Expansion screw for orthodontic appliances, comprising at least one stem (1) with at least a threaded portion (10) extending along the longitudinal extension of said stem (1), at least one receiving body (3) for receiving said threaded portion (10) provided with a receiving hole complementarily shaped with respect to said threaded portion (10) so as to allow its screwing, guide means (2) for guiding said at least one receiving body (3), driving means (11, 12) for driving said stem (1), and comprising a positioning tab (6) composed of multiple parts (60, 61) associated with each other to support the expansion screw (100) when the orthodontic appliance is made, the tab (6) being provided with at least an appendix (62) that can be stably inserted into a cavity (12) exhibited by the expansion screw (100).