Stainless steel and ortho archwires sunanda

orthodontics

1. G O O D MORNING

2. STAINLESS STEEL & ORTHODONTIC WIRES DR. SUNANDA PAUL DEPT OF ORTHODONTICS & DENTOFACIAL ORTHOPAEDICS

3. STAINLESS STEEL HISTORY TERMINOLOGY STEEL CLASSIFICATION STRUCTURE PHASE TRANSFORMATION IN STEEL SUMMARY OF PROPERTIES DUPLEX STEEL PRECIPITATION HARDENABLE STEEL SOFT STAINLESS STEEL APPLICATION OF SS IN ORTHODONTICS

4. ORTHODONTIC ARCHWIRES PROPERTIES PHASES OF ARCHWIRE DEVELOPMENT SS WIRE COBALT CHROMIUM AUSTRALIAN ARCHWIRE NICKEL TITANIUM ALLOYS ALPHA TITANIUM BETA TITANIUM ESTHETIC ARCHWIRE OPTIFLEX

5. Internal force(per unit area)within a structure subjected to an external force Relative change in the shape or size of an object due to externally applied force

6. ELASTIC LIMIT It is a point at which any permanent deformation first observed

7. PROPORTONAL LIMIT GREATEST STRESS PRODUCED IN A MATERIAL SO THAT Stress  Strain

8. YIELD STRENGTH PROPERTY THAT REPRESENTS THE STRESS VALUE AT WHICH A SMALL AMOUNT(0.1% OR 0.2%)OF PLASTIC DEFORMATION OCCURED

9. Modulus of Elasticity (Young’s modulus) (E) RELATIVE STIFFNESS OR RIGIDITY OF A MATERIAL MEASURED BY THE SLOPE OF THE ELASTIC REGION OF STRESS STRAIN DIAGRAM

10. RANGE T he distance that the wire will bend elastically before permanent deformation occurs .

11. FORMABILITY amount of permanent deformation that a wire can withstand before failing. RESILIENCY AREA UNDER THE STRESS STRAIN CURVE UPTO PROPORTIONAL LIMIT. 13 Strain Stress Resiliency Formability Proportional limit Yield strength

12. When a loop is bent in a wire , it is differentially stretched so that the outer surface becomes more workhardened and thus has better spring properties than the inner surface. If the spring is deflected in the same direction as previous bending , its elastic recovery is better than if it is deflected in opposite direction . BAUSCHINGER EFFECT

13. Iron based alloys Contain less than 1.2% carbon Stainless steel When chromium is added to steel(12% - 30%) Polymorphism-it crystallizes into more than one structure (ferritic, martensitic & austenitic) property called ALLOTROPY . At room temp pure iron is BCC structure ferrite (alpha form) stable till 912 º C. At temp. between 912-1394 º C FCC Structure austenite (gamma form) STEEL

14. FUNCTION OF EACH CONSTITUENT : 1.Fe-Main constituent 2:Cr-Increases tarnish and corrosion resistance. 3 . Ni -tarnish & corrosion resistance 4. C –hardness 5.Si - acts as deoxidizer & scavenger 6.Mn - acts as scavenger & increase hardness 7.Ti - inhibits precipitation of chromium carbide

15. CLASSIFICATION TYPE AISI NO FERRITIC 430 AUSTENITIC 302, 304, 316L MARTENSITIC 400 ACCORDING TO AISI(AMERICAN IRON & STEEL INSTITUTE)

16. 18 BASED ON THE CROSS-SECTION SQUARE ROUND RECTANGULAR MULTISTRANDED TWISTED

17. BASED ON SIZE 19 GAUGE 20 GAUGE 21 GAUGE SUPPLIED IN VARYING DIAMETERS RANGING FROM 0.1 TO2.0MM FOR ROUND WIRES

18. ACCORDING TO CRYSTAL LATTICE STAINLESS STEEL IS CLASSIFIED AS- Cr Ni C FERRITIC BCC 11.5 - 27% 0% 0.2% AUSTENITIC FCC 16 - 26% 7 - 22% 0.25% MARTENSITIC BCT 11.5 - 17% 0 - 2.5% 0.15 - 1.2% SP LATTICE COMPOSITION

19. Steel Crystal Structure FERRITE MARTENSITE AUSTENITE BCC Low solubility for C Stable at room temp Distorted BCC – BCT Higher C solubility than Ferrite Metastable at room temp Results from quenching Austenite FCC Larger interstitial sites, higher C solubility Stable at high temps 21

