- A small amount of decay on a portion of a back tooth
A silver (or amalgam) filling is a mixture of approximately 50% silver/tin alloy and 50% mercury. After tooth decay is removed and cleaned, this gray colored material is packed into the tooth and shaped.
Silver fillings have been used for more than 125 years. Their biggest advantage is that they are quickly placed, making them relatively inexpensive. They are also relatively durable.
Silver fillings do not bond (stick) to the tooth structure. This requires the preparation to be "undercut," creating a chamber that is smaller at the surface of the tooth and wider inside. This undercut keeps the filling from falling out of the tooth.
The problem is that the creation of this undercut requires the removal of more healthy tooth structure than is necessary. This weakens the tooth and predisposes it to fracture when biting into hard items. Since fillings will break down from normal wear, they will eventually need to be replaced, and this will require the removal of even more healthy tooth structure.
Composite (white) fillings are an excellent alternative, limiting the removal of healthy tissue and posing no known environmental risk. In cases of extensive decay, inlays/onlays or crowns are a much better restoration.