Posterior Crossbite

Design: Two-arm parallel randomized clinical trial in mixed dentition (6-12 years). Arms: (1) 9 mm, 900 g leaf expander; (2) 9 mm Hyrax expander. Follow-up: From appliance insertion → completion of intended expansion → 6-month retention. Primary outcome: Pain perception during the first 7 days post-insertion (daily patient-reported scale). Secondary outcomes: Skeletal and dental changes on CBCT.

This randomized clinical trial aims to evaluate and compare the effectiveness of the Quad Helix (QH) appliance versus Rapid Maxillary Expanders (RME) in treating posterior cross-bite in Egyptian children during the mixed dentition stage. The study will also assess patient comfort and pain levels associated with each appliance.