Factors regulating and modifying dental root resorption.

A comparison is made between the resorption of bone and the resorption of the mineralized tissues of teeth. The structure and function of osteoclasts are described well as the factors that regulate their activity. The cells resorbing the dental mineralized tissues are of the same cell type as osteoclasts. The dental tissues are covered by cementoblasts or odontoblasts which differ from the osteoblasts in that they do not respond to hormones and cytokines that stimulate bone resorption. Root resorption therefore seem to require damage of the cementoblastic layer in combination with necrosis or inflammation or replacement of the cementoblastic layer by osteoblasts. The root resorption that occurs at the shedding of the primary teeth is induced in a different way possibly by substance(s) from the reduced enamel epithelium. There seems to be no systematic study on the frequency and extension of root resorption in association with inflammatory or neoplastic conditions. It is suggested that dentigerous cysts and some epithelial tumors induce root resorption in the same way as the erupting tooth. The mechanisms by which some other tumors or tumor-like conditions cause root resorption are essentially unknown.