An intra-oral expander device comprises: a transverse expansion assembly, which can be anchored in opposed positions to the upper dental arch and is expandable in a respective plane of action to produce a palatal expansion； and a longitudinal expansion assembly, which is carried by the transverse expansion assembly and is able to exert an action of postero-anterior thrust on the upper front teeth. The longitudinal expansion assembly is mounted on the aforesaid transverse expansion assembly, with possibility of adjustment of the orientation with respect to the plane of action of said transverse expansion assembly.
