Titanium /certified fixed orthodontic courses by Indian dental academy


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Titanium /certified fixed orthodontic courses by Indian dental academy

  1. 1. Titanium and its alloys INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Introduction • The unparalleled tissue tolerance and biocompatibility of titanium have made it the leading metal for dental implants. • Titanium and titanium-based alloys have the greatest corrosion resistance of any of the known metals • Although stainless steel is highly corrosion-resistant, it has been found to be attacked by artificial saliva which has dissolved nickel and chromium from the alloy. • Most alloys used in orthodontics contain potentially toxic nickel, chromium, and cobalt. www.indiandentalacademy.com
  3. 3. • Nickel has produced more reported allergic reactions than all the other metals combined. Women are believed to be especially susceptible, because of sensitization from nickel leaching from irregularities in the surface coatings of costume jewelry. • According to Hamula et al in JCO 1996, the problems of nickel sensitivity, corrosion, and inadequate retention of SS brackets has been solved with the introduction of new, pure titanium bracket (Rematitan). • Its one-piece construction requires no brazing layer, and thus it is solder- and nickel-free. www.indiandentalacademy.com
  4. 4. • A computer-aided laser (CAL) cutting process generates micro- and macro-undercuts, making it possible to design an “ideal” adhesive pattern for each tooth. • Sernetz et al in 1997 evaluated the qualities and advantages of titanium brackets. • The biocompatibility of these brackets is maintained by preserving the integrated base made of a single piece of pure titanium. • Lesser stiffness of titanium compared to stainless steel allows torque to be fully expressed without deforming the bracket wings. www.indiandentalacademy.com
  5. 5. • Titanium brackets are made from a pure, medicalgrade titanium that has advantages in miniaturization over stainless steel because of its greater strength (made possible by special cold-working processes) and its lower elastic modulus. • Single-piece construction allows the lowest possible bracket height, since clinical in-and-out depths remain the same. • This makes the miniaturized appliance even less conspicuous. • A low bracket profile can be helpful in assessing lip balance during treatment, especially in cases of lip insufficiency and protrusion. www.indiandentalacademy.com
  6. 6. • Many patients prefer the appearance of the silver-gray titanium brackets over shiny, reflective stainless steel. • Titanium also has low thermal conductivity, and thus alleviates the sensitivity to extreme temperature changes often experienced by patients wearing metal appliances. • It imparts none of the metallic taste of stainless steel brackets. • Such brackets may provide an alternative to SS brackets for those communities who are concerned with nickel toxicity, since their tribologic properties are quite comparable to the currently accepted standard, SS. www.indiandentalacademy.com
  7. 7. Composition • A commercially pure (cp) medical grade 4 Ti (designation DIN 17851-German standards) is used as the basis for the manufacture of titanium brackets. • Composition is Titanium - over 99% Iron - < 0.30% Oxygen - < 0.35% Nitrogen - < 0.35% Carbon - 0.05% Hydrogen - 0.06% www.indiandentalacademy.com
  8. 8. Surface characteristics • The surface texture of the Ti brackets is much rougher than that of the SS brackets. • According to Harzer et al in Angle 2001, the surface structure and the color of titanium and steel brackets are very different. • The surface of the rolled wings of titanium brackets is very rough, and the biocompatibility of titanium supports plaque adherence. • These are the reasons for significantly more plaque accumulation and a more marked change of color with titanium brackets. • The slots of titanium brackets are not as rough as the wings because the slots are milled and not rolled. www.indiandentalacademy.com
  9. 9. • According to energy dispersive x-ray microanalysis (EDX), the titanium brackets appeared to be comprised solely of Ti. • Ti is found to exist mostly in the oxidized form, TiO2. • Titanium is prone to fretting and galling, despite its excellent resistance to corrosion at physiological temperatures and its high specific strength. • Nonetheless it has proven biocompatibility in medical and dental applications. www.indiandentalacademy.com
  10. 10. Titanium and sliding mechanics • Some clinicians have found titanium brackets to be superior to stainless steel brackets in sliding mechanics. An oxidation treatment of the titanium bracket, in addition to creating chemical and mechanical passivity, hardens the bracket slot. • The smooth, Teflon-like surface of titanium is due to a thin layer of titanium oxide and prevents direct contact between the metallic atoms on the surfaces of the wire and the bracket, thus reducing interatomic adhesion and friction. • Early testing of friction between stainless steel wires and titanium brackets has shown a nearly 30% reduction in friction compared to stainless steel brackets www.indiandentalacademy.com
