Abstract: An improved ball-and-socket joint for use with dental model articulators of a vertex type comprising two brackets hinged together at one end and each connected at the other end by a ball-and-socket joint to a separate one of two stone plates bearing dental castings. The ball-and-socket joints have releasable mechanical means for affixing the ball in the socket after the plates have been aligned for bite and occlusal fit between the dental castings. Affixing the ball in a socket is achieved by mechanically adjusting the diameter of one relative to the other of the socket and the ball to create a friction force that affixes the ball in the socket. In one embodiment, the mechanical means comprises a C-clamp having a concave band with a cross-sectional diameter substantially equal to the ball diameter and a gap to allow the ball to be snap-fit into the C-clamp.