The effects of first- and second-order gable bends on forces and moments generated by triangular loops

Triangular loops are frequently used for space closure. Studies of this loop have focused on dimensional and in-plane (second-order) gable-bend influences on the generated forces and moments, but there have been no investigations into the effects of out-of-plane (first-order) gable bends. Both bends are generally needed to accomplish tooth translation. The primary purpose of this project was to ascertain whether first- and second-order bend effects were uncoupled.

Ninety triangular loops were divided into 9 groups with combinations of 0 degrees and 30 degrees first- and second-order gable bends in the anterior and posterior positions. Forces (F(x), F(y), F(z)) and moments (M(x), M(y), M(z)) generated along 3 mutually perpendicular axes-x (mesiodistal), y (occlusogingival), and z (buccolingual)-were measured, and moment/force ratios (M(z)/F(x), M(y)/F(x)) were calculated. Statistical comparisons were made between the 9 groups and between activation distances. The Sidak multiple-comparison adjustment method was used to control the overall confidence level at 95%.

It was shown that the magnitude of M(z)/F(x) increased significantly with second-order gable bends but did not change with first-order bends. The opposite was found for M(y)/F(x).

Thus, in triangular springs, first- and second-order gable bends produce the desired effects without interfering with each other.