抄録
For the purpose of investigating the developmental process of the periodontal membrane and the physiologic tooth movement, 44 female rats were sacrificed. They were examined roentgenologically and histologically by several staining methods to differentiate the precollagenous and collagenous fibers. The findings were as follow: 1. The different stages and patterns of maturation of the periodontal membrane of the maxillary first molars are described in the rats. 2. The intermediate plexus which was splicing the fiber bundles of the outer and inner zones was confirmed. 3. The fiber bundles in the outer zone were less in number and larger in diameter than those in the inner zone. 4. Four sites of active collagen formation were pointed out: (1) The root bifurcation area, (2) The root apex area, (3) The intermediate zone, and (4) The alveolar bone resorption area on the distal side. 5. Many anastomoses of fiber bundles were observed on the alveolar bone surface of the mesial side. 6. The maxillary molars erupted and drifted distally during the period from birth to 210 days of age. The distal drifting was accomplished by the apposition of the alveolar bone on the mesial side and resorption of the bone on the distal side of the roots.
