A silver amalgam filling is used to repair a tooth that is affected by decay, cracks, fractures, etc. The decayed or affected portion of the tooth will be removed and then filled with a silver filling.
An amalgam filling is more commonly used in the back teeth since the color is not as aesthetic as a composite filling.
As with most dental restorations, amalgam fillings are not permanent and may someday need replacement. They are very durable, and will last many years, giving you a long lasting smile.