General Information

In order to understand the role of wires in orthodontics, let’s imagine that orthodontic treatment is like driving a car from Point A to Point B. The tooth is the car that needs to be moved from point A (crooked teeth) to point B (a beautiful smile). To have a smooth and easy trip, everything needs to be coordinated:

Parts of Braces Pt 1

Tooth: The car - it moves from point A to point B
Wires: The engine of a car - it generates the force necessary to move the tooth
Brackets/Braces: Tires of the car - they transfer the force from the wire (engine) so that the tooth (car) can move
Color ties: Parts that connect the tires to the engine
Regular dental cleaning and check-up: Oil change and maintenance
Dr. Amin Movahhedian and Dr. Hamed Vaziri: The drivers

From the information above, it is clear that brackets do not move the teeth. They are a part of the system necessary for tooth movement. The actual “engine” that generates the force is the wires and other accessories such as rubber bands and power chains.

Now that you know about the role of wires in orthodontics, let’s get a little bit more specific about the physics and characteristics of each wire.

Orthodontic archwires are used to generate the force necessary for tooth movement. Depending on the stage of treatment, these wires are used to move the teeth or maintain them in a certain spot and prevent them from any undesirable movement.

Orthodontic wires are classified based on different properties, materials, the shape of the cross-section, and overall forms.

Material

Nickel-Titanium (NiTi)

  • It's an alloy of Nickel and Titanium
  • This material was first developed for the space program 1959
  • This wire has a tendency to go back to its original shape
  • Superelasticity: This wire generates almost the same amount of force regardless of the amount of deflection
  • Cannot be bent easily
  • Usually used in the initial stages of treatment

Nickel Titanium – NiTi

Copper (NiTi)

  • Similar to NiTi wires, but with the addition of Copper in the alloy
  • Adding Copper makes the wire react to different temperatures
  • It is more flexible in lower temperatures and stiffer in higher temperatures
  • It's easier to place in the brackets on severely crowded teeth

Beta Titanium

  • Also known as TMA wires
  • First introduced in early 1980
  • Has properties between Stainless Steel and NiTi
  • It is not as stiff as stainless steel and not as flexible as NiTi
  • It can be bent easier than stainless steel wire
  • It has the highest friction with braces that makes it the last choice for space closure

Stainless Steel

  • Stiff wire
  • It can be bent to any desirable shape
  • Minimal friction with braces makes it ideal for space closure
  • Its moldability and strength make it a material of choice to fabricate appliances such as a Nance or Forsus

Cross Section

If all of the other features are the same, wires will act differently if the cross-section is not the same. There are a few different common shapes of cross-sections, the following are the most common ones:

Round: These wires are usually more flexible
Rectangular: These wires are generally stiffer

Size

  • It usually refers to the dimension of the cross section
  • The measurement unit is in inches
  • Round wires are measured by their radius, so one number represents their size
  • .014, .018, .020 are common sizes for round wires
  • Rectangular wires are represented by two sets of numbers, one for length and one for width
  • .016 x .022, .019 x .025 are common sizes for rectangular wires

Arch Form

Since every individual has a unique dental arch shape, orthodontic wires are made in different arch forms. Below are some of the most common ones are oval, standard and square.