Archwires in orthodontics

Basic properties and different archwires used in orthodontics

1. Dr.ABIRAJ K R POST GRADUATE ARCHWIRES

2. TABLE OF CONTENTS

3. INTRODUCTION

4. EVOLUTION OF ORTHODONTIC ARCH WIRES

5. PHASES OF ARCH WIRE DEVELOPMENT

6. PHASE ONE

7. PHASE TWO

8. PHASE THREE

9. PHASE FOUR

10. PHASE FIVE

11. CLASSIFICATION OF ARCH WIRES

12. ROUND WIRES Initial and intermediate stages of treatment to correct crowding,level the arch,close spaces SQUARE OR RECTANGULAR WIRES Final stages of treatment to position the crown and root in the correct maxillary and mandibular relationship SHAPES OF ARCH WIRE

13. REQUIREMENTS OF IDEAL ARCH WIRES

14. STRESS Internal distribution of load STRESS= FORCE UNIT AREA Expressed as pascal 3 types BASIC PROPERTIES

15. Internal distortion produced by the load STRAIN= CHANGE IN DIMENSION ORIGINAL DIMENSION No unit of measurement Dimensionless quantity STRAIN

16. STRESS STRAIN CURVE

17. INTERPRETATION

18. Stress is proportional to strain within the elastic limit HOOKE’S LAW

19. Greatest stress that is produced in a material such that the stress is directly proportional to strain SUPER ELASTIC A- NiTi WIRES EXCEPTION!! PROPORTIONAL LIMIT

20. strength at which material begins to function in a plastic manner. Limiting deviation of 0.1% from proportionality of stress to strain. YIELD STRENGTH

21. Maximum load the wire can sustain,before breaking. ULTIMATE TENSILE STRENGTH

22. The point at which the wire breaks. FAILURE POINT

23. Relative stiffness or rigidity of a material Ratio of stress to strain within proportional limit Measured by slope of elastic region MODULUS OF ELASTICITY

24. CLINICAL APPLICATION

25. : LATERAL STRAIN AXIAL STRAIN For an ideal isotropic material,ratio is 0.5 POISSON’S RATIO

26. Force required to bend or deform the material over a definite distance STIFFNESS= FORCE DISTANCE Proportional to the slope of the linear portion of curve STIFFNESS

27. STRENGTH

28. STRENGTH AND STIFFNESS

29. RESILIENCY

30. FORMABILITY

31. RANGE

32. STRENGTH = STIFNESS × RANGE SPRINGINESS= 1 STIFFNESS Factors that influence strength,stiffness,range Mechanical arrangement by which force is applied to teeth,eg.bracket width,length of arch wire,span and loops Form of the wire itself-size and shape of cross section,alloy formula,hardness RELATION BTWEEN THREE ELASTIC PROPERTIES

33. STIFFNESS STRENGTH RANGE α Modulus of elasticity α Resiliency α Elastic limit α 1/L 3 α 1/length α L 2 α d 4 α d 3 α 1/d α 1/no. of coils ---- α n. of coils α 1/coil diameter 3 ---- α coil diameter 2 RELATIONSHIP B/W STIFFNESS,STRENGTH,RANGE AND VARIABLES OF WIRE COMPONENTS

34. SPRING BACK

35. FLEXIBILITY

36. TOUGHNESS

37. BRITTLENESS

38. FATIGUE

39. DUCTILITY

40. MALLEABILITY

41. Describes functional charecteristics of orthodontic appliance LDR = LOAD DEFLECTION Dependant on length and diameter of wire LOAD DEFLECTION RATE

42. For orthodontic spring—LOW LDR For retentive units---HIGH LDR CLINICAL APPLICATION

43. Cantilever beams Beams supported on only one end Eg : finger spring Supported beams Beams supported on both the ends Eg:arch wire segment b/w two teeth EFFECTS OF GEOMETRY OF BEAMS

