Silver fillings are made of amalgam, which is a mixture of mercury with silver, tin and sometimes copper. A filling is used to replace part of a tooth that has been lost due to decay or accidental damage. Silver fillings are very strong due to the amalgam that is used to make them. This means that they are very good for filling back teeth that have been heavily worn away by chewing. Also a filling rebuilds the tooth, which will enable you to chew and can end toothache or prevent toothache from developing.