Comparing the distribution of strains with the distribution of bone tissue in a human mandible: a finite element study

Comparative anatomy and experimental studies suggest that the mass and distribution of tissue within a bone is adapted to the strains the bone experiences during function. Finite element analysis is a powerful tool that can be used to investigate this since it allows the creation of hypothetical models with unadapted morphology. Here we use FE models of a human mandible with modified internal morphology to study the relationships between the gross distribution of bone tissue (i.e., the presence or absence of bone in a certain area), the variation of cortical bone thickness within the mandible and the distribution of strain magnitudes. We created one model in which all internal cavities were filled with cortical bone material and a second, hollow model with constant cortical bone thickness. In both the models, several load cases representing bites at different positions along the tooth row were applied and peak strain magnitudes across these load cases were calculated. The peak strain distributions in both models show striking similarities with the gross distribution of bone tissue and the variation of cortical thickness in the real mandible, but the correlation coefficients are rather low. These low coefficients could be explained by confounding factors and by the limited spectrum of load cases that were simulated. However, the correspondences we find between strain magnitude and bone tissue distribution suggest that models with altered internal geometry are useful in studying the mechanical adaptation of bone, especially in the absence of any in vivo strain data.