Skeletal displacements and upper airway changes following tooth-borne and tooth-bone-borne rapid palatal expansion in adolescents: secondary analysis of a randomized clinical trial

This study aimed to compare three-dimensional displacements of the maxilla and mandible, and upper airway changes, following tooth-borne rapid palatal expansion (TB-RPE) (Hyrax) and tooth-bone-borne miniscrew-assisted rapid palatal expansion (TBB-MARPE). Additionally, the correlation between skeletal movements and upper airway changes was evaluated. This was a secondary analysis of a previous randomized clinical trial (RCT), recruiting patients with transverse maxillary deficiency and allocating them to TB-RPE or TBB-MARPE. Low-dose cone-beam computed tomography images obtained at pre-expansion and after 3 months of consolidation post-expansion were analyzed for 32 patients (TB-RPE group: n = 13, mean age = 13.15 ± 3.85; TBB-MARPE: n = 19, mean age = 13.68 ± 4.20). Skeletal displacements and changes in airway volume and cross-sectional area of the nasal cavity, nasopharynx, and total upper airway were assessed. Intergroup comparison and correlation analysis were performed. The level of statistical significance was set at 0.05. For multiple comparison correction of skeletal movements and upper airway changes, the significance level was determined using false discovery rate (FDR) adjusted p-values < 0.05. TBB-MARPE resulted in significantly greater maxillary expansion than TB-RPE; however, no significant difference was observed in maxillary and mandibular displacement between groups. Both groups demonstrated a slight forward and downward displacement of the maxilla (FDR-adjusted p < 0.05), with no significant mandibular position changes (FDR-adjusted p > 0.05). Significant increases were observed in anterior and middle airway cross-sectional areas, nasal cavity volume, and total upper airway volume in both groups, with greater improvement in the TBB-MARPE group (FDR-adjusted p < 0.05). No significant changes were found in the posterior cross-sectional area or nasopharynx volume (FDR-adjusted p > 0.05). Maxillary expansion were positively correlated with the increase in nasal cavity volume and total upper airway volume ( p < 0.05). TBB-MARPE facilitated greater maxillary expansion and upper airway enlargement after consolidation; however, both approaches presented similar skeletal displacement patterns, characterized by slight forward and downward maxillary movement and insignificant mandibular position changes. Within the limitations of this study, orthopedic maxillary expansion positively enhances the nasal airway but has minimal influence on the nasopharynx. The original trial was retrospectively registered at the WHO International Clinical Trial Registry Platform (Registration number: KCT0006871 / Registration date 27/12/2021).