Rapid maxillary expansion (RME) is used to correct transverse deficiencies of the maxilla. This randomized controlled trial compares three RME devices in adolescents (age 10-15) with at least 8 mm maxillary transverse deficiency: (1) bone-borne expander supported by two palatal miniscrews, (2) bone-borne expander supported by four palatal miniscrews, and (3) conventional tooth-borne Hyrax expander. Devices were placed using static computer-guided miniscrew insertion (where applicable). All participants received the same activation protocol to reach 8 mm expansion. Cone-beam CT scans were obtained pre-treatment (T0) and at 6 months post-treatment (T1). The trial assesses skeletal, dentoalveolar, periodontal, and nasal/airway outcomes. Enrollment: 36 subjects. Study sites: Sapienza University of Rome.