Archwire Materials And Application Of Newer Materials in Begg Appliance.
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Introduction
Advancements in orthodontic materials have been progressing by leaps and bounds.
Plethora of archwires varying widely – material, geometry, configuration, manufacturing process and physical properties.
Lack of an ideal archwire – clinician – select the best – for the intended use. www.indiandentalacademy.com
Evolution of Archwire Materials
Availability of archwire materials – determined mechanotherapy.
Requirements changes initial stages to finish.
Variable cross section Orthodontics,
Prior to 70’s – only gold & SS – available
Difft. Requirements met – changing cross section – & geometry. www.indiandentalacademy.com
Variable Modulus Orthodontics.
Varying modulus of elasticity.
TMA , Nitinol etc.
Lower moduli – initial stages and higher – finish.
Varying Transformation Temperature Orthodontics.
NiTi archwires – super elastic & thermodynamic.
Cu NiTi & Neosentalloy. www.indiandentalacademy.com
Desirable Properties of Archwire
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Ultimate Tensile Strength Yield Strength Proportional limit Force (stress)
Deflection ( Strain) www.indiandentalacademy.com
Failure Point
Spring back.( Range of Activation or Working range)
Measure of how far a material can be deformed without exceeding the limits of the material. Related to Y.S E Higher spring back – large activations – increase in working time of appl.
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Stiffness ( Load Deflection Rate ).
Measure of resistance to any kind of mechanical deformation,
Proportional to Modulus of Elasticity.
Low stiffness or LDR provide
Ability to apply lower forces
A more constant force
Greater ease & accuracy in applying a given force. www.indiandentalacademy.com
Strength.
It is the measure of the max. possible load, the greatest force which the wire or arch arrangement can sustain or deliver if it is loaded to the limit of the material.
Formability.
Ability to bend a wire into desired configurations without failure. www.indiandentalacademy.com
Modulus of Resilience or Stored energy.
Work available to move the teeth.
Area – elastic portion of the stress- strain curve.
Bio compatibility & Environmental stability.
Resistance to corrosion and tissue tolerance to elements in the wire.
Maintenance of desirable properties for extended periods after manufacture. www.indiandentalacademy.com
Poor Biohostability.
Neither actively nurture nor passively act as a substrate for microorganisms.
Cause foul smell Color changes – detract from esthetics. Remove or build up material – compromise mech prop.
Joinability.
Permit welding and soldering www.indiandentalacademy.com
Friction,
Excessive amount
Loss of anchorage
Less tooth movement.
Esthetics.
Color stability
Inconspicuous
Non Ferromagnetic. www.indiandentalacademy.com
Classification.
Based on material constituent:
Metals. Gold Alloys. Stainless Steel. Cobalt – Chromium Alloys. Nickel- Titanium Alloys
NiTinol Chinese Ni Ti Japanese Ni Ti Niobium Ti Copper NiTi Cv NiTi www.indiandentalacademy.com
Metal Non metal
Beta Ti
Alpha Ti
Non Metals.
Polymeric materials.
Composite / Coated Archwires.
Optiflex.
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Gold Alloys.
Pure gold – too soft for orthodontic purpose.
Initial round wire, Begg - .020 platinised gold.
Hardened – cold working or hardening heat trt.
Marginal properties & price – obsolete. www.indiandentalacademy.com
Stainless Steel
Developed b/w 1903 & 1921
Harry Brearley of Sheffield, F.M. Beckett of the U.S, Edward Maurer of Germany.
1933 – Archie Brusse presented table clinic – 1 st Stainless Steel Appliance system.
Displaced Gold alloys.
SS wires - work horse of the orthodontic industry for generations www.indiandentalacademy.com
Composition.
Steels – iron based alloys – contains < 1.2% C
SS
Types.
Cr. ( 12 – 30%) + steel.
Ferritic
Martensitic.
Austenitic. www.indiandentalacademy.com
Ferritic.
Body Centered Cubic Str.
AISI series 400.
Low sth. & not hardenable by heat trt.
