Examination on the role and the proliferation mechanism of the epithelial rests of Malassez.

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17591995
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Conservative dentistry
• Research Institution: KYUSHU UNIVERSITY
• Principal Investigator: HASHIGUCHI Isamu Kyushu University, Faculty of Dental Science, Research Associate, 大学院歯学研究院, 助手 (10150476)
• Co-Investigator(Kenkyū-buntansha): AKAMINE Akifumi Kyushu University, Faculty of Dental Science, Professor, 大学院歯学研究院, 教授 (00117053)
• Project Period (FY): 2005 – 2006
• Keywords: epithelial rests of Malassez / rat / induced periapical lesion / TrkA

Research Abstract

We examined immunohistochemically the distribution of inflammatory cells, epithelial rests of Malassez (ERM) and nerve fibers in induced rat periapical lesion. In the apical periodontium, inflammatory cells infiltrated and nerve fibers increased in density in a time dependent fashion. In the cervical and bifurcational periodontium, however, severe inflammatory reactions were not observed and the density of nerve fibers seemed to be normal as compared to the findings of control rats among the all experimental periods. Cross relationships between ERM and nerve fibers were not found histologically. In this situation, the proliferation of ERM was not recognized. In the periodontium of rats with accidentally perforated pulp floor, however, severe inflammatory responses took placed and the enlarged mass of ERM were observed at 6 weeks after the operation. This finding indicated that inflammatory factors might be responsive to the proliferation of ERM. In the cervical and bifurcational periodontium, ERM and osteoblasts were immunoreactive to TrkA. As time passed after the surgery, the immunoreactivity of both ERM and osteoblasts decreased. It was of particular interest that osteoblasts distributed on opposite site to ERM showing weak or negative TrkA immunoreactivity decreased in number and also showed weak or negative TrkA immunoreactivity. It was reported that the furcation area of molars was area at which the alveolar bone and periodontal ligament was remodeled actively. It was suggested that fibroblast-derived NGF, which was subject to receptor-mediated internalization by odontoblasts, might regulate odontoblasts. Taking these findings into consideration, TrkA-positive ERM might play important role in regulation of bone remodeling in the cervical and bifurcational periodontium.