A new study from researchers in Brazil compared the force system produced by nickel titanium T-loop spring made with wires of different dimensions. They found the larger wires tested produced higher forces with slight increase on the moments, but the moment-force rations (M/F) produced by the 0.016” x 0.022” wire was the highest found.
The researchers divided 30 compound T-loop springs into three groups according to dimensions of the nickel titanium wire used for its design: 0.016” x 0.022”, 0.017” x 0.025”, and 0.018” x 0.025”. Using the Orthodontic Force Tester, the loops were tested at an interbracket distance of 23 mm and activated at 9 mm. The force in the y-axis and the moment in the x-axis were registered while the calculated moment to force ratio was recorded at each .5 mm of deactivation. The data was then analyzed by three analyses of variance of repeated measures to detect differences and interactions between deactivation and wire size on force, moment, and M/F
According to the findings, published in The Angle Orthodontist, all groups had significantly different forces (P < .001). The 0.016” × 0.022” wire produced 1.78 N of force while the 0.017” × 0.025” and the 0.018” × 0.025” produced 2.81 N and 3.25 N, respectively. The 0.016” × 0.022” wire produced lower moments (11.6 Nmm) than the 0.017” × 0.025” and 0.018” × 0.025” wires, which produced similar moments (13.9 Nmm and 14.4Nmm, respectively). The M/F produced was different for all groups; 0.016” × 0.022” T-loops produced 6.7 mm while the 0.017” × 0.025” and 0.018” × 0.025” T-loops produced 5.0 mm and 4.5 mm, respectively. The researchers detected an interaction for all variables between deactivation and groups.
