Three-dimensional evaluation of the nasomaxillary complex before and following rapid maxillary expansion compared to normal subjects

Objectives: The objectives of the study were to evaluate the nasomaxillary complex (NMC) measurements before and following rapid maxillary expansion (RME) compared to normal subjects. Materials and Methods: Thirty consecutive patients (14 males and 16 females) with a mean age of 9.5 ± 1.8 years for males and of 11.8 ± 1.7 years for females, who underwent RME to correct their posterior unilateral or bilateral crossbite, were selected. Computed tomography (CT) scans done before treatment (BT) formed the Group BT and those after treatment constituted the Group AT. An untreated normal sample (Group NC) presenting a normal transverse occlusion and needing a cone beam CT for other purposes was formed by 30 subjects (14 males and 16 females) with a mean age of 10 ± 0.9 years for males and of 11.6 ± 1.0 years for females. The CT scans were compared between both groups BT and AT with Group NC and measurements were performed on scanned images. The mean differences between measurements were compared using the t -test (α = 0.05