameter will both increase the number of potential insertion sites and facilitate the surgical removal www.indiandentalacademy.com
  24. 24. Titanium Brackets • Of all the different materials tested so far, stainless steel brackets are preferred for their low frictional force values • However, concerns have been expressed in the literature about the nickel content in the stainless steel causing hypersensitivity and corrosion in the oral environment. In addition, there are instances where MRI or CT imaging may have been distorted because of the stainless steel alloys. www.indiandentalacademy.com
  25. 25. • To overcome these difficulties, pure titanium brackets have been made available. • These brackets have excellent corrosion resistance and are biocompatible, • As a consequence of its passivity over a broad pH range, its high breakdown potential, and its low current density to corrosion, Ti exhibits the minimum tissue response of all commonly used metals. • Only when the passive layer is broken down does galling and fretting occur, problems common to all Ti alloys; ultimately frictional and biocompatible breakdown occur. www.indiandentalacademy.com
  26. 26. • The currently available titanium bracket products consists of two products a commercially pure titanium and a titanium alloy ti-6al-4v • Base-pure titanium • Wing- titanium alloy --more prone to galvanic corrosion • Base + wing –pure titanium—low hardness than stainless steel wear of slot—reduce transfer of torque and plastic deformation of the wing— require surface treatment www.indiandentalacademy.com
  27. 27. • Recently, Deguchi et al (J Dent Res 1996) reported on the feasibility of manufacturing titanium brackets by metal injection molding (MIM). • The brackets tested exhibited mechanical properties and bond strengths equivalent to or better than that of stainless steel brackets, while providing better corrosion resistance and absence of nickel leaching. www.indiandentalacademy.com
  28. 28. • Kusy et al (AJODO 1998) evaluated the static and kinetic frictional coefficients of commercially pure titanium brackets in the passive configuration in the dry and wet states against stainless steel, nickel-titanium, and betatitanium archwires. • For comparison, stainless steel brackets were evaluated under identical conditions. • Titanium brackets were grayer in color and rougher in texture than the stainless steel brackets. www.indiandentalacademy.com
  29. 29. Scanning electron micrographs show overall morphologies of as-received Ti bracket versus SS www.indiandentalacademy.com bracket
  30. 30. • Remarkably, the static and kinetic frictional coefficients of the couples formed by titanium and stainless steel brackets were comparable. • When evaluated against stainless steel and nickel-titanium archwires in the dry state at 34°C, the static coefficient averaged .12 and .20, respectively, independent of bracket alloy. • When evaluated against stainless steel and nickel-titanium wires in the wet state at 34°C using human saliva, the static coefficient averaged .15 and .20, respectively, independent of bracket alloy. www.indiandentalacademy.com
  31. 31. • Kusy and O‘Grady (AJODO 2000) tested the hypothesis that in the active configuration, when brackets are subjected to higher levels of stress, the thin passive layer of Ti brackets will break down causing the archwire–bracket couple to gall and seize. www.indiandentalacademy.com
  32. 32. • Contrary to theoretical reasoning, however, the testing showed that this passive layer of Ti brackets does not break down in the active configuration. • Furthermore, the sliding properties of Ti brackets remained comparable to SS brackets and compared favorably with other biocompatible brackets such as monocrystalline and polycrystalline ceramic brackets. • The authors concluded that Ti brackets are a suitable substitute for SS brackets in sliding mechanics. www.indiandentalacademy.com
  33. 33. • Kapur, Sinha and Nanda (AJODO 1999) compared the level of frictional resistance generated between titanium (Rimatitan, Dentaurum) and stainless steel brackets (Dentaurum and GAC). • Both 0.018 and 0.022 inch slot size edgewise brackets were tested with different sized rectangular stainless steel wires in a specially designed apparatus. • The titanium brackets showed lower static and kinetic frictional force as the wire size increased, whereas stainless steel brackets showed higher static and kinetic frictional force as the wire size increased. www.indiandentalacademy.com
  34. 34. • A possible explanation could be offered by the chemical structure and mechanical properties of titanium and titanium-based alloys. • Titanium brackets have a different chemical structure or hardness compared with the stainless steel brackets. In addition, frictional forces are due largely to the atomic and molecular forces of attraction at the small contact areas between materials. • For example, friction is greater between two surfaces of the same material than two surfaces of different materials. www.indiandentalacademy.com
  35. 35. • The desirable mechanical properties of titanium for use in orthodontics are low rigidity, super elasticity, and shape memory effect. • These qualities allow early engagement of a full size wire during treatment, it allows the bracket to elastically deform and creates a reactive working environment for three-dimensional control of orthodontic tooth movement with rectangular wires. www.indiandentalacademy.com
