Does rapid maxillary expansion enlarge the nasal cavity and pharyngeal airway? A three-dimensional assessment based on validated analyses.

OBJECTIVES: To evaluate the three-dimensional changes following rapid maxillary expansion (RME) of the nasal cavity (NC) and pharyngeal airway (PA) in growing patients, using innovative and validated evaluation methods. To investigate whether a correlation between skeletal expansion and increase in airway volume exists. SETTINGS AND SAMPLE POPULATION: Records of patients who had cone-beam computed tomography taken before and after orthodontic treatment with or without RME, were retrospectively collected and divided into two groups: 1) RME, 39 patients (mean age 10.40 ± 1.74 years); and 2) control, 29 patients, matched for age (mean age 11.07 ± 1.45 years) and follow-up period. MATERIAL AND METHODS: Total and partial volumes of the NC and the PA were calculated. The PA centerline was determined to assess the minimal cross-sectional area and hydraulic diameter. Paired and unpaired t-test were applied to compare the difference between time points and between groups. One-way ANOVA and post hoc Tukey's tests were used to compare subgroups with respect to changes in palatal width and lacrimal ducts distance. RESULTS: All of the NC, PA, and skeletal parameters were significantly enlarged after RME. The NC volume and inter-molar distance in the RME were significantly larger compared to the control group. The initially lower mean values of minimal cross-sectional area and hydraulic diameter in the RME group when compared to the control group, normalized after RME treatment. CONCLUSIONS: Based on validated analyses, the nasal cavity volume increase was evident after RME in the long term after controlling for growth.