BRAIDED ARCHWIRES

INTRODUCTIONOver the last century, material science

has made rapid progress. This has been evident in our day to day lives also. And Orthodontics, particularly, has benefited largely from this. In this branch of dentistry, not only have the materials been improved, but also the philosophies have changed. Orthodontics has come a long way since the days of the E-arch and various removable appliances used in the early 20th century.

Orthodontic wires which generate the biomechanical forces communicated through brackets for tooth movement are central to the practice of the profession.

BRAIDED ARCHWIRESThe characteristics desirable in an orthodontic

wire are:Large spring backLow stiffness High stored energy Good formability Bio compatibility & environmental

stability

BRAIDED/MULTISTRANDEDWHATS IS ?-They are composed of specified number of thin wire sections coiled around eachother to provide round or rectangular cross section.The wires-twisted or braidedVery small diameter S.S wire can be braided or twisted together by the manufacturer to form wires for clinical orthodontics DIAMETER Separate strands may be as small as 0.005 or

0.010,comprised of five or seven wrapped around a central wire of same diameter.

It affords extreme flexibility and delievers extremely light forces,full engagement of the arch wire at the an early stage

BRAIDED WIRES

USESUsed at the beginning of the treatment to

align labiolingual displaced or rotated anterior teeth.

These wires are available with bright smooth finish to give minimal friction

They resist permanent deformation and not unravel when cut

They are cost efficient wires in comparision to titanium wires.

MULTI-STRANDED/BRAIDED WIRES

ADVANTAGESFLEXIBLESUSTAIN LARGE DEFLECTIONSAPPLY LOWER FORCES WHEN DEFLECTEDGOOD WORKING RANGECAN BE USED DURING INTIAL LEVELLING ALIGNINGPSEUDO-VARIABLE MODULUS MATERIAL

ON BENDINGOn bending individual strands slip over each

other and the core wire, making bending easy. (elastic limit)

2 or more wires of smaller diameter are twisted together/coiled around a core wire.

Diameter - 0.0165 or 0.0175, but the stiffness is much less.

They are available in both round and rectangular shape.

Different type of multi-stranded wires are available 1. Triple stranded – 3 wires twisted2. Coaxial – 5 wires wrapped around a core wire3. Braided – 8 strand rectangular wire.

MULTISTRANDED WIRES

TRIPLE STRANDED-3 WIRES TWISTEDCOAXIAL- 5 WIRES WRAPPED AROUND A CORE WIREBRADED- 8 STRANDS RECTANGULAR WIRE

AVAILABLE

VARIATION IN STIFFNESS

This means that the stiffness of an archwire can be varied in three ways.

The first and traditional approach has been vary the second moment of area ‘I’ about the axis of bending.

Thus small changes in dimensions d and D can result in large variations in stiffness.

The difference between .016” and .014” diameter is approximately 40%.

The second approach to vary the elastic modulus E. that is, use various archwire materials such as Nitinol which has E = 10 x 10 6 psi, Beta-Titanium 15 x 106 psi Gold alloys 20 x 10 6 psi and stainless steel 28 x 10 6 psi, giving a variation of approximately 3 to 1 with stiffness.

A third approach, which is really an extension of the second, is to build up a strand of stainless steel wire, for example, a core wire build up a stand of stainless steel wire for example, a core wire of .0065” and six .0055” wrap, wires will produce an overall diameter approximately .0165 inches. The second moment of area of the strand and an equivalent solid wire would be essentially the same. Young’s modulus in the same for both stainless steel wires yet there is a considerable difference in their respective stiffness.

The reason why the stand has a more flexible feel is due to the contact slip between adjacent wrap wires and the core wire of the stand.

When the strand is deflected the wrap wires, which are both under tension, and torsion will slip with respect to the core wire and each other. Providing there is only elastic deformation each wire should return to its original position.

SUBSTITUTE TO NEWER ALLOY WIRES

Kusy noted that the stiffness of a triple stranded 0175” ( 3 X 008”) stainless steel arch wire was similar to that of 0.010” single stranded stainless steel arch wire. The multistranded archwire was also 25% stronger than the .010” stainless steel wire. Then .0175” triple stranded wire and .016” Nitinol demonstrated a similar stiffness. However nitinol tolerated 50% greater activation than the multistranded wire. The triple stranded wire was also half as stiff as .016” beta-titanium. Multistranded wire can be used as a substitute to the newer alloy wire considering the cost of nickel titanium wire.