  36. 36. • Kapur, Sinha and Nanda (AJODO 1999) evaluated the distortion of brackets after the application of torsional forces, and discovered that the titanium brackets showed significantly lower bracket slot widening. • Thus, the titanium brackets demonstrated superior structural stability compared with conventional stainless steel brackets on application of torsional forces www.indiandentalacademy.com
  37. 37. Non-nickel titanium archwires www.indiandentalacademy.com
  38. 38. Properties of archwire required during different stages of treatment www.indiandentalacademy.com
  39. 39. Beta titanium (TMA) wires • Beta titanium was introduced by Dr. CHARLES BURSTONE and JON GOLDBERG in the university of CONNECTICUT ( Early 1980s ) • • • • • Composition Titanium - 73.5% Molybdenum - 11.5% -to stabilize beta phase Zirconium - 6% Tin - 4.5 % www.indiandentalacademy.com
  40. 40. • ADVANTAGES: • • • • • • • Low stiffness Good formability High spring back Weldable Ductile Corrosion resistance www.indiandentalacademy.com
  41. 41. Composition (wt%) Modulus of Elasticity (GPa) Yield Strength (MPa)a Springbackb 17-20% Cr. 8-12% Ni. 0.15% C (max), balance mainly Fe 160-180 1100-1500 0.0060-0.0094 (AR) 0.00650.0099 (HT) Cobalt-chromiumnickel (Elgiloy Blue) 40% Co. 20%Cr. 15% Ni. 15.8% Fe, 7% Mo, 2% Mn, 0.15% C, 0.04% Be 160-190 830-1.000 0.0045-0.0065 (AR) 0.00540.0074 (HT) Beta-titanium (TMA) 77.8% Ti, 11.3% Mo, 6.6 %Zr, 4.3% Sn 62-69 690-970 0.0094-0.011 Nickel-titanium 55% Ni, 45%Ti (approx. and may contain small amounts of Cu or other elements) 34 210-410 0.0058-0.016 Wire Alloy Austenitic steel stainless www.indiandentalacademy.com
  42. 42. Properties of beta titanium wires • The modulus of elasticity of beta titanium is approximately twice that of nitinol and less than one half that of stainless steel. • The forces that are produced are approximately 0.4 that of steel, producing a more gentle delivery of forces with an edgewise wire; for example, an 0.018 by 0.025 inch wire in beta titanium delivers about the same force as an 0.014 by 0.020 inch stain steel wire when activated in a second-order direction www.indiandentalacademy.com
  43. 43. • Its stiffness makes it ideal in applications where less force than steel is required but where lower modulus materials would be inadequate to develop required force magnitudes • Furthermore, it would have the advantage of full bracket engagement and third order or torque control if used in an 0.018 inch slot bracket • Clinical application • Initial tooth alignment • Finishing arches www.indiandentalacademy.com
  44. 44. • Because of the much lower value of elastic modulus, despite lower values for yield strength, the beta-titanium wires have significantly improved values of springback (YS/f), which markedly increase their working range for tooth movement. • The high spring back properties [working range] may offer simplification of the overall design of loops www.indiandentalacademy.com
  45. 45. • A second clinical advantage of the betatitanium wires is excellent formability, which is due to their BCC structure. The addition of molybdenum to the alloy composition stabilizes the high-temperature bcc -phase polymorphic form of titanium at room temperature, rather than the hexagonal closepacked alpha-phase. • However, the titanium alloy cannot be bent over as sharp a radius as stainless steel, so that some care in the selection of pliers and bending procedures is required. www.indiandentalacademy.com
  46. 46. • The many slip systems available for dislocation movement in the bcc crystal structure account for the high ductility of the -titanium wires. The zirconium and zinc in the alloy composition contribute increased strength and hardness, www.indiandentalacademy.com
  47. 47. • The high ductility [ability of the material to withstand permanent deformation without rupture under tensile load] of -Titanium allow it to be formed into arches with tieback loops or segments with complicated loop configuration. • It also offers the possibility of varying force magnitude by a choice of material rather than cross section of the wire. (variable modulus www.indiandentalacademy.com orthodontics)
  48. 48. • Clinical use • K-SIR ARCH WIRE.0.019‘‘/0.025‘‘ www.indiandentalacademy.com
  49. 49. Pendulum appliance – 0.032’’ www.indiandentalacademy.com
  50. 50. • The third clinical advantage of -titanium is that it is the only orthodontic wire alloy possessing true weldability. • The welded joints for stainless steel and Elgiloy Blue appliances require additional mechanical reinforcement with solder. • Detailed optimum settings for welding titanium wires with the capacitance (singlepulse) and transformer (multiple-pulse) welding apparatuses available to the orthodontist have been published www.indiandentalacademy.com
  51. 51. • Springs for alignment or retraction can be directly welded to an arch wire (Only TMA can be welded to TMA; it is not possible to weld stainless steel to TMA • Unlike steel, where too much heat will produce softness in the wire, overheating of titanium could lead to brittleness of an energy-imparting finger spring. www.indiandentalacademy.com
  52. 52. • Welding of TMA wire • • • • • • 5 basic principles; 1. Proper positioning 2. Minimum voltage 3. Small contact area 4. Single short pulse 5. Pressure www.indiandentalacademy.com
  53. 53. Biocompatibility • With increased interest in the biocompatibility of orthodontic materials, another important feature of the Beta-titanium wires is their absence of nickel that is present in the other three major wire alloy types. • The excellent corrosion resistance and biocompatibility of -titanium is due to the presence of a thin, adherent, passivating surface layer www.indiandentalacademy.com of titanium oxide (TiO2).
