IN VITRO STUDIES OF BONE RESORPTION BY THE ROOT-RESORBING TISSUE FROM THE BOVINE DECIDUOUS TOOTH

Granulation tissue which is responsible for root resorption of deciduous tooth lies between root of the deciduous tooth and its permanent tooth germ. This tissue is called “root resorbing tissue”. Its bone-resorbing activity was investigated in vitro. Bovine root-resorbing tissue was cultured in close contact with 45Ca-labeled dead calvaria of rats. Bone-resorbing activity was determined by measuring 45Ca released from labeled calvaria during culture. It was found that only the root-resorbing tissue which was rich in odontoclasts and had a good blood supply in its surface layer had bone-resorbing ability, and that bone resorption occurred only when it was placed in close contact with calvarium. The root resorbing tissue which was poor in odontoclasts and blood vessels failed to stimulate bone resorption. Bone resorption by the root-resorbing tissue was enhanced markedly by 25-hydroxy-vitamin D3 or heparin, but not by larger amounts of parathyroid hormone, vitamin D3, and dihydrotachysterol when added to the culture