Methods: This study compared the force delivery characteristics of double helical and non-helical Z springs manufactured from two different brands of commercially available orthodontic stainless steel wires, namely Remanium® (18/9) 0.5mm diameter wire and Unitek®(18/8) 0.51mm diameter wire. The Z springs were formed by hand and four sizes of each design type were formed for each brand. The mesiodistal widths of the Z springs used were 6,7,8 and 9mm respectively. Three springs in each width category were formed for each spring variant. The force delivery characteristics were tested using a Zwick 2010 Universal Material Tester® using a 50N load cell at a crosshead speed of 10mm/min for up to 2mm deflection. The data was analysed using ANCOVA (P<0.05).
Results: There were statistically significant differences between: the different wire types used, the double helical and non-helical Z springs and the width of springs. The Remanium® wires demonstrated a lower LDR as compared to the Unitek® wires (P <0.05). The double helical Z springs demonstrated a lower LDR as compared to the non-helical Z springs (P <0.05). As the mesiodistal width of the springs increased the LDR of the springs decreased (P <0.05).
Conclusion: The design of Z springs, the brand of wire used and the mesiodistal width of the spring will play a significant role in the LDR of the spring and therefore need to be considered in the clinical situation.