The Effect of Gable Bends on Triangular and T-Loops of Similar Dimension

Abstract

T-loops and triangular loops have been commonly used to consolidate space in orthodontic treatment. It has been shown that increasing the height and width of each loop will increase the moment-to-force (M/F) ratio. It has also been shown that a T-loop with gable bends could produce a M/F ratio which will allow translation to occur. The object of this study was to determine if there are any significant differences in the M/F ratios generated by T-loops and triangular loops of identical height and width, and also to determine if there are any significant differences in the forces and moments generated by altering the magnitude of the gable bends in a triangular loop. The null hypotheses are that there will be no differences in the forces and moments generated by altered gable bends in triangular springs, and there will be no differences in the M/F ratios generated by triangular and T-loop springs of similar height and width. The springs, measuring 6 mm tall and 8 mm wide, were divided into 5 groups of 22 each. One group consisted of triangular loops with no gable bends (TR 00). Two of the groups consisted of triangular loops with symmetric gable bends of 15° (TR15 15) and 30° (TR30 30). Another group of triangular loops had asymmetric gable bends with 15° on one side and 30° on the other side (TR 15 30). The fifth group consisted of T-loops with symmetric 30° gables (T30 30). The test apparatus measured the forces and moments along 3 mutually perpendicular axes (x, y, and z). Measurements were taken upon initial ligation, and at 1 mm, 2 mm, and 3 mm of horizontal activation. The springs were then deactivated to 2 mm, 1 mm, and 0 mm. The springs were compared for differences in moments and forces using repeated measures analysis of variance models. As the degree of gabling increased in the triangular loop design, the magnitude of Fx and Mz increased significantly at all activation distances. While the Mz/Fx ratio was significantly greater in the gabled triangular loops than in TR 0 0, there was no significant difference between TR15 15 and TR30 30. The study demonstrated that the M/F ratios produced by T-loops and triangular loops are not significantly different. Thus, the triangular loop and T-loop of similar dimension can be used interchangeably to close space.