20. Austenite The austenite-martensite phase transformation occurs by non-diffusional , distortion rearrangement of atoms. Phase Transformation in Steels 22 The austenite-ferrite phase transformation occurs by diffusional rearrangement of atoms. Ferrite Martensite

21. 23 THE FERRITIC GROUP P lain chromium stainless steels with varying chromium content between 11% and 18%, but with low carbon content. M oderate to good corrosion resistance N ot hardenable by heat treatment . M agnetic Formabilty is not as good as austenite Little application in dentistry TYPES

22. 24 Type 430 A 17% Chrome, low alloy Ferritic steel. G ood corrosion resistant properties up to about 800°C.

23. SUPERFERRITIC STEEL Belongs to the category having chromium as much as 19% to 30% N ickel free and highly corrosion resistant. Corrosion resistance is further achieved by containing small amount of aluminium and molybdenum and very little carbon.

24. THE MARTENSITIC GROUP T he first stainless steels commercially developed R elatively high carbon content (0.1 - 1.2). C ontain 12 and 18% chromium. 26

25. 27 Moderate corrosion resistance Hardened by heat treatment resulting in high strength and hardness. P oor weldability and is magnetic. C ommonly used for knife blades, surgical instruments, shafts, spindles and pins, pliers. THE MARTENSITIC GROUP

26. 28 Type 410 A 13% Chrome, 0.15% Carbon alloy possessing good ductility and corrosion resistance. C an be easily forged and machined. Exhibits good cold working properties. THE MARTENSITIC GROUP

27. Type 416 Similar to Type 410 but has added Sulphur giving improved machinability. Type 431 A 17% Chrome, 2.5% Nickel, 0.15% max Carbon . Has superior corrosion resistance to types 410 & 416 due to the Nickel. 29 THE MARTENSITIC GROUP

28. AUSTENITIC STAINLESS STEELS M ost corrosion resistant of stainless steels. AISI 302 is the basic type containing 18% Cr, 8% Ni and 0.15% carbon. Type 304 has similar composition, chief difference being that the carbon content is limited to 0.08%. Both 302 and 304 may be designated as 18/8 stainless steel and are most commonly used in orthodontics in form of bands and wires.

29. Type 316 L (0.03% max. carbon) -> employed for implants The 316 & 316 L types have been recently introduced and 316 differs in that it contains 2% more Nickel in addition to about 2% Molybdenum, thus improving its corrosion resistance AUSTENITIC STAINLESS STEELS

30. Austenitic FCC structure is unstable at lower temperature where it tends to turn into BCC (ferrite ). If austenizing elements ( nickel, manganese and nitrogen) are added highly corrosion resistant solid solution phase can be preserved even at room temperature. If these elements are absent these steels even with high chromium content are ferritic at room temperature . AUSTENITIC STAINLESS STEELS

31. Generally, austenitic stainless steel is preferable to the ferritic alloy because of : Greater ductility & ability to undergo more cold work without breakage. Substantial strengthening during cold working. Greater ease of welding. Ability to overcome sensitization. Less critical grain growth. Comparative ease in formation.

32. Bands & tubes Bands - Also prepared from stainless steel. It is a stainless steel strip that encircles the crown. Brackets are welded to bands. Tubes - allows the wire to slide through it . It may be rounded to square. It may be single or combination of several tubes-single, double or triple. USES OF SS IN ORTHODONTICS

33. Steel remains the standard material for many years to be used for brackets. But now recently titanium brackets have been introduced. These are made by casting or metal strips stamped to shape. Casting ones are more precise & accurate. There is mesh at the back of the bracket which is used for bonding. However corrosion is a problem BRACKETS

34. Summary of Properties Austenitic Ferritic Martensitic Alloying elements 18% Cr; >8% Ni; 0.1% C (wt%) 15-30% Cr; <1% Mo; <1% C (wt%) 12-17% Cr; 0.1-1%C (wt%) Corrosion resistance Excellent (except Cl environments) Good Moderate Oxidation resistance Good Good Moderate Strength Moderate Low-moderate High Toughness High Moderate Moderate Formability Good Moderate Moderate Weldability Good Poor-moderate Poor-moderate Cost High Moderate Moderate 36

