Why do all restorations (fillings, crowns, etc) need to be replaced?
Every restoration always has an interface or space between it and the tooth. Although our goal is to place restorations in the tooth that provides a perfect seal there will always end up being a gap between these two surfaces. As an example, the amalgam filling corrodes over time. This corrosion process leads to the amalgam “shrinking” away from the tooth. Thus, the gap widens and the bacteria that causes tooth decay moves into the space in great numbers. The return of tooth decay, now under the restoration, is called recurrent decay. All of the various types of restorations are going to ultimately be undermined by this process. We refer to the process as micro-leakage because it involves micro-organisms (bacteria).