44. GEOMETRY:SIZE AND SHAPE CANTILEVER BEAMS In orthodontic applications, this is the type of spring often used in removable appliances, in which a wire extends from the plastic body of the removable appliance as a finger spring. When a round wire is used as a finger spring, doubling the diameter of the wire increases its strength eight times EFFECT ON ELASTIC PROPERTIES OF BEAM

45. SUPPORTED BEAMS

46. Torsion is actual twisting that take place in the material STRENGTH α size of wire Springiness α 1 size of wire RANGE α 1 size of wire IN TORSION

47. ROUND WIRES RANGE α 1 DIAMETER STIFFNESS depends on value called MOMENT OF INERTIA , property of shape that is used to predict deflection, bending and stress in  beams . STIFNESS α DIAMETER 4 STRENGTH α DIAMETER 3 EFFECT OF CROSS SECTION

48. RECTANGULAR WIRES

49. Geometry:length and attachment

50. IN TORSION

51. BEHAVIOUR OF ARCHWIRE IN BENDING

52. BENDING MOMENT

53. Maximum bending moment in a cantilever is at the supported end. In beam terminology the location of this maximum bending moment is called CRITICAL or DANGEROUS section. CRITICAL SECTION

54. Part of beam that is niether elongated nor compressed in bending Midway b/w outer and inner curved sides No longitudinal stress or Strain NEUTRAL AXIS

55. NOMOGRAMS

56. 1977—ADA specification number 32 was published. Properties of orthodontic wires are commonly determined by means of various laboratory tests like --BENDING TEST --TORSION TEST LABORATORY TESTS

57. Provides information on behaviour of wires when subjected to 1 st and 2 nd order bends METHOD Bending couple is applied at one end of the specimen where only rotation is permitted; at the other end of test span wire is held against fixed knife edge stop --Angular deformation measured is rotation of the shaft --plot of applied couple versus angular deformation is done Bending test

58. Reflect wires characteristics in third order direction TORSION TESTS

59. MANUFACTURE OF ORTHODONTIC WIRES

60. Considerable work hardening of the alloy occurs during rolling. It may fracture if rolling is continued beyond this point TO PREVENT THIS: Rolling process is interrupted Metal is ANNEALED by heating to suitably high temperature

61. RECTANGULAR WIRES

62. PROCESS OF MANUFACTURE

63. Greater flexibility Greater Resiliency Permits usage of small diameter wire resulting in lighter and more constant force SIGNIFICANCE IN PRODUCTION OF ORTHODONTIC SPRINGS

64. BAUSCHINGER EFFECT

65. SPRING PROPERTIES OF WIRE

66. PRINCIPLES IN THE CHOICE OF ARCHWIRES

67. Dental arch form varies among individuals Basic principle - the patient's original arch form should be preserved CATENARY CURVE It was first described by MacConaill who suggested that normal human dental arches conform closely to a  catenary curve For all patients, the fit is not as good ARCHWIRE FABRICATION

68. 1972--BRADER Based on a trifocal ellipse. The anterior segment closely approximates the anterior segment of a catenary curve Gradually constricts posteriorly More closely approximate the normal position of the second and third molars. BRADER ARCH FORM

69. SPRING BACK LOAD DEFLECTION RATE FORMABILITY MODULUS OF RESILIENCE BIOCOMPATIBILITY AND ENVIORNMENTAL STABILITY JOINABILITY FRICTION WIRE CHARECTERISTICS OF CLINICAL RELEVANCE

70. WILLIAM R PROFFIT,5 TH EDITION GRABER,VANARSDALL PHILLIPS SCIENCE OF DENTAL MATERIALS,11 TH EDITION GOOGLE REFERENCES

71. GOLD ALLOYS

72. HEAT TREATMENT OF GOLD WIRES SOFTENING HEAT heating at 700⁰ for 10 min TREATMENT followed by quenching AGE HARDENING heating b/w 200 and 450⁰ TREATMENT for 15 to 30 min. followed by quenching

