Orthodontic Wires Part 2

1. 1 Orthodontic wires Orthodontic wires Part 2 Part 2 Prepared by: Prepared by: Dr Mohammed Alruby Dr Mohammed Alruby ميدق تتح باارت هارا هيدي ينب ابهذ نياري لا نم ميدق تتح باارت هارا هيدي ينب ابهذ نياري لا نم O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

2. 2 Titanium alloys At room temperature it is an alpha phase, hexagonal, closely packed structure lattice Above 833 degree is beta phase, center cubic structure 1-Alpha- titanium wires Developed in 1988 by Aj- Wilcok , closely packed hexagonal lattice structure Manufactured by process called: feed centerless grinding Supplies as square and rectangular wires Composition: Titanium: 90%, Aluminum: 6%, Vanadium: 4% Properties: = readily absorb free hydrogen ion in the oral environment at body temperature and become titanium hybrids, so it become: -Brittle to bend -Stiffness between stst and nitinol -Poor formability -High cost -Quite resilient used in root torqueing and finishing 2-Beta titanium wires TMA: Was introduced in 1979 as titanium molybdenum alloy Introduced in orthodontics in 1970 by Jon Goldberg and Burston Composition: = 77.8% titanium, 11.3% molybdenum, 6.6% zirconium, 4.3% tin Structure: = At room temperature, the metal is stable in the alpha phase hexagonal closed packed lattice HCP = At higher temperature above 833 degree, metal rearrange to body cubic centered BCC or beta crystalline = By addition of elements like molybdenum the beta form can stabilized at room temperature It supplies in both round and rectangular wires Properties and clinical relevance: 1-Spring back twice than stst 2-Stiffness: deliver ½ force of stst 3-High friction than stst and cobalt chromium wire 4-High corrosion resistance, high compatible 5-Highly ductile which allow it to be formed into loops and helices 6-High resistance and high tensile strength 7-Can be soldered or welded without losing resiliency 8-Nitrogen ion implantation on wire surface has reported to cause surface hardening and decrease frictional force by much as 70% Advantages: 1-Intermediate force delivery between stst and titanium 2-Excellent formability 3-Excellent spring back action 4-Excellent bio-compatibility O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

3. 3 Disadvantages: 1-High arch wire bracket friction 2-Most expensive Uses of beta titanium: TMA: 1-Auxiliary leveling arch: In case of bracket 18 slot, if the main wire arch is not heavy enough to complete levelling put wire TMA 0.017 X 0.025 inserted into the auxiliary tube on molar and tied anteriorly beneath the main arch ---------- this correct the curve in the basal arch and complete leveling 2-Retraction of anterior segment: By using 0.019 X 0.025 TMA wire with closing loops which provide better properties than 0.018 X 0.025 3-Root paralleling at extraction sites: 0.017 X 0.025 wire correct great degree of tipping of teeth adjacent to extraction sites and must be followed by stst wire to obtain final positioning 4- torqueing of incisors: For torque , the best finishing arch wire 0.021 X 0.025 TMA in slot 0.022, TMA is superior to M niti wire Nickel titanium arch wire Introduction: Nitinol was invented in early 60’s by William F Buchler, a research metallurgist of the novel ordinance laboratory in silver spring Nitinol: nickel, titanium = introduced in orthodontic community by Andresen 1971 as provided for orthodontic use = in late 1980, new nickel titanium wires with an active austenitic gain structure appeared Composition: 52%: nickel, 45%: titanium, 3%: cobalt Are commercially available as: nitinol, NiTi, estinol, orthonol, titnol Nickel is added to provide the alloy with an appropriate hardness = cobalt is added to lower the transitional temperature range TTR of the wire to the temperature of oral cavity Structure: 1-Martensitic form: ------ exist at lower temperature 2-Austenitic form: -------- exist at higher temperature Mechanical properties: = when compare nitinol with other orthodontic wires such as: stst, cobalt, chromium, beta titanium TMA. It was found; -Lowest modulus of elasticity -Lowest yield strength -Lowest stiffness -Poor formability -Increase brittle and cannot be soldered or welded -Highest resilience -High spring back action O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

