The Effect Of Different Deflection Range And Ligation Methods On The Mechanical Properties Of Auxiliary Superelastic Ni-Ti Wires

Aims:In this study, we compared the mechanical properties(plateau width and plateau force) generated by different auxiliary superelastic Ni-Ti wires in association with different deflections ,ligations, and steady wires.Methods:A full-arch bending model was used for bending the auxiliary superelastic Ni-Ti wires, which was loaded and unloaded by Instron universal testing machine.Two dimensions(0.012inch,0.014inch)of NiTi wires from two companies, three dimensions of steady wires(0.019×0.025 inch SS rectangular wires,0.018 inch SS round wires and 0.017×0.022 inch SS rectangular wires), two different ligation methods(stainless steel ligature and''relaxed''elastomeric ligature) were employed. The tests were repeated five times under each condition. Ten power equation which fitting the load-deflection curve, was used to define the deflection at the beginning and the end of the plateau, and then the plateau width and the force level of the plateau .Comparisons were made of plateau width and plateau force. Analysis of Variance (two-way ANOVA) and Bonferroni test were conducted to determine statistical difference (α= 0.05).Results:1. Among these four auxiliary superelastic Ni-Ti wires, the ideal plateau was disturbed as deflection range increased.2. Mechanical properties:(1) For 0.012inch auxiliary superelastic Ni-Ti wires, plateau width shortened 0.2mm and plateau force stayed stable when deflection changed from 3mm to 4mm.(2) For 0.014inch auxiliary superelastic Ni-Ti wires, plateau width stayed stable when deflection changed from 3mm to 4mm but shortened 0.24mm when deflection changed from 4mm to 5mm. Plateau force declined when deflection changed from3mm to 4mm but stayed stable when deflection changed from 4mm to 5mm . (3) In all combination, the plateau width and plateau force of 0.014inch auxiliary superelastic Ni-Ti wires were basicly were bigger than that of 0.014inch.The load of 0.012inch auxiliary superelastic Ni-Ti wires were always below 85g and that of 0.014nch were above 120g.3. The two kinds of Ni-Ti wires from different companies almost performed the same properties.4. 0.019×0.025 inch SS rectangular wires are the most appropriate for steady wires. Most auxiliary superelastic Ni-Ti wires combined with 0.018 inch SS round wires always showed the smallest plateau width and plateau force.5. Conservative suggestions would be to sling-tie activations with serious deflections, because the extra frictional resistance generated by huge deformation.6. When ligated by''relaxed''elastomeric ligature, the type of steady wires had no influence on the plateau force of Ni-Ti wires.7. Compared to the wires ligated by stain stees ligature,the plateau force of 0.014IMD Ni-Ti wires ligated by elastomeric ligature decreased dramatically but the plateau width increased significantly. 8. In both deformations, the plateau force of 0.014IMD Ni-Ti wires ligated by elastomeric ligature were about 34~56g.Conclusions:1. The mechanical properties of every wire tends to be harmed as deflection increased.2. We can chose 0.012 inch or 0.014 inch auxiliary superelastic Ni-Ti wires according to circumstances.3. 0.019×0.025 inch SS rectangular wires are the most appropriate for steady wires. 4. In the combination system of steady wires and auxiliary wires,using elastomeric ligature is not recommended.