Immunohistochemical localization of calbindin D28k during root formation of rat molar teeth

The present study was undertaken to examine the localization of calbindin D 28k (CB)-like immunoreactivity (-LI) during the root formation of the rat m olar. In the adult rat, CB-LI was detected in some of the cells of the epit helial rest of Malassez at the bifurcational region and in certain cells be tween the root dentin and cementum at the apical region. These cells had in dented nuclei and many tonofilaments, and cementocytes lacked CB-LI. Moreov er, CB-LI was observed in the periodontal fibroblasts in the alveolar half of the apical region. During root formation, the cells in the Hertwig's epi thelial root sheath (HERS) lacked CB-LI, but most fragmented cells along th e root surface began to express CB-LI when HERS was disrupted. Preodontobla sts and odontoblasts at the apical portion of the root also showed CB-LI. A fter the formation of cellular cementum, the CB-immunoreactive (-IR) cells were entrapped between the root dentin and cementum in the apical portion o f the root. The number of CB-IR cells at the root surface decreased gradual ly, while that between the root dentin and cementum increased. The fibrobla sts in the periodontal ligament began to express CB-LI after commencement o f the occlusion, and the number and the staining intensity of CB-IR fibrobl asts increased gradually with the passage of time. The present results sugg est that CB may play an important role in the survival of the epithelial ce lls, in the cellular responses of periodontal fibroblasts against mechanica l forces caused by the occlusion, and in the initial mineralization by the odontoblasts through the regulation of intracellular Ca2+ concentration.