Post and core procedures are done to anchor a crown or stabilize weakened tooth. When tooth structure is inadequate to reinforce a conventional restoration then a small rod or post is inserted into the root space with a few millimeters of protrusion. This protrusion which is the core supports the large crown or filling, whichever is appropriate. The missing coronal tooth structure is replaced sufficiently to restore full functionality and aesthetics of the tooth.
For a tooth that has already undergone root canal therapy: