A survey on questionnaire was made of the frequency of dental radiography by the site of exposure at Osaka Dental University Hospital and 700 dental clinics in Osaka.The data obtained were used with those for dental radiography frequency in Japan, and phantom human dosimetry data, to estimate the average critical organ dose per film, and the critical organ doses per capita per year from dental radiography in Japan.
The results obtained were as follows:
1.Doses to the lens and thyroid gland varied with the skin surface beam size. Lens and thyroid gland doses using 6.5, 8 and 10 cm field sizes during full mouth radiography with 14 films were 264, 1240, 1770 mrad and 342, 1190, 1810 mrad, respectively.
The highest doses to the lens were incurred by upper cuspids and upper bicuspids examinations;the highest doses to the thyroid, by lower molars examinations.
2.Total dental X-ray examinations increased abruptly after 1962 and there were 2.9 billion of the“usual”type in 1970.This was the equivalent of 0.3 X-ray examinations per person that year for Japan.
3.The average doses per dental radiography exposure were 80.1 mrad to the lens, 2.9 mrad to the pituitary gland, 153 mrad to the thyroid gland and 955 mrad to the skin.
4.The average doses per capita in 1970 were 22.1 mrad to the lens;0.80 mrad to the pituitary gland;42.2 mrad to the thyroid gland and 263 mrad to the skin.
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