Changes of Airway Space and Flow in Patients Treated with Rapid Palatal Expander (RPE): An Observational Pilot Study with Comparison with Non-Treated Patients

Abstract

Background/Objectives. With a rapid palatal expander (RPE) is reported to be effective in increasing the volume of nasal cavities, with a restoration of physiological nasal airflow. The purpose of this retrospective clinical study was to evaluate, using Cone Beam Computed Tomography (CBCT), the volumetric changes and airflow velocity changes in the nasal cavities, retro-palatal and retro-glossal airways, resulting from the use of RPE with dental anchorage (group A), also comparing these data with patients non treated with RPE (group B). Methods. Sixteen subjects (aged 9.34 years) with transverse maxillary deficiency and unilateral posterior crossbite were treated with RPE with dental anchorage. Additionally, 8 patients (aged 11.11 years) with juvenile idiopathic arthritis, who did not undergo any orthodontic treatment, were selected as a control group. Expansion was performed until overcorrection was achieved, and the device was left in place for 6 months as fixed retention, followed by another 6 months of night-time removable retention. From the retrospective evaluation, all patients presented two CBCT scans at baseline (T0) and 1-year follow-up (T1). The 3D-Slicer software was used for each CBCT to measure the nasal (VN), retropalatal (VRP), and retroglossal (VRG) volumes, while an iterative Excel spreadsheet allowed for a pilot approximated modeling and calculation of airway flow-related data. Results. Regarding mean age, a statistically significant difference (p = 0.01 *) was found between groups, suggesting that group B is closer to the pubertal growth peak. Analysis between T0 and T1 revealed: (i) a statistically significant increase for volumes VN, VRP and VRG in group A; (ii) a statistically significant increase for VN in group B; (iii) a statistically significant decrease for all variables related to airflow velocity in both groups. Furthermore, comparison between group A and B, regarding variations between T0 and T1, found a statistically significant difference only for VN. Conclusions. Within the limitations of this pilot evaluation, the treatment with RPE revealed promising outcomes for retro-palatal, retro-glossal and nasal volumes, together with clinical changes in airflow velocities.

Keywords: airway flow; airway volume; cone beam computed tomography; rapid palatal maxillary expansion.

Figure A1

McNamara RPE device with resin splints.

Figure A2

Hyrax RPE device with one cemented band on the first molars (a) or two bands cemented on the first molars and premolars (b).

Figure 1

Upper airways segmentations without external air from the nostrils and maxillary sinuses and the 3D model obtained from 3D-Slicer software.

Figure 2

Landmarks and planes for identifying volumes. The figures illustrate: the points PNS, Nose Tip, Hormion, Nasion, Ba, PISP, SE (a); the corresponding planes: Hormion-Nasion, Hormion-PNS, Nasal Perpendicular, Ba-PNS, Soft palate plane, and Epiglottis plane (b).

Figure 3

3D view of the model of upper airways (a); Sagittal view of the 3D model of the nasal cavity (b).

Figure 4

3D model of the subdivision of the retro-palatal and retro-glossal volume segmentation.

Figure 5

CBCT visualization of the subdivision of the nasal cavity with the respective references and measurements for the study of airflow: diameter (Ad1) and height (Ah1) of solid A1 and the height (Ah2) of solid A2; length (Bh) and diameter (Bd) of solid B; length (Ch) and diameter (Cd); length (Dh) and diameter (Dd2) of solid D; diameter 1 (Ed1), diameter 2 (Ed2), and height (Eh) of solid E.

Figure 6

Axial view of regions of retro-palatal and retro-glossal sections: axial view of the URPc (a); axial view of the LRPc (b); axial view of the LRGc (c); sagittal view of the heights RPh and RGh (d).