The dose reduction effect of the thyroid protective shields in the dental roentgenography was investigated. They were designed to cover the entire neck region. Lead equivalent values of them were 0.25 and 0.50mm. With and without thyroid protective shields, absorbed doses in thyroids, breasts, ovaries and the testis were measured in an examination of the upper incisor region with a thermoluminescent dosimetry (TLD), and a protective apron (0.25mmPb) was wore on a phantom during these

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... Following results were obtained. 1. Thyroid doses with thyroid protective shields were reduced to approximately 15% of those without shields. Any significant difference was not found between thyroid dosds with 0.25 and 0.50mmPb shields. 2. With thyroid protective shields, absorbed doses in breasts were reduced to less than 10% of those without shields. The amount of breast doses with a 0.50mmPb shield was significantly smaller than that with a 0.25mmPb shield.