[Study on mercury in dental calculus].

It has been reported that dental calculus contains trace elements of mercury besides lead, cadmium and zinc. The mercury is one of the hazardous metal elements from the environmental point of view. The purpose of this study was to clarify the mechanism of the accumulation of mercury in the dental calculus. The results were as follows: 1. The concentration of mercury was 1.6 ppm in the dental calculus collected from the subjects with no amalgam fillings. 2. The most of the mercury was found in the organic fraction of the dental calculus. 3. In the culture study of Bacterionema matruchotii in vitro, with the increase of Bacterionema matruchotii the uptake of mercury by the bacteria increased. And the maximum uptake of mercury was seen between 7 to 14 days of the culture period. 4. After 7 days of culture, the bacterial cells were destroyed into several fractions and the quantity of the mercury in the respective fractions was assayed. About 90% of mercury was found in the cell wall. From these results, it was suggested that the uptake of mercury by the bacteria was the cause of mercury accumulation in the dental calculus.