This device is an evolution in the design of the previous spring-loaded expander, designed with technical and scientific collaboration of Dr. Claudio Lanteri and Mr. Filippo Francolini. It includes all advantages of the Leaf expander without the need for periodic reactivation. The effectiveness of this expander is based entirely on the elastic capacity of the leaf springs made of Nickel Titanium that release controlled and continuous forces. The choice of the expander is decided on the basis of the transversal discrepancy of the patient: the therapy is predetermined and does not require any further action either by the clinician nor by the patient. The expander is supplied with leaf springs readycompressed by two metal staples that the technician will remove after the construction of the device. The package includes a special clip with safety leash to keep the leaf springs compressed, facilitating the technician and the clinician in specific phases of the realization and treatment. Inside the package are also available practical instructions for use where all the construction steps and methods of delivery to the clinician are illustrated.