Although extensive investigations of radiation exposure in the medical field have been conducted, no concrete investigations of young patients as the subjects under conditions approximating the daily clinical situations have been undertaken in the field of dentistry. As compared with adults, youths are in the growing stages, keenly susceptible to radiation, likely to be subjected to various medical irradiation exposures, and they have many reproductive age ahead. Therefore, in order to clarify the trend in dental radiography for young patients up to 18 years old and the accompanying radiation exposures, surveys were made at Fukuoka Dental College Hospital and thirty-five dental offices in Fukuoka city and Kitakyushu city. The trend in radiography was examined in the clinic of college hospital and three dental offices where reading of the treatment and irradiation records from 1973 to 1978 was permitted. On the basis of the data thus obtained, experimental data of radiation exposure of patients were calculated and average doses in organs per patient per year were estimated. The results were as follows : 1. Of the patients, under 18 years old, visiting the clinic of college hospital or dental offices, the most out-patients consisted of early childhood around 5 years old. In the clinic of college hospital, 51.9% of the young patients were given radiography of one kind or another. In 35 dental offices, the rate of radiography taken was about one-tenth of that of the clinic of college hospital. 2. Of the radiography in dentistry, periapical radiography accounted for over 90%. In the clinic of college hospital, however, periapical radiography accounted for 50.2%, cephalometric radiography 24.5%, and panoramic radiography 13.7%. A trend to use a variety of radiography was seen in the clinic of college hospital. 3. In the clinic of college hospital, the great average number of radiography per patient by age were 2.12 and 2.05 times in periapical radiography for ages 16-18 and 4-6 groups respectively, 1.42 and 1.56 times in cephalometric radiography for ages 7-9 and 10-12 groups respectively, and 0.69 and 0.82 times in panoramic radiography for the latter two age groups respectively. Each kind of radiography increased in average number with age and 16-18 group was given 4.60 times of radiography of one kind or another in the clinic of college hospital. In the dental offices, the number of radiography taken was about one-fourth that of the clinic of college hospital. By the site of periapical radiography, the upper and lower canines and premolars were radiographed most. By all sites of periapical radiography, the number of radiography taken increased with age. 4. Although exposure dose varies with exposure factors, distance and angle of exposure, in addition to time factor, were found to affect doses subtly. 5. In the clinic of college hospital the average of estimated doses to organs per person per year were 105.4 mrad (25.2 mrad for 5-year-old children) in the salivary gland, 55.9 mrad (18.9 mrad for 5-year-old children) in the thyroid gland, 52.1 mrad (15.0 mrad for 5-year-old children) in the lens of the eye and 52.2 mrad (8.7 mrad for 5-year-old children) in the sella turcica. And in the dental offices, the same average of estimated doses to organs were 40.5 mrad (7.4 mrad for 5-year-old children) in the salivary gland, 17.4 mrad (8.0 mrad for 5-year-old children) in the thyroid gland, 12.2 mrad (6.1 mrad for 5-year-old children) in the lens of eye and 13.1 mrad (1.3 mrad for 5-year-old children) in the sella turcica. In all radiography, the estimated doses in genital glands were in μrad. 6. In the dental offices, both the percentage of young patients to all patients and the radiographing rate were lower as compared with those in the clinic of college hospital. The estimated doses were also lower at one-half to one-fifth and those by age and by organ were found to be one-tenth or lower.
