Amalgam (mercury fillings) was the filling of choice used by most dentists until recently. The disadvantages of silver amalgam fillings are that the silver was visible and interrupted the whiteness of your smile. In addition, amalgam is known to actually damage your tooth in the long run by expanding and contracting with heat and cold. Therefore, as the filling ages, tooth fractures can occur. Amalgam is also known to leak over time, which allows new decay to develop.