A three-dimensional scanning system (2,3,4) connectable to a smartphone and controllable via the smartphone user interface, provided with a front face and a rear face opposite to the front face, as well as a micro-USB or lightening port, wherein the three-dimensional scanning system (2,3,4) includes: - An elongated bridge device (3,4) for three-dimensional scanning, which has a first end and a second end opposite to the first end, which are rigidly connected through a body to form a "C"; - Removable fastening means (2,4) of said elongated bridge device (3,4) for fastening it to said rear face or a cover for said rear face; the three-dimensional scanning system (2,3,4) being characterized in that it further comprises: - A micro-USB or lightening jack rigidly secured to said second end of said elongated bridge device (3,4) for data connection with the smartphone; - A sensor for the three-dimensional scanning fixed to said body so that, in use, it points in a direction away from said rear face or said cover; wherein the removable fastening means (2,4) comprise: • A mechanical guide separated from said elongated bridge device (3,4) and that can be fastened to said rear face or to the cover for said rear face; • Removable engagement means for engagement to said mechanical guide provided on said first end of said elongated bridge device (3,4); - Said mechanical guide and said bridge device (3,4) are configured in such a way that, by making said removable engagement means slide along said back face or said cover, said removable engagement means are rigidly connected to said mechanical guide, and said micro-USB or lightening jack is simultaneously inserted into said smartphone micro-USB or lightnening port; - Said elongated bridge device (3,4) forms, in use, an empty space with said rear face of the smartphone, the empty space having dimensions such as to allow one or more fingers of one hand to be inserted; - Said second end is configured to present a concavity facing a direction away from said empty space, said concavity being configured to receive at least partially an annular or little finger; and - Said sensor is powered by a battery fixed to or enclosed in said body; Wherein said mechanical guide and said elongated bridge device (3,4) have a weight distribution such that the center of gravity of the overall system constituted, in use, by the three-dimensional scanning system (2,3,4) and the smartphone falls on a plane parallel to said back face and intersecting said concavity. - An elongated bridge device (3,4) for three-dimensional scanning, which has a first end and a second end opposite to the first end, which are rigidly connected through a body to form a "C"; - Removable fastening means (2,4) of said elongated bridge device (3,4) for fastening it to said rear face or a cover for said rear face; - A micro-USB or lightening jack rigidly secured to said second end of said elongated bridge device (3,4) for data connection with the smartphone; - A sensor for the three-dimensional scanning fixed to said body so that, in use, it points in a direction away from said rear face or said cover; wherein the removable fastening means (2,4) comprise: • A mechanical guide separated from said elongated bridge device (3,4) and that can be fastened to said rear face or to the cover for said rear face; • Removable engagement means for engagement to said mechanical guide provided on said first end of said elongated bridge device (3,4); • A mechanical guide separated from said elongated bridge device (3,4) and that can be fastened to said rear face or to the cover for said rear face; • Removable engagement means for engagement to said mechanical guide provided on said first end of said elongated bridge device (3,4); - Said mechanical guide and said bridge device (3,4) are configured in such a way that, by making said removable engagement means slide along said back face or said cover, said removable engagement means are rigidly connected to said mechanical guide, and said micro-USB or lightening jack is simultaneously inserted into said smartphone micro-USB or lightnening port; - Said elongated bridge device (3,4) forms, in use, an empty space with said rear face of the smartphone, the empty space having dimensions such as to allow one or more fingers of one hand to be inserted; - Said second end is configured to present a concavity facing a direction away from said empty space, said concavity being configured to receive at least partially an annular or little finger; and - Said sensor is powered by a battery fixed to or enclosed in said body;