Martensitic.
AISI series 400.
Body Centred Tetragonal Structure.
Strength & Hardness
Corrosion Resistance & Ductility www.indiandentalacademy.com
Austenitic.
Most corrosion resistant.
AISI 302 basic type.
18% - Cr., 8% - Ni., 0.15% C.
AISI 304 – C ltd to 0.08 % 302 & 304
18-8 SS
316 L - <0.03 % C – implants.
Str. – Face Centered Cubic. www.indiandentalacademy.com
A J Wilcock Archwires.
Early 1940’s – acquainted – Mr. Arthur J Wilcock.- Metallurgist – Whittlesea, Victoria.
Years of research – Develop wire – objectives.
Thin tensile wire – distribute force – optimal level
Considerable period of time.
Over long distances.
Minimal loss of force intensity.
Initially 0.018 wire produced.
Dia. - progressively decreased to 0.014. www.indiandentalacademy.com
Wilcock wires mainstay of Begg Technique.
Grades of wire used initially-
Special Plus
Extra Special plus – cases resistant to bite opening.
1984 – A J Wilcock Jr. – request of Dr. Mollenhauer of Australia – ultra high tensile strength – round wire
Supreme grade
0.010 & 0.009 www.indiandentalacademy.com
Pulse Straightening Vs Spinner Straightening.
Spinner Straightening.
Straightening resistant materials – cold drawn condition.
Wire pulled – rotating bronze rollers
Dis Adv.
Resultant Deformation.
Decreased Yield stress value.
Strain softened. www.indiandentalacademy.com
Pulse Straightening.
Pulsed in a special machine.
High tensile wires – straightened.
Lower dia. wires
Yield Strength – not altered.
Surface – smoother finish. www.indiandentalacademy.com
Types of A J Wilcock Archwires.
Regular Grade.( Pink label )
Dia – 0.012 – 0.024
Regular plus (Green label )
Dia – 0.012 – 0.020 Easily formed & excellent for general use & utlility wires.
Special grade ( Blue label )
Dia – 0.012 – 0.020. 0.016 inch – initial stages.
Special Plus ( Yellow label )
Dia – 0.012 – 0.024
Premium
( Purple label )
Dia – 0.012 – 0.020. Ideal for bite opening . Where high resiliency is required www.indiandentalacademy.com
Premium Plus ( Gold label ).
Size – 0.010 – 0.018 In early trt. – alignment & levelling. Mollenhauer recommends – 0.011 wire – high angle cases, undue molar extrusion.
Supreme ( Biege label ).
Size 0.008 – 0.011 Unravelling crowded ant. teeth. Boxed reciprocal torquing aux. Mini uprighting springs. Aligning 2nd molars towards the end of stage II. www.indiandentalacademy.com
Substituted Titanium Alloys.
Ti – used as Structural metal – 1952 .
Became available – Orthodontics – 1970’s.
Allotropy – Crystallographic change – 885°C .
Below 885°C – HCP or α lattice.
Above 885°C – BCC or β lattice.
Addn. of Molybdenum or Columbium stabilize this str. At room temp. www.indiandentalacademy.com
Trends in SS Metallurgy. Eliminate or minimize Nickel content. Nearly Ni free SS Steel Din 1.4456 – one of them Composition: 15 – 18 % Cr. 3 – 4 % molybdenum. 10 – 14 % Manganese 0.9 % nitrogen – compensate for nickel.
Trade names – Menzanium, Noninium. www.indiandentalacademy.com
Nickel – Titanium alloys
Developed by William F Beuhler – Naval Ordinance laboratory – 1960.
1970 - Dr. George Andreasen recognized the potential of this alloy.
Largely through his efforts and those of the Unitek Company, the first nitinol alloy was marketed to orthodontists as Nitinol™. www.indiandentalacademy.com
Andreasen – 2 types.
Elastic Nitinol. Thermal Nitinol.
Thermal Nitinol.
1:1 atomic ratio of Ni and Ti. Ni – 55% , Ti – 45% Co – 1.6% - brings TTR - 37°C. Unique feature – Shape Memory Phenomenon.
