Metal dental fillings, also known as dental amalgams, are made of approximately 50 percent silver and 50 percent mercury. You can tell if you have them in your teeth, because they are grey or almost black from corrosion. The corrosion is a natural and harmless result of the silver content.

The major reason to take into consideration when deciding whether or not to change amalgam fillings is the age of the fillings. After about 10 years in the mouth, there are signs of wear and tear. The margins or joints between the metal and tooth starts to crumble at the top where they meet. A ditch or open space develops, which collects food and bacteria and leads to decay creeping down between the tooth and filling. Eventually you have decay under the filling. About three out of four amalgams over 12 years old have this condition to some extent. Another natural tendency of amalgam is to expand over time. The microscopic expansion leads to cracks in the tooth structure appearing.

If your tooth hurts when you bite down on food, it often means that either the tooth or filling has a crack in it.

The most common material used for fillings today is composite resin. This material is tooth colored. Another major advantage of composite is that it can be bonded to the tooth – that is, “glued” to the tooth. This not only results in a very good seal between the tooth and filling, which keeps out leakage, but it also adds support to the walls of the cavity. The support strengthens the tooth which in turn reduces breaking. The opposite of amalgam, which puts expansion pressure on the tooth, leading to cracking and breakage.

If you are concerned, ask your dentist if it is time to replace your amalgam fillings because of age.