A dental implant is a "root" device, usually made of titanium, used in dentistry to support restorations that resemble a tooth or group of teeth to replace missing teeth. A dental restoration is also called a filling. It is the repair of a damaged or decayed tooth, restoring it back to its normal shape, appearance and function. A tooth is repaired to protect the part of the tooth that has become exposed by the decay or injury. It can prevent the loss of a tooth, since decay may spread and destroy the tooth.