Expansion screw for orthodontic appliances, including at least one stem (1) with at least a threaded portion (10) extending along the longitudinal extension of the stem (1), at least one receiving body (3) for receiving the threaded portion (10) provided with a receiving hole complementarily shaped with respect to the threaded portion (10) so as to allow its screwing, guide structure (2) for guiding the at least one receiving body (3), driving mechanism (11, 12) for driving the stem (1), and including 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).