shaped projections and recesses respectively upon inserting the tooth structure stem portion 10 into the longitudinal opening of the distal stem portion 20 the inclined flank surfaces 18 and 28 of the projections and recesses respectively meet on an inclined plane thus upon further insertion into the longitudinal opening of the distal stem portion 20 the tooth structure stem portion 10 slides until it reaches its axial final position and in that situation rotates until all mutually opposite flank surfaces 18 and 20 are in uniform contact with each other as a result the tooth structure stem portion 10 is forced into its desired final position without impediment to its sliding movement and can then be fixed by a screw pin 40 extending in the longitudinal direction of the stem see fig7 that screw pin 40 is tightened with a force of 30 ncm the corresponding flank surfaces 18 and 28 which serve simultaneously as a longitudinal abutment and as a rotation preventing securing means are then advantageously sunk in the interior of the longitudinal opening of the distal stem portion 20 and are not disposed in the region of the implant shoulder as in other systems the implant shoulder can thus be held at exactly the same level in the variants shown in fig1 to 5 no particular measures are shown for.