βTi T-type loops are a frictionless, efficient alternative for extraction space closure.Changes in the upper horizontal portion of T-type loops to improve their mechanical behavior have been proposed, but differences in their biomechanical characteristics have not been well described.This stu dy analyzed the biomechanical differences among three T-type loops with differential bends in their upper horizontal portion.Ninety loops (0.017"x0.025" βTi) were bent and randomly divided in 3 groups according to the form of their upper horizontal portion (T [straight], M [convex], and C-loops [concave]), to evaluate force characteristics up to 6 mm of activation.Stiffness, maximum horizontal loads, total loop moments, and moment-to-force ratios were obtained.Nonparametric statistical analyses were used to test differences among groups.M-loops demonstrated lower force than T-and C-loops, and higher total loop moment than T-loops.A significant increase in M-loop moment-to-force ratio compared with T-or C-loops was obtained.C-and T-loops did not demonstrate significant differences in moment-to-force ratio between them.The convex upper bend in M-loops produced an increased total loop moment compared with T-loops.M-loops demonstrated moment-to-force values slightly higher than translation values, while the other loops reported only controlled inclination values at 6 mm of activation.M-loops are ideal when a higher control of root movement is indicated since the beginning of dental retraction in segmented arch mechanics.