Summary Objective To assess three rapid maxillary expansion (RME) appliances in nasal ventilation. Trial design Three-arm parallel randomized clinical trial. Methods Sixty-six growing subjects (10–16 years old) needing RME as part of their orthodontic treatment were randomly allocated (1:1:1 ratio) to groups 22 patients receiving Hyrax (H), Hybrid-Hyrax (HH), or Keles keyless expander (K). The ...