  54. 54. DISADVANTAGES • High coefficient of friction • Unaesthetic • costly www.indiandentalacademy.com
  55. 55. • Studies indicated( Kusy RP et al AJO 1990, Kapila S et al AJO 1990) that TMA wires have higher coefficients of friction and produce significantly greater frictional resistance to sliding through orthodontic brackets than stainless steel. • As the titanium content of an alloy increases, its surface reactivity increases and the surface chemistry is a major influence on frictional behavior. KUSY RP 1989 • Thus, β-titanium, at 80% titanium, has a higher coefficient of friction than nickel-titanium at 50% titanium, and there is greater frictional resistance to sliding with either than with steel www.indiandentalacademy.com
  56. 56. • Under laboratory conditions, the surface of the titanium wire can become cold-welded to stainless steel brackets, making sliding closure of even small spaces difficult. ―stick-slip‖ phenomena • REMEDY • A recently developed Nitrogen ion implantation technique for beta-titanium (Ormco) has markedly improved the measured values of in vitro sliding friction. • Implantation of nitrogen ions into the surface of this wire causes surface hardening and can decrease frictional force by as much as 70%. www.indiandentalacademy.com
  57. 57. MECHANISM • The ions penetrate the surface of the wire on impact, building up a structure that consists of both the original wire and a layer of tin compounds (TiN and TiO) on the surface and immediate subsurface. This layer is extremely hard and creates a considerable amount of compressive forces in the material at the atomic level • The compressive forces and increased surface hardness improve the fatigue resistance and ductility and reduce the coefficient of friction of the wire. The superficial compressive forces also minimize any detrimental effects of surface flaws www.indiandentalacademy.com
  58. 58. Low-Friction And Coloured TMA Burstone CJ, Farzin-Nia JCO 1995 • Two varieties of TMA— low-friction and colored— were produced by varying the type and thickness of ions. • Low-friction TMA has a light golden hue, and several different wire colors are also being manufactured www.indiandentalacademy.com
  59. 59. • Results of a friction study by Burstone and Farzin-Nia JCO 1995 showed the static coefficient of friction of untreated TMA (.52) to be significantly higher than stainless steel (.19). • However, the static coefficient of friction of treated TMA was significantly reduced (.13). Concerning friction in a wet environment, such as the mouth versus the laboratory bench, wet ion-induced TMA (honeydew color) had slightly lower coefficients than wet stainless steel. • This study concluded that the frictional forces of treated TMA are likely to be less than 40 percent that of stainless steel because of the above-cited differences in frictional force and the fact that TMA is only 40 percent as stiff as stainless steel. • There was no significant difference in the modulus of elasticity or the tensile strength of the treated and untreated TMA wires. www.indiandentalacademy.com
  60. 60. www.indiandentalacademy.com
  61. 61. Clinical Applications of Low-Friction And Coloured TMA • In Early Treatment • extremely useful in the early stages of treatment where the bracket slides along the archwire during initial leveling and rotation of single-tooth discrepancies. These irregularities can be corrected much more efficiently when the frictional force is only 60 percent that of stainless steel. www.indiandentalacademy.com
  62. 62. • With Ceramic Brackets • Another simple extrapolation concerning efficient utilization of Low Friction and Colored TMA is in its incorporation with ceramic brackets without metal slots, where friction can be quite a problem. • When the Low Friction and Colored TMA can be adequately engaged in the bracket, it will likely outperform nickel titanium wires. www.indiandentalacademy.com
  63. 63. • 3.With Mildly Crowded, Bimaxillary Protrusive Four-Bicuspid Extraction Cases • since its flexibility allows for ideal bracket engagement right from the inception of treatment. Once initial leveling and aligning are complete, retraction of the cuspids can begin www.indiandentalacademy.com
  64. 64. precaution • It is at this point that certain treatment concepts should be considered. First, when employing this technique, as with most cuspid retraction, it is advisable to retract the maxillary cuspid before retracting the mandibular cuspid .By doing so, the Class I cuspid relationship is preserved or even established. If the lower is fully retracted before the upper, it is likely to create a Class II relationship, which is difficult to convert. • Second, in maximum anchorage situations, it is advisable to use a Nance palatal button during retraction. Due to the low friction of this wire, it can protract molars if particular caution is not exercised. The Nance button has been efficiently used with this wire with no unfavorable side effects. www.indiandentalacademy.com
  65. 65. ALPHA TITANIUM • The composition of α-titanium include 88.9% titanium, 7.86% Aluminum and 4.05% Vanadium. • The elastic modulus and yield strength at room temperature for α-titanium is approximately 110 GPa and 40 MPa respectively • Certain elements, such as aluminum, carbon, oxygen and nitrogen, stabilize the α-titanium structure. That is, they raise the temperature for transformation to β-titanium www.indiandentalacademy.com
  66. 66. • Hexagonal lattice possesses fewer slip planes making it less ductile than β-titanium. • Alloy is strictly near alpha phase of titanium rather than pure alpha titanium alloy because there is certain amount of beta phase retained in them at room temperature. • The wires are soft enough for initial gentle action on teeth in spite of large wire dimension as also for intraoral activation. • They seem to harden and become brittle with passage of time in the mouth, possibly due to the absorption of hydrogen and formation of titanium hydrides. www.indiandentalacademy.com
  67. 67. • A.J. Wilcock produces combination wires, which are rectangular in the anterior segment to maintain torque while the round posterior segments allow sliding mechanics. Rectangular section wire is also available in preformed arches. • Rectangular wires of sizes of 0.022‖ x 0.018‖ (Ribbon mode) or 0.020 x 0.020‖ (square) for finishing stage www.indiandentalacademy.com are recommended.