35. PASSIVATION - Cr is added to steel as passivating agent . It reacts to the atmospheric oxygen to form its oxides thus preventing corrosion. SENSITIZATION - L oss of corrosion resistance of 18/8 stainless steel when heated to high temperature due to formation of Cr carbides . Hence its not available to react with oxygen. Causes -high temp used in soldering & welding Prevention -use low fusing flux & less time

36. STABILIZATION It is done to prevent sensitization. Here titanium is added to 6 times that of carbon in stainless steel. Ti has more affinity to form carbides than Cr making Cr free to react with oxygen. Such stainless steel are called stabilized stainless steel

37. HEAT TREATMENT Use of heating or cooling normally to extreme temperature to achieve a desired result. 2 types of heat treatment Softening heat treatment ANNEALING Hardening heat treatment TEMPERING

38. A) Annealing Effects associated with cold working ( eg strain hardening, lowered ductility and distorted grains ) can be reversed by simple heating the metal. This process is called annealing. The more severe the cold working, more rapidly the effects can be reversed by annealing. Annealing in general comprises of three stages : 1)Recovery 2) Recrystallization 3) Grain growth

39. RECOVERY It is considered the stage at which the cold work properties begin to disappear. There is slight decrease in tensile strength and no change in ductility. RECRYSTALLIZATION significant change in the microstructure Deformed grains replaced by new strain-free grains Original soft and ductile properties return Recrystallization occurs only if metal has been sufficiently cold worked

40. GRAIN GROWTH The recrystallized structure has a certain average grain size depending on the number of nuclei. The more severe the cold working the greater the number of such nuclei. Thus the grain size for the completely recrystallized material can range from fine to fairly coarse. If fine grain structure is further annealed,grain growth occurs to minimize the grain boundary area,with large grains consuming the small grains. The process continues till a course grain structure is produced.

41. CORROSION OF STAINLESS STEEL Defined as destruction or deterioration of material by a chemical or electrochemical reaction. Causes- If surface in-homogenesity is present it allows corrosion cells to form in presence of saliva.

42. Rust - It’s the formation of iron oxide when iron & steel alloy corrodes. It may be brown , black or reddish in color. Can take form of pits and blisters . Catastrophic corrosion - When stainless steel is sensitized as in brazing or welding & then exposed to chemical agents then Cr depleted boundaries are readily attacked by oxygen. This phenomenon is called as catastrophic corrosion .

43. DUPLEX STEELS Consists of assembly of both austenite and ferrite grains 28 % Chromium, 6% Nickel, and equal amounts of Austenite and Ferrite . Along with Fe these steels have Mo and Cr and low amounts of Ni. As opposed to austenitic ones these steels are attracted to magnets . When improperly heat treated there is a tendency to form a brittle phase with very poor corrosion resistance (sigma phase). Used for manufacturing one piece brackets

44. PRECIPITATION HARDENABLE STEELS (PH STEEL)- it can be hardened by heat treatment. It has got high tensile strength & thus widely used in mini brackets & edgelock brackets. SOFT STAINLESS STEEL- it is the thoroughly annealed steel to remove all the stresses incorporated during cold working. These are commonly used as ligature wires

45. ARCH WIRES Stainless steel & Cobalt-Chromium has replaced precious metals because of better properties like strength, springiness & equivalent corrosion resistance. Can be softened by annealing and hardened by cold working. Fully annealed wires are used ligature wires. Special type of stainless steel arch wire has been prepared by A J Wilcock called Australian arch wire.

46. Requirements of an ideal archwire (Kusy ) Esthetics Stiffness Strength Range Springback Formability Resiliency Coefficient of friction Biohostability Biocompatibility Weldability 48

47. PROPERTIES

48. --------- PROPERTIES

49. STAINLESS STEEL WIRES Most important use of stainless steel in orthodontics is in the form of wires. Used for making clasps, springs, bows, arch wires etc. It is dispensed in various thickness or gauges

50. PROPERTIES Low modulus of elasticity High flexibility High resiliency Easy to weld & solder Good corrosion resistance Easy to manipulate

51. ADA. SPECIFICATION NO.32 Alloy Modulus Of Elasticity Yield Strength ( Mpa ) Utility Tensile Strength SS 179 GPA 1759 MPA 2117

