ULTRASTRUCTURAL-STUDY OF THE EFFECT OF CYCLOPHOSPHAMIDE ON THE GROWTHAREA OF INCISOR TEETH OF DBA 2 AND C57BL/6 MICE/

The effect of a single dose of 300 mg/kg of cyclophosphamide (CY) on t he ultrastructure of the basal area of lower incisor teeth was investi gated in two strains of mice (DBA/2 and C57BL/6) which are very differ ently affected by the delayed toxicity of CY. As in the rat, CY produc ed necrosis in the primitive mesenchymal cells and preodontoblasts of the pulp. Moreover, important changes were noticed in the associated l ayers of the enamel organ (presumptive stratum intermedium cells and s tellate reticulum); thus, most of the cells displayed degenerative cha nges including extensive vacuolization, cytoplasm sequestration and va riable nuclear alterations ranging from relative integrity to complete disorganization. In contrast, non-dividing columnar odontoblasts and ameloblasts were not affected by the drug. The alterations appeared as early as 21 hours after CY and progressed in the following 2 and 3 da ys. Normality of the formative tooth end was regained 7 days after CY. These results indicate that in addition to the effect on the pulp, CY produces severe cytopathological changes in the cells of the stratum intermedium and stellate reticulum of the enamel organ. The different sensitivity of DBA/2 and C57BL/6 mice to the delayed toxicity of CY do es not seem to be related to its effect on odontogenesis since both st rains showed the same response to CY in this respect.