Inlays or onlays can become necessary to restore the cusp, or chewing surface, of decayed or fractured teeth. Usually made from gold or porcelain, inlays are used for minor restorations within the remaining tooth structure; onlays are used for more advanced decay and cover a greater restored area.
An inlay/onlay procedure is done in two parts:
Gold traditionally has been used for inlays and onlays because of its ability to be molded onto the tooth in a way that ensures minimal chance of additional decay. However, advances are such that the same effect can be had with porcelain materials, which are custom-made to match the exact color of the existing tooth.