A prospective CBCT study of upper airway changes after rapid maxillary expansion.

OBJECTIVE: The aim of this prospective study was to investigate the upper airway changes after rapid maxillary expansion utilizing CBCT. METHODS: 16 children (10 male, 6 female) with a mean age of 12.73 +/- 1.73 years underwent RME as part of their comprehensive orthodontic treatment with4,6-banded hyrax expanders. The screws were activated 2 turns a day. Depending on the expansion amount (2.7-6.3mm), the activation period ranged from 2 to 3 weeks. CBCT images were taken immediately before (T1) and three months after expansion (T2) in upright position, with patients' heads kept in consistent position. All CBCT data were processed with the software EZ3D2009. After orienting the CBCT images, a set of linear, area and volumetric parameters of the upper airway were measured and calculated. Student paired t test and one-way ANOVA were applied. The significance level of P<0.0033 was used according to the Bonferroni correction. RESULTS: After expansion, with molar-to-molar width increasing 4.4 +/- 1.3 mm and molars tipping 6.2 +/- 6.2 degrees , the nasal floor width and nasal lateral width increased 1.6, 1.5, and 1.6mm and 1.3, 1.7, and 1.4mm from the anterior to the posterior part, respectively. And there was no difference among the anterior, median and posterior part. The lower nasal volume increased 1348.5mm(3) with the percentage change being 8.1%. The pharyngeal airway showed no positive change. CONCLUSION: RME can expand the nasal cavity and the expansion pattern may follow the parallel opening configuration. However, the influence on the pharyngeal airway is limited.