73. ADVANTAGES Good formability capable of delivering low forces corrosion resistant Excellent stability and biocompatibility DISADVANTAGES High cost Low spring back USES Only crozat appliance is still occasionally made from gold

74. COBALT CHROMIUM ALLOYS Following World War II, returning servicemen complained that their Elgin watches couldn't take the corrosive environmental situations in various theatres of the war. Developed by Dr.ROBERT RICKETTS

75. A fter 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.

76. ELIGILOY PROPERTIES

77. COMPOSITION COBALT 40 % CHROMIUM 20 % NICKEL 15 % MOLYBDENUM 7 % MANGANEESE 2 % CARBON 0.15 % BERYLLIUM 0.4 % IRON 15 %

78. 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

79. 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.

80. Green (Semi resilient) More resilient than yellow can be shaped with pliers before heat treatment. Red (Resilient) Most resilient with high spring qualities. Withstands only minimal working. Fractures easily after heat treatment, all adjustments should be made before this precipitation hardening process .

81. APPLICATION IN ORTHODONTICS Finishing arches for post treatment provide long term stability Five arch forms Delivered unheat -treated allowing complex bends and loops to be easily made After bending eligloy arches can be heat treated to increase their springiness

82. ROUND .016 .018 SQUARE .016 × .016 .019 × .019 RECTANGULAR .016 × .022 .017 × .025 .018 × .025

83. Clinical applications MAXILLARY AND MANDIBULAR CUSPID RETRACTOR Blue eligloy .016 × .016 , unheat treated

84. WARREN ANTERIOR TORQUING SPRING

85. Maxillary quad helix 0.38” blue eligloy Coil springs Red eligloy

86. NICKEL TITANIUM ALLOY WILLIAM F BUEHLER in 1960’s invented Nitinol Ni—nickel Ti—titanium Nol —naval ordinance laboratory,U.S.A ANDREASEN G.F and coworkers introduced the use of nickel titanium alloys for orthodontic use in 1970

87. METALLURGY Titanium was discovered by w.Gregor and named by KLAPORTH Atomic number 22,atomic weight 47.9,9 th place in abundance of metals in earth crust

88. PROPERTIES OF TITANIUM

89. NICKEL –TITANIUM ALLOYS-GENERATIONS FIRST GENERATION Reported by ANDREASEN in 1971 Marketed as nitinol by unitek /3M Did not exhibit super elastic behaviour,but possessed two features A very low elastic modulus An extremely wide working range SECOND GENERATION Super elastic chineese NiTi Exhibits non-linear loading and unloading characteristics more pronounced than those of original nitinolwire

90. THIRD GENERATION Japaneese NiTi marketed as SENTALLOY Super elastic behaviour and shape memory characteristics of these alloys are based on reversible transformation between the austenitic and martensitic NiTi phases FOURTH GENERATION In 1990’sthermally activated NiTi wire introduced Transition temperature close to thebody temperature

91. KUSY (1991) classified NiTi into: MARTENSITIC-STABILIZED ALLOYS Do not possess shape memory or super elasticity They are non super elastic wire alloys such as originally developed Nitinol MARTENSITIC-ACTIVE ALLOYS Employ thermo elastic effect to achieve shape memory Deformed arch wire with martensitic form Oral environment Transforms back to austenite , to starting shape AUSTENITIC-ACTIVE ALLOYS Undergoes SIM transformation when activated Display super elastic behaviour

92. MECHANICAL PROPERTIES OF NITINOL

93. 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 ACTIVE AUSTENITIC FORM Appeared in late 1980’S Exhibited the remarkable property of NiTi alloys-SUPER ELASTICITY Referred to A- NiTi

94. PROPERTIES

95. PROPERTIES SPRINGBACK AND FLEXIBILITY Good spring back and flexibility Low stiffness High spring back is useful in situations that require large deflections but low forces LOAD DEFLECTION RATE Produce lower,constant,continuous forces JOINABILITY Not joinable Hooks cannot be bent or attached to Nitinol,crimpable hooks and stops are used