52. Application of ss in clinical practice Types 302 and 304 of 18-8 stainless austenitic wires are used in Orthodontics. For the tooth alignment and leveling phase even steel wires with a smaller cross-section result in high loads, which are not consistent with physiological forces. Used in making loops that increase the wire’s activation range and disguise,as it were, the low resilience and high stiffness of the wire. Orthodontic wires: knowledge ensures clinical Optimization - Dental Press J. Orthod 2009

53. The disadvantage of using loops lies in the fact that as these loops lose their original shape they change the direction of force vectors. Loops can also hinder hygiene by entrapping food particles. If not positioned properly, loops can damage adjacent soft tissues. Stainless steel wires boast excellent resistance to corrosion and exhibit higher elastic limits and modulus of elasticity, Orthodontic wires: knowledge ensures clinical Optimization - Dental Press J. Orthod 2009

54. AUSTRALIAN ARCH WIRE A J Wilcock of Australia came with a new wire called Australian arch wire. It become famous because it combines high resiliency with toughness. Wilcock’s archwire have been the mainstay of Begg’s technique. Due to high resiliency its diameter is reduced to 0.018 - 0.014 inch Application – it is highly useful in deep over bite correction as it does not undergo permanent deformation

55. Types : Regular Regular plus Special Special plus Special plus pulse straightened Premium Premium plus Premium plus pulse straightened Supreme j) Supreme pulse straightened

56. MULTI STRANDED OR BRAIDED WIRES - To increase the strength and to decrease the stiffness wire is braided or twisted together by the manufacturer which increases flexibility and can sustain large elastic deflection in bending. CO-AXIAL WIRE Has got a central core wire with 5 outer wires wrapped around . It increases resiliency & flexibility It applies light continuous force . twist coaxial Straight woven

57. When to use multistranded stainless steel archwires By using multi-stranded stainless steel arch wires one can employ stainless steel arch wires in the initial stage of tooth alignment and leveling without the need for loops . The elastic recovery of multi-stranded wires is 25 % higher than that of a conventional stainless steel wire of identical diameter. Orthodontic wires: knowledge ensures clinical Optimization - Dental Press J. Orthod 2009

58. The rigidity of interbracket segments is much lower than that of conventional stainless steel wires of identical diameter. Although less formable than conventional steel wires multi-stranded wires are responsive to contours and bends, such as omega loops for posterior tying, thus preventing tooth projection. Orthodontic wires: knowledge ensures clinical Optimization, Dental Press J. Orthod 2009

59. Following World War II, returning servicemen complained that their Elgin watches couldn't take the punishment of corrosive environmental situations in various theatres of the war. The Elgin Watch Company took those complaints to heart, and after four years of research, " Elgiloy ", a non-corroding watch spring material with an infinite life span, was born. Introduced into orthodontics because their properties are excellent for orthodontic purposes. COBALT-CHROMIUM ALLOYS History

60. Available commercially as Elgiloy (Rocky Mountain Orthodontics), Azura (Ormco Corporation) and Multiphase (American Orthodontics). Elgiloy is manufactured in four tempers. Blue – soft. Yellow – ductile. Green –semi resilient Red -resilient COBALT-CHROMIUM WIRES

61. Blue(soft) Softest – high formability. Recommended when considerable bending soldering or welding is required. Heat treatment increases its resistance to deformation. Yellow (Ductile) More resilient than blue Elgiloy. Good formability. heat treatment increases its strength and spring performance. Green (Semi resilient) More resilient than yellow and can be shaped with pliers before heat treatment. Red (Resilient) Most resilient , high spring qualities. Withstands only minimal working. Fractures easily after heat treatment, all adjustments should be made before this precipitation hardening process .

62. NICKEL TITANIUM ALLOYS Nickel titanium alloys have certain characteristic properties associated with them . These properties are primarily exhibited due to its crystal structure. At higher temperatures the crystal structure is that of a body centered cubic(BCC) and is called AUSTENITE . At lower temperatures the crystal structure is that of a hexagonal closed packed structure called MARTENSITE. The two most important properties of nickel titanium alloys are 1.Shape memory 2.Super elasticity

63. SUPERELASTICITY This is a mechanical equivalent of the change , which is observed due to cooling of austenite. This is possible because the TTR for these alloys is very close to room temperature. Kary has also called it PSEUDOELASTICITY. Whether,it is thermo or pseudo-elasticity, the transition from martensite to austenite occurs with ease.