  11. 11. • Kusy and whitley in AJO 1998 found that in the dry state, both the SS brackets and Ti brackets are comparable for SS wires. • Ti brackets compare favorably against the conventional SS bracket for all couples evaluated with SS, Ni-Ti, and beta -Ti archwires.The Ti bracket displays an adhesive effect for all couples when tested in the wet versus the dry state at 34°C in the pasive configuration. • In the active configuration, kusy and Grady in AJO 2000 found that as the force or angulation between the bracket and archwire increases, the passive oxide layer on titanium (Ti) brackets does not break down • The passive oxide layers on Ti brackets provide a good medium for sliding mechanics. www.indiandentalacademy.com
  12. 12. • Against SS archwires, the static and kinetic coefficients of friction of SS and Ti brackets are comparable in both the passive and active configuration, regardless of testing under dry or wet conditions. • By using Ti brackets, biocompatible archwire–bracket couples may be chosen that have more favorable sliding characteristics than other biocompatible ceramic brackets. Thus, Ti brackets are a suitable substitute for SS brackets in sliding mechanics • Titanium brackets present superior structural dimensional stability as a result of favorable material properties when compared to SS brackets. www.indiandentalacademy.com
  13. 13. • Kapur and sinha in AJO 1999 found that Titanium brackets have different frictional characteristics when compared with stainless steel brackets using similar wires. Stainless steel brackets showed higher static and kinetic frictional force values as the wire size increased. However, for the titanium brackets the frictional force decreased as the wire size increased. • The desirable mechanical properties of titanium allow early engagement of a full size wire during treatment, it allows the bracket to elastically deform for threedimensional control of tooth movement with rectangular wires. www.indiandentalacademy.com
  14. 14. Titanium and corrosion • Toumelin-Chemla et al tested the corrosive properties of fluoride-containing toothpastes on titanium in vitro and found substantial corrosion processes in the fluoridated acidic media. • Reclaru and Meyer suggested that fluoride ions are the only ions acting on the protective layer of titanium and causing localized pitting and crevice corrosion. • The aggressiveness of the environment at pH 3 is such that it is no longer possible to maintain passivation zones, and titanium will, therefore, undergo a continuous degradation. www.indiandentalacademy.com
  15. 15. conclusion • In essence, titanium brackets are a suitable alternative to conventional metal brackets in many aspects. Their biocompatibility, absence of nickel, good corrosion resistance, superior dimensional stability, comparable frictional characteristics and decreased conspicuousness along with low thermal conductivity make these brackets a suitable alternative to conventional S.S brackets specially in nickel sensitive patients. www.indiandentalacademy.com
  16. 16. Titanium implants • Implants are an excellent alternative to traditional orthodontic anchorage methodologies, and they are a necessity when dental elements lack quantity or quality, when extraoral devices are impractical, or when noncompliance during treatment is likely. • The growing demand for orthodontic treatment methods that require minimal compliance, particularly by adults, and the importance placed on esthetic considerations by all patients have led to the expansion of implant technology. www.indiandentalacademy.com
  17. 17. Indications • Implants have been used to extrude impacted teeth, to retract anterior teeth, for space closure and to correct dental position in preprosthetic orthodontic treatment. In addition, they have been applied in the treatment of Class III malocclusion, anterior open bite, and dental alignment, and as an aid to the retention of teeth with insufficient bone support. • These osseointegrated implants are usually used as anchorage to assist orthodontic tooth movement. Many different orthodontic osseointegrated anchorage systems (OOAS) have been developed. www.indiandentalacademy.com
  18. 18. • Implants can be used in the following conditions: 1. as a source of anchorage alone ( indirect anchorage) a. orthopedic anchorage 1. for maxillary expansion 2. headgear like effects (singer et al in angle 2000 used implants placed in the zygomatic buttress of the maxilla to protract it in class III pts with maxillary retrognathism) b. dental anchorage 1. space closure 2. intrusion of teeth a. of anteriors b. of posteriors 3. for distalization www.indiandentalacademy.com 2. in conjunction with prosthetic rehabilitation (direct
  19. 19. Implant designs Modified implant designs meant specifically for orthodontic usage are 1. 2. 3. 4. 5. Onplants Mini implants skeletal anchorage system The micro implants The Aarhus implants www.indiandentalacademy.com
  20. 20. Materials used • The material must be nontoxic and biocompatible, have favorable mechanical properties, and be able to resist stress and strain with proven effectiveness in clinical and experimental studies. • The materials commonly used for implants can be divided into 3 categories: – Biotolerant - stainless steel, chromium-cobalt alloy. – Bioinert - titanium, carbon and – Bioactive - vetroceramic apatite hydroxide, ceramic oxidized aluminum. www.indiandentalacademy.com
  21. 21. Advantages of titanium • 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. • titanium is considered an excellent material • Osseointegration is defined as a direct structural and functional connection between ordered living bone and the surface of a load carrying implant • no allergic or immunological reactions • Mechanical characteristics -very light weight, excellent resistance to traction www.indiandentalacademy.com and breaking.
