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. 2014 Mar;84(2):350-7.
doi: 10.2319/031413-219.1. Epub 2013 Aug 29.

Effects of first- and second-order gable bends on the orthodontic load systems produced by T-loop archwires

Thomas R Katona  1 , Serkis C Isikbay, Jie Chen
Affiliations

Effects of first- and second-order gable bends on the orthodontic load systems produced by T-loop archwires

Thomas R Katona et al. Angle Orthod. 2014 Mar.

Abstract

Objective: To measure the effects of first- and second-order gable bends on the forces and moments produced by a commercially available closing T-loop archwire.

Materials and methods: A dentoform-simulated space closure case was mounted on an orthodontic force tester. Sixteen gable bend combinations were placed in the archwires, which were then activated using standard clinical procedures. At each activation, the three force components and three moment components on the maxillary left lateral incisor and canine were simultaneously measured.

Results: The first- and second-order gable bends showed low load coupling effects when used independently, but the load systems became unpredictable when bends were combined. Gable bends affect the magnitudes and directions of the forces and moments that are applied to teeth. The resulting moment to force ratios are sensitive to the bends.

Conclusion: Gable bends alter the orthodontic load systems; however, the three-dimensional interactions produce complex and unpredictable tradeoffs.

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Figures

Figure 1.
Figure 1.
Schematic of complete generic load system acting on a maxillary left lateral incisor bracket. The ±Fx, ±Fy, and ±Fz force components act in the buccal/palatal, distal/mesial, and apical/incisal directions, respectively. The moment vector components' (±Mx, ±My, and ±Mz) directions are defined by the right-hand-rule convention: the thumb of the right hand points in the direction of the moment (open) vector arrow, and the fingers indicate the direction of rotation. Thus, as an example, −Mz would produce a mesial-in distal-out (third order) rotation of the incisor.
Figure 2.
Figure 2.
(a) Occlusal view of first-order gable bends. (b) Buccal view of second-order gable bends.
Figure 3.
Figure 3.
The OFT showing the load cells.
Figure 4.
Figure 4.
Load systems on the incisor. (a) Fx. (b) Fy. (c) Fz. (d) Mx. (e) My. (f) Mz.
Figure 5.
Figure 5.
Load systems on the canine. (a) Fx. (b) Fy. (c) Fz. (d) Mx. (e) My. (f) Mz.
Figure 6.
Figure 6.
The Mx/Fy (mm) on incisor and canine for the 16 combinations of gable bends and 0 mm, 1 mm, and 2 mm of activation of each combination. The M/F ratios range between −578 and +788 and −303 to +35.2 mm on the incisor and canine, respectively. Ratios within or close to the ideal range, −8 to −10 mm (gray strip), are indicated by arrows.
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References

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