64. Stress strain curve

65. SHAPE MEMORY Shape memory refers to ability of a material to “remember”its original shape after being plastically deformed while in the martensitic form. Also called THERMELASTICITY .

66. HYSTERESIS When the austenitic nickel titanium wire is stressed,it can be observed that the loading curve differs from its unloading curve. The reversalibilty has an energy loss associated with it,this is know as hysteresis .

67. CONVENTIONAL/STABILIZED NICKEL-TITANIUM ALLOYS “Nitinol”was developed in the early 1960’s by William F.Buehler,a research metallurgist at the Naval Ordinance Laboratory,Silver springs,Maryland. Clinical use of nickel-titanium was started by Andreasen in May,1972 The shape memory effect(SME)had been suppressed by cold working Proffit refers to these alloys as M-NiTi’s.

68. Advantages Low stiffness Outstanding range High sringback Disadvantages Lack of formability No shape memory,super elasticity and hysteresis

69. SUPERELASTIC NICKEL TITANIUM ALLOYS(Active austenitic) Chinese NiTi developed by Dr.Tieun Hua Cheng Reported by BURSTONE(1985). Japanese NiTi produced by the Furukawa Electric Co.,which was first reported by Miura(1986) T hese wires,in their”as received”condition were in the austenitic phase,and they showed the property of superelasticity . Superelasticity results from stress induction,as in archwire ligation.

70. “Hysteresis”is seen in these wires. Disadvanatges Wire bending is all bit impossible with these alloys.

71. NEW APPLICATION OF SUPERELASTIC NiTi rectangular wire (Miura 1990)in heat treatment,the superelastic NiTi alloy not only changes its force level,but memorizes form.The latter characteristic makes it possible to condition an archwire so that it memorizes a particular archform,including torque,angulation and buccolingual movemens.The archwire can therefore be formed in the laboratory ahead of time,rather than using precious chairtime.The archform will also be more accurate than if it were bent at chairside.

72. Types of of thermodynamic nickel titanium TYPE I:At temperature 10-15 C TYPE II:At temperature 27 C TYPE III: At temperature 35 C TYPE 1V:At temperature 40 C

73. COPPER NiTi Rohit S achdeva developed a new type of niti with the addition of copper and chromium to nickel and titanium.These copper niti wires were superior to other niti wires by exhibiting decreased hysteresis and more constant forces were produced. The addition of copper wax to increase strength,decrese hysteresis and to enhance the thermal reactive properties of nickel titanium alloys.

74. Due to decreased mechanical hysteresis in these wires it makes it easier to insert larger rectangular wires without patient discomfort. The addition of copper has enabled in the development of new quarternary alloy with four constant transformation temperatures for four distinct force levels,thus enabling the clinician to select archwires on a case specific basis

75. They are classified as Type I (at 15 degree Celsius) Generate very high forces Very few clinical indicatins Type ii(at 27 degree Celsius) Generates highest forces of the four types and is best used in patients with healthy periodontium When rapid tooth movement is required

76. Type iii(at 35 degree Celsius) Generate tooth driving forces when the mouth temperature exceeds 35 degree Celsius These forces are intermittent in nature Best used in patients who are sensitive to pain,compromised periodontal condition These variant would provide activation only after consuming hot food and beverages

77. Nickel is the most common metal to cause contact dermatitis in orthodontics. Nickel-containing metal alloys, such as nickel-titanium and stainless steel, are widely used in orthodontic appliances. Nickel-titanium alloys may have nickel content in excess of 50 per cent and can thus potentially release enough nickel in the oral environment to elicit manifestations of an allergic reaction .   BIOCOMPATIBILITY NICKEL SENSITIVITY

78. NICKEL FREE STAINLESS STEEL Recently new kind of nearly nickel free austenitic stainless steel was developed and introduced to the market. A lloyed with 15-18% chromium, 3-4% molybdenum, 10-14% manganese, and about 0.9%nitrogen to compensate for nickel. H igh corrosion resistance. The low nickel concentration results in the reduction of nickel allergy potential. Orthodontic wires under the name Manzanium (Scheu), or Noninium (Dentaurum) are already in the market. Unfortunately the melting and forming of this steel is very costly.

