Rapid Maxillary Expansion (RME) is a commonly used intervention to address posterior crossbite and alleviate functional issues associated with anterior crowding. The purpose of the study is to compare the quality and quantity of expansion of two different Haas devices with anchorage on deciduous elements, one custom-made (HIRME), through a three-dimensional analysis of the changes in the palatine vault after expansion. The study retrospectively examined a total of 30 patients, equally divided into two groups, and showed an average increase in palatal surface area of 28.81 % for the traditional Haas expander and 24.38 % for the HIRME device. The increase in surface and volume was significant for both devices (p < 0.001), while no significant differences in surface or volume increase were found between the two devices (Haas: p = 0.365; Hirme: 0.354). This study underlined the efficacy of the custom HIRME device in increasing palatal surface and volume in patients with transverse discrepancy.
