A composite resin is a tooth-colored plastic mixture filled with glass (silicon dioxide). Composites are not only used for restoring decay, but are also used for cosmetic. Improvements of the smile by changing the color of the teeth or reshaping disfigured teeth. Esthetics are the main advantage, since dentists can blend shades to create a color nearly identical to that of the actual tooth. Composites bond to the tooth to support the remaining tooth structure, which helps to prevent breakage and insulate the tooth from excessive temperature changes. Following preparation, the dentist places the composite in layers, using a light specialized to harden each layer. When the process is finished, the dentist will shape the composite to fit the tooth. The dentist then polishes the composite to prevent staining and early wear. Because a composite is more difficult to place than silver fillings, it takes the dentist about 10-20 minutes longer to place. Placement time depends on the size and location of the cavity. Studies have shown that composites last 7-1 0 years, which is comparable to silver fillings except in very large restorations, where silver fillings last much longer than composites.