96. FORMABILITY

97. SHAPE MEMORY ANDREASEN and MORROW described the “shape memory” phenomenon as capabilty of wire to return to a previously manufactured shape when it is heated through TTR FRICTION Garner,Allai and Moore(1986) and kapila et al(1990) Bracket wire frictional forces with Nitinol wires are higher than those with SS wire and lower than those with β - Ti,in 0.018 inch slot

98. TRANSITION TEMPERATURE RANGE Specific temperature range when the alloy nickel titanium on cooling undergoes martensitic transformation from cubic crystallographic lattice(AUSTENITIC PHASE) Range for most binary NiTi alloys 40-60⁰ c Transformation from austenite to martensite can occur by Lowering the temperature Applying stress (SIM)

99. SHAPE MEMORY Shape memory refers to the ability of material to “remember” its original shape after being plastically deform while in martensitic form Also called THERMOELASTICITY There are two major NiTi phases in the nickel titanium wires Austenitic NiTi Martensitic NiTi

100. Controlling low and high temperature,a change in crystal structure called martensitic transformation can be produced The phenomenon causes change in physical properties in martensitic phase,the metal is ductile in austenitic phase,it is difficult to induce deformation

101. SHAPE MEMORY FORMING THE ARCH WIRE IN THE DESIRED SHAPE AT AN ELEVATED TEMPERATURE WIRE COOLED BELOW TRANSITION TEMPERTURE,WIRE CAN BE PLASTICALLY DEFORMED TAKING WIRE AGAIN THROUGH TTR WILL RESULT IN ORIGINAL SHAPE

102. HYSTERESIS Transformation from austenite to martensite and reverse do not take place at the same temperature. The range for most binary NiTi alloys is 40⁰cto 70⁰c

103. TWINNING

104. PSEUDOELASTIC NITINOL Also referred as A- NiTi This group Includes --- chineseNiTi --- japanese NiTi ---27⁰super elastic cu- NiTi In Austenitic active alloy both Martensitic and austenitic phases play an important role during mechanical deformation

105. SUPER ELASTICITY

106. MECHANISM OF SUPER ELASTICITY Stress induced martensitic transformation Phase transition in grain structure from Austenite to martensite In response to applied force,not to temperature This transformation is mechanically analogue to thermally induced shape memory effect This mechanism is possible as their TTR is close to room temperature

107. THE UNLOADING CURVE CHANGES AT DIFFERENT ACTIVATIONS

108. CHINESE NiTi

109. PROPERTIES SPRING BACK At 80⁰ of activation --1.4 times the spring back of Nitinol wire --4.6 times the spring back of SS wire STIFFNESS is 36% that of Nitinol wire and 73% ss wire

110. Temperature dependant changes

111. JAPANESE NiTi

112. PROPERTIES

113. Clinical applications Alignment of badly malposed teeth Distalize the molar Expansion of arch Gain/close space Periodontally compromised pts

114. ADVANTAGES OF SUPER ELASTIC NiTi Constant force over wide range of deflection Low stiffness High Spring back More effective in initial toothalignment Less patient discomfort LIMITATIONS OF SUPERELASTIC NiTi Cannot be soldered or welded Poor formability Tendency for dentoalveolar expansion Expensive

115. COPPER NiTi Invented by Dr.ROHIT SACHDEVA COMPOSITION Nickel Titanium Copper (5-6%) Chromium (0.2-0.5%)

116. COPPER Icreases strength Reduces hysteresis These benefits occur at expense of increasing TTR above that of oral cavity CHROMIUM To compensate for the above mentioned unwanted effect 0.5% chromium is added to return TTR close to oral temperature

117. TYPES OF CU- NiTi TYPE I - A F 15⁰ C -Not used for clinical application due to high force TYPE II -A F 27⁰ C -This generates heavy force than type III,IV wires -Best used in pts with average or high pain threshold -patients with normal periodontal health -patients in whom rapid tooth movement is required