  22. 22. Fixture size and shape • Implanted fixtures must meet the demands of primary stability and effectively withstand forces • The maximum load that can be applied to the fixture is proportional to the quantity of osseointegration, making it dependent on the surface area of osseoimplant-tissue contact. Because implants are usually cylindrical, the parameters that contribute to the contact surface are length, diameter, and shape. • Traditional dimensions 3-4 mm in diameter, 6-10 mm in length • The shape most used is cylindrical or cylindrical-conical (flared), with a smooth or threaded surface www.indiandentalacademy.com
  23. 23. Onplants • Introduced by Block anf Hoffman in 1995 • It is in the form of a circular disc 810 mm in diameter with provision for abutments • Made of Cp titanium and the undersurface of the disc is coated with hydroxyapatite • Placed by a process called tunneling in the posterior region of the palate www.indiandentalacademy.com
  24. 24. Skeletal Anchorage System • Reported by Umemori and Sugawara et al in AJO 1999 • for correction of skeletal open bites by controlling the height of the posterior dentoalveolar region • Titanium miniplates might be used as a source of stationary anchorage • L-shaped miniplate is used fixed by bone screws with the long arm exposed to the oral cavity • can provide a significant amount of intrusion of the molars • advantages: no preparation is necessary, stable rigid anchorage is ensured, and tooth movement is www.indiandentalacademy.com possible shortly after implantation.
  25. 25. Orthosystem implants • Orthosystem developed for anchorage reinforcement of posterior teeth- reported by Wehrbein et al in AJO 1999 • pure titanium 1-piece device with an endosseous implant body, a transmucosal neck section, and an abutment • implant body has a selftapping thread with a sandblasted, large grit, acidetched surface • inserted in the midsagittal palate for anchorage reinforcement of posterior teeth provided a means for reducing patient compliance, reducing treatment time, minimal anchor loss www.indiandentalacademy.com
  26. 26. Mini implants: • These were introduced by Ryuzo Kanomi in 1997. the implant is a modified surgical screw and is placed interdentally under local anaesthesia. For intrusion and retraction Micro implants The Aarhus implant system: • This was introduced by Birte Melsen. Micro implants: • These are small diameter implants that can be placed interdentally either buccally or palatally. www.indiandentalacademy.com Mini implants
  27. 27. Anatomical sites • Sites normally used are -alveolar bone in an agenesic or extraction site, the palate in the median or paramedian area, the retroincisive and retromolar site, the anterior nasal spine, and the chin symphysis. • Fixtures in an extraoral site, eg, the zygomatic bone • Shigeru et al in 2000 - endosseous implants in experimental animal as anchors for long term mesiodistal movement of teeth. • When used for orthodontic anchorage alone, a 1-phase surgical procedure is preferred. • Block and hoffman on onplants suggest 10-12 weeks of healing time. Costa and Melsen suggest 4 weeks of healing time www.indiandentalacademy.com
  28. 28. Nickel –titanium wires Introduction • Nickel-titanium alloys - introduced to the orthodontic speciality by Andreasen and Hillman in 1971. • The first nickel-titanium alloy, nitinol- based on the original research of Buehler. • The name nitinol was derived from the elements that make up these alloys— "ni" for nickel, "ti" for titanium, and "nol" for Naval Ordinance Laboratory, its place of origin. • available as NiTi, Nitinol, Orthonol, Sentinol and Titanal • advantageous properties of nitinol are the good springback and flexibility • high springback of nitinol is useful in circumstances that require large deflections but low forces www.indiandentalacademy.com
  29. 29. Properties required in an orthodontic wire: • It should be possible for the wire to be deflected over long distances without permanent deformation; hence, a large springback. This assures better control over tooth movement and minimizes intervals for adjustment • Low stiffness and produce light forces • wire should be highly formable and should be formed into complicated configurations, such as loops, without fracture. • Springback, or maximum elastic deflection, is related to the ratio of YS/E. • ability and ease of joining is an important clinical parameter. • The corrosion resistance of such joints and the wires themselves should be satisfactory www.indiandentalacademy.com
  30. 30. Basic definitions • Springback - also referred to as maximum elastic deflection, maximum flexibility, range of activation, range of deflection, or working range. Springback is related to the ratio of yield strength to the modulus of elasticity of the material (YS/E). It is a measure of how far wire can be deflected without permanent deformation • Stiffness or load deflection rate. It is the force magnitude delivered and is proportional to the modulus of elasticity. Low stiffness provides (1) ability to apply lower forces, (2) a more constant force over time, and (3) greater ease and accuracy. www.indiandentalacademy.com
  31. 31. • Formability - ability to bend a wire into desired configurations • Modulus of resilience- This represents the work available to move teeth. • Biocompatibility and environmental stabilityincludes resistance to corrosion and tissue tolerance to elements in the wire. • Joinability- The ability to attach auxiliaries to orthodontic wires by welding or soldering • Friction- The preferred material for moving a tooth relative to the wire would be one that produces the least amount of friction at the bracket/wire interface. www.indiandentalacademy.com
