Response in Rat Incisor Dentin to Injected Strontium, Fluoride, and Parathyroid Extract

S>Rat incisor dentin was examined by microradiography after subcutaneous injection of 1 to 8 mg NaF/100 g body thyroid extract (PTE)/100 g. With NaF, some alteration in mineralizition was domonstrable in every incisor examined; even at a dose of 1 mg/100 g, a distinct hypermineralized layer of dentin was present. At 2 mg/100 g, the hypermineralized layer was wider, and a slightly hypomineralized layer could be detected. The lowest dose of SrCl/sub 2/ (2 mg/ 100 g) produced no response, but at 5 mg/100 g a hypomineralized layer was detectable and a 20 mg/100 g and higher the hypomineralized component produced by NaF areas examined. Its thickness was frequently greater than that of the hypomineralized component produced by NaF, and the Sr-hypomineralized layer was usually more radiolucent. No distinct hypermineralized component was found. In animals injected wth PTE, no response was found with doses of 100 units/100 g and lower but at higher doses a hypomineralized layer was clearly defined, continuous, and wider than the hypomineralized component producerd by F. As in the Sr series, no hypermineralized component was found. These findings are contrary to the conclusions reached from examination of hematoxylin-stained sections, where the responses in dentin produced by NaF, SrCl/sub 2/, and PTE appeared identical. When examined in microradiographs, the Sr and PTE responses contained a hypomineralized component but no hyperjmineralized component, while the F response included both. The hypomineralized components in the Sr and PTE responses were wider than that of the F response. These differences suggest that the etiology of the response is different for each of these causative agents. (BBB)