Mechanical responses to orthodontic loading: A 3-dimensional finite element multi-tooth model

Introduction: The initial mechanical response to orthodontic loading comprises biologic reactions that remain unclear, despite their clinical significance. We used a 3-dimensional finite element analysis to investigate the stress-strain responses of teeth to orthodontic loading. Methods: The model was derived from computed tomography data, with adequate boundary conditions and tissue characterization, with orthodontic hardware to provide a more accurate reflection of events during orthodontic therapy. This study also incorporated the adjacent dentition. Two cases were analyzed: a single-tooth system with a mandibular canine, and a multi-tooth system consisting of the mandibular incisor, the canine, and the first premolar, subjected to orthodontic tipping forces. Results and Conclusions: The systems experienced elevated distortion strain energies in the alveolar crest, whereas the tensile and compressive stresses coincided with the apical sites clinically associated with root resorption. Stress levels were considerably greater in the multi-tooth system than in the single-tooth system. The results for the single-tooth model agree with those previously reported. The numeric studies show how orthodontic tooth movement develops different stress fields and how root resorption might occur as a result of hydrostatic compressive stress-induced tissue necrosis. (Am J Orthod Dentofacial Orthop 2009; 135: 174-81)