4. 4 == shape memory phenomena: Described by Andresen and Marrow as it is the ability of wire to return to its original shape when heated through its transition temperature range TTR Nitinol can deformed within certain limit, from which it can recover to original shape if heated through its TTR At temperature below TTR, nitinol is present in martensitic phase can be deformed plastically. But when wire heated to above its TTR, crystallographic transformation from martensitic phase occur. Associated with recovery to original shape. This phenomenon is important in clinical application of wire; hence a small percentage of cobalt can be added to the alloy to adjust the TTR of the wire near the temperature of the oral cavity. Only these wires with TTR less than 37 degree exhibit a super-elastic property Physical properties of wire: = surface electron microscope studies done by Sarker and others demonstrate lower quality of surface tomography of nitinol compared with stst = nitinol exhibit some surface roughness which increase the frictional resistance between the wire and bracket slots Biological properties of nitinol: = some authors found that nitinol is resistant to corrosion as stst, however Sanker and Bishara found that nitinol is more susceptible to corrosion than other orthodontic alloys = the corrosion products cause biological response in the form of allergic reaction = some authors reported decrease in the elasticity and fracture of wire by using Clinical implication of various properties: 1-Low modulus of elasticity means that: High resilient wire High working range Activated larger distance to fit, displaced tooth without permanently deformed and at same time exerting low and constant force = the increased working range implies: -Minimum reactivation is required -Less need to change the wire -Longer interval between visits 2-High spring back (maximum flexibility): nitinol can return to its original shape after deflected a larger distance without permanent deformation 3-Shape memory phenomenon can be useful in alignment and space consolidation Based upon this phenomenon performed nitinol: = coil spring = molar distalizing spring = canine retractor spring = molar uprighting spring 4-The poor formability of nitinol special precautions in manipulation of this wire, the wire cannot be formed into loops or coils, use an alternative as clamp stops and hooks. 1st, 2nd, 3rd, order bends cannot be reproduced, so nitinol more suitable with Preadjusted brackets 5-The brittleness of the wire requires special precautions; the wire should not bend over shape edge or into complete loops otherwise may be fractured O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

5. 5 6-The wire cannot be soldered or welded, climbable hooks and stops are available as an alternative. The wire joined mechanically 7-The surface roughness increases the frictional resistance, so that special consideration should be taken to prevent anchorage loss 8-The low stiffness of the wire is both advantage and disadvantage: Advantage: when rectangular nitinol arch can be inserted during alignment and levelling to full engage the bracket and provide more control for levelling, torqueing and correction of rotation Disadvantage: when nitinol provides inadequate stability of occlusion at the final stage of treatment. So it should be replaced with stst wire at this stage. Advantages of nitinol: 1-Fewer arch changes 2-Less chair time 3-Rapid alignment and levelling 4-Large interval between visits 5-Less patients discomfort than multilooped arch Disadvantages: 1-Poor formability limits its use to Preadjusted system 2-Brittleness which make the wire more susceptible to fracture in use 3-Low stiffness 4-Cannot welded or soldered 5-Biological risk: release of nickel ions 6-High friction 7-High cost N: B: The wires can be shaped and their properties can alter however by heat treatment. This can be done in the orthodontic office by passing an electric current between electrodes attached to the wire Types of Nitinol wires 1-Nitinol martensitic stable: Good spring back Does not possess super elastic properties or shape memory Higher friction than stst Low stiffness: cannot be welded or soldered 2-Nitinol, thermos-elastic: active martensitic: sent-alloy: M niti 1st titanium alloy introduced in orthodontics in late 1970 Wire has poor formability so it did not allow any loops or bends to be made in wires and restricting its use for Preadjusted bracket in which all built in the bracket Characteristics: 1-Thermal activation can be set at different temperature 2-Thermal activated shape memory 3-Higher range of action 4-Higher strength = constant unloading forces 5-Higher resiliency 6-Higher range of deflection O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

6. 6 Clinically: = M niti wire exert light continuous forces that is ideal for the 1st stage of orthodontic treatment = large size rectangular wire can be used from the early stages of treatment with advantage of early torque control = temperature of oral cavity will increase the force exerted by the wire gradually SO: low temperature------- low force --------- low patient discomfort = when refrigerated it become soft and full engagement is possible. In mouth temperature become active and exert force Contraindication: -To give final arch shape -For retraction because it is bended and thus causing dumping of the teeth Uses: 1-Initial alignment 2-Levelling of curve of spee 3-Root paralleling at extraction site: during space closure, some cases have tipping of the teeth adjacent to extraction sites so, we use rectangular niti wire to correct it: As: 0.017 X 0.025 niti – in slot 18 Or: 0.021 X 0.025 niti --- in slot 22 4-Torque of incisors: with pretorqued appliance M niti is used in torque incisors as: 0.021X0.025 in slot 22 3-Austenitic nickel titanium alloys wires: Super elastic A niti = Produced in late 1980 with active austenitic grain structure Super elasticity due to phase transformation from body centered cubic austenitic form to hexagonal closed packed martensitic form of niti when stress reaches a certain level during activation = Greater force and greater stiff = Can return to original shape after distortion Uses: 1-Initial alignment: the load deflection of A niti make wire best available for initial alignment stage 2-Coil springs: for distalization, open spaces, canine retraction. N: B: 1-Martensitic stabilized alloys: = does not possess shape memory or super-elasticity, because the cold working of wire create a stable structure = non super elastic wire such as nitinol 2-Martensitic active alloys: = employ thermos-elastic effect to achieve shape memory = oral environment raises temperature and transformation back to austenitic structure and change to starting shape such as: copper niti, neo sentalloy 3-Austenitic active alloys: = undergo stress- induced martensitic SIM transformation when activated = display super-elastic behavior = reverse reaction transformation from martensitic back to austenitic during deactivation or annealing as Japanese wires O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

