Determination of Uranium Content in Dental Porcelains by Means of the Fission Track Method and Estimation of Radiation Dose to Oral Mucosa by Radioactive Elements

Abstract

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 in recent publications.In the present study, the authors carried out the determination of uranium concentrations in four major brands of porcelain teeth marketed in Japan using the fission track method, and the absorbed doses to oral tissues were calculated by a formula introduced by the authors for calculation of alpha radiation.Average uranium concentrations of the brands studied were determined to be 3.6 ppm (0.33-10 ppm, Japan), 18 ppm (0.69-81 ppm, Japan), 9.4 ppm (2.5-14 ppm, Japan) and 82 ppm (1 1-205 ppm, US.), respectively. The corresponding dose equivalents at the surface of oral mucosal membrane were 2.9 rem . yr-', 14 rem . yr-', 7.6 rem . yr-' and 66 rem . yr-'.

Determination of dose rates from natural radionuclides in dental materials

“…The measured values for uranium and thorium were below the levels found in previous works, ranging from few tenths of Bq kg À1 up to several thousands of Bq kg À1 (Papastefanou et al, 1987;Sairenji et al, 1980), dating back to the period when addition of uranium to dental porcelain materials was still permitted. The specific activities of 40 K were in good agreement with the earlier determinations.…”

“…Already Sairenji et al (1980) had pointed out that the beta dose to oral mucosa due to 40 K was about the same order of magnitude as the dose due to beta particles emitted by the radionuclides of the U/Th chains (mainly by 234m Pa) in porcelains containing 50e200 ppm U (about 600e2500 Bq kg À1 ), and that alpha contribution to the dose was negligible. Their calculation had indeed shown that already at depths greater than 20 mm the main contribution to the dose was due to the beta particles, since the emitted alpha particles have maximum ranges in tissue of less than 30 mm, and they may additionally be absorbed already in the layers of saliva and/or dental plaque deposited on the surface of teeth.…”

“…Their calculation had indeed shown that already at depths greater than 20 mm the main contribution to the dose was due to the beta particles, since the emitted alpha particles have maximum ranges in tissue of less than 30 mm, and they may additionally be absorbed already in the layers of saliva and/or dental plaque deposited on the surface of teeth. So it seems reasonable to assume that only beta particles can deliver significant dose to the radiosensitive cells in the basal layer of the oral mucosa, covered by an epidermal tissue with average thickness of about 100 mm (range: 10e460 mm (Sairenji et al, 1980)). The elimination of uranium and thorium from dental porcelains has thus removed the source of an undue radiation exposure for patients with artificial dental prostheses, however, the nearly equivalent dose contribution of 40 K and, to a lesser extent, that of 87 Rb (at least one of order of magnitude lower) has remained.…”

“…This approach, patented in the United States in 1942 (Dietz, 1942), had been widely used by all the major manufacturers up to the early 1980s. During the 1970se1980s, the results of a number of studies that evaluated the uranium concentration in dental products and the correlated dose to oral mucosa tissues were published by various authors (Moore and Mac Culloch, 1974;Papastefanou et al, 1987;Sairenji et al, 1980). On consideration that uranium was added only for cosmetic purposes, without any other beneficial effect for the patients, the American Dental Association developed Specification No.…”

Radioactivity Measurement on Dental Resin Composites

“…In order to mimic the optical properties of living natural teeth, natural radioactive elements such as uranium and natural or depleted uranium salts were added into porcelain powder, used in the construction of artificial porcelain dental crowns-bridges prosthesis [2][3][4]. Used in dentistry the concentration of uranium in porcelain teeth and porcelain powder and the dose rate absorbed by the oral mucosa has been investigated in several studies [5][6][7][8][9]. In a study conducted in Sweden prosthesis porcelain teeth in different brands available on the market in amounts ranging from 15 to 186 ppm uranium content was determined [10] and stopping the use of dental ceramics containing over 100 ppm uranium were requested [2].…”