Verification of the mechanostat theory in mandible remodeling after tooth extraction: Animal study and numerical modeling

摘要

Bone tissue is capable of remodeling in response to environmental and physiological conditions. Mechanical loading is thought to be one of the most important environmental factors, affecting bone status. Mechanostat theory, which classifies bone behavior on the basis of the mechanical strain, has been vastly applied in cases of long bones. The present study surveyed the applicability of mechanostat theory in interpretation and anticipation of structural changes of the mandible due to tooth extraction, through experimental measurements and numerical modeling. The mandibular left first molar tooth of a 2-year-old male mongrel dog was extracted. Computed tomography (CT) images of the mandible were taken before, immediately after, and 1 year after extraction. Finite element models were constructed from the CT images and analyzed to evaluate the von Mises strain distribution within the mandible, specifically near the extraction site. Marked resorption around the extraction site and significant height reductions in the buccal and lingual ridges around the socket were observed one year after tooth removal. The deep socket made by extraction was filled and replaced by a smooth surface through bone remodeling in response to masticatory loading. Resultant strain analyses revealed a noticeable decline in strain level around the socket after tooth extraction, which activated bone remodeling according to mechanostat theory. At 1-year post-extraction, the strain magnitudes had increased significantly to near pre-extraction values. Alterations in the strain magnitudes along the mesio-distal axis were quantified for each stage and compared with the Mechanostat predefined regions. The FE results were surveyed in combination with the ridge height reductions, along the mesio-distal direction. Strain contours of the post-extraction stages were compatible with predictions by mechanostat theory. These findings validate the ability of mechanostat theory to describe mandible remodeling and predict post-extraction structural changes that occur near the extraction site. These results could be applied in dental treatment planning and implant design.