Numerical experiments on long-time orthodontic tooth movement.

In orthodontic treatment, teeth are moved by the use of specific force systems. The force system used depends on the patient's orthodontic situation characterized by the geometry of the tooth and the surrounding alveolar bone, which defines the position of the center of resistance. Therefore, the simulation of bone remodeling could be helpful for the treatment strategy. In this study, the optimal force system for bodily movement of a single-root tooth, with an orthodontic bracket attached, was determined. This was achieved by the use of the numerical finite element method, including a distinct mechanical bone-remodeling algorithm. This algorithm works with equilibrium iterations separated in 2 calculation steps. Furthermore, a parametric 3-dimensional finite element model, which allows modifications in the root length and its diameter, is described. For different geometries, the ideal moment-by-force ratios that induce a bodily movement were determined. The knowledge of root geometry is important in defining an optimal force system.