THE EFFECT OF MOLAR UPRIGHTING SPRING LENGTH ON FORCE SYSTEMS GENERATED BY NICKEL-TITANIUM SPRINGS

This study evaluated the force system generated by the Memory Titanol Spring (MTS) with different nickel-titanium segment lengths for molar uprighting using an orthodontic force tester (OFT). The springs were activated at 30° in the posterior segment (β) and divided into four groups (G0, G1, G2, G3). The nickel-titanium and steel connection were fixed at 0 mm, 1 mm, 2 mm, and 3 mm from the molar auxiliary tube curvature. Each group had five MTS, with steel measuring 0.017" by 0.022" and nickel-titanium 0.018" by 0.025". Molars showed extrusion in all groups, with mean values of -0.54 N (G0), -0.68 N (G1), -0.66 N (G2), and -0.66 N (G3). The anterior reacting unit showed mandibular premolar intrusion from 0.56 N (G0, G2) to 0.67 N (G3). Uprighting moments (Ty) of the molars indicated distal moments of 17.62 N·mm (G0), 16.47 N·mm (G1), 16.58 N·mm (G2), and 14.76 N·mm (G3). Distal premolar moments were 1.49 N·mm (G0), 2.63 N·mm (G1), 2.44 N·mm (G2), and 2.42 N·mm (G3). Nickel-titanium segment length showed statistical differences. All pre-activations generated molar extrusion and premolar intrusion at low intensity. G0 was most favorable for molar uprighting. All groups showed low-intensity distal moments on the anterior anchorage side, likely sub-optimal.