Slow miniscrew-assisted palatal expansion: a clinical approach for long-term skeletal stability and enhanced nasal airway function

To assess whether slow-activation miniscrew-assisted palatal expansion (MAPE) improves skeletal dimensions, nasal airflow and patient-reported symptoms in maxillary transverse hypoplasia (MTH). In this prospective cohort, 45 subjects underwent slow-activation MAPE and were stratified as pediatric (< 18y; n = 22) and adult (≥ 18y; n = 23). Outcomes were collected at baseline (T0), post-expansion (T1), post-orthodontics (T2) and 1-year retention (T3). CBCT quantified zygomatic and nasal widths and internal nasal valve (INV) area/angle and intermolar widths. Peak nasal/oral inspiratory flows (PNIF/POIF) were measured at T0–T3. Patient-reported outcomes included a 23-item binary questionnaire and the Epworth Sleepiness Scale (ESS). Zygomatic and nasal widths and INV area/angle increased in both cohorts (all p < 0.001), with larger INV changes in pediatrics (p < 0.05). PNIF increased and remained above baseline at T3 (p < 0.001), while morning mouth dryness upon waking and daytime mouth breathing decreased (both p < 0.01). Sleepiness outcomes were not uniformly improved. Using Johns ESS categories, from T0 to T3, 67% of pediatric participants shifted to lower-normal and 33% remained higher-normal, whereas all adults remained higher-normal. Using a two-group threshold informed by Korean validation (ESS ≥ 8 vs. < 8), 35% were ≥ 8 at baseline; at T3, all pediatric participants and 25% of adults who were ≥ 8 shifted to < 8, while 75% remained ≥ 8. Slow-activation MAPE was associated with skeletal and nasal complex widening, INV enlargement, and sustained PNIF improvement, but daytime sleepiness improved inconsistently, particularly in adults. Without polysomnography, findings reflect changes in upper-airway physiology and symptoms rather than definitive changes in sleep-disordered breathing severity.