An improvement of upper airway flow in patients treated with rapid maxillary expansion: a Cone Beam Computed Tomography study

Rapid Maxillary Expansion (RME) is an orthopaedic treatment used to correct the transverse deficit of the maxilla. Most often, this defect is diagnosed in mouth-breathing patients. Rapid Palatal Expander (RPE) treatment increases the upper airways’ volume and decreases resistance, promoting physiological nasal breathing. The aim of this study is to measure the volume of the upper airways by employing Cone-beam Computed Tomography (CBCT) to evaluate the anatomical space where the major effects of RME occurred. Twenty-four subjects (mean age, 10.17 ± 1.75 years) treated with McNamara-type rapid palatal expander were selected. Two CBCT scans were taken for each patient: the first at the beginning (T0) and the second at the end of the treatment (T1). For each CBCT scan, Total Volume (TV), Retropalatal Volume (RPV) and Retroglossal Volume (RGV) were measured with the software ITK-Snap. The statistical analysis was performed using the paired samples t-test, with a p-value of 0.05. RPV significantly increased (Δ T1-T0: 680.75 mm3 ± 792.63 mm3, P<0.05). No significant changes were found in TV (Δ T1-T0: 452.92 mm3 ± 3091.7 mm3, P>0.05) and in RGV (Δ T1-T0: 166.92 mm3 ± 666.97 mm3, P>0.05). In this study, patients showed a statistically significant increase in RPV after RPE treatment. The CBCT scans provide only quantitative volumetric data, so it would be appropriate to determine the clinical significance of the obtained results with a functional examination (for example, rhinomanometry). The radiological protocol should be standardised to overcome limitations such as tongue posture during scan recording, swallowing and breathing control. Further studies are needed to evaluate the long-term stability of these effects on the airways.