That part of an orthodontic appliance that is placed into the bracket slots and applies the force through the brackets to the teeth to guide tooth movement. It may be passive or active in applying a force to one or more teeth. In cross-section, the archwire may be either round, which in a rectangular slot will produce a tipping force around the fulcrum of the tooth in response to a buccolingual force, or it may be rectangular, which in a rectangular slot can produce buccolingual apical movement. The wire used is usually stainless steel, variations of nickel titanium, or tungsten molybdenum alloy (TMA) based. A pre-posted archwire has hooks already attached; these hooks are fixed in a set position on the wire. A sectional archwire occupies less than the complete arch; it engages only a few teeth (e.g. only the four incisors or only a posterior dental segment), through crown attachments.