  32. 32. Stainless steel • Austenitic stainless steel wires are the wires most commonly used. • contains approximately 18 percent chromium, 8 percent nickel, and less than 0.20 percent carbon. • high modulus necessitates the use of smaller-diameter wires for alignment. • decreased wire size results in poorer fit in the bracket and loss of control. • stainless steel has excellent formability. • can be soldered, but the technique is moderately demanding. • has good corrosion resistance. www.indiandentalacademy.com
  33. 33. Cobalt chromium wires • Composition is 40 percent cobalt, 20 percent chromium, 15 percent nickel, 7 percent molybdenum, and 16 percent iron. • Has excellent formability • Spring characteristics are similar to those of stainless steel • Can be soldered, but technique is demanding. • Corrosion resistance of the wire is excellent. www.indiandentalacademy.com
  34. 34. Composition and manufacture of niti wires • Nitinol is approximately 52 percent nickel, 45 percent titanium, and 3 percent cobalt • Solid-state solution hardening and cold working are the basic strengthening mechanisms employed • With proper heat treatment, the alloy demonstrates significant changes in mechanical properties and crystallographic arrangement. • Have a stabilised martensitic phase formed by cold welding, were the shape memory effect has been supressed. • Surface characteristics of the nickel-titanium alloy wires are a result of its complex manufacturing process www.indiandentalacademy.com
  35. 35. • Nickel and titanium are most commonly manufactured into the nickel-titanium alloy by the process of vacuum induction melting or vacuum arc melting. • Segregation is often a problem because there is a relatively wide disparity of melting points. • Several remelts are often needed to improve homogeneity of the nickel-titanium alloy. • Powders are then made of the alloy. The process of hot isostatical pressing is used by the manufacturer to form the powders into wires. • Voids occur in areas where the powders are not completely pressed together. The wires obtain their final shape by the process of drawing or rolling. The process of drawing or rolling may leave scratch marks on the surface. www.indiandentalacademy.com
  36. 36. Classification of Ni-Ti wires Kusy has classified nickel titanium wires as 1. Martensite stabilised alloys- do not possess shape memory or superelasticity; processing creates a stable martensite structure. These are the nonsuperelastic wires such as Nitinol. 2. Martensite active alloys- employ the thermoelastic effect for shape memory. Oral environment raises the temperature of the deformed archwire in the martensitic structure so that it transforms to the austeinitic form. These are the shape memory alloys such as Neo-Sentalloy and Copper Ni-Ti 3. Austenitic active alloys undergoes a stress induced martensitic transformation (SIM) when activated. These alloys are the superelastic wires that do not possess thermoelastic shape memory at the temperature of the oral environment such as Nitinol SE www.indiandentalacademy.com
  37. 37. Phase transformations Two major NiTi phases are: 1. Austenitic Niti - a ordered BCC structure occurs at high temperatures / low stress. 2.Martensitic NiTi- distorted monoclinic, triclinic or hexagonal structure and forms at low temperatures / high stress. • shape memory effect is associated with a reversible martensite to austenite transformation, which occurs rapidly by crystallographic twinning • When these alloys are subjected to high temperatures, detwinning occurs, and the alloy reverts to the original shape or size - shape memory effect. www.indiandentalacademy.com
  38. 38. • Some cases an intermediate R-phase having a rhombohedral crystal structure may form during the transformation process • Since transformation occurs as a result of specific crystallographic relationship between the two phases -the rearrangement of atoms in the cells has been named the Bain distortion • Martensitic transformations do not occur at a particular temperature, but rather within a range known as the temperature transition range(TTR). • TTR refers to the temperature range for the start and completion of the transformation for that particular structure www.indiandentalacademy.com
  39. 39. • Start of martensitic formation is designated as Ms (martensite start) and the end as Mf (martensite finish). • The temperature at which Mf begins to decline and the austenite begins to form is designated as As (austenite start) and the temperature at which the whole structure is austenitic is termed as Af (austenite finish). • For stress induced martensite (SIM) formation, an additional Md (martensite deformation) temperature is defined as the highest temperature at which it is possible to have martensite. www.indiandentalacademy.com
  40. 40. Martensitic transformation www.indiandentalacademy.com
  41. 41. Shape memory effect • Buehler and Cross- shape-memory phenomenon was related to the inherent capability of a nickel-titanium alloy to alter its atomic bonding as a function of temperature • At a high temperature range the crystal structure of these alloys is noted to be in an austenitic phase, although at a lower temperature the structure is in a martensitic phase. • In the martensitic phase, these alloys are said to be ductile and readily capable of undergoing plastic deformation. However, when heated through the TTR, they revert back to the austenitic phase and regain their original shapes www.indiandentalacademy.com
  42. 42. • Hurst and Nanda in AJO 1990 -specific TTR depends on the chemical composition of the alloy and its processing history. The TTR can be changed by altering the proportion of nickel to titanium or by substituting cobalt for nickel in the alloy. • Memory configuration of the alloy must be first set in the material by holding it in the desired shape while annealing it at 450° F to 500° F for 10 minutes • Through deflection and repeated temperature cycles, the wire in the austenitic phase is able to “memorize” a preformed shape, including specific orthodontic archforms. • Once a certain shape is set, the alloy can then be plastically deformed at temperatures below its TTR. On heating through the TTR, the original shape of the alloy is restored. www.indiandentalacademy.com
