Transversal hypoplasia of the upper maxilla is a frequent condition between malocclusions. The rapid maxillary expansion (RME) is an already consolidated technique for these types of defects. This case report analyzes the outcome of a novel surgical technique that we named TOPP (Partial Palatal osteotomy technique) aiming to provide scientifically proven data over the percentage of relapse and the long-term stability of this type of surgical assisted palatal expansion. A 24 year old male patient with a hyperdivergent class III, presenting the absence of 1.1 due to a teenage trauma and a transversal contraction of the upper arch was selected for the surgery. The mucoperiosteal flap was performed at a palatal level with a paramarginal arch shape (from region 1.4 to 2.4) due to preserve the nasal-incisal vascular bundle and the mucoperiosteum was detached from the floor of the nose. A horizontal osteotomy was performed at 4-5 mm above the roots apexes; a sagittal osteotomy in a posterior direction was done at the level of the midline to divide the mesiopalatine suture and separate the maxilla in two halves. The only bony attachment that remained was represented by the perpendicular lamina of the palatal bone. The TOPP technique showed that it is possible to have a better control of both the intercanine and intermolar expansion, that is more difficult in the case of a conventional SARME. Other goals were a greater view and access to the site and the reduction of the risk of damaging the palatine fibromucosa. The incision of the archform paramarginal flap improves certainly the conditions of the palatal fibromucosa in the post operative and allows the reduction of the soft tissues? elastic return.