There is a dispute about the potential adverse health effects of “black” fillings, which is close to 50% of μερψθρυ and generally less than 40% silver in them. Although mercury is toxic, it is deemed not circulate in the body when used as an occluding material.
Recent research, however, seems to indicate that the “black” fillings release a very small amount of mercury vapor during chewing. Whether and how this small percentage of mercury is harmful to the body, is disputed. However, it never fully proved by fault accuracy of the concentration of mercury in amalgam fillings