[Histological study of the change of pulp tissue during shedding of the deciduous tooth]

To understand the pulp change of root resorption of human deciduous teeth from a histological point of view, one hundred and twenty specimens were collected for study. The teeth (caries-free) were extracted for occlusal reason or because they exhibited various degrees of mobility and discomfort. The extent of root resorption was classified into five grades: Res. i, Res. 1/4, Res. 1/2, Res. 3/4 and Res. Co., according to Moorrees et al. and Haavikko. All teeth were fixed in 10% formalin (pH 7.2) immediately after extraction for 3-7 days. They were then decalcified for 14 days in 5% formic acid-sodium citrate, sectioned serially at 7 microns and stained with hematoxylin and eosin, Masson's stain, and silver impregnated stain. All sections were examined under a light microscope. The results obtained were as follows: 1. While the root was resorbed more than one half way, some normal pulp was replaced by the connective tissue as in inflammation. Internal resorption could be seen. 2. By the time deciduous root resorption was essential as complete, normal pulp tissue was no longer present. 3. Because the nerve degenerated during initial tooth resorption, there was no evidence that deciduous root resorption was under nervous control. 4. The present observation suggests that in addition to odontoclasts, several other cells such as fibroblast-like cells and macrophages, were actively involved in root resorption during the shedding of deciduous teeth.