The use of an inverted NiTi is indicated in those patients that have a bilateral posterior cross bites in themixed dentition with no more than 2 mm of cross bite, in which we need to expand the dentoalveolarprocess to correct the malocclusion. This method is based upon the elasticity that the NiTi wires have andthe tendency that the arches have to return to their original position.To apply this technique we must use O.OlS" x 0.025" or 0.019" x 0.025" rectangular NiTiwires, to prevent the wire from turning around in the slot of the brace. Bioforce wire, from GAC, is mucheasy to manipulate if sprayed with tetrafluoro ethane before placing them inverted. We must take accountthat the first movement that these teeth are going to experience is a crown inclination, meaning that it isinto the teeth are going to tip first due to the compression of the periodontal fibers ; after this the alveolarprocess will remodel. This is the moment in which the bodily movement will begin.