Mechanical Gradients in Adult Alveolar Cortical Bone under Orthodontic Tipping: A Finite Element Study (I)

Background: Orthodontic tooth movement in adults occurs within a mechanically constrained alveolar environment, where cortical bone remodeling capacity is limited and mechanical responses may be spatially heterogeneous. Objectives: To characterize the spatial distribution of mechanical fields in adult alveolar cortical bone under coronal and radicular orthodontic tipping using finite element analysis. Materials and Methods: A finite element model of a maxillary segment was constructed from cone-beam computed tomography data. Two orthodontic loading configurations were simulated: coronal tipping induced by aligner displacement and radicular tipping induced by a pure moment. Equivalent elastic strain, hydrostatic stress and principal stresses were analyzed to describe the spatial organization of the mechanical environment within the alveolar cortical bone. Results: Both loading configurations generated heterogeneous and spatially organized mechanical fields rather than uniform stress or strain distributions. Coronal tipping produced localized strain and hydrostatic stress concentrations, predominantly in cervical cortical regions, whereas radicular tipping resulted in lower peak values and more evenly distributed mechanical gradients along the root length. In both scenarios, global strain magnitudes remained within low-to-moderate ranges consistent with an adult homeostatic context, while local gradients and stress transitions defined distinct mechanical domains. Conclusion: Orthodontic tipping in adult alveolar cortical bone is characterized by structured mechanical fields governed by spatial gradients rather than by force magnitude alone. These findings are consistent with a gradient-based mechanical interpretation of Wolff’s law in adult orthodontics, in which finite element analysis delineates zones of potential biological relevance without predicting direct remodeling outcomes.