Fillings: Fillings are used to replace missing tooth structure when the loss is relatively small and the tooth structure is sound. Fillings are usually placed in a single visit and generally cost less than crowns or inlays. They fall into two major categories:
Composite resins are comprised of a mixture of a porcelain particles suspended in a plastic matrix. They are chemically bonded to tooth structure and typically cured with a powerful light. Their tooth color and translucency make them the material of choice for fillings on front teeth and smaller restorations on back teeth. The softer plastic matrix does not resist abrasive wear as well as silver amalgam or a crown especially when the restoration is large.
Silver amalgam is a mixture of silver, mercury, copper and traces of other metals. It is the least expensive and most durable of filling materials. They are held in place mechanically rather than bonded like composite resin. Given its dark color it is used mostly for larger fillings on back teeth. They are sometimes used in situations where a bonding light is impractical or isolation from moisture is difficult.
An alternative to a filling is an inlay. An inlay is a small cast restoration made from porcelain or gold that is cemented into place. It is much harder than a resin or amalgam and therefore more durable. Inlays generally require two visits and are more expensive than fillings.