[An attempt of experimental study to clarify the rearrangement mechanisms of transseptal fibers during mechanical retention periods].

The present investigation has been attempted to clarify the remodeling mechanisms of transseptal fibers during mechanical retention periods. Orthodontic forces of 25 gm and 150 gm were respectively applied to upper molars of rats for 10 days and retained mechanically. Retention periods were 10, 30 and 60 days. The trend of transseptal fibers after these retention periods was observed by the methods of histology and histochemistry. Histological study was observed rearrangement of fibrous tissue by light and electron microscopy and histochemical one was observed acid phosphatase activity. The following results were obtained: 1. Very little was observed about the rearrangement of transseptal fibers by the orthodontic force applied for 10 days. 2. The mechanical retention was kept longer, stretched transseptal fibers were slowly restored to original shape. This means transseptal fibers were gradually rearranged. 3. The collagen containing fibroblast and fibroblast characterized by abundant rough endoplasmic reticulum and Golgi complex were ultrastructurally observed. 4. The reaction of ACPase activity in some fibroblasts can be observed. These results suggest that transseptal fibers were rearranged during mechanical retention periods and that fibroblasts were engaged in this remodeling by synthesizing and degrading collagen fibers.