A filling or restoration is a material that the dentist uses to fill a cavity after the removal of tooth decay. A filling is needed when tooth decay has caused a cavity (hole) on a tooth surface. If you don't get a filling, the cavity will get worse and lead to more severe problems such as bone loss and a root canal. Worn fillings or "silver" (amalgam) fillings should also be replaced before decay begins and causes infection.
Composite resin is used to fill the tooth. It is a tooth-colored filling and is used to create a more natural-looking smile.