Physical Characteristics of Orthodontic Wires and Archwires—Part 2

Abstract

The characteristics of single spans of plain and looped archwires are examined. Plain archwires have similar flexibility in both vertical and horizontal deflections but even with thin wires, the loads applied by small deflections are very high. The incorporation of vertical loops reduces span stiffness particularly for horizontal deflections. However, if maximum flexibility is to be obtained, careful attention must be paid to the dimensions of the loops. The stiffness of the looped arch is very much greater in the vertical plane than in the horizontal plane. Bracket width has a greater influence on span stiffness than has generally been acknowledged. The wider the bracket, the stiffer a span will be. This effect is particularly important with plain arches and with looped arches in vertical deflection. The forces exerted even by small deflections of initial aligning arches are high and exceed by a considerable margin the values normally considered as light.