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Objectives: To evaluate temporal changes in gingival blood flow (GBF) during progression of periodontitis in rats using a laser Doppler flowmeter (LDF) approach and to characterize morphological and biochemical features in the periodontium associated with GBF. Materials and Methods: Forty‐two Wistar rats were divided into a ligature‐induced periodontitis group and a control group. To induce periodontitis, ligatures were tied around maxillary first molars bilaterally. GBF was measured in palatal gingiva at pretreatment and following ligature placement after 30 min, 1, 3, 7, 14, 21, and 28 days using LDF with a non‐contact probe. Bone loss and gene expression in gingival tissues were assessed using micro‐computed tomography (μCT) and quantitative polymerase chain reaction (PCR), respectively. Immunostaining for vascular endothelial growth factor (VEGF) in the maxilla was also histologically evaluated. Results: GBF in the ligature group increased significantly compared with the control group 30 min after ligation. However, on days 3 and 7, GBF decreased in the ligature group. Also, after day 10, there was no difference in GBF between groups. The levels of alveolar bone loss, gene expression (interleukin‐6, cluster of differentiation‐31, VEGF‐A, and lymphatic vessel endothelial hyaluronan receptor‐1), and immunostained VEGF‐positive vessels correlated well with changes in GBF. Conclusion Progression of Periodontitis: In rats was associated with a triphasic pattern of GBF, consisting of a short initial increase, followed by a rapid decrease, and then a gradual plateau phase. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background and Objective: Theaflavins (TFs), the major polyphenol in black tea, have the ability to reduce inflammation and bone resorption. The aim of this study was to evaluate the effects of TFs on experimental periodontitis in rats. Material and Methods: Thirty rats were divided into five groups: Control (glycerol application without ligation), Ligature (glycerol application with ligation), TF1 (1 mg/mL TF application with ligation), TF10 (10 mg/mL TF application with ligation), and TF100 (100 mg/mL TF application with ligation). To induce experimental periodontitis, ligatures were placed around maxillary first molars bilaterally. After ligature placement, 100 μL glycerol or TFs were topically applied to the rats daily, and rats were euthanized 7 days after ligature placement. Micro‐computed tomography was used to measure bone resorption in the left side of the maxilla, and quantitative polymerase chain reaction was used to measure the expression of interleukin (IL)‐6, growth‐regulated gene product/cytokine‐induced neutrophil chemoattractant (Gro/Cinc‐1, rat equivalent of IL‐8), matrix metalloproteinase‐9 (Mmp‐9), receptor activator of nuclear factor‐kappa Β ligand (Rankl), osteoprotegerin (Opg), and the Rankl/Opg ratio in gingival tissue. With tissue from the right side of the maxilla, hematoxylin and eosin staining was used for histological analysis, immunohistochemical staining for leukocyte common antigen (CD45) was used to assess inflammation, and tartrate‐resistant acid phosphatase (TRAP) staining was used to observe the number of osteoclasts. Results: The TF10 and TF100 groups, but not the TF1 group, had significant inhibition of alveolar bone loss, reduction in inflammatory cell infiltration in the periodontium, and significantly reduced numbers of CD45‐positive cells and TRAP‐positive osteoclasts compared with the Ligature group. Correspondingly, the TF10 and TF100 groups had significantly downregulated gene expression of IL‐6, Gro/Cinc‐1(IL‐8), Mmp‐9, and Rankl, but not of Opg. Consequently, Rankl/Opg expression was significantly increased in the Ligation group but was attenuated in the TF10 and TF100 groups. Conclusion: The results of this study suggest that topical application of TFs may reduce inflammation and bone resorption in experimental periodontitis. Therefore, TFs have therapeutic potential in the treatment of periodontal disease. [ABSTRACT FROM AUTHOR]