[Electron microscopic study of periodontal tissues in the pressure side by intermittent forces].

The intermittent forces (10g and 30g) were applied to the upper right first molars of mature Wistar rats to move them lingually for 1, 5 and 9 days with wire springs. The periodontal tissues in the pressure side were investigated light/electron-microscopically and cytochemically (localization of acid phosphatase activity). The periodontal tissues in the pressure side divided into the following three areas were observed. The area I: The area of hyalinized tissues. The area II: The area situated within 100 microns from the end of hyalinized tissues. The area III: The area situated within 100 microns from the border of area II. The following results were obtained. I Tooth movement Experimental teeth applied with 30 g were moved much more than those applied with 10g. II Light microscopic findings 1) The narrowness of the periodontal space in the area I was not observed remarkably on 1 and 5 day experiment of 10g and 1 day experiment of 30g, though hyalinized tissues had appeared in them. 2) Semi-hyalinized tissues observed in some parts of area II degenerated into hyalinized tissues during the experimental periods. 3) Direct resorption of alveolar bone by osteoclasts was seen initially in the area III on 5 day experiment of 10g and 1 day experiment of 30g. III Electron microscopic findings 1) The hyalinized tissues (area I) and semi-hyalinized tissues (some parts of area II) were characterized to contain only a few necrotic cells and cell debris. The localization of Acpase activity could not be seen in these cells and cell debris. 2) Fibroblasts in the area II and III showed various appearances; autophagy, heterophagy of collagen fibrils, fusion with other fibroblasts and cell degeneration. And the localization of Acpase-activity was observed remarkably in lysosomes, secondary lysosomes and Golgi apparatus. A few macrophages were observed in the area II and III, but the other inflammatory cells and foreign body giant cells could not be seen. 3) On the other hand, active and inactive osteoclasts were seen on the bone surface in both area II and area III.