The role of the periodontal ligament in bone modeling: the initial development of a time-dependent finite element model.

Current remodeling theories, as applied to long bones, suggest that such processes are controlled by mechanical strains either within or on the bone surface. In this study, the stresses and strains within the periodontal ligament and surrounding bone, consequent to orthodontic loading of a tooth, were investigated by application of the finite element method. Previously, various authors have applied two and three dimensional instantaneous (essentially static) models to analyze the problems. The study reported in this article describes an initial time-dependent (continuous/dynamic) finite element model for tooth movement that uses newly developed software, the results being cross-referenced against historical data. These early results, from a two-dimensional mathematical model of a loaded canine tooth, suggest that the remodeling process may be controlled by the periodontal ligament rather than the bone. In the finite element model, bone was found to experience a low strain of 1 x 10(-5), whereas the periodontal ligament experienced a strain of 0.1 when the "tooth model" is loaded. Only this latter figure is above the threshold usually reported to be necessary to initiate the remodeling process. Further developments in this rapidly advancing area of biomechanical research should facilitate a greater increase in our knowledge of tissue stress and strain after loading.