The effects of X-ray irradiation of the head region of eight-day-old rats on the development of molar and incisor teeth.

The effects of irradiation on the development of molars and incisors up to the age of 57 days was studied applying locally a single dose of 9.6 Gy of X-rays to the head region of eight-day-old female rats. Radiography of jaws revealed the absence of the third molar in all irradiated rats, as a result of germ stunting which was, at the moment of irradiation, in the phase of histodifferentiation. In the case of the first and second molar, being at the time of irradiation in the phase of root formation, changes were noted in the development and morphological features of the roots. In animals sacrificed 18 days after irradiation, the radiographs of jaws showed a break in the continuity of the incisors located under the mesial root of the first molar. In all animals the break in continuity of the incisors became macroscopically visible between the 28th and 42nd day after irradiation. 15 days after the loss of incisors, the incisival functional occlusion was restored in all animals.