79. ALPHA TITANIUM PURE TITANIUM: Below 885 C- Hexagonal closed packed or alpha lattice is available. At higher temperature-body centered cubic or beta crystal HCP-Possess few slip planes Gets hardened by absorbing intraoral free hydrogen ions , which turn it into titanium hydride, at the oral temperature of 37 C and 100% humidity. Any modification should be done within 6 weeks- Mollenhauer

80. Beta titanium (titanium molybdenum alloy or t.m.a.) Introduced by Dr. Burstone(1980) COMPOSITION 80% TITANIUM 11.5% MOLYBDENUM 6% ZIRCONIUM 4.5% TIN

81. ADVANTAGES OF T.M.A. V/S NITINOL SMOOTHER WELDABLE GOOD FORMABILITY ADVANTAGES OF T.M.A V/S S.S. GENTLER FORCES MORE RANGE HIGHER SPRINGBACK DRAWBACK : HIGH COEFFICIENT OF FRICTION

82. LOW FRICTION T.M.A. Introduced by Ormco Done by ion implementation bean mechanism T.M.A C O L O U R S Also developed by Ormco Implantation of oxygen and nitrogen ions Ensures colour fastness

83. property SS CO-Cr-Ni TMA Ni- ti COST LOW LOW HIGH HIGH FORCE DELIVERY HIGH HIGH INTERMEDIATE HIGH ELASTIC RANGE (SPRINGBACK) LOW LOW INTERMEDIATE HIGH FORMABILITY EXCELLENT EXCELLENT EXCELLENT POOR EASE OF JOINING CAN BE SOLDERED& WELDED CAN BE SOLDERED &WELDED TRIED WELDABILITY CANNOT BE SOLDERED OR WELDED ARCHWIRE BRACKET FRICTION LOWER LOWER HIGHER HIGHER BIOCOMPATABILTY SOME SOME SOME

84. Nomograms 89

85. Nomograms With the nomograms shown it is clear that the Stainless steel wire is the stiffer wire with low range of action and more strength. Ni-Ti wires has good range of action but with decreased stiffness and strength Beta titanium has good amount of range of action but less stiffer than that of the s.s

86. Esthetic archwire Composites: can be composed of ceramic fibers that are embedded in a linear or cross-linked polymeric matrix. Developed by a process known pultrusion.

87. optiflex Made of clear optical fibre ;comprises of three layers: A silicon dioxide core A silicon resin middle layer A stain resisted nylon outer layer.

88. properties The most esthetic orthodontic arch wire to date. completely stain resistant Exerts light continuos force Very flexible

89. Other esthetic archwires E.T.E coated Nickel titanium(E.T.E-ELLASTOMERIC POLY TETRA FLORETHYLENE EMULSION). Stainless steel or nickel titanium archwire bonded to a tooth coloured EPOXY coating

90. conclusion It can be seen that not archwire meets all the requirements of orthodontists.We still have long way to go,in terms of finding the “ideal” archwire.But with such progress in science and technology,I am sure that we will see significant improvements in archwires in the near future. Also, we must consider ourselves fortunate to have wide array of materials to choose from.Just imagine working with just a single type of gold alloy wire,like they used to not so long ago.So we should appreciate this fact and try to make the most of what we have.

91. Dr.Rajkumar.Alle. Dr. Shwetha. Dr.Shashikumar. Dr.Suma. Dr.Kiran. Dr.Lokesh. Dr.Dharmesh. Dr.Prabhavati Dr.Siddharth

92. references 1 .Science of Dental materials , Anusavice 2.Dental Materials – Craig. 3 .Contemporary orthodontics- William.R.Proffit,Henry.W.Fields,David M. Sarver 4.Mechanical principles and clinical applications of orthodontic wires – Sunil Kapila and Rohit Sachdeva – AJO August 1989. 5.Mechanical properties of Orthodontic wires in tension bending and torsion. AJO 1982 September – Scot R. Drake, Kamal Asgar , John M. Powers. 6.Orthodontics Current Principles and Techniques – Thomas M. Graber and Robert L. Vanarsdall . Comparison of nickel-titanium and beta titanium wire sizes to conventional orthodontic arch wire materials AJO-1981 Jun- Kusy 7.Effect of composition and cross section on elastic properties of orthodontic wires-AO- kusy and greenburg volume 51 no 4 october 1981. references

93. 8.Cátia Cardoso Abdo Quintão et al, Orthodontic wires: knowledge ensures clinical optimization, Dental Press J. Orthod ., nov./ dec. 2009 references