Abstract
At present it is almost impossible to conduct a precise dental examination without X-ray films, especially in pedodontics. However, children obviously face more risks from radiation than adults, because their tissues which have much metabolic activity are much more sensitive to radial rays than adults. Therefore it is necessary to protect the child's immature organs from these rays, particularly the thyroid gland, the eyes (crystalline lens), gonad etc.
Recently the influence of exposure doses for long p eriods of time has been attracting much attention also in the field of the study of dosimetrics in dental radiation. Therefore we are compelled to study its influence, especially on children who are by nature relatively more sensitive to radiat on.
For this investigation the author employed the stabi l i zed TLD and measured the effect of doses on several organs (of children) using water and Mix-D phantom. Based upon this data, the author developed an exposure cone (of children) which was thought to be the best concrete method for reduction of absorbed doses for children who are most frequentry X-rayed and therefore most likely to reduced absorbed doses in a considerable amount. The major findings have been obtained concerning this cone compared with the standard cone as follows.
1. The full mouth 6-film examination showed the largest of the absorbed doses to be on skin, eyes and the thyroid gland.
2. For example, the dose on thyroid gland with a full mouth 6-film examination was 0.734R.
3. The dose on the gonad was less than 0.001R with every technique.
4. Using the developed exposure cone for children we have succeeded in reducing the amount of doses on these organs. In addition the image quality im proved due to the reduction of scattered X-rays.
5. Using the developed exposure cone (for children) the risk of thyroid cancer can be reduced a level of 10-6 to a level of 10-7 as compared with the sta n dard exposure cone.
6. Supposing that it is over the crystalline lens limits of dose-equivalent in a year at several times with full mouth 6-film examinations can be estimated wh ich with standard cone was about three times, developed cone was about e i ghtyeight times in a year.
