Fan screw for the expansion of the upper jaw, comprising two bodies (1, 2) connected by at least one driving screw (4； 7) and placed on opposite sides with respect to a sagittal plane (x-x), the longitudinal axis (v-v； k-k) of said at least one expansion screw (4； 7) being perpendicular to said plane (x-x), each of said bodies (1, 2) having a lingual side (L1, L2) and an opposite upper side and being provided with means for its anchorage to several teeth of a dental arch destined to be expanded. The longitudinal axis (v-v； k-k) of the at least one driving screw (4； 7) is at a predetermined distance (h) from the lingual sides (L1, L2) of bodies (1, 2), said distance (h) being measured along a lingual direction (L) parallel to said plane (x-x), such that the distance between the axis (v-v) of the at least one driving screw (4； 7) and the upper sides of bodies (1, 2) is greater than the distance between the upper and the lower sides of bodies (1, 2).