  43. 43. • To obtain maximum shape recovery, the amount of plastic deformation at temperatures below the TTR should be limited to 7% or 8% of the original linear length. • When an external force is applied, the deformation of NiTi alloy is induced with martensitic transformation. • The martensitic transformation can be reversed by heating the alloy to return to the austenite phase and it is gradually transformed by reversing back into the energy stable condition. • This means that the alloy can return to the previous shape. This phenomenon is called shape memory. www.indiandentalacademy.com
  44. 44. Superelasticity / Pseudoelasticity • Superelasticity is determined by the typical crystallographic characteristics of NiTi. • In response to temperature variations, the crystal structure undergoes deformations • The alloys essentially undergo a reorganization to meet the new environmental conditions - a property that has earned them the designation of “smart materials.” • The transformation from the austenitic to the martensitic phase (thermoelastic martensitic transformation) is reversible and is called as pseudoshearing. www.indiandentalacademy.com
  45. 45. • On activation, the wire undergoes a transformation from austenitic to martensitic form due to stress • it is necessary to manufacture a wire in the austenitic phase for the superelastic behaviour to occur • original Nitinol alloy and other nonsuperelastic Ni Ti wires have principally a work-hardened martensitic structure • clinically useful consequence of superelastic behavior variations in heat treatment can result in differing stress levels to initiate phase transformations in the same nickel-titanium wires. • Japanese NiTi alloy is available in three different superelastic force ranges of light, medium, and heavy for individual wire sizes. www.indiandentalacademy.com
  46. 46. • The unique force deflection curve for austenitic Ni-Ti wire is that its unloading curve differs from the loading curve –i.e reversibility has an energy loss associated with it -HYSTERESIS. • The different loading and unloading curves produce the remarkable effect the the force delivered by the austenitic NiTi wire can be changed during clinical use by merely releasing the wire and retying it. • Deflection generates a local martensitic transformation and produces stress-induced martensite (SIM). • The highest temperature at which the martensite can form is referred to as Md, and in austenitic alloys Md is usually located above Af, allowing the SIM to form in the stressed areas even if the rest of the wire remains austenitic. • SIM is unstable, and if the specimen is maintained at oral temperature it undergoes reverse transformation to the austenitic phase as soon as the stress is removed. www.indiandentalacademy.com
  47. 47. • In orthodontic clinical applications, SIM forms where the wire is tied to brackets on malaligned teeth so that the wire becomes noticeably pliable in the deflected areas, with seemingly permanent deformation • In those areas, the wire will be superelastic until, after tooth movement, a self-controlled reduction of the deflection will restore the stiffer austenitic phase. • Formation of SIM partially compensates for the lack of a thermally induced martensite and contributes to the superelastic behavior of austenitic NiTi alloys. This property, termed pseudoelasticity, can be considered a localized stress-related superelastic phenomenon. Only in cases of very severe crowding will an austenitic alloy behave superelastically. www.indiandentalacademy.com
  48. 48. Recycling of NiTi wires: • Nitinol wires corrode when exposed to a chloride environment, and this effect is potentiated by contact with stainless steel. • Mayhew and Kusy 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, the effects of the oral environment on the wire properties are still inconclusive. • Retreived NiTi wires are characterised by the formation of a proteinaceous biofilm, the organic constituents of which are mainly alcohol, amides and carbonate. Delamination, pitting and crevice corrosion defects as well as decreased grain size were found. www.indiandentalacademy.com
  49. 49. Friction and NiTi: • Stannard in AJO 1986 -These wires are found to have moderate friction which is greater than stainless steel but lesser than beta titanium. • Prososki AJO 1990- Elgiloy and NiTi wires were found to have comparable friction and this was lesser than beta titanium and stainless steel. Findings on resistance to corrosion of nitinol wires have been inconsistent. • Sarkar, and Foster have noted that corrosion does not affect flexural properties of nitinol wires, some reports indicate an increase in permanent deformation and a decrease in elasticity caused by corrosion or the cumulative effects of cold-working www.indiandentalacademy.com
  50. 50. Clinical usage • Most advantageous properties of nitinol -good springback and flexibility, which allow for large elastic deflections • The high springback of nitinol is useful in circumstances that require large deflections but low forces • nitinol has greater springback and a larger recoverable energy than stainless steel or beta-titanium wires • This results in increased clinical efficiency of nitinol wires since fewer arch wire changes or activations are required. • for a given amount of activation, wires made of titanium alloys produce more constant forces on teeth than stainless steel wires. A distinct advantage of nitinol is realized when a rectangular wire is inserted early in treatment. This accomplishes simultaneous leveling, torquing, and correction of rotations. www.indiandentalacademy.com
