USE OF RAT INCISOR DENTIN FOR EVALUATING TOXIC EFFECTS ON MINERALIZATION IN VIVO

A simple, convenient, and useful experimental procedure is demonstrated for evaluating the toxic effects of drugs on mineralization of a collagenous matrix, using rat incisor dentin continuously mineralizing throughout life. Themineralization of incisor dentin was disturbed by drugs known to decrease the plasma calcium or the physicochemical mineral deposition. The disturbance was observed in contact microradiographs of incisor dentin as the radiolucent layers of hypomineralization surrounding thedental pulp. Thehypomineralization could be evaluated in accordance with the degree of the radiolucent layers. There are three advantages of using dentin to evaluate drug-induced disturbance of mineralization. First, the toxic effects of several doses/drugs on the mineralization could be evaluated simultaneously in one animal. Second, the intensity and duration of the toxic effect could easily be detected on contact microradiography. Third, a drug's effect on mineralization can be separated from the effect on bone resorption, in contrast to the bone nonresorbing process involved in dentin formation. Thus, rat incisor dentin is a useful material for evaluating acutely toxicological effects of drugs on mineralization in vivo. Further studies on the physicochemical actions in remineralization and tissue culture should help elucidate the mechanism of drug action on mineralization.