When you have tooth decay, the dentist will remove the damaged part of the tooth and fill the hole (cavity) with a filling. There are several types of fillings, such as grey (amalgam), white (composite), porcelain, and gold. Amalgam fillings are normally used on back teeth because they are not as natural looking as white or porcelain fillings. These are the least expensive and strongest type of filling which can help save more of the tooth. Amalgam is made with several materials, such as tin, copper, silver, zinc, and mercury. These fillings are the longest lasting, with most lasting more than 10 years. Some individuals are worried about the filling containing mercury, but there is such a small amount in amalgam fillings that it poses no danger. In fact, you get more exposure to mercury from the environment than you would from an amalgam filling.