WIRES IN ORTHODONTICS

CONTENTS

INTRODUCTIONCLASSIFICATION

IDEAL REQUIREMENTSGOLD AND GOLD ALLOYS

STAINLESS STEEL NICKEL TITANIUM ALLOYS

BETA TITANIUMCOBALT CHROMIUM NICKEL ALLOYS

OPTIFLEX ARCH WIRES MULTISTRANDED ARCH WIRES

CONCLUSIONREFERENCES

INTRODUCTIONWires are one of the active components of fixed appliances. They can bring about various tooth movements through the medium of brackets and buccal tubes, which act as handle on the teeth.In early days pure gold arch wires were used .Their high cost and mechanical inefficiency led to the use of stainless steel arch wires. In the 70's and 80's a number of titanium based arch wires were introduced into orthodontics.

CLASSIFICATION

BASED ON MATERIAL USED • Gold and gold alloys • Stainless steel• Nickel titanium alloys • Beta titanium• Cobalt chromium nickel alloys • Optiflex arch wires

BASED ON CROSS SECTION• Round• Square• Rectangular• Multistranded

IDEAL REQUIREMENTS

Spring back: It is the measure of how far a wire can be deflected without causing permanent deformation. It is also called elastic deflection. The arch wire should ideally possess high spring back, which results in an increase in its range of action.

Stiffness: The presence of a low stiffness provides the ability to apply lower forces and a more constant force over time.

Formability: The orthodontic arch wire material should exhibit high formability so as to bend the arch wire into desired configuration such as coils,loops,etc,without fracturing the wire.

Resilience: Resilience is the amountof force the wire can withstand before permanent deformation. Arch wires should exhibit high resilience so as to increase the working range of the appliance.

Biocompatibility and environmental stability: Orthodontic arch wires should exhibit resistance to tarnish and corrosion and should be non toxic. The material should maintain its desirable properties for extended periods of time after manufacture

Joinability : The wire should be amenable to soldering and welding.

GOLD AND GOLD ALLOYS Prior to 1940, gold was extensively used in the manufacture of orthodontic arch wires. The high cost involved led to the invention of gold alloys in which other metals like copper,silver and palladium were added and the percentage of gold reduced. Gold and gold alloy arch wires exhibit excellent formability, environmental stability and biocompatibility. The drawbacks of these arch wires include low spring back and high cost.

STAINLESS STEEL Austenitic stainless steel which is sometimes referred to as 18/8 stainless steel is used to make orthodontic arch wires. Stainless steel arch wires exhibit adequate strenght,resilience,formability and adequate spring back. In addition they are biocompatible and economical.

NICKEL TITANIUM ALLOYS Nickel titanium alloy also called Nitinol (Nickel

Titanium Naval Ordinance Laboratory) was invented by William R. Buchler at the Naval Ordinance Laboratory. This alloy exhibits super-elasticity and shape memory. They were introduced to the orthodontic community by Anderson in 1971. Nitinol arch wires exhibit high spring back, high working range and low stiffness. Thus these arch wires on activation produce lower and more constant force on teeth.

BETA TITANIUM Beta titanium was intoduced by Jon Goldberg and C.J. Burstone. It is available by tradename T.M.A. wires. These wires exhibit a high range of action and spring back. They also permit making of loops and helices due to their high formability. An added feature of these wire is that they can be welded.

COBALT CHROMIUM NICKEL ALLOYS Cobalt chromium nickel alloys drawn into wires can be used successfully in orthodontic appliances. These alloys are available commercially as Elgioly. These arch wires exhibit adequate spring back,formability and are biocompatible.

OPTIFLEX ARCH WIRES It is a new type of arch wire developed by M.F TALASS in 1992. These arch wires are made of clear optical fibre and are therefore highly esthetic. In addition,they exhibit high resilience.The drawback of this wire is that it cannot accept a sharp bend.

Multistranded arch wires These arch wires are made up of a number of thinner wires. These wires can be either twisted or coaxial in form. The advantage of these multistranded wires is that they exhibit increased flexibility.

CONCLUSION

It can be seen that there is not archwire meets all the requirements of the orthodontist. We still have a long way to

go, in terms of finding the ‘ideal’ archwire. But, with such rapid progress being made 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 such a 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.

REFERENCES