7. 7 4-Copper Niti wire: Recently introduced at 1994 by: Robil Sachdeva and Suchio Mivasaki Contain 5% - 6% copper, 0.2 -0.5% chromium, in addition of nickel titanium Exert tooth moving forces only after reaching certain temperature Advantages: 1-Relatively loading forces is 20% less, so it possible to engaged severely malposed tooth with less patient discomfort 2-decreased hysteresis result in more constant force 3-more resistant to permanent deformation, therefore exhibit better spring back than other 4-patient can control the deactivation of the engaged wire by cold application. Types: Type I: at 15 degree: not used clinically, exert high force Type II: at 27 degree: normally used in patient with average pain, tolerance, constant force generated Type III: at 35 degree: used in patient with low threshold, used only when low forces are desired Type IV: at 40 degree: used in patient with low threshold, used as initial aligning arch, intermittent force generated 5-Chinese Niti wires: austenitic: = new super elastic orthodontic wires = developed by Huo-cheng Tien – china 1978 = behavior superior to niti for alignment in vitro but Chinese niti fracture more easily = has increased spring back more times than stst = has lower transition temperature rate = produced constant force and maintain higher magnitude of force level due to its super-elasticity and shape memory 6-Japanese Niti wires: Sentalloy: = exhibit a usual super-elasticity = excellent shape memory = produced in 3 different forces: light, medium, heavy = developed during mid 1980 by Furkava electric Co. of japan Heat treatment: When wire is heated at 500 degree from 5minutes to 2 hours: there is a significant alter the super- elasticity of force. When heated at 600 degree eliminated the super elasticity behavior Recycle of Nitinol wire = Due to high cost of nitinol and its favorable physical properties, recycling of nitinol has been attempted by many clinicians = Recycling involves repeated exposure of wire to mechanical stress and elements of oral environment and sterilization between uses = Kusy among others have been reported no appreciable changes in the mechanical properties of nitinol after 3 cycle of various forms of heat sterilization and mechanical disinfection O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

8. 8 Esthetic wires 1-Optiflex arch wire: Developed by Talass in 1992, it is made of clear optical fiber with 3 layers, available in round and rectangular wires Layers: a-Silicon dioxide core that provides the force for moving teeth b-Silicon resin middle layer that protect the core from moisture and added strength c-Nylon outer layer that prevent damage to wire and increase its strength Properties: -Wide range of action -Ability to apply light force -Sharp bend must be avoided because can fracture core -Highly resilient wire and more effective in aligning teeth 2-Plastic / Teflon coated niti: Plastic coated, tooth colored super-elastic nickel titanium arch wire Wires are available in round or rectangular wires After time of using in the oral environment it lose their coat 3-Esthetic composite orthodontic wires: Polymer matrix + glass fibers 4-Metal wire with white colored Teflon: Have some mechanical properties of other orthodontic wires Modulus of elasticity decrease by water emersion Turbo wire or braided nickel titanium rectangular wire Preformed braided niti wire combine the advantages of: 1-Highly resilient with rectangular braided wire 2-Exert early torque control due to its rectangular section. Variables modulus orthodontics = approach of force control, as wire size remain constant and the material of wire selected is changed according to clinical requirements = this means that orthodontic can control the stress on teeth from the beginning of treatment by using low stiffness wire to more stiff one at the end of treatment Example: start treatment with niti with high spring back action over steel with loops and at the end of treatment use more stiff wire stst Advantages: 1-Stress exerted by appliance can be controlled by using different material and kept low at stages of treatment 2-Allow better torque control over dentition from the start of treatment 3-Keep dimension of wire constant and change only the stiffness of materials 4-Less taxing on the clinical chair time O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

9. 9 Nickel free stainless steel and TMA To overcome nickel allergy, nickel free austenitic stst wire developed 0.9%: nitrogen to compensate nickel 18%: chromium 3%: molybdenum 14%: manganese Available in single strand, triple strand, and 6 strand stst and TMA Dual-flex arch wires Special NiTi arch wire have two types of wire material and / cross section in anterior or posterior section of same wire This type of wire affords multiple function of same wire so, improve control and reduce treatment time Super cable wires = Super elastic niti coaxial, compressed of seven individual strand of niti together in a long gentle spiral to: increase flexibility and decrease force delivery = exert low force when compared with solid nickel titanium wire = Introduced by Hanson in 1993 = 0.018-inch cable wire, full slot engagement in case of sever crowding and rotation cases because of its low force delivery = this wire used in speed self-ligating system Effect of oral environment on properties of orthodontic arch wires = wires and orthodontic attachment are continuously exposed to oral environment which may affect their clinical properties = major corrosion products of stst are: Ni, Cr, Fe = Cr, Ni most carcinogenic and allergic potential Significant increase in nickel blood level not found in first 4 to 5 months of orthodontic therapy O Orthodontic rthodontic Wires Part 2 Wires Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby