STIFFNESS-DEFLECTION BEHAVIOR OF SELECTED ORTHODONTIC WIRES

Treatment of horizontal and vertical tooth discrepancies requires wire s of low stiffness to produce forces as the teeth are leveled and alig ned. In this investigation, the stiffness characteristics of several s olid and multistrand nickel-titanium and stainless steel orthodontic w ires were determined at selected clinically relevant deflections. Twen ty specimens of 24 different wires were tested in both three-point and three-bracket bending modes. The unloading force deflection plot of e ach wire was described by a polynomial regression from which wire stif fnesses were obtained by mathematical differentiation. Graphs of the f unctional relationship between stiffness and deflection are presented. The results of this investigation show that wire stiffness can be alt ered not only by changing the size, but also by varying the number of strands and the alloy composition. An equally important finding was th e dependence of stiffness on deflection for most of the wires measured . Comparisons were also made between the stiffness values obtained in three-point bending and the three-bracket bending systems.