Final answer:
The arch wire is part of braces used in orthodontics to apply controlled forces to teeth for alignment, attached to brackets on the teeth, not bonded directly nor used solely with headgear.
Step-by-step explanation:
The arch wire in orthodontics is an element of braces that is used to apply forces to teeth to realign them. It does this by being attached to brackets that are bonded to the teeth. While forces are exerted by the arch wire on the teeth to move them into the desired position, it is not a pattern itself, nor is it bonded directly to the teeth. The arch wire is typically made out of metal and can be attached to labial hooks or other parts of braces for adjustment purposes.
The arch wire acts through tension applied to the teeth, as exemplified in the provided figure, where the applied force, Fapp, repositions a protruding tooth. This careful application of force over time allows the teeth to shift into a more aligned arrangement within the dental arch. Additionally, arch wires are not worn only with headgear but are a common component of braces used in everyday orthodontic treatment.