A dental restoration or dental filling is a dental restorative material used to restore the function, integrity and morphology of missing tooth structure. The structural loss typically results from caries or external trauma. It is also lost intentionally during tooth preparation to improve the aesthetics or the physical integrity of the intended restorative material. Dental restoration also refers to the replacement of missing tooth structure which is supported by dental implants. Dental restorations may be fabricated out of a variety of materials, Common direct restorative materials include dental amalgam, glass ionomer cement and composite resins. Common indirect restorative materials include acrylic, porcelain, zirconia, gold and other metals. Dental restorations can be divided into two broad types: direct restorations and indirect restorations. All dental restorations can be further classified by their location and size.