A connection device includes a holding shell and a retention insert. The retention insert has an end side and a substantially ring-shaped retention rim projecting therefrom. The holding shell has an end side and a substantially ring-shaped holding rim projecting therefrom. An outer surface of the retention rim is at least partly spaced from and adjacent to an inner surface of the holding rim when the retention insert is arranged in the holding shell and when essentially no radial forces are acting on the holding rim and on the retention rim. In that the outer surface of the retention rim and inner surface of the holding rim are at least partly not contacting each other when essentially no radial forces are acting, it can be achieved that the retention insert is connected relatively loosely with the holding shell when the connection device has not yet been placed on the implant structure.