Fillings are done to remove decay and replace the affected tooth structure. It is called a filling because a new material is used to fill a hole left by decay. Most teeth are treated with bonded tooth-colored composite resin fillings, usually a plastic and glass mixture. Caught early enough, cavities can be treated easily and painlessly. If left untreated, decay can lead to tooth pain and infection and the tooth will eventually need root canal treatment or extraction.

Fillings can also be used for cosmetic improvements of the smile such as changing the color of the teeth or reshaping disfigured teeth.