  68. 68. TITANIUM-NIOBIUM • Nickel free Titanium alloy • COMPOSITION • Ti - 82% • Mo - 15% ( or) • Nb - 3% Ti - 74% Nb - 13% Zr - 13% www.indiandentalacademy.com
  69. 69. • • • • • • PROPERTIES Easy to bend, formability is less than TMA Stiffness - ¼ of SS Load deflection rate is lower than TMA Yield strength is lower than SS Indicated when lower forces than those exerted by TMA are needed. www.indiandentalacademy.com
  70. 70. • ADVANTAGES; • • • Substitute for SS No leaching of nickel CLINICAL IMPLICATIONS • Finishing wire with multiple bends • Fixed retainers ( Biocompatible ) www.indiandentalacademy.com
  71. 71. TIMOLIUM WIRES • • • • • Improved titanium wires Smooth surface texture Less friction Accelerate treatment time Resistance to breakage www.indiandentalacademy.com
  72. 72. BETA –III WIRES • • • • • • • • Introduced by RAVINDRA NANDA Bendable High force Low deflection rate Co-efficient of friction is more Nickel free titanium wire with memory Ideal for multilooping, cantilever, utility arches First choice of wire for finishing stages where tip & torque corrections fully accomplished during initial stages. www.indiandentalacademy.com
  73. 73. BASIC CONCEPTS ABOUT NICKEL TITANIUM ALLOYS www.indiandentalacademy.com
  74. 74. 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 TRANSFORMATION :Process of phase transformation which is DIFFUSIONLESS, occurring from within and without any chemical change which results in transformation of Austenite (parent phase) to Martensite following rapid cooling. • MARTENSITE has got distorted monoclinic, triclinic or HCP structure More deformable, lower temperature phase present in NiTi. www.indiandentalacademy.com
  75. 75. • The relative concentration of the 2 phases in the alloy will determine the resultant stiffness of the wire and the amount of force delivered www.indiandentalacademy.com
  76. 76. HYSTERESIS 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 www.indiandentalacademy.com Mp.
  77. 77. TWINNING :In certain metals that crystallize in Hexagonal closed pack (HCP) structure, (martensite) 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. • responsible for the alloy‘s ―Shape Memory‖ and Superelasticity, properties that derive from the twinning-detwinning mechanism e.g., :- NiTi alloys are characterized by multiple rather than single twining throughout the metal www.indiandentalacademy.com
  78. 78. www.indiandentalacademy.com
  79. 79. Austenite and Martensite have different crystal structure and mechanical properties the most notable mechanical properties of Nitinol wires i.e. super elasticity and shape memory are result of reversible nature of Martensitic transformation www.indiandentalacademy.com
  80. 80. 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.- Martensitic-active alloys Applying stress (Stress induced Martensite) SIM. -Austenitic-active alloys www.indiandentalacademy.com
  81. 81. 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 . Reduce the hysteresis Bring TTR close to body temperature. www.indiandentalacademy.com
  82. 82. • • • • Kusy ( 1991) classified NiTi alloys into : Martensitic-stabilized alloys Martensitic-active alloys Autenitic-active alloys www.indiandentalacademy.com
  83. 83. • 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. www.indiandentalacademy.com
  84. 84. • 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 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. www.indiandentalacademy.com
  85. 85. Conventional Nitinol is available as - Nitinol classic Unitek corporation. - Titanal Lancer pacific. - Orthonol -Rockymountainorthodontics. www.indiandentalacademy.com
  86. 86. PROPERTIES 1. Springback and Flexibility Most advantageous properties of Nitinol . Nitinol wires have greater springback and larger recoverable energy than Stainless Steel or Ti when activated to same extent. High spring back is useful in circumstances that require large deflections but low forces. . www.indiandentalacademy.com
  87. 87. • 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 • 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. www.indiandentalacademy.com
  88. 88. 2. Spring Rate / Load Deflection Rate: Load deflection rate of Stainless Steel is twice that of Nitinol. Delivers 1/5th – 1/6th force per unit of deactivation 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
  89. 89. Formability : Nitinol has poor formability. Therefore best suited for preadjusted systems. - Joinability: • Not joinable • Since hooks cannot be bent or attached to Nitinol, crimpable hooks and stops are recommended for use www.indiandentalacademy.com
  90. 90. . 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 -Ti, in 0.018 inch slot. • In 0.022 inch slot – NiTi and -Ti wires demonstrated similar levels of friction. • Although NiTi has greater surface roughness Beta – Ti has greater frictional resistance www.indiandentalacademy.com
  91. 91. CLINICAL APPLICATIONS: Leveling 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. www.indiandentalacademy.com
  92. 92. ADVANTAGES : Fewer arch wire changes. Less chair side time. Less patient discomfort. Reduction in time to accomplish rotations. www.indiandentalacademy.com
  93. 93. 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. www.indiandentalacademy.com
  94. 94. Martensitic-active alloys • CHARACTERISTIC FEATURE • employ the thermoelasticity to achieve shape memory; • By lowering the temperature the alloy is transformed into martensite and becomes pliable and easily deformed • 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. (An orthodontic archform ) • The clinician can observe this thermoelastic shape memory if a deformed archwire segment is warmed in the hands. www.indiandentalacademy.com
