Objectives: The use of cone beam computed tomography (CBCT), to observe through retrospective study the alterations in the nasal airway following rapid maxillary expansion (RME) of butterfly hyrax versus distalization without or with expansion. Material and Methods: Data from 48 adolescent female patients were divided into three equal groups, depending on whether they had a constricted maxilla, reduced maxillary intermolar width. Group 1 was a conventional hyrax (E) with an average age of 13.27 years (Y), group 2 was a distalization assisted by expansion (DE) with an average age of 13.38 Y, and group 3 was a distalization without expansion (D) with mean age 13.25 Y. CBCT records were taken before and after six months of RME and/or distalization, so a total 48 CBCTs were analyzed. The airway was segmented and quantified using Romexis software (version 5.3.4.39 USA). Results: The intragroup difference between T1 and T2 showed that all groups showed a significant increase in total airway, nasopharynx, retropalatal airway, and nasal cavity, but that all groups showed a non-significant increase in SNA, or Position of maxilla, which was represented by A point to Nasion vertical (NV) in groups 1&3 but does not occur in group 2. The retroglossal airway, in group 3 exhibited a non-significant rise, whereas groups 1 and 2 showed a significant increase. Conclusions: Expansion and distalization can increase the total airway volume. Maxillary distalization assisted by expansion does not reduce the airway volume because pure backward skeletal action does not occur as what happens after a maxillary setback in orthognathic surgery.

Nasal airway, Rapid Maxillary Expansion, Distalization, Hyrax expander, Miniplates, Cone beam computed tomography, CBCT.