Dynamic microstructural changes in alveolar bone in ligature‐induced experimental periodontitis

Periodontitis is an inflammatory disease that causes bone resorption. This study used a ligature‐induced experimental periodontitis model to observe the kinetic process of microstructural changes in alveolar bone and introduced star volume analysis as a new methodology to assess microstructural changes. Thirty Wistar rats were used. To induce experimental periodontitis, ligatures were placed around the maxillary first molar. Rats were euthanized on days 0, 1, 3, 7, 14, and 28 after ligature placement. In addition to using hematoxylin and eosin staining, tartrate-resistant acid phosphatase (TRAP)/alkaline phosphatase (ALP) double staining, and micro-computed tomography were performed to analyze bone remodeling. From day 0 to day 7 (initiation phase), the model showed predominant inflammation with increased numbers of TRAP-positive cells, while ALP expression decreased. In contrast, from day 14 to day 28 (resolution phase), inflammatory cells and TRAP-positive cells decreased, whereas ALP expression recovered to levels comparable to that on day 0. Regarding microstructure parameters, in the initiation phase, bone volume fraction, bone mineral density, trabecular thickness, and star volume of the trabeculae decreased significantly, whereas trabecular separation and star volume of the marrow space increased significantly, indicating bone resorption. In the resolution phase, microstructure parameters normalized, indicated bone formation. We confirmed dynamic alveolar bone remodeling in ligature-induced periodontitis in rats. Furthermore, we assessed the potential for using star volume analysis as a sensitive new tool to clarify microstructural changes to alveolar bone in this model.