Oral

[O2-E-PM2-01] Large-scale three-dimensional imaging of the detailed structure of periodontal ligament in the early stages of tooth movement

〇Haruka Takahashi¹, Mana Hashimoto², Hiroshi Kamioka² (1. Dept Orthodont, Okayama Univ Grad Sch Med Dent Pharm Sci, 2. Dept Orthodont, Okayama Univ Grad Sch Med Dent Pharm Sci )

Keywords:歯根膜、FIB-SEM、メカニカルストレス

Orthodontic forces applied to tooth in orthodontic treatment cause alveolar bone remodeling via the periodontal ligament(PDL). PDL is composed of fiber bundles and cells and is known to undergo compressive deformation on the compression side during early orthodontic tooth movement. However, the full extent of the histomorphological changes on the compression side is not clear because the PDL is an extensive tissue connecting the root to the alveolar bone. Here, Using Xe plasma FIB-SEM, we will attempt to reveal the histomorphology of the PDL on the compression side by acquiring 3D images of several hundred micrometers with high nano-resolution.Tooth movement was performed by ligating nickel-titanium coil springs to the incisors and maxillary left first molar of an 8-week-old ICR mouse.After perfusion fixation, the periodontal tissues were electron-stained and the proximal periodontal tissues at the palatal root of the first molar, which is the compression side, were observed using Xe-plasma FIB-SEM. From SEM images, three-dimensional morphometry of the PDL was measured by 3D image processing software and compared with the non-moved.Results of Xe plasma FIB-SEM observations, 1642 images of a 205 × 179 × 82 μm area of periodontal tissue on the compression side were taken with a resolution of 50 nm/pixel. The non-moved tissue area of 208 × 238 × 105 μm was taken by 2100 images. Then, morphometrics were performed by applying machine learning and deep learning to automatically extract the root, alveolar bone, blood vessels, PDL fiber bundles, and cells. PDL fiber bundles ran regularly between the root and alveolar bone, and repeatedly anastomosed and branched off from each other. They were surrounded by PDL cells and cell protrusions. The diameter and surface area increased significantly as it approached the alveolar bone wall. The cross-sectional morphometry of the fiber bundles on the alveolar side showed a significantly increased deformation rate when compared to the non-moved tissue in each region(root side, central region, and alveolar side). Thus, the PDL fiber bundles on the compressed side appears to actively deformed in compression, on the alveolar side, during the early tooth movement.