Evaluation of Respiratory Conditions in Individuals Undergoing Rapid Maxillary Expansion: A Computational Fluid Dynamics Study

<b>Background/Objectives:</b> The effect of rapid maxillary expansion (RME) on the nasal and pharyngeal airways in children remains uncertain. This retrospective study utilized computational fluid dynamics (CFD) to assess the changes in ventilation parameters caused by RME in children. <b>Methods:</b> Pre- and post-RME cone beam computed tomography (CBCT) images of 20 patients (4 males, mean age 13 ± 2 years) treated with RME for maxillary transverse insufficiency were evaluated. The RME treatment was conducted using two distinct techniques: tooth-borne and tooth-bone-borne. CFD simulations were used to investigate the airflow conditions (pressure and velocity) in the whole upper airway, nasal airway, and maxillary sinus. Morphological alterations and variations in ventilation parameters before and after RME treatment were statistically compared. The extent of changes in the morphological and ventilatory characteristics of the upper airway, depending on the type of RME, was assessed. Additionally, changes in the ventilation conditions of the upper airway, nasal airway, and maxillary sinus after RME treatment were statistically analyzed. Statistical analyses using IBM SPSS v22 (New York, USA) software included paired <i>t</i>-tests, Mann-Whitney U tests, Wilcoxon matched-pairs signed-rank tests, intraclass correlation coefficients, and coefficients of variation (<i>p</i> < 0.05). <b>Results:</b> The CFD study revealed a notable reduction in both air flow velocity and pressure after the RME treatment (<i>p</i> < 0.05). A statistically significant increase was seen in the parameters used to assess the morphological changes following RME treatment, including nasal width, anterior and posterior nasal cross-sectional area, intermaxillary and intermandibulary molar width, and oropharyngeal airway width (<i>p</i> < 0.05). Regarding the change in airway ventilation, there was no statistically significant difference between tooth-borne and tooth-bone-borne RME treatments (<i>p</i> > 0.05). <b>Conclusions:</b> RME not only treats orthodontic issues in childhood but also increases airflow, which enhances ventilation. CDF is an effective method for the detection of ventilation improvement.