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Figure 1. Numerically simulated stress distributions within an orthodontic bracket resulting from 3D force and moment application. (A) Finite-element model of an orthodontic bracket with inserted wire and underlying (cubic) tooth crown. The model was constructed with 87,253 elements (ANSYS element Solid 92) leading to a total number of 126,673 nodes. These tetrahedral structural elements having 10 degrees of freedom are highly suitable for structural mechanical simulations. The model was selectively loaded at the cube’s center with the 6 force and moment components by exertion of adequate couples of forces with equal or opposite directions on opposing cube surfaces, while keeping both wire ends fixed. Black arrows: spatial orientation of the x, y, and z axes. (B) Illustration of the 2 stress components (shear stress 
xy and normal stress difference xx-yy) extractable from piezoresistive microsensors positioned in the xy-plane. Grey: Unloaded form. Black: Forces and resulting deformations. (C) Shear and normal stress fingerprints in the xy-plane, resulting from selective application of each of the 6 force or moment components. Red: Positive stress. Blue: Negative stress.