118. TYPE III-A F -35⁰ C -this generates mid range of forces -used in periodontally compromised patients -patients with low to normal pain threshold - whn reltively low forces are requested TYPE IV-A F -40⁰ C -generates tooth moving forces when mouth temp exceeds 40⁰c -patients sensitive to pain - Periodontally compromised patients -beneficial as an initial rectangular wire

119. ADVANTAES OF CU NiTi OVER OTHER NiTi CU- NiTi generates more constant force over long activation spans More resistant to permanent deformtion Exhibits better spring backproperties Reduced hysteresis Enables clinician to select archwires on a case specific

120. β -TITANIUM OR T.M.A In 1979 β titanium was introduced In 1981 it was introduced to orthodontics by CHARLES J BURSTONE and JON GOLDBERG COMPOSITION Titanium -77.8% Molybdenum-11.3% Zirconium-4.3%

121. STRUCTURE At room temp. it is stable in alpha phase and is HCP lattice At temp. above 1625⁰F titanium rearranges into a BCC-beta phase By adding molybdenum, the beta form of titanium can be stabilized even when cooled to room temperature Such alloys are referred as beta stabilized titaniums These alloys are strengthened by coldworking or precipitation of HCP

122. PROPERTIES ALLOY MODULUS OF ELASTICITY YIELD STRENGTH ULTIMATE TENSILE STRENGTH Β -Titanium 71.7 × 10 3 931 1276

123. CLINICAL APPLICATION Rectangular TMA used during retraction K-SIR arch wire .019” Utility arches

124. ALPHA TITANIUM Developed by A J WILCOCK jr IN 1988 Possess closely packed hexagonal lattice Manufactured by a process called feed centerless grinding Supplied as square and rectangular wires COMPOSITION Titanium 88.9% Aluminium 7.86% Vanadium 4.05%

125. PROPERTIES

126. TIMOLIUM WIRES

127. Clinical application

128. AESTHETIC WIRES

129. OPTIFLEX POLYNORBOGEN TEFLON COATED WIRES BIOFORCE ARCH WIRES ORGANIC POLYMER WIRE (QCM)

130. OPTIFLEX

131. 3 layers

132. It the most aesthetic orthodontic archwire . It is completely stain resistant , and will not stain or loose its clear look even after several weeks in mouth . Its effective in moving teeth using light continuous force Its very flexible it has an extremely wide range of actions when indicated it can be tied with elastomeric ligatures to severely malaligned teeth without fear of fracturing the arch wire. Due to superior properties optiflex can be used with any bracket system

133. clinical applications It is used in adult patients where esthetics is chief concern Can be used as initial archwire in cases with moderate amounts of crowding in one or both arches. ideal for non extraction cases and also cases with no partially edentulous areas Optiflex can be used in presurgical stage in cases which require orthognathic intervention

134. Precaution’s while using optiflex archwires Optiflex archwires should be tied into brackets with elastomeric ligatures. Metal ligatures should never be used since they will fracture the glass core. Sharp bends should never be attempted with optiflex , as these bends will immediately fracture the glass core. Using instruments with sharp edges, like the scaler etc should be avoided To cut the end of the archwire distal to the molar, it is recommended to the use the mini distal end cutter which is designed to cut all 3 layer’s of optiflex .

135. POLYNORBOGEN

136. TEFLON COATED WIRE EPOXY COATED ARCH WIRE Tooth colored arch wire Superior wear resistance and color stability of 4 to 8 weeks LEE WHITE WIRE Manufactured by lee pharmacuetical It’s a resilient ss or NiTi arch wire bonded to a colored coating

137. BIOFORCE ARCH WIRES

138. PROPERTIES

139. ORGANIC POLYMER WIRE Made from 1.6 mm diameter round polytheline terephthalate Easy to fabricate and fit into dental arches Can be used as esthetic maxillary retainers

140. SUPER CABLE 1993-HANSON combined advantages of multistranded cables and super elastic wires to create super elastic NiTi coaxial wire Comprises seven individual strands that are woven together in a long, gentle spiral form Maximize flexibility and minimize force delivery.

