http://drtavsblog.blogspot.com - When it's in your teeth!Q. Why is it important to replace old silver fillings with a crown or onlay?A. Old silver fillings usually have leakage around the margins, which means that bacteria is getting in between the filling and the tooth and can be a cause of tooth decay or the nerve of the tooth dying (when the nerve dies a root canal therapy is needed on the tooth). Silver also acts as a wedge and can actually eventually help to fracture a tooth. If the fracture is vertical, the tooth has to be extracted. A crown encircles the remaining tooth structure so it protects it and an inlay or onlay is prepared by a laboratory to fit perfectly to the tooth and is more protective to the remaining tooth structure than silver. Fillings prepared by the lab can be done in porcelain to match the existing tooth structure and are a great cosmetic choice.