In-Vitro evaluation of load-deflection characteristics and force levels of nickel titanium orthodontic archwires

Abstract

Background: Nickel-titanium (NiTi) archwires have become increasingly popular because of their ability to releaseconstant light forces, which are especially useful during initial alignment and leveling phase. The aim of the presentstudy was to investigate and compare the load–deflection characteristics of four commercially available NiTiarchwires.Materials and methods: 200 NiTi 0.014, 0.016, 0.018, 0.016x0.022 and 0.019x0.025-inch nickel–titanium archwires fromfour different manufacturers (3M, Ortho Technology, Jiscop and Astar) were tested. The load-deflection properties ofthese archwires were evaluated by a full arch bending test in both palatal and gingival directions at 37°Ctemperature using a universal material testing machine. Forces generated at maximum loading of 2mm and atunloading of 1.5mm were measured.Results: All the tested NiTi wires showed an increase in loading and unloading force with increased wire dimension.Generally, 3M gave the most flexible round wires and relatively stiff rectangular wires; with linear load deflectioncurves. Ortho Technology wires were flexible. Jiscop gave the stiffest round wires and the most flexible rectangularwires. Astar wires were stiff which gave the highest force levels during unloading.Conclusion: Force levels vary greatly from brand to brand and so NiTi wire brands must be selected withconsideration to their load-deflection characteristics and mechanical properties