The derotation of premolars and canines with NiTi elements

Canines or premolars must often be derotated during fixed appliance therapy. If such derotation is carried out on the continuous archwire during the leveling phase, it may lead to unwanted side effects on the neighboring teeth. At the University of Ulm a .018" x .018" nickel-titanium segmental derotation archwire was developed to start derotation as early as possible. This wire can be inserted during leveling. This system consists of a vertical slot bracket, an elastic ligature, and the derotation archwire. We tested the derotation archwire under clinical application. The occurring forces and torquing moments were measured in vitro via a hexapode and a sensor working in three dimensions. In this investigation, a derotation moment of 12 Nmm occurred in the canine with a 140 degrees archwire rotation and a force in lingual direction. This archwire also made overcorrection possible, since it remains active after complete derotation. A complete derotation of the tooth was effected with no reactivation, due to the wire's superelasticity.