Determination of uranium in porcelain teeth by the fission track method.

Porcelain teeth have been widely used in restorative and prosthetic dentistry because of their fine natures in aesthetics and hardness as an artificial denture. Among them there are some to which the uranium compounds have been added in order to simulate the fluorescence of the natural teeth. Recently, it was pointed out by several researchers that the radiations from uranium and its descendant nuclides might well exceed the dose limit[1] to the public recommended by ICRP. O'Riordan and Hunt[2] reported the results of their analysis of twenty porcelain powders of five brand names using G-M counter, which suggested the mean uranium content of 410 ppm and the maximum of about 1000 ppm. They recommended that the use of uranium as a fluorescer should be discontinued and that non-radioactive fluorescers should be developed. In 1976, Thompson[3] determined the uranium contents of the porcelain teeth and powders used in USA by NaI(T1) detector coupled to a multi-channel analyzer, and found some of them contained uranium with concentrations higher than the limit[4] of 0.05 percent (500 ppm) for license-exempt use in ceramics. He presented recommendations regarding substitution of non-radioactive agents and interim guidelines on the maximum permissible concentration of uranium in dental porcelains.