Capability of a wire to return to a previously manufactured shape when it is heated through its TTR.
Martensitic Grain Structure www.indiandentalacademy.com
Elastic Nitinol.
Alloy of Ni & Ti without Co,
Elasticity , Flexibility
Lighter continuous forces.
Austenitic Grain Structure.
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Classification ( Kusy )
Conventional Nitinol.
Pseudoelastic Nitinol.
Thermoelastic nitinol.
Conventional – Martensitic stabilized alloy
Passive – SME suppressed – cold working during wire drawing - >8 – 10%.
Attractive feature – Low Stiffness.
Limitation – lack of formability. www.indiandentalacademy.com
Pseudoelastic Nitinol.
Active.
Capable of undergoing anticipated phase transformation.
Undergo some form of SME + Superelastic.
Two types –
Austenitic active alloy
Martensitic active alloy. www.indiandentalacademy.com
Austenitic Active alloy.
Martensite – low stiffness phase.( E = 31 -35 GPa)
Austenite – high stiffness phase. ( E = 84 – 98 GPa)
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On loading – Austenitic alloy – Stiffness 3x, conventional martensitic stabilised alloy.
Plateau like area – Stress induced transformation – martensitic phase. + ve slope – stiffness comparable to martensitic nitinol.
Deactivation – reverse occurs.
2nd Plateau – Martensite shape to maintain force
Austenite. Changes
key attribute – Pseudoelasticity. www.indiandentalacademy.com
Thermoelastic Nitinol.
Martensitic active alloy.
Exhibits thermally induced SME.
Transition temp.- ambient oral temperature.
Medical advances – Trt. Of Scliosis.
Desired shape set by heat.
Distortion & insertion into patient’s mouth
Appliance activated – warmth of oral cavity.
Return to its predetermined shape. www.indiandentalacademy.com
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Chinese NiTi.
Developed by Dr. Tien Hua Cheng & AssociatesGeneral research institute of Non – Ferrous Metals, Beijing, China.
Little work hardening , parent phase – austenite mech prop. differ from Nitinol.
Burstone, Qin, Morton – compared three prop. with SS and Nitinol.
Springback
Stiffness.
Maximum moment. www.indiandentalacademy.com
Springback.
Diff. b/w deflection of 80º & residual deformation after unloading. Chinese Niti > Nitinol > SS
SS Nitinol NiTi
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Stiffness
Steel and Nitinol – average unloading stiffness – same regardless of amount of activation. Chinese Niti – lower stiffness value – value changes with degree of activation.
Maximum moment.
Niti ( 805 gm-mm at 1º of permanent deformation)< Nitinol ( 975 gm-mm) < SS( 1400 gm-mm)
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Applications.
Low stiffness & large deflections are needed.
No time dependent deformation in mouth.
High stiffness at small activations - adequate force levels.
Larger cross sections – larger moments – root movement and transalation. www.indiandentalacademy.com
Japanese Niti
1978 – Furukawa electric company.
Fujio Miura – studied mech. Properties.
Excellent springback & Super elastic properties.
Superelasticity – Stress – fairly constant upto a certain point of deformation - & during rebounding. ( Stress induced martensitic transformation. BCC HCP ) www.indiandentalacademy.com
Continous force – long period during deactivation of the wire.
Physiologic tooth movement.
Possible to modify – force – individualized segment of the arch wire – applying controlled heat. www.indiandentalacademy.com
Introduced in 1994 – Rohit Sachdeva & Suchio Miyasaki 1994.
Major advance – Variable transformation temperature orthodontics.
Stability of Martensite / Austenite at a given temp. – Transformation temp. of the alloy.
Impt. marker Austenite finish temperature.Af.
Working temp. of orthodontic appliance – > Af www.indiandentalacademy.com
Compositon.
LDR charecteristics.
Low hysteresis.
Surface.
Austenitic structure.
Elements Ti Ni Cr Cu
Rough & porous – comparable to TMA.