  95. 95. Active martensite thermodynamic wire • Neo Sentalloy • CO NiTI 37 • CO NiTI 40 www.indiandentalacademy.com
  96. 96. • Orthodontic clinical application requires setting the TTR of these alloys very close to the intraoral temperature or even corresponding to it, so that a greater amount of martensite is constantly available. (Sachdeva,1990) • According to the data available in the literature, most of the commercially available the thermoelastic wires TTRs are set at higher temperatures, from 35°C to 40°C • This type of thermoelastic alloy, however, will be completely austenitic at oral temperature, and the austenite presents a higher modulus of elasticity that results in a greater stiffness of the wire. www.indiandentalacademy.com
  97. 97. advantages • This wire is pliable both intraorally and extraorally and it will accept bends. The forces exerted on the dentoalveolar structures are remarkably low; therefore the alloy is recommended for the treatment of patients with periodontal problems www.indiandentalacademy.com
  98. 98. drawback • The low stiffness of copper NiTi 40°C also presents the mechanical disadvantage of not allowing for complete dental alignment or full control of transverse dimensions. • A second wire with a larger diameter or greater stiffness is usually required. www.indiandentalacademy.com
  99. 99. Active Austenitic Nickel Titanium Alloys • undergo a stress-induced martensitic (SIM) transformation when activated. These alloys display superelastic behavior , which is the mechanical analogue of the thermoelastic shape-memory effect (SME). • Chinese NiTi • Japanese NiTi [Sentalloy] • Copper NiTi 27 C www.indiandentalacademy.com
  100. 100. • The unique force – deflection curve of A-NiTi wire occurs because of a phase transition in grain structure from austenite to martensite, in response not to a temperature change but to applied force • When the austenite is transformed into stress induced Martensite SIM, a horizontal plateau appears as an indicator of the expression of superelastic properties. www.indiandentalacademy.com
  101. 101. • • SIM is unstable In orthodontic clinical applications, SIM forms where the wire is tied to brackets on malalligned teeth so that the wire becomes pliable in deflected areas. A LOCALISED STRESS RELATED SUPERELASTIC PHENOMENON • In those areas the wire will be super elastic until tooth movement occurs. www.indiandentalacademy.com
  102. 102. • 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). www.indiandentalacademy.com
  103. 103. • However, once the SIM is formed, the horizontal plateau appears and the alloy ‗absorbs‘ any additional load stress and releases it in constant amounts during the deactivation phase. • This means that an initial archwire would exert about the same force whether it were deflected a relatively small or a large distance, which is a unique and extremely desirable www.indiandentalacademy.com characteristics
  104. 104. • Actually, the linear region corresponding to the deactivation plateau is lower than the activation plateau and parallel to it. This phenomenon is called mechanical hysteresis. • The main clinical interest of hysteresis is that the force delivered to the periodontal structures is lower than the force necessary to activate the wire. www.indiandentalacademy.com
  105. 105. • The different loading and unloading curves produce the even more remarkable effect that the force delivered by an A-NiTi wire can be changed during clinical use merely by releasing and retying it. • The amount of force exerted by a niti-A wire that had been previously activated to 80 could be considerably increased by untying it from a bracket and then retying again • CUNiTi 27 C wire generates high force 137g/mm (Segner, 1994) and best indicated for patients with average or high pain threshold. Also a small, round wire is preferable for most application www.indiandentalacademy.com
  106. 106. TTR FOR AUTENITIC ACTIVE NiTi ALLOYS • In austenitic alloys, the formation of SIM will guarantee the presence of the superelastic behavior necessary for the release of light and continuous forces. • Therefore, the Af of the alloy should not be set at a temperature considerably below oral temperature or the formation of SIM will not occur. • It would actually be advisable to evaluate alloys on the basis of their stress related TTRs because the application of stress usually raises the Af of the alloy. • According to the data available in the literature, most of the commercially available superelastic wires exhibit stress-related Afs ranging from 22°C to 28°C, www.indiandentalacademy.com
  107. 107. Recent advances in NiTi wires • Bioforce sentalloy • Nitrogen coated archwires • Nitinol Total Control www.indiandentalacademy.com
  108. 108. • Bioforce Sentalloy – (Miura F,EJO-1988) • 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. www.indiandentalacademy.com
  109. 109. • 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 www.indiandentalacademy.com
  110. 110. 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 - 3 m Nitrogen coating. www.indiandentalacademy.com
  111. 111. 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. www.indiandentalacademy.com
  112. 112. 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. www.indiandentalacademy.com
  113. 113. • 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 • ―Residual strain‖ is the amount of permanent deformation that remains in the archwire material after unloading. • In other words, bendability is indicated by increased levels of residual strain. www.indiandentalacademy.com
