A dental implant is actually a replacement for the root or roots of a tooth. Like tooth roots, dental implants are secured in the jawbone and are not visible once surgically placed. They are used to secure crowns (the parts of teeth seen in the mouth), bridgework or dentures by a variety of means. They are made of titanium, which is lightweight, strong and biocompatible, which means that it is not rejected by the body. Titanium and titanium alloys are the most widely used metals in both dental and other bone implants, such as orthopedic joint replacements. Dental implants have the highest success rate of any implanted surgical device.