141. BRAIDED AND TWISTED WIRE

142. Available in both round and rectangular shape. Different type Triple stranded – 3 wires twisted Coaxial – 5 wires wrapped around core wire Braded – 8 strand rectangular wire. Used at the beginning of the treatment to align labiolingually displaced or rotated anterior teeth.

143. FIBRE REINFORCED COMPOSITE ARCH WIRES Excellent combination of high elastic recovery, high tensile strength and low weight. Excellent formability Allow for flexural and torsional properties . Excellent aesthetics because of their translucency . Ability to form wires of different stiffness values for the same cross-section.

144. Made of glass fibres and acrylic resin Manufactured by photopulstration or electromagnetic radiation

145. Recent Reports on Fiber Reinforced Composite Archwires Recent modification (Reports by Zufall , Kennedy and Kusy , Angle Orthod 2000; 70: 34-47 ) They compared the frictional characteristics of composite archwires against stainless steel and nickel titanium They found composite archwires had higher kinetic coefficients of friction than stainless steel but lower than nickel-Titanium or beta titanium.

146. RECENT ADVANCES

147. COMBINED ARCH WIRES The key to success in a multi attachment straight wire system is To have the ability to use light tipping movements in combination with rigid translation They used three specific combined wires for the technique Dual Flex-l, Dual Flex-2, and Dual Flex-3 (Lancer Orthodontics) .

148. The Dual Flex-1  it consists of a anterior section made of 0.016-inch round Titanal and a posterior section made of 0.016-inch round steel.  The flexible front part easily aligns the anterior teeth and the rigid posterior part maintains the anchorage and molar control by means of the “ V ” bend, mesial to the molars.  It is used at the beginning of treatment.

149. The Dual Flex-2 it consists of a flexible anterior segment composed of an 0.016 ´ 0.022-inch rectangular Titanal and a rigid posterior segment of round 0.018-inch steel. The Dual Flex-3 , consists of a flexible anterior part of an 0.017 ´ 0.025 -inch Titanal rectangular wire and a posterior part of 0.018 round steel wire. The Dual Flex-2 and 3 wires establish anterior anchorage and control molar rotation during the closure of posterior spaces. They also initiate the anterior torque

150. BIO TWIST NiTi

151. NITANIUM TOOTH TONE PLASTIC COATED ARCH WIRE Nitanium  is a special hybrid non-heat-treated form of Chromoly steel that contains trace elements of Titanium and Niobium Stain and crack resistant Plastic and friction reducing tooth colored coating blend with natural dentition as well as ceramic and composite brackets Blend with tooth anatomy Delivers 29 to 150 gms of force on teeth

152. TRIFORCE WIRE Makes titanium more esthetic Delivers force constantly Pre programmed wire to deliver the right amount of force for each area of mouth Delivers high force on molar,medium force to bicuspids,light forces to incisors Prevents unwanted rotations of premolar Provides 3 dimensional controls from beginning of treatment

153. TRIANGULAR WIRE BROUSSARD and GRAHAM in 2001 introduced SS triangular wire Equilateral in cross sectionof .030” to a side with rounded edges Used for making retainer,removable appliance and bonded lingual retainer

154. GOLD NiTi WIRES NiTI wire is coated with super hard gold 24carat Allows silky smooth sliding mechanics and give a fabulous rich look

155. CONCLUSION It is important to know the properties of the archwires as it is widely used in orthodontics. Proper handling of the material gives the best result. Materials with excellent aesthetics and strength expected to replace metals in orthodontics in the near future

156. REFERENCES William R Proffit , Henry Fields, David M Server; Contemporary Orthodontics, 5 th edition Phillips’ science of dental materials, 11th ed , Anusavice Graber, Vanarsdall , Vig ; Orthodontics - Current principles and Techniques Recent modification (Reports by Zufall , Kennedy and Kusy , Angle Orthod 2000; 70: 34-47 Google