[Disturbed formation of dental hard tissues after cyclophosphamide administration]

The changes appeared in the developing dentin and enamel of rat upper incisor after single intraperiotoneal injection of cyclophosphamide (4-8mg/100g body weight) were investigated histologically and microradiographically. 1) Changes appeared immediately after the injection were karyolysis, necrosis and intercellular accumulation of tissue fluid in the preodontoblast layer at the cell proliferating stage and its neighboring pulp tissue, however, no particular change was observed in the adjacent inner enamel epithelium cells. Those changes were more prominent in the labial side than the lingual side and expanded their range with time after the injection and then were replaced gradually by the fibroblasts proliferated. 2) Changes appeared in the dentin secondarily were as follows: a. Hypoplasia of dentin made by the odontoblasts which were at the stage of cell differentiation at the time of the injection. This is probably due to early cessation of dentinoplastic activity. b. Hypoplasia of the dentin induced by the odontoblasts which were at the stage of cell proliferation at the time of the injection. This change was induced by odontoblasts recovered from the changes described in 1). c. Hypomineralization appeared in the dentin which places more incisally than the site of change a and have commenced its matrix formation after the injection. This change did not accompany hypoplasia. d. Slight hypoplasia appeared at the basal side of change b. This change was made by the odontoblasts proliferated after the injection. With time after the injection, "niche" formation became observable at the pulpal surface of dentin due to hypoplasias mentioned above. 3) Osteodentin formation became appear secondarily and expanded its range in the pulp adjacent to the portion of the changes described in 2). Early cessation of dentin described in b and c of 2) is due to cell dysfunction occurred by pressure induced by osteodentin formation. 4) At the developing enamel adjacent to the hypoplastic dentin, no particular change was observed in the progressive mineralization pattern, although distortion of contour of surface or slight hypoplasia were observed.