[The practical aspects of using "superelastic" arch wires in the edgewise technic].

Ever increasing refinements in orthodontic treatment and the corresponding increase in technical demands are challenges to both the dentist in his/her practice and to the manufacturers of orthodontic materials. One interesting development has been the introduction of "super-elastic" arch wires, which have now been on the market for some years. Such arch wires are characterized by an excellent "shape memory", various levels of super-elasticity, a remarkable hysteresis, and temperature sensitivity. On the basis of findings from temperature controlled tests of arch wires in a "Lloyd 1000 R" testing machine, the following conclusions can be drawn. Shape memory can, from a clinical point of view, be regarded as being a positive feature. "Super-elasticity" is of lesser value, because conventional activation of edgewise arches rarely reaches the level of deformation necessary for super-elasticity to be called into play. Hysteresis and temperature sensitivity make a biomechanical control of the arch wires difficult. Reducing active forces by chilling the archwire brings relief to sore teeth. Whether this possibly leads to an improvement in blood circulation in the periodontal tissue, which would be biologically advantageous, should be made the subject of further research.