[Estimating organ doses of dental students in dental radiographic exercises].

To estimate doses absorbed in organs of dental students in the exercises of dental radiography, we measured the average organ doses of the dental radiographic examinations and sent out questionnaires about the radiographic exposure of the dental students. We selected five organs in the head and neck regions: lens of the eye, parotid gland, submaxillary gland, thyroid and pituitary fossa. The dose determinations were made for the full mouth intra-oral radiography with 10 films, and panoramic radiography and cephalometric radiography. Doses for all organs, except for the parotid gland, were widely distributed with one peak. The highest average dose per dental student was about 5000 microGy for the parotid gland, about 2900 microGy for the submaxillary gland, about 900 microGy for the lens of the eye, about 480 microGy for the thyroid and about 140 microGy for the pituitary fossa. Dose limits for dental students in such exercises have not been yet established. But the organ doses, especially for the parotid gland, appear very high. To reduce exposure in the exercises and to protect the dental students from excess exposure, we need to reconsider the study of dental radiographic techniques.

[Statistical analysis of nuclear medicine in the Higashi Nippon Gakuen University Dental Hospital].

The number of radionuclide in vivo tests carried out at the Higashi Nippon Gakuen University Dental Hospital was statistically analyzed and discussed. The subjects were all patients admitted to the Division of Nuclear Medicine during the seven years between 1981 and 1989. The total number of the patients included those introduced through medical facilities in Toubetsu-cho and others. The results of this analysis were as follows: 1) The proportion of the first time patients admitted to the Higashi Nippon Gakuen University Dental Hospital was only 11 percent of all patients. 2) Cases of radionuclide in vivo tests at the Higashi Nippon Gakuen University Dental Hospital decreased in number, annually. However the proportion of tumor scintigraphy and bone scintigraphy increased gradually.

[Experimental study on tooth fractures in young rats].

The influence of tooth fractures on growth of rat incisors was examined with soft X-ray radiography, xeroradiography and microradiography. Thirty young rats were used in this study and experimental fractures were produced on the mandibular left incisors. Radiological observations were carried out immediately, 7, 14, 21, 28 and 35 days after fracturing. The soft X-ray radiograms obtained immediately after fracturing showed clear radiolucent images. The radiopacity of the fractured regions gradually increased from the 7th day. Enamel hypoplasia was observed from the 7th day, and it moved towards the edge of the incisors with the growth of the fractured teeth. The xeroradiograms obtained at each term demonstrated as same findings as those obtained with soft X-ray radiography. The microradiograms obtained immediately after fracturing showed no noteworthy findings except for the clear radiolucent area of the fractured regions. Fine radiopaque lines along the edges of fractured regions were observed from the 7th day. Dentin-like radiopaque calcified masses were observed from the 14th day.