Uranium Containing Dentures (ca. 1960s, 1970s)
Modern dentures are typically made from acrylic
plastic, but at least until the 1980s, porcelain was also very commonly
In the 1940s, manufacturers began adding uranium to the porcelain powder used to make dentures. The idea was that the fluorescence of the uranium would help mimic the look of real teeth under a variety of natural and artificial light conditions. Uranium had the advantage over some of the alternative materials because its fluorescence is unaffected by the high temperatures (800 – 1400 degrees centigrade) used to bake the porcelain. According to NCRP 95, it seems that manufacturers had stopped adding uranium to porcelain dentures by 1986 or so.
Papastefanou et al (1987) measured uranium levels in
22 samples of porcelain powders used in Greece and found that the
concentrations ranged from 3.6 Bq/kg (0.1 pC/g) to 5600 Bq/kg (151 pCi/g).
A more limited study in 1977 by Binney and Scherpelz indicated an
average uranium concentration of 224 ppm (2,760 Bq/kg or 70 pCi/g). In
Note that the naturally occurring potassium-40 in these dentures can contribute significantly to their overall radioactivity.
It is likely that the dose to the oral mucosa as a result of the uranium in dentures is primarily due to the beta particles emitted by the decay products of U-238: Th-234 and Pa-234m. The contribution of the alpha particles to the dose is hard to predict due to the tremendous uncertainties in their attenuation.
One investigation in
The pertinent Nuclear Regulatory Commission regulations (2003), found in 10 CFR 40.13a are as follows:
Unimportant quantities of source material.
Any person is exempt from the regulations in this part and from the
requirements for a license set forth in section 62 of the Act to
the extent that such person receives, possesses, uses, transfers or
delivers source material in any chemical mixture, compound, solution, or
alloy in which the source material is by weight less than one-twentieth of
1 percent (0.05 percent) of the mixture, compound, solution or
This limit of 0.05 % (500 ppm uranium) equates to approximately 167 pCi/g or 6,170 Bq/kg.
Binney, S. and Scherpelz, R. Technique for Rapid Analysis of Uranium in Porcelain Dentures. Health Physics 33: 341-343; 1977
NCRP. Radiation Exposure of the
Papastefanou, C., Vitsentzos, S. and Garefis, P. Uranium in Dental Porcelain Powders and Dose Induced in Oral Mucosa. Radiation Protection Dosimetry 19(1): 49-53, 1987.
Thompson, D. Recommendations on the Use of Uranium in Porcelain Teeth. in NUREG/CP-0001, Radioactivity in Consumer Products. August 1978.
Copyright 1999, Oak Ridge Associated Universities