Strength – resist distortionSeparate strands - .007” but final wire can be

either round / rectangular Sustain large elastic deflection in bending

Thurow: rough idea – multiply

General considearation

As the diameter of a wire decreases – Stiffness – decreases as a function of the 4th powerRange – increases proportionatelyStrength – decreases as a function of the 3rd power

Multistranded wires Small diameter wires, High strength

Gentler force

ELASTIC PROPERTIESElastic properties of multistranded archwires depend on –1. Material parameters – Modulus of elasticity2. Geometric factors – wire dimension and moment of

inertia3. Twisting or braiding or coaxial4. Constants:

Number of strands coiled The distance from the neutral axis to the outer most fiber of a

strand Plane of bending or bending shape factor Poisson’s ratio

Deflection of multi stranded wire= KPL3

knEIK – load/support constantP – applied forceL – length of the beamK – helical spring shape factorn- no of strandsE – modulus of elasticityI – moment of inertia

Helical spring shape factor Coils resemble the shape of a helical spring. The helical spring shape factor is given as –

2sin α

2+ v cos2 αα - helix angle and v - Poisson’s ratio (lateral strain/axial strain)

Angle α can be seen in the following diagram :-

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Multistranded Wires

Typical geometry of a simple multistranded wire shown is a wire of diametre D composed of three wire strands,each of diametre d,The axial distance which wire strand traverses per rotation equals S.The helix angleα ,which a wire strand makes with normal to the wire axis may be decsribed in term d,D and S

Schematic definition of the helix angle(a).if one revolution of a wire strand is unfurled and its base length[p(D-d)] an corresponding distance traversed along the orginal wire axis(S*) ARE DETERMINED.then a ratio of these two distance equals tan a.everything else being equal.the greater p(D-d) or the less S* is the compliant a wire will be

Wildcat

-Springy -High tempered -Three strand twist wire

TRICAT

-Three twisted rounded wires - Preformed GAC

QUAD-Cat - Preformed - Three strand - Twisted wirePENTACAT - Coaxial wire - Spooled or preformed - Five strands around one

GAC

Super cable

In 1993,Hanson combined the mechanical advantages of multi-stranded cables with the material properties of super elastic wires to create a super elastic nickel titanium coaxial wire.

This wire called super cable comprises seven individual strands that are woven together in a long,gentle spiral to maximize flexibility and minimize force delivery.

Source: JCO,Apr 1998

Clinical use of supercable

The most clinically significant finding was that the .016 and .018 supercable wires were the only ones that tested at less than 100g of unloading force over a deflection range of 1-3 mm.

Supercable thus demonstrates optimum orthodontic forces for the periodontium.

It offers the clinician the advantage of engaging a relatively large archwire at the start of treatment.

By occupying more of the bracket slot,the .018 supercable is able to accomplish a greater degree of uprighting,leveling,and rotational control than other initial arch wires.

Supercable’s unique construction and super elastic properties permit it to be gently engaged in even the most crowded cases without patient discomfort.

A. Placement of initial mandibular .016" Supercable archwire. B. Segmented .016" Supercable wire, seated in auxiliary slot of maxillary lateral and first bicuspid brackets, is flexible enough to be fully engaged in main arch wire slot of palatally displaced cuspid.

FORCE DELIVERY TEST A three-point bending test was carried out

to compare the force delivery of .016", .018", and .020“ Supercable with that of common nickel titanium initial archwires.

Instron universal testing machine was used for load deflection test.

All arch wires were loaded with a maximum deflection of 4 mm, and then unloaded slowly JCO-98 JEFF BERGER

.016" and .018" Supercable wires exerted only 36-70% of the force of .014" solid nickel titanium wires.

Comparing wires of the same diameter, .016" Supercable demonstrated 65% less force than .016" solid superelastic wires

while .018" Supercable exerted 78% less force than .018“ solid superelastic archwires.

STUDY RESULTS

JCO-98 JEFF BERGER

CLINICAL USES OF SUPER CABLE

.016" and .018" Supercable wires were the only ones that tested at less than 100g of unloading force over a deflection range of 1-3mm.

Supercable thus demonstrates optimum orthodontic forces for the periodontium, as described by Reitan and Rygh.

Relatively large archwire like 0.18” can be placed at the starting of treatment.

When cutting Supercable, always use a sharp distal end cutter (No. 619). A dull cutter tends to tear the component wires and thus unravel the wire ends.

END STOP

ADVANTAGES

• Improved treatment efficiency.• Simplified mechanotherapy.• Elimination of archwire bending.]• Flexibility and ease of engagement regardless of crowding.• No evidence of anchorage loss.

• A light, continuous level of force, preventing any adverse response of the supporting periodontium.• Minimal patient discomfort after initial archwire placement.• Fewer patient visits, due to longer archwire activation.

• Tendency of wire ends to fray if not cut with sharp instruments.

• Tendency of archwires to break and unravel in extraction spaces

• Inability to accommodate bends, steps, or helices.

• Tendency of wire ends to migrate distally and occasionally irritate soft tissues as severely crowded or displaced teeth begin to align.

DISADVANTAGES

CASE REPORT Use of SPEED Supercable with Sectional Mechanics

MARIELLE BLAKE, JCO-2003

A maxillary permanent central incisor can fail to erupt because of a midline supernumerary or a retained deciduous incisor. When spontaneous eruption of the permanent incisor does not occur after removal of the supernumerary or deciduous tooth, orthodontic traction may be required to bring the incisor into the arch.