  114. 114. www.indiandentalacademy.com
  115. 115. 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 temperature dependent. www.indiandentalacademy.com
  116. 116. It can avoid the need to change archwires, , into he following situations: • Repositioning due to improper bracket placement • Repositioning brackets to maintain torque control] • Placement of extrusion, intrusion, or utility arches •Functional finishing with detailing bends that address variations in tooth morphology and interarch occlusal relationships www.indiandentalacademy.com
  117. 117. • 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. • Precaution • Because of relatively low stiffness, it should not be used for space closure. www.indiandentalacademy.com
  118. 118. SELECTION OF NITI WIRES • The rationale for making an educated clinical choice of a NiTi alloy includes two primary considerations • (1) a proper stress-related TTR, corresponding to or slightly below oral temperature and • (2) a low deactivation force released to the dentoalveolar structures to prevent deleterious side effects, such as pain after bone hyalinization and possible root resorption. • the delivery force is strictly correlated to the presence of martensite in the alloy and is therefore dependent on the TTR as well as on the amount of stress induced. www.indiandentalacademy.com
  119. 119. Selection related to severity of crowding • • The amount of loading used to test the superelastic behavior has shown that at least 2 mm of deflection are necessary for the formation of SIM in austenitic wires. A deflection below the 2-mm threshold may translate into a higher force delivery correlated with the constant presence of the stiffer austenitic phase.. www.indiandentalacademy.com
  120. 120. • An optimal performance of austenitic superelastic NiTi wires will be obtained in cases of severe dental crowding, when an accentuated deflection due to the irregular interbracket span will generate SIM in a localized area of the arch, usually the lower incisor area. • Mild crowding does not necessarily require the use of superelastic wires, and a classic small diameter work-hardened alloy or a wellestablished multistranded round stainless steel wire will generally perform as well www.indiandentalacademy.com
  121. 121. Selection related to periodontal status www.indiandentalacademy.com
  122. 122. • In periodontally compromised patients, and some-times in the lower incisor area, it would be advisable to maintain the force level delivered to each tooth below 100 g. • Data available from properly designed experi-ments with 2 mm or more of wire deflection at oral temperature show that the average delivery force of an austenitic superelastic NiTi .016 x .022-in ranges between 200 g and 300 g. • Co NiTi 27 C wire generates high force 137g/mm (Segner, 1994) not preferred and best indicated for patients with average or high pain threshold. Also a small, round wire is preferable for most application www.indiandentalacademy.com
  123. 123. • Instead, 35°C and 40°C Thermo-Active Copper Ni-Ti rectangular, Nitinol SE and Nitinol XL, and Neo Sentalloy F240 wires of similar diameters deliver forces around 100 g • In order to obtain lower forces from austenitic NiTi or multi-braided stainless steel, it is necessary to select smaller diameters and abandon the use of rectangular wires during the alignment phase of treatment www.indiandentalacademy.com
  124. 124. Force level related to torque • True pseudoelastic behavior generated by torquing forces at nominal oral temperature has not been demonstrated, even in copper NiTi alloys and with a considerable increase of the twist. • Only with a lowering of the temperature, with cold rinses for example, can the baseline torque be consistently reduced; in 40°C Thermo-Active Copper Ni-Ti the delivery force can be dropped to 200 g/mm for a less than transient time interval. www.indiandentalacademy.com
  125. 125. • True thermoelastic alloys may therefore be indicated for early torque control during the alignment phase of treat-ment and in periodontally compromised patients. www.indiandentalacademy.com
  126. 126. • Randomized clinical trials, at least those conducted with austenitic NiTi, on the rate of tooth movement and pain experienced, failed to demonstrate a significantly better performance of superelastic wires compared with conventional alloys, such as multistranded stain-less steel wires www.indiandentalacademy.com
  127. 127. Property Stainless Steel Cobalt-Chromium-Titanium Nickel (Elgiloy Blue) (TMA) Nickel-Tita Cost Low Low High High Force delivery High High Intermediate Light Elastic range (springback) Formability Low Low Intermediate High Excellent Excellent Excellent Poor Ease of joining Can be soldered. Welded joint m ust be reinforced with solder. Lower Can be soldered. Welded joints must be reinforced with solder. Lower Only wire alloy that has true weldability Cannot be welded Higher Higher Some Some None Some Archwire-bracket friction Concern about biocompatibility www.indiandentalacademy.com
  128. 128. Corrosion Susceptibility of Titanium alloys Archwires • The use of fluoride-containing rinses and gels might be harmful to titanium devices if the pH of these prophylactic materials is below neutral Thus the corrosion of titanium seems to depend not only on fluoride concentration but also on pH. {Nakagawa J D R 1999} • A recent study by Watanabe{ AJO 2003} reported on the effect of fluoride prophylactic agents on the surfaces of titanium based Orthodontic wires. The βtitanium wires, particularly the TMA wire showed less tarnish resistance to APF agents than did the nickelwww.indiandentalacademy.com titanium alloy wires.
