Gamma-Irradiated Mouse Incisor

¹ Loyola University School of Dentistry, Chicago College of Dental Surgery, Chicago, Illinois

The effects of gamma radiation on the continuously erupting incisor of the mouse, on the rate of eruption, and on the turnover time were studied in CAF-1 mice given the following multiple low doses.

Twelve mice were subjected to wholebody radiation at the rate of 12r per day for 100 days, a cumulative dose of 1,200r. In a similar manner, 18 mice were irradiated over a 200-day period with a cumulative dose of 2,400r. Littermate mice of the same ages were used as controls.

After 100 days of low-level, chronic gamma radiation, no effect was noted on the cell renewal ratio of the mouse incisor. In addition, no histologic changes were observed in the incisors of mice that had been subjected to 1,200r gamma radiation. Furthermore, special histochemic stains showed normal morphology in the incisors of control mice and mice irradiated for 100 days. Therefore, 1,200r delivered over 100 days had no discernible effect on the continuously developing incisor of the mouse.

A cumulative dose of 2,400r over a 200- day period showed, once again, no effect on the eruption of the mouse incisor. Histologically, there were no primary effects in the incisors as a result of radiation. The special stains showed no change in the controls or the mice irradiated for 100 days. Several secondary effects (pulp edema and incorporation of pigments in the dentin) were observed toward the fundal end of the incisor, however.

Macroscopic changes, after 200 days of whole-body gamma radiation, were observed in the eyes and skin of the mice. These mice also, showed a reduced rate of body weight gain. Only 1 mouse did not survive the 200-day period of irradiation; death on the 195th day was caused by pneumonia.