2026 年 35 巻 3 号 p. 131-138
Tooth eruption occurs as the tooth germ forms roots and migrates vertically toward the oral mucosa. This process is facilitated by alveolar bone formation surrounding the tooth germ and by periodontal ligament and gingival fiber traction. Despite these phenomena being well described in relation to tooth eruption, the role of periodontal tissues in the furcation area of multirooted teeth during vertical eruption remains unclear. The present study compared the developmental processes of periodontal tissues in the furcation and cervical regions and investigated the growth characteristics of furcation during the eruptive phase. Paraffin sections of the maxillary second molars of rats aged 18, 20, 32, and 56 days were prepared for histological observations. Sections were stained with hematoxylin and eosin and subjected to immunohistochemical staining with anti-Osterix, anti-proliferating cell nuclear antigen (PCNA), and anti-periostin antibodies, as well as histoenzymatic staining for tartrate-resistant acid phosphatase (TRAP), to examine osteoblasts, proliferative activity, periodontal fibers, and osteoclasts. Numerous highly active osteoblasts, identified as Osterix-immunopositive cells, were observed in the furcation area until day 20, followed by rapid formation of the interradicular septum by day 32. PCNA-immunopositive cells exhibited a distribution similar to that observed for osteoblasts. Osteoclasts, identified by TRAP positivity, appeared after establishment of the interradicular septum. Periostin-immunopositive periodontal fibers were observed during the formation of the interradicular septum. No temporal changes were observed in cellular activity, osteoblasts, osteoclasts, or the maturation of periodontal fibers in the cervical region, and alveolar bone formation capacity was maintained at a constant level. These findings suggest that the rapid formation of the interradicular septum promotes the maturation of the periodontal ligament, thereby supporting the vertical eruption of multirooted teeth.