  51. 51. • Andreasen and Morrow - fewer arch wire changes, less chairside time, reduction in time required to accomplish rotations and leveling, and less patient discomfort. • The poor formability of these wires implies that they are best suited for preadjusted systems. • Any first-, second-, and third-order bends have to be overprescribed to obtain the desired permanent bend. • Nitinol fractures readily when bent over a sharp edge.In addition, bending also adversely affects the springback property of this wire. • The bending of loops and stops in nitinol is therefore not recommended. www.indiandentalacademy.com
  52. 52. • Since hooks cannot be bent or attached to nitinol, crimpable hooks and stops are recommended for use. • Cinch-backs distal to molar buccal tubes can be obtained by resistance or flame-annealing the end of the 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
  53. 53. Beta titanium wires • Introduced BY BURSTONE AND GOLDBERG • Commercial name – TMA (Titanium Molybdenum Alloy) • Nitinol, has excellent springback characteristics and a low stiffness. unfortunately, its has low formability which limits its application in conditions where considerable bending of an appliance is required. • At temperatures above 1,625° F pure titanium rearranges into a body-centered cubic (BCC) lattice, referred to as the ''beta" phase. • With the addition of such elements as molybdenum or columbium, a titanium-based alloy can maintain its beta structure even when cooled to room temperature. Such alloys are referred to as beta-stabilized titaniums. www.indiandentalacademy.com
  54. 54. Composition • It is composed of Titanium – Molybdenum – Zirconium – Tin – 77.8 % 11.3 % 6.6 % 4.3 % • A clinical advantage of β - titanium is its excellent formability which is due to the BCC structure of beta stabilised titaniums • The addition of molybdenum to the alloy composition stabilises the high temperature BCC β - phase of polymeric titanium at room temperature. • Zirconium and zinc - contribute to increased strength and hardness. www.indiandentalacademy.com
  55. 55. Properties of β - titanium ∀ β - titanium wires have improved springback which markedly increases their working range • Excellent formability • High ductility - dislocation movement of the different slip systems in the BCC crystal structure • Wire has a relatively rough surface due to adherence or cold welding • Only wire that possesses the property of true weldability • Absence of nickel makes it more biocompatible and hence these wires can used in nickel sensitive patients. • Excellent corrosion resistance and biocompatibility due to the presence of a thin, adherent passivating surface layer of titanium oxide. www.indiandentalacademy.com
  56. 56. Friction and β - titanium • Kusy et al ( AJO 1990) and several other authors - Beta titanium archwires produce highest friction owing to substantial cold welding or mechanical abrasion. • The surface of the titanium wire can become cold welded to the S.S bracket, making sliding space closure difficult • Ion-implantation - alters the surface composition of a wire. Implantation of nitrogen ions into the surface of this wire causes surface hardening and can decrease frictional force by as much as 70%. • ion-implantation process tends to increase stress fatigue, hardness, and wear regardless of the composition of the material www.indiandentalacademy.com
  57. 57. • Reduction in friction is significant only when both the wire and the opposing surface are ion implanted. • Katherine Kula and proffit in AJO 1998 concluded that there was no significant difference when ion implanted TMA wire was compared to unimplanted TMA wire in sliding mechanics clinically. • Ion implantation takes place in vacuum and involves the implantation of oxygen and nitrogen onto the TMA wires • These ions penetrate the wire surface by reacting with the tin in TMA to change the surface and immediate subsurface of the material • This layer is very hard and creates considerable compressive forces. These forces improve the fatigue resistance and ductility while reducing the co-efficient of friction roughly to that of steel. www.indiandentalacademy.com
  58. 58. Clinical application • Due to its unique and balanced properties, beta titanium wire can be used in a number of clinical applications. • For a given cross section, it can be deflected approximately twice as far as stainless steel wire without permanent deformation • This allows a greater range of action for either initial tooth alignment or finishing arches. • Beta titanium is ductile, which allows for placement of tieback loops or complicated bends. • High formability of β-titanium allows the fabrication of closing loops with or without helices. • Allows direct welding of auxiliaries to an arch wire without reinforcement by soldering. www.indiandentalacademy.com
  59. 59. • Beta titanium wires are the most expensive of all the orthodontic wire alloys but the increased cost is offset by its combined advantageous properties. Beta 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
  60. 60. Important properties of orthodontic wire alloys Property Stainless steel Cobalt chromium β - titanium TMA Nickel titanium 1. Cost Low Low High High 2. Force delivery High High Intermediate Low 3. Springback Low Low Intermediate High 4.Formability Excellent Excellent Excellent Poor 5. Ease of joining Welded joints must be reinforced with solder Welded joints must be reinforced with solder Only wire that has true weldability Cannot be soldered or welded 6. Friction Low Low High High 7. Biocompatibility Some Some None some www.indiandentalacademy.com
  61. 61. Chinese Ni Ti wire • Introduced by Dr. Tien Cheng and studied by Burstone, Qin, and Morton • The parent phase is austenite which yields mechanical properties that differ significantly from nitinol wire. • Has much lower transition temperature than nitinol wire. Mechanical properties • Springback has 1.4 times the springback of nitinol wire and 4.6 times the springback of stainless steel wire. • average stiffness of Chinese NiTi wire is 73% that of stainless steel wire and 36% that of nitinol wire www.indiandentalacademy.com
