Kunikazu Noguchi

Estimation of Radiation Dose from Porcelain Teeth Containing Uranium Compound

Uranium concentrations of porcelain teeth were determined using the fission track method. The uranium contents of each brand range 0.33-10 ppm,* 0.69-81 ppm,§ 2.5-14 ppm, † and 11-205 ppm, # respectively. In addition, corresponding dose equivalents to the oral mucosa were calculated.

フィッショントラック法による人歯, 人骨, 組織中のウランの定量

The uranium content of several human tooth, bone and soft tissue samples was determined by the fission tract method. The average uranium content in teeth, bones and soft tissues were 6.7, 8.4 and 64 ppb ash, respectively. The distribution of uranium in bones is less uniform than that of teeth, and the uranium content of soft tissues is generally higher than that of teeth and bone. The presence of thorium does not interfere with the uranium determination in most cases.

Neutron activation analysis of mercury contents in head hair of dentists in Japan

Mercury contents in head hair of 58 dentists employed at the NUSD hospital and 50 dentists employed at the private hospitals or clinics were determined using neutron activation analysis. The arithmetic means were 5.8 ppm and 5.2 ppm, and geometric means were 5.4 ppm and 4.8 ppm, respectively. They were much lower than the values reported in the past year, and agreed well with those of normal Japanese men of the same age. Therefore, it was concluded that the mercury pollution in the working environment of dentists might be practically non-existent in Japan today.

Uranium content and 235U/238U isotopic ratio in dental porcelain powders determined by neuron activation analysis

Abstract The uranium contents and 235 U/ 238 U isotopic ratios in 48 dental porcelain powders of 8 brands marketed in Japan were determined by non-destructive neutron activation analysis. The photopeak counts at 277.6 keV of 239 Np formed by the 238 U (n, γ) 239 U → β − 239 Np reaction and at 1595.2 keV of 140 La produced by 235 U fission were measured with a Ge(Li) semiconductor detector system to determine the uranium content and 235 U/ 238 U isotopic ratio. The results of the analysis are tabulated and their significance discussed.

Distribution of Uranium in Dental Porcelains by Means of the Fission Track Method

Porcelain teeth, some of which contain uranium compounds for aesthetic purpose, have been widely used in dental clinics. Hazardous effects due to uranium radiation have been suggested by recent publications. In the previous study, the authors reported the uranium content of porcelain teeth and radiation dose by it. In this study, using the fission track method, the authors examined spatial distribution of uranium in dental porcelain teeth (4 brands) which were marketed in Japan. From each sample of porcelain tooth, a 1-mm-thick specimen was sliced, and uranium content was measured at every 0.19 mm from labial side to lingual side for making a uranium distribution chart. Higher uranium concentration was found in Trubyte Bioblend porcelain teeth (USA) and they showed almost uniform distribution of uranium, while those of the Japanese three brands indicated, in most case, comparatively lower concentration and found to be non-uniform distributions. Range of uranium concentration in these brands were N.D. approximately 5.2 ppm (Shofu-Ace), N.D. approximately 342 ppm (Shofu-Real), N.D. approximately 47 ppm (G.C. Livdent) and N.D. approximately 235 ppm (Trubyte Bioblend), respectively.