Orthodontic Wires: Types, Properties

Orthodontic Wires

Write a short note on orthodontic wires.
Answer:

Various types of orthodontic wires are used in both fixed and removable prosthodontics for tooth movement and stabilization.

Classification Of orthodontic wires:

1. On Basis of Elastic Behavior
   • Type1: Wires displaying linear elastic behavior during unloading at temperatures till 50°C
   • Type 2: Wires displaying nonlinear elastic behavior during unloading at temperatures till 50°C.
2. On Basis of Material Used
   • Stainless steel
   • Co– Cr– Ni alloy
   • β – titanium alloys
   • Ni – Ti alloys
   • Gold alloys.
3. Based on Cross Section
   • Round
   • Square
   • Rectangular
   • Multistranded.
4. Based on Gauge Size
   • 0.018”
   • 0.016”
   • 0.07”.

Properties of Orthodontic Wires:

• Force generated:
  • Force generated by the wire on the tooth depends on its composition and design.
  • For a given design, force generated is proportional to stiffess of the wire.
• Elastic deflection and working range: Large elastic deflection produces low constant forces which are less damaging. This also leads to greater working range.
• Springiness: Springiness is the measure of how far a wire is deflected without leading to permanent deformation.
• Stiffess: It is the amount of force required to produce specific deformation. It is inversely proportional to springiness.
• Resilience: This is the energy storage capacity of wire which is the combination of strength and springiness.
• Formability: It represents the amount of permanent bending the wire tolerates before it breaks.
• Ductility of wire.
• Ease of joining: Most of the wires are soldered or welded together
• Corrosion resistance and stability: It is important for the durability of the appliance and biocompatibility.
• Biocompatibility: Most of orthodontic wires satisfy this property. People who are allergic to nickel may get allergic reactions from nickel-containing orthodontic wires.
• Cost factor: Titanium alloy wires are expensive as compared to stainless steel or cobalt-chromium nickel wires.

Manufacturing of an Orthodontic Wire:

Following are the steps in the manufacturing of an orthodontic wire:

• Melting and Casting: Raw materials from the ore are melted by an electric furnace for several hours.
• Metal is poured into dies from which an ingot is manufactured.
• Drawing: Set metal ingot on the machine which will pull the ingot via a die with a hole in it. Here the shape of the hole is determined by the cross-section of wire. Ingot should be pulled via various dies with holes of progressively decreasing size till the desired gauge is reached.
• Annealing: In this, heating and cooling under controlled conditions should be done. This leads to the removal of stress in the wire by recrystallizing metal. This softens the metal and produces back its original flexibility
• Finishing: Now wire is finished by fier abrasives and buffing. This provides a mirror-like luster to the wire.