  62. 62. • Change in stiffness among different activations is related to a clinically interesting finding - the magnitude of force increases if a wire is retied into a bracket Clinical significance • Chinese NiTi wire is applicable in situations where large deflections are required • used in conditions were teeth are badly malaligned and in appliances designed to deliver constant forces. • there is a force difference if the appliance is left in place throughout the deactivation or if it is removed and retied. If the force levels have dropped too low for a given type of tooth movement, then the simple act of untying and retying can increase the magnitude of the force. www.indiandentalacademy.com
  63. 63. Japanese Ni-Ti wires • 1978- Japanese NiTi alloy, possesses all three properties - excellent springback, shape memory, and superelasticity • The unique feature was that the stress value remained fairly constant during deformation and rebound • Japanese NiTi alloy wire, yields a significantly higher value of elastic modulus than the Nitinol wire. • Japanese NiTi alloy wire possesses superelastic property. • Tensile testing - When the wire is stretched upto 2%, stress – strain curve is proportional. But when the strain was increased upto 8%, there was no change in stress. This phenemenon is called as superelasticity. www.indiandentalacademy.com
  64. 64. • Wire is manufactured by a different process than Nitinol, and demonstrates the superelastic property • Elastic deformation occurs with the strain range of 0% to 2% in the austenite phase. The martensitic transformation begins at the 2% strain level and the transformation continues up to the 8% to 10% strain level. • When the martensitic transformation is completed, the whole specimen is transformed into the martensitic phase. Later, the martensitic transformation occurs again in the direction of the austenite phase. • The Japanese NiTi alloy wire possesses the property in which the load becomes almost even when the deflection was decreased. This is termed "super-elastic property" www.indiandentalacademy.com
  65. 65. Clinical application • • • Classic NiTi alloy wire used in clinical orthodontics is the work-hardened type wire called Nitinol. The Japanese NiTi alloy wire possesses excellent springback property, shape memory, and super-elasticity. Nitinol wire provides a light force and a lesser amount of permanent deformation in comparison with stainless steel and Co-Cr-Ni wires. super-elastic property provides a light continuous force so that an effective physiologic tooth movement can be delivered. Super-elasticity is especially desirable because it delivers a relatively constant force for a long period of time, which is considered a physiologically desirable force for tooth movement www.indiandentalacademy.com
  66. 66. Copper Ni – Ti wires • In 1994 copper Ni –Ti wires were introduced by the ormco corporation. • It is available in three temperature variants: 270 C, 350 C and 400 C corresponding to the austenite finish temperatures • Shape memory behaviour is reported to occur for each variant at temperatures exceeding the specified temperature. • The addition of copper to nickel titanium enhances the thermal- reactive properties of the wire, thereby enabling the clinician to provide optimal forces for consistent tooth movement. www.indiandentalacademy.com
  67. 67. Composition They are composed of Nickel – 44% Titanium – 51% Copper – less than 5% Chromium – 0.2 – 0.3% • Kusy - wire contains nominally 5-6 wt% of copper and 0.20.3 % of chromium. • The 270 C variant contains 0.5% of chromium to compensate for the effect of copper in raising the Af above that of the oral environment. • The addition of copper to Ni-Ti not only modifies the shape memory , but also increases the stability of transformation and also helped to control hysteresis width and improved corrosion resistance. superelastic wires contain copper (5–6 per cent) to increase www.indiandentalacademy.com energy loss. strength and reduce
  68. 68. Differences between Copper Ni-Ti and traditional nickel titanium alloys: • Copper Ni-Ti is more resistant to permanent deformation and exhibits better springback. • Copper Ni-Ti demonstrates a smaller loading force for the same degree of deformation, making it possible to engage severely malposed teeth with less patient discomfort and potential for root resorption. • Copper Ni-Ti exhibits a more constant force/deformation relationship, providing superior consistency from archwire to archwire. • As copper is an efficient conductor of heat, Copper NiTi demonstrates consistent transformation temperatures that ensure consistency of force. This equates to consistent effectiveness in moving teeth. www.indiandentalacademy.com
  69. 69. Phase transformation • Differential scanning calorimetry curves demonstrate that the 27°C coppet Ni-Ti wire contains a single peak both on heating and cooling. • This indicates a direct transformation from martensite to austenite on heating and from austenite to martensite on cooling without an intermediate R phase. • The 35°C and 40°Copper Ni-Ti wire alloys exhibit two overlapping peaks on heating, corresponding to transformation from martensite to R-phase followed by transformation from R-phase to austenite www.indiandentalacademy.com
  70. 70. Uses of copper Ni - Ti wires • 27°C Copper Ni-Ti generates forces in the high range of physiological force limits and produces constant unloading forces that can result in rapid tooth movement. Engagement force is lower than with other superelastic wires. This variant would be useful in mouth breathers. • 35°C Copper Ni-Ti generates mid-range constant force levels when the wire reaches mouth temperature. Early ligation is easier with full-size archwires due to the lower loading forces. When earlier engagement of fullsize wires and sustained unloading forces at body temperature are desired, 35°C Copper Ni-Ti is the ideal wire. This variant is activated at normal body www.indiandentalacademy.com temperature.
