Post through root. It souynds like the procedure no longer used. Endo was done on a tooth, then a long implant type rod was inserted through the prepared root and into the bone. This created a metal implant support system, but left asome regular root structure to use for the final restoration.
Post thru tooth. This procedure was replaced by extracting the tooth in question and placing an endosseous dental implant in the defect. It was used years ago in an effort to stabilize periodontally involved teeth by placing a post directly thru the tooth into the bone.