Objective: To evaluate and compare a serial of volume changes of the nasal cavity (NC), nasopharynx, oropharynx and maxillary sinuses (MS) in growing Class III patients after either rapid palatal expansion (RPE) or alternate rapid maxillary expansion and constriction (Alt-RAMEC) followed by facemask (FM) therapy using cone-beam computed tomography (CBCT).
Methods: Forty growing Class III patients were retrospectively selected and divided into two matched groups: RPE/FM (14 females, 6 males; mean age, 9.66 ± 1.23 years) and Alt- RAMEC/FM groups (14 females, 6 males; mean age, 10.28 ± 1.45 years). The anteroposterior and vertical displacements of Point A relative to fixed cranial references, the volumes of NC, nasopharyngeal, oropharyngeal airway, and MS were measured at different time points: pretreatment (T1), postexpansion (T2), and postprotraction (T3).
Results: Both groups had a significant maxilla advancement by 1.3 mm during expansion, with a statistically significant intergroup difference during protraction (RPE/FM, 1.1 mm; Alt-RAMEC/FM, 2.4 mm; P < .05) and throughout the treatment (RPE/FM, 2.4 mm; Alt-RAMEC/FM, 3.7 mm; P < .05). The NC and nasopharyngeal airway volumes increased significantly in both groups after expansion, protraction and entire treatment. Oropharyngeal and MS volumes increased in both groups postprotraction and posttreatment. But no volumetric difference was observed between the two groups.
Conclusions: There seems no difference in airway volume changes, including NC, nasopharyngeal, oropharyngeal airway, and MS between RPE/FM and Alt-RAMEC/FM at different stages. Although in Alt-RAMEC/FM, there was a significantly more forward movement after protraction, the difference was deemed too small to be clinically relevant.

Keywords: CBCT, Face mask, Class III treatment, Airway