  71. 71. • 40°C Copper Ni-Ti provides intermittent forces that are activated when the mouth temperature exceeds 40°C. It is useful as an initial wire and can be used to engage severely malaligned teeth (such as high cuspids) without creating damaging or painful levels of force or unwanted side effects. It is also the wire of choice for patients scheduled for long intervals between visits when control of tooth movement is a concern. This variant would provide activation only after consuming hot food and beverages. Advantages of copper Ni – Ti wires: 1. a more constant force delivery on a larger field of activation 2. a better resistance to permanent deformation 3. slower drop of the deactivation force (less hysteresis www.indiandentalacademy.com
  72. 72. Heat activated wires • A Martensitic wire, Heat Activated Titanium wires exhibit excellent shape memory and superelastic characteristics. • It transforms to its Austenitic state at 35° C, delivering a very gentle continuous force. Because it is soft and pliable at room temperature, it can be easily engaged to even the most severely misaligned teeth. • Nitinol Heat-Activated is a thermally activated super-elastic archwire. It is the easiest of Nitinol wires to engage, and it delivers light continuous forces that effectively move teeth with minimal discomfort to the patient. • Can be cooled or chilled resulting in a softer, more pliable wire for easy engagement • Provides light continuous forces • Force activation at 27° C www.indiandentalacademy.com
  73. 73. • Thermoelastic alloys exhibit a thermally induced shape/memory effect whereby they undergo structural changes when heated through a transitional temperature range (TTR) (Kusy, 1997). • At room temperature the alloy is soft and easily ligated to badly displaced teeth. At mouth temperature the ratio of austenite increases and along with it the stiffness of the wire, so that it more readily attempts to regain the original archform (Bishara et al., 1995). • The extent of this effect depends upon the TTR, which can be set specifically by modifying the composition of the alloy or by appropriate heat treatment during manufacture (Buehler and Cross). www.indiandentalacademy.com
  74. 74. Alpha titanium wires The composition of α- titanium is Titanium – 90 % Aluminium – 6% Vanadium – 4% • The alloy is different in that its molecular structure resembles a closely packed hexagonal lattice as against the BCC lattice of beta titanium. • The hexagonal lattice possesses fewer slip planes. Slip planes are planes in a crystal that glide past one another during deformation. The more the slip planes, the easier it is to deform the material. BCC structure has two slip planes while HCP lattice has only one slip plane. Thus the near α- phase titanium alloy is less ductile than TMA. www.indiandentalacademy.com
  75. 75. Timolium wires • New entry into the arena of titanium – based alloys. • alloy with titanium, aluminium and vanadium as its components. • This alloy has a smooth surface texture, less friction at the archwire –bracket interface, and better strength than existing titanium based alloys. • Vinod Krishnan et al (Angle 2004) -tensile evaluation of the weld joint was beta titanium > stainless steel > timolium. • Weld surface of timolium exhibited a smooth and symmetrical flow of the alloy, less surface distortions, and an intact weld surface. Timolium with proper flow of weld flash uniformly on both sides, had better surface properties on surface evaluation. www.indiandentalacademy.com
  76. 76. Titanium Niobium wires • This alloy has low spring back (equivalent to stainless steel) and is much less stiffer than TMA. • It is useful when a highly formable wire with low forces in small activations is required. • Titanium Niobium is an innovative archwire designed for precision, tooth-to-tooth finishing. • At 80% of the stiffness of TMA, it is perfect for holding bends, yet light enough not to override the arch-to-arch relationship. It is recommended for use with finishing elastics and even though it feels soft and pliable, it possesses a resiliency after bending that is equal to stainless steel. www.indiandentalacademy.com
  77. 77. Nitinol total control • IN 1988 Miura demonstrated the use of electrical resistance heat treatment to introduce permanent bends in their NiTi wires. The technique requires special pliers attached to an electric power supply. This helps in imparting bends without affecting superelasticity. • A new pseudo super elastic NiTi alloy Nitinol total control accepts specific 1st, 2nd and 3rd order bends while maintaining its desirable super elastic properties. NTC combines super elasticity with light continuos forces over a desired treatment range with bendability required to account for variations in tooth morphology arch form and bracket prescription. www.indiandentalacademy.com
  78. 78. Supercable • Hanson combined the mechanical advantage of multistranded cables with material properties of super elastic wires to create a super elastic NiTi Coaxial wire. This wire called super cable comprises of 7 individual strand woven together to maximize flexibility and minimize force delivery. 1. 2. Elimination of archwire bending. More effective and efficient control of rotations, tipping and levelling mechanics with an 0.018'' arch wire at the beginning of the treatment. 3. Flexibility and ease of engagement regardless of crowding 4. A light continuous force delivery 5. Minimal patient discomfort and fewer visits due to longer arch wire activation. www.indiandentalacademy.com
  79. 79. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com