Effects of Hyrax Maxillary Expander on Nasal Cavity and Upper Airway in Adolescents: A Systematic Review and Meta-Analysis.

Background: Whether Hyrax maxillary expander is an effective treatment for maxillary transverse deficiency as well as expansion of the upper airway is still controversial. The study's purpose was to evaluate 3D changes in upper airway dimensions of adolescent patients measured primarily by cone-beam computed tomography (CBCT) after rapid maxillary expansion (RME) with the Hyrax maxillary expander.

Methods: Studies up to 1 April 2024 were searched in the following databases: PubMed/MEDICINE, Web of Science, Cochrane Library, and Embase. Inclusion criteria were clinical trials and cohort studies that assessed the effect of RME in adolescent patients with upper airway stenosis using CBCT-based three-dimensional analysis. The risk of bias in the study outcomes was assessed using the Cochrane Collaboration's risk of bias tool, the GRADE method, and a tool for evaluating non-randomized controlled study (non-RCT) literature from a previous systematic review, depending on the types of articles. The study was reported in accordance with PRISMA guidelines.

Results: The study conducted a random effects meta-analysis of mean differences and 95% confidence intervals for changes in upper airway volumes, including the nasal cavity (NC), in the outcomes of 16 included studies, followed by subgroup analyses.

Conclusion: A significant increase in nasopharynx volume was observed after rapid maxillary expansion (RME) by Hyrax maxillary expander (MD = 0.69, 95% CI (0.09~1.28), p = 0.02).