Placement of a full fixed appliance may not be feasible in the early mixed dentition because of a lack of teeth available for bonding. There is also a risk of root resorption if the lateral incisors are bonded when the incisor roots are in close proximity to the crown of the developing permanent canine .

This article describes such a case that was resolved by the use of a sectional SPEED appliance with a SPEED Supercable archwire.

After exposure of maxillary central

incisor.

Initial treatment involved the removal of the retained deciduous incisor and exposure of the maxillary left central incisor . Four months after the surgery, some spontaneous eruption of the permanent incisor had occurred, but it was evident that orthodontic intervention would be required to bring the tooth into the arch

SPEED brackets were placed on the two central incisors, and an .016" Supercable archwire was engaged in the brackets. Light-cured composite stops were added to the archwire to prevent archwire disengagement or fraying of the wire ends

RESULTS

A marked improvement in tooth position was evident eight weeks later . The appliance was removed after six months of active treatment and the final radiograph showed good tooth alignment with no evidence of root damage. A bonded palatal retainer was placed to counteract any vertical or rotational relapse tendency.

SPEED Supercable is a superelastic nickel titanium coaxial wire consisting of seven interwoven strands. The superelastic properties of Supercable allow full bracket engagement with extremelylow unloading force delivery. In this case, full ligation of any other wire might have resulted in permanent deformation of the archwire, debonding of the brackets, or application of excessive force.

Supercable is designed to accept sharp bends without taking a permanent set. Therefore, distal end bends are impossible. Although light-cured composite stops were used in this case, specially designed Supercable stops are also available.

The SPEED system is ideally suited to segmental mechanics. When the spring clip is closed, the bracket acts as a tube. This allows fewer teeth to be incorporated into the system without the problems of archwire disengagement that occur with wire ligation of twin brackets.

Elastic Flexural Properties of Multistranded Stainless Steel Versus Conventional Nickel Titanium Archwires*

Brian K. Rucker, PhDa; Robert P. Kusy, PhDa–d

Kusy (ajo-do 2002)physiologically acceptable tooth movement can be

achieved if light, continuous forces are used rather than heavier, intermittent forces.Low-stiffness wires are used to deliver these light forces, typically single-stranded nickel titanium (NiTi) wires or multistranded stainless steel (SS)

elastic materials that include SS and con- ventional NiTi, which is stabilized martensite, deliver forc- es that are proportional to the amount of activation.

These forces decrease as the teeth move and the wires deactivate. Alternatively, pseudoelastic (so-called ‘‘superelastic’’) NiTi archwires are now available3 that deliver a nearly constant

Three stranded twisted and coaxial wire configurations indeed attain the best elastic properties among basic multistranded geometries, and (2) multistrand- ed SS archwires often matched the elastic properties of con- ventional NiTi leveling wires These findings were based on several assumptions,Two of which were that there was no strand interaction(eg, interstrand friction) during flexure and that the stress at the proportional limit .

Three-stranded (triple) and six-stranded coaxial (coax) SS archwires, each from four manufacturers, were com- pared to single-stranded (single) SS and conventional NiTi leveling wires.

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Multistranded Wires

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MULTISTRANDED WIRES Results

Interaction between individual strands was negligible.

Range and strength Triple stranded Ξ Co-axial (six stranded)

Stiffness Coaxial < Triple stranded

Range of single stranded SS wire, triple stranded and co-axial were similar.

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Multistranded Wires

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Multistranded Wires

Kusy ( AJO-DO 1984)

Compared the elastic properties of triple stranded S.Steel wire with S.Steel, NiTi & B-TMA

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Results

Results

AJO-86Ingram, Gipe and Smith (AJO 86)

Range of independent of wire sizeRange seems to increase with increase in diameter It varies only from11.2-10.0-largest size having slightly

greater range than smallest wire

Results: NiTi>MS S.Steel>CoCr>Steel

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Multistranded Wires Nanda et al (AO 97)

WIRE STIFFNESS CAN BE ALTERED BY NOT ONLY CHANGING THE SIZE OR ALLOY COMPOSITION BUT BY VARYING THE NUMBER OF STRANDS

Increase in No. of strands stiffness

UNLIKE SINGLE STRANDED WIRES

Stiffness varies as deflection varied

conclusionIn the last few decades , a variety of new wire alloys

have been introduced in orthodontics. These wires demonstrate a wide spectrum of mechanical properties and have added to the versatility of orthodontic treatment. Appropriate use of all the available wire types may enhance patient comfort and reduce chair side time and the duration of treatment.

The restricted use of only stainless steel wires to treat an entire case from start to finish therefore may be indicated only in relatively few patients. It may be beneficial instead to exploit the desirable qualities of a particular wire type that is specifically selected to satisfy the demands of the presenting clinical situation. This, in turn, would provide the most optimal and efficient treatment results.

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