Biomechanical model of incisor avulsion: a preliminary report.

The aim of the current study was to produce a two-dimensional finite-element model (FEM) of a maxillary incisor being palatally displaced with sufficient force to result in avulsion. The viscosity and elastic coefficient of bone were chosen from previous studies to model the properties of the periodontal complex. A ramped impact of 100 N was applied over a period of 1.5 ms in the direction perpendicular to the labial surface of the incisor model. Changes in the periodontal ligament (PDL) length (elongation and compression) started immediately after the impact and progressed to strain developing in the alveolar bone. In accordance with these changes in the PDL length, the tooth started to rotate with the center of rotation located at the edge of the palatal alveolar bone, combining the stress concentrations at the labial and cervical edges of the bone. When the elongation reached the designated limit, PDL disconnection occurred, leading to tooth avulsion. The resulting two-dimensional FEM is capable of modeling changes in the PDL length and compression, rotation and avulsion.