  129. 129. 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. Recycling involves (1) repeated exposure of the wire for several weeks or months to mechanical stresses and elements of the oral environment and (2) sterilization between uses www.indiandentalacademy.com
  130. 130. • 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. www.indiandentalacademy.com
  131. 131. • Mayhew and Kusy;AJO1988 and Buckthal and Kusy AJO1988 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 • the effects of the oral environment on the wire properties are still inconclusive. www.indiandentalacademy.com
  132. 132. 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. www.indiandentalacademy.com
  133. 133. • 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. www.indiandentalacademy.com
  134. 134. • 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. • Also the force delivery of superelastic coil springs can be substantially affected by small changes in temprature www.indiandentalacademy.com
  135. 135. Other uses of Ti alloys in orthodontics • Open and close coil springs (Gain/Close the space) • Molar distalizer • Expansion of arch • Individualized presurgical archforms www.indiandentalacademy.com
  136. 136. Ni Ti Palatal expander William Arndt ( JCO 1993) Nickel titanium expanders come in eight different intermolar widths, ranging from 26mm to 47mm, that generate forces of 180-300g. www.indiandentalacademy.com
  137. 137. Miura et al Jco 1990 Individualized presurgical archforms www.indiandentalacademy.com
  138. 138. conclusion • Titanium is a new orthodontic material with unique properties and an excellent balance of properties suitable for many orthodontic applications • Titanium not only offers an improvement in the properties of presently designed orthodontic appliances with its increased springback, reduced force magnitudes, good ductility, and weldability, but its excellent balance of properties should permit the design of future appliances which deliver superior force systems with simplified configuration www.indiandentalacademy.com
  139. 139. References 1. 2. 3. 4. 5. Irfan Dawoodbhoy, Valiathan Ashima: Implants as anchors in Orthodontics. Journal of Indian Orthodontic Society. 1994; 25(4): 124-127. Gautam P, Valiathan A. Implants for anchorage. Am J Orthod Dentofacial Orthop. 2006 Feb;129(2):174; author reply 174. Lien-Hui Huang, Jeffrey Lynn Shotwell, and Hom-Lay Wang. Dental implants for orthodontic anchorage Am J Orthod Dentofacial Orthop 2005;127:713-22 Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997;31:763-7. Drago CJ. Use of osseointegrated implants in adult orthodontic treatment: a clinical report. J Prosthet Dent www.indiandentalacademy.com 1999;82:504-9.
  140. 140. 6. Gray JB, Smith R. Transitional implants for orthodontic anchorage. J Clin Orthod 2000;34:659-66. 7. Gray JB, Steen ME, King GJ, Clark AE. Studies on the efficacy of implants as orthodontic anchorage. Am J Orthod 1983;83: 311-7. 8. Roberts WE, Helm FR, Marshall KJ, Gongloff RK. Rigid endosseous implants for orthodontic and orthopedic anchorage. Angle Orthod 1989;59:247-56 9. Deguchi T, Takano-Yamamoto T, Kanomi R, Hartsfield JK Jr, Roberts WE, Garetto LP. The use of small titanium screws for orthodontic anchorage. J Dent Res 2003;82:377-81. 10. Chen F, Terada K, Hanada K, Saito I. Anchorage Effect of Osseo integrated vs Nonosseointegrated Palatal Implants. Angle Orthod. 2006 Jul;76(4):660-5. www.indiandentalacademy.com
  141. 141. 11.Oyonarte R, Pilliar RM, Deporter D, Woodside DG. Peri-implant bone response to orthodontic loading: Part 2. Implant surface geometry and its effect on regional bone remodeling. Am J Orthod Dentofacial Orthop. 2005 Aug;128(2):182-9. 12.Oyonarte R, Pilliar RM, Deporter D, Woodside DG. Peri-implant bone response to orthodontic loading: Part 1. A histomorphometric study of the effects of implant surface design. Am J Orthod Dentofacial Orthop. 2005 Aug;128(2):173-81. 13.Chen F, Terada K, Handa K. Anchorage effect of various shape palatal osseointegrated implants: a finite element study. Angle Orthod. 2005 May;75(3):378-85. 14.Robert P. Kusy- Ongoing Innovations in Biomechanics and Materials for the New Millennium Angle Orthod 2000;70:366–376 15.Celenza F, Hochman MN. Absolute anchorage in orthodontics: direct and indirect implant-assisted modalities. J Clin Orthod. 2000 Jul;34(7):397-402 www.indiandentalacademy.com
