HISTOLOGIC CHANGES IN THE INCISOR TEETH OF RATS SERIALLY SACRIFICED AFTER RECEIVING 1,500 R OF 200 KV. X-RAY IRRADIATION

¹ Naval Dental School and Naval Medical Research Institute Bethesda, Md.

An experiment was undertaken to observe changes in the incisor teeth of rats when exposed to a single dose of x-ray irradiation. It was planned to observe the locus of damage and to determine the point from which the "second tooth"¹ had originated.

Fifty white rats were irradiated locally to the head with 1,500 r of 250 kv. x-ray. These rats were serially sacrificed simultaneously with 50 littermate control rats at various intervals beginning at 16 hours following exposure.

Estimation of the histologic sections revealed that the locus of radiation injury was principally within the young, metabolically active, functioning odontogenic layers of cells. It appeared that, even though this damaged tissue underwent severe retrogressive changes, the irradiation was not sufficient to destroy either the undifferentiated epithelial and mesenchymal cells, or those odontogenic cells that had completed their physiologic function.

The "second tooth" was observed to arise from these surviving undifferentiated cells of the tooth germ. The reason there were 2 separate segments of tooth arising from a single tooth germ was because of a severe interruption in tooth formation following radiation, and during the early recovery period abnormal tooth substance was formed. Finally, relatively normal tooth structure was again formed by the odontogenic cells.

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