An endosseous dental implant system employs an implant member designed to be embedded into the jawbone of a patient at a location vacated by a missing tooth, and a mating abutment member. Both the abutment member and the implant member have mutually facing gingival ends. A socket of uniform, noncircular cross section throughout is defined into the gingival end of either the implant member or the abutment member while a post of corresponding cross-sectional configuration extends from the gingival end of the other member. At least one, and possibly a plurality, of transversely directed projections are formed on the post. These projections are small enough to allow the post to enter the socket in close fitting, seated engagement therewith, but large enough to create an interference fit between the post and the socket to obstruct twisting of the post within the socket. Apart from the transversely extending projections, the post has a uniform cross sectional shape and dimensions throughout its length.