Three-dimensional changes of the naso-maxillary complex following rapid maxillary expansion

Objective: To assess the volumetric changes and the maxillary response of the naso-maxillary complex (NMC) following rapid maxillary expansion (RME). Materials and Methods: Thirty consecutive patients (14 males and 16 females) with a mean age at first observation of 9.5 ± 1.8 years for males and of 11.8 ± 1.7 years for females, presenting a posterior unilateral or bilateral crossbite and requiring RME, were selected for the study. Each patient underwent expansion to correct the transverse occlusal relationships. Computed tomography scans were taken before RME (T1) and at the end of the active expansion phase (T2). Measurements were performed on scanned images. The Kolmogorov-Smirnov test was performed; the mean differences between measurements at T1 and T2 were compared using the t-test (α  =  .05). Results: All volumetric, maxillary, transverse skeletal anterior and posterior variables as well as all dental anterior and posterior linear and angular variables representing the NMC displayed statistically highly significant increases after RME (P < .001). Conclusions: After RME the total volume of the NMC increased by 12%, the nasal volume by 17%, and the maxillary volume by 10.6%. The maxillary and the nasal contributions represented 69.75% and 30.25%, respectively.