  142. 142. 16. Lorenzo Favero, Paolo Brollo, and Eriberto Bressan, Orthodontic anchorage with specific fixtures: Related study analysis; (Am J Orthod Dentofacial Orthop 2002;122:84-94) 17. Park HS, Jeong SH, Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2006 Jul;130(1):18-25. 18. Ohashi E, Pecho OE, Moron M, Lagravere MO. Implant vs screw loading protocols in orthodontics. Angle Orthod. 2006 Jul;76(4):721-7. 19. Melsen B. Mini-implants: Where are we? J Clin Orthod. 2005 Sep;39(9):539-47 20. Deguchi T, Ito M, Obata A, Koh Y, Yamagishi T, Oshida Y. Trial production of titanium orthodontic brackets fabricated by metal injection molding (MIM) with sintering. J Dent Res 1996; 75: 1491-6 www.indiandentalacademy.com
  143. 143. 21. Kusy RP, Whitley JQ, Ambrose W. , J. G. Newman. Evaluation of titanium brackets for orthodontic treatment: Part I. The passive configuration. Am J Orthod Dentofacial Orthop 1998;114:558-7 22. Kusy RP, O‘Grady P. Evaluation of titanium brackets for orthodontic treatment: Part I. The passive configuration Am J Orthod Dentofacial Orthop 2000;118:675-84) 23. Kapur R, Sinha P, Nanda RS. Comparison of frictional resistance in titanium and stainless steel brackets. (Am J Orthod Dentofacial Orthop 1999;116:271-4) 24. Denny JP, Valiathan Ashima, Surendra Shetty V : Wires in orthodontics. JIOS : 1993;24:60-65. 25. Kapila Sunil, Sachdeva Rohit: Mechanical properties and clinical application of orthodontic wires. AJODO 1989; 96:100-109. www.indiandentalacademy.com
  144. 144. 26. Miura F, Mogi M, Ohura Y, Hamanaka H.: The superelastic property of the Japanese NiTi alloy wire for use in orthodontics. Am J Orthod Dentofac Orthop 1986; 90: 1-10. 27. Miura, F.; Mogi, M.; and Ohura, Y.: Japanese NiTi alloy wire: Use of the direct electric resistance heat treatment method, Eur.J. Orthod. 1988. 10:187-191, 28. Theodore Eliades, Christopher Bourauel : Intra oral aging of Orthodontic materials: the picture we miss & its clinical relevance. AJODO 2005,127 ; 403-412. 29. Burstone CJ, Qin B, Morton JY : Chinese NiTi wire – a new orthodontic alloy. AJO 1985; 87: 445-452. 30. JIOS interviews Dr.Rohit Sachdeva on diagnosis, anterior esthetic finishing and newer wires. JIOS 1996; 27: 74-80. www.indiandentalacademy.com
  145. 145. 31. Waters NE: Orthodontic products update. Superelastic nickel titanium wires. BJO; 1992;19:319-322. 32. Kusy RP : Nitinol alloys: so, who‘s on first? AJO 1991 ; 100: 25A-26A. 33. Hurst CL, Duncanson MG Jr, Nanda RS, Angolkar PV.: An evaluation of the shape-memory phenomenon of nickeltitanium orthodontic wires. AJO 1990; 98: 72-76. 34. 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. 35. Segner D, Ibe D.: Properties of superelastic wires and their relevance to orthodontic treatment. EJO 1995; 17:395-402 www.indiandentalacademy.com
  146. 146. 36. 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. 37.Rucker KB, Kusy RP: Elastic flexural properties of multistranded stainless steel verses conventional nickel titanium archwires. Angle Orthod 2002; 72:302-309. 38.Barrett RD, Bishara SE, Quinn JK : Biodegradation of orthodontic appliances: part I, biodegradation of nickel and chromium in vitro. AJODO; 1993;103:8-14. 39.Krishna Prasad K, Valiathan A: Nickel Toxicity. Biomedicine. 1993 ;13(1) :1-7. 40.Kim H, Johnson J: Corrosion of stainless steel, nickeltitanium, coated nickel-titanium, and titanium orthodontic wire. Angle Orthod 1999; 69: 39-44. www.indiandentalacademy.com
  147. 147. 41.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. 42.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. 43.Puneet Batra,Ritu Duggal, Hari Prakash: Efficacy of Nitinol Expander in cleft and non cleft patients, JIOS 2003;36:130-34. 44.Arndt WV: Nickel Titanium Palatal expander. JCO 1993, 27; 129-137. 45.Burstone CJ, Farzin-Nia. Production of low-friction and colored TMA by lon implantation. J Clin Orthod 1995; 29:453-461 www.indiandentalacademy.com
  148. 148. 46.Nakagawa M, Matsuya S, Shiraishi T, Ohta M. Effect of fluoride concentration and pH on corrosion Behaviour of Titanium for Dental use. J Dent Res 1999; 78: 1568-1512. 47.Locatelli R, Bednar J, Gianelly A : Molar distalization with super elastic NiTi wire. JCO 1992,26, 5;277-279. 48.Kusy RP, Whitley JQ. Coefficients of friction for archwires in stainless steel and polycrystalline alumina bracket slots. I. The dry state. Am J Orthod Dentofac Orthop 1990; 98 :300-312. 49.Kapila S, Angolkar PV, Duncanson GM et al. Evaluation of friction between edgewise stainless steel brackets and orthodontic wires of four alloys. Am J Orthod Dentofac Orthop 1990; 98: 117-126. 50.Angolokar PV, Kapila S, Duncanson MG, et al. Evaluation of friction between ceramic brackets and orthodontic wires of four alloys. Am J Orthod Dentofac Orthop 1990; 98: 499-506. www.indiandentalacademy.com
  149. 149. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com