A connecting pin for a socket connection for fastening dental crown or jaw segments to a model base comprises a fixing shank and a socket shank. The socket shank can be inserted releasably into a seat in a guiding sleeve which is accommodated in the model base. In order to make available a connection which is inexpensive and easy to produce, the outer radial surface area of the fixing shank, not loaded by external forces, has a radial undercut at least in the area of the smallest radius (r.sub.min) of the surface area as viewed along the length of the fixing shank.
