ORAL MANIFESTATIONS OF IONIZING RADIATION

II. EFFECT OF 200 KV. X-RAY ON RAT INCISOR TEETH WHEN ADMINISTERED LOCALLY TO THE HEAD IN THE 1,500 R. DOSE RANGE

¹ Naval Medical Research Institute, National Naval Medical Center, Bethesda, Md.

Three littermate groups of a well-controlled colony of white rats were used in a radiation study involving a single dose of localized head x-ray radiation to 21-day-old animals, with a maximum dose of 1,500 r. (200 KVP, 20 Ma., 0.82 mm. Cu half-value layer, to target skin distance 50 cm.). Striking changes were observed in the developing incisor teeth of irradiated animals sacrificed 100 days following treatment. Roentgenograms taken at forty-three days posttreatment revealed that all exposed animals already had a visible break in incisor tooth formation, located at the region which was forming at the time of exposure. The incisor teeth of sacrificed animals were separated into two segments: in the maxilla, the first segment was frequently lost at 100 days, leaving a stumplike tooth; in the mandible, the second-formed segment frequently grew lateral to the first, producing in effect an "extra" incisor tooth. As a result, many rats appeared to have four lower incisor teeth, whereas upper incisors were short or "missing." In histologic section, it was seen that extreme damage had been done to the tooth-forming elements which were physiologically active at the time of exposure, as evidenced by stoppage of tooth formation. The tooth-germ was also damaged, but to a lesser degree, as exhibited by the flaws in tooth formation during the 100-day period following irradiation. Although random odontogenic elements were completely obliterated, there appeared to be a general recovery of tooth-forming tissues.