[The force level of pseudoelastic leveling wires in relation to interbracket distance]

One of the arguments for the introduction of pseudo-elastic wire materials was "the way they work biologically", that is to say, on the one hand small and uniform force over an extended period of time and on the other the avoidance of excessive forces during the leveling phase. Since an evaluation of the operative force of such an arch wire is dependent on temperature, stress-strain curve, and method of activation, and because the extent of the activation is no longer directly proportional to the operative force, the result is that it is often difficult to determine clinically, whether a safe maximum force is not being exceeded. To clarify this issue arch wires were tested in a three bracket test simulating to the greatest degree possible a clinical situation. The inter-bracket distance was selected in accordance with the situation in the upper and lower incisor region independent of the width of the bracket. The results showed rather high forces for some of the wires. Often these forces were higher in the mandibular situation due to non-ideal force deflection curves than in the supramaxilla. One of the tested materials did, however, effectively limit the operative force in the upper and lower jaw. Especially significant is that the differing characteristics of the tested wire materials result in a completely different action in relation to force development.