Extension piece for a dental implant, transfer aid for transferring the position of an implant and of an extension piece, and method for producing a basis for a retention element

An extension piece (2) for a dental implant (1) has a head part (20) which serves as a basis for a retention element (7). The extension piece (2) can be screwed in the dental implant (1) with a threaded stem (29). The extension piece (2) is provided with a reference surface (24) via which the position of the extension piece (2) in the circumferential direction can be transferred to a transfer aid (4) having a transfer surface (42) shaped to complement the reference surface (24). The position of the extension piece (2) is transferred via the transfer aid (4) into an impression (93). The extension piece (2) is then provided with a manipulation implant (5) and is repositioned in the impression (93). From this, a working model (M) is formed in which the desired shape of the extension piece (2) can be defined. The extension piece (2) which has been machined to the desired shape is then screwed into the implant (1) with the same torque as is used for taking the impression.