Abstract
Immature permanent teeth of young adult dogs were displaced by placing forces of 50 g and 200 g and the changes in the structure of the cells on the compression and tension areas were investigated by a transmission electron microscope.
The results obtained were as follows:
1. Structural changes in the cells of the compression area. Three days after the operation, fibroblasts and osteoblasts had degenerated. In the degenerated cells, mitochondria of which the structure had been changed and dense bodies like lysosome were observed. Necrosis of the osteocytes was observed. Formation of a ruffled border was observed in the osteoclasts by the treatment. Figures of macrophage-like cells were detected near the ruffled border. The number of degenerated cells after treatment for two weeks was smaller than that after the treatment forthree days, suggesting repairment of the cells.
2. Structural Changes in the cells of the tension area. Three days and two weeks after the operation, development of some kind of organelles was observed in the fibroblasts and osteoblasts. In the organelles, the development of rough surfaced endoplasmic reticulum and Golgi apparatus was predominant. Osteocytes, which were located on the surface of alveolar bone, were similar to the osteoblasts in structure, but the osteocytes in the alveolar bone had fewer organelles than those located on its surface. A month after the operation, the decreases in the number ofmitochondrion and the rough surfaced endoplasmic reticulum in the fibroblasts, osteocytes and cementoblasts were observed, accompanying the formationof dental root.
3. Changes of collagen fibers. The periodicity of the stria of the collagen fibers did not change by the treatment on the compression area and the arrangement of them onthe tension area became slightly scarcer than those on the compression area without affecting the periodicity.
