Upper airway changes before and after maxillary expansion in growing patients: A CBCT-based systematic review and meta-analysis

Background/Objective This systematic review and meta-analysis evaluated CBCT-derived volumetric changes in the upper airway after maxillary expansion in growing patients with maxillary deficiency (transverse and/or sagittal). Methods A literature search was performed in PubMed, ScienceDirect, Taylor & Francis, Wiley Online Library, and Sage Journals until May 2026. Data extraction and methodological quality assessments were performed independently by two reviewers using the Cochrane Risk of Bias 2 (RoB 2) tool for randomized controlled trials and the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for non-randomized studies. Comprehensive Meta-Analysis software was used to synthesize standardized mean differences (SMDs) for airway volume changes. This meta-analysis was prospectively registered in PROSPERO (CRD42025118257). Results Thirteen studies were included in the qualitative synthesis and 12 studies were included in the quantitative synthesis. Maxillary expansion was associated with a significant increase in nasal cavity volume (SMD = 0.91; 95% CI: 0.66 to 1.16; p < 0.001), nasopharyngeal airway volume (SMD = 0.71; 95% CI: 0.44 to 0.97; p < 0.001), and oropharyngeal airway volume (SMD = 0.54; 95% CI: 0.42 to 0.66; p < 0.001). Nasal cavity volume showed the largest pooled effect; however, substantial heterogeneity was observed for nasopharyngeal and nasal cavity outcomes. Conclusion Maxillary expansion was associated with significant CBCT-derived volumetric increases in upper airway dimensions in growing patients, with the largest effect observed in the nasal cavity. However, the clinical significance, long-term stability, and relationship of these volumetric changes to functional respiratory outcomes remain uncertain and require further investigation through prospective controlled trials with validated respiratory endpoints.