Tooth decay is caused by acid that is created by the bacteria on your teeth. When the decay reaches the layer past the outer enamel of the tooth, the decayed part must be removed to prevent the decay from progressing. Dental fillings are used to fill the void in the tooth after the decayed portion has been removed. Silver amalgam fillings were once the most common type. However, advances in composite resin technology have allowed this material to be used as an alternative option. Composite fillings are designed to match the color of your teeth. These tooth-colored fillings using a bonding agent to chemically bond the filling to the tooth. They are placed in the tooth in layers and require a curing light that is used to harden the material.