Alloy types.
Type I – Af = 15°C.
Type II – Af = 27 °C. Type III – Af = 35 °C. Type IV – Af = 40°C
Wt% 42.99 49.87 0.5 5.64
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Type I – high force levels – not used clinically.
Type II – Highest force & best used.
Average or higher pain threshold.
Normal periodontal health.
Rapid tooth movement required.
Type III wire
Low to normal threshold.
Slightly compromised periodontium.
Relatively low forces required. www.indiandentalacademy.com
Type IV –
Sensitive to pain.
Compromised periodontal conditions.
Tooth movement – deliberately slowed down.
Beneficial – initial rectangular wire.
Advantages.
Low hysteresis – more constant force levels.
Difft. Types – match archwire force levels – specific early treatment requirements & goals. www.indiandentalacademy.com
CV NiTi.
Copper free NiTi.
In the same types as CuNiTi.
Similar mechanical properties.
Slower recovery pattern.
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Beta – Titanium Alloys. Charles J Burstone – 1980 ( TMA). Composition.
Titanium79% Molybdenum – 11% Zirconium – 6% Tin – 4%
Addition of elements - molybdenum or columbium, a titanium-based alloy can maintain its beta structure even when cooled to room temperature. www.indiandentalacademy.com
Advantages.
Force levels less than half of stainless steel. Highly ductile – complicated configurations – formed. Weldable. Good spring back.
Disadvantage.
Rough surface – High friction.
Ion implantation – Burstone – 1995. Elements or compounds – ionised and accelerated – to a target. N & O ions from a plasma Ti oxide and nitride formed www.indiandentalacademy.com
Alpha Titanium Alloy:
AJ Wilcock Jr. – 1988 – near α phase Titanium alloy – Orthodontic purpose.
Composition. Titanium – 90%. Aluminium – 6% Vanadium – 4%
Crystal structure. – Closely packed hexagonal lattice (HCP).
Only one active slip plane along its base. BCC – two slip planes ( β Titanium ). Less ductile than TMA www.indiandentalacademy.com
Near α phase Ti alloy – certain amount β phase retained at room temp.
Stiffer with passage of time
Absorption of H+ ions – surface layer – titanium hydride.
Weldable
Dimensions available.
.016 x .022 and .018 x .022.
Rectangular finishing wires. www.indiandentalacademy.com
Non metallic archwires. Esthetic arch wires – Optiflex Unidirectional Fiber Reinforced Polymeric archwire – ( UFRP ) – Composite Archwires. Manufacture.
Photopultrusion Pultrusion - The process of manufacturing components having continuous lengths and a constant cross-sectional shape, such as in archwires. www.indiandentalacademy.com
UFRP compared to NiTi.
Elastic until failure occurs.
Resilience and springback are comparable.
Parlene : poly ( chloro – p- xylylene) – coating
Risk of glass fiber release during clinical use eliminated. www.indiandentalacademy.com
Applications of newer materials in Begg technique. Stage I :
Pulse straightened SS wires and Super elastic NiTi wires – replaced multi loop archwires. 0.010 or 0.011 supreme PS wires – MAA. Better root control in early stages of trt. 0.014 premium plus – in high angle cases to prevent undue molar extrusion.
End of stage II
0.011 – alignment of 2nd molars www.indiandentalacademy.com
Stage III :
Mini uprighting springs – 0.008 – 0.010 supreme P.S wires.
Finishing :
Stiff Rectangular 0.018 x 0.022 α Titanium wires
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Conclusion ď Ž
Recent advances in material science and technology has resulted in an array of newer archwire materials, opening new vistas in Orthodontic treatment. Materials with widely diverging properties are on the market today and their usage has profound implications on the appliance mechanics. www.indiandentalacademy.com
As Kusy points out, composites will increasingly encroach the use of metals, ceramics and polymers as functional and esthetically pleasing appliances become popular. The orthodontist therefore has to clearly outline the phases of treatment and select the archwire most suited for attaining specific goals for treatment. www.indiandentalacademy.com
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