βTi-Mo T-type loops are a frictionless, efficient alternative for extraction space closure. Changes in the upper horizontal portion of T loops have been proposed, with not well-described biomechanical characteristics. The purpose of the study was to analyze the biomechanical differences among three T-type loop groups with differential bending in their upper horizontal portion.
Method:
90 T-type loops (0.017" x 0.025" βTi-Mo) were randomly divided into 3 groups (T-, M- and H-loops) to assess axial force, total moment, and moment-to-force ratio up to 6 mm of activation. Nonparametric statistical analyses were used to test differences among groups.
Result:
M-loops demonstrated less force and higher total moment than T-loops. M-loops produced less force than H-loops, but no differences were found regarding total moment. A significant increase in M-loop moment-to-force proportion (9.45:1) compared with T-loops (8.39:1), and H-loops (8.26:1) were obtained. The H-loops and T-loops demonstrated no significant differences between them.
Conclusion:
M-loops produced a significant decrease in force than H- or T-loops and had a higher total moment than T-loops. M-loops demonstrated moment-to-force values near to translation at 6 mm of activation. However, none of the groups obtained ideal values despite the pre-activation bending used (125%), due to the increased interbrackets distance. M-loops are ideal when a higher control of root movement is indicated.