If a tooth is broken, or if a cavity or hole becomes so large that it reaches into the root canal, then bacteria may enter and destroy the nerves. This can be extremely painful and lead to abscess formation and infection in the gum or jawbone. Root canal fillings may avoid the need for extraction of the affected tooth. In these cases, the nerve in the tooth chamber is removed and the space it leaves is filled with a material that helps support the tooth. Once the root filling is completed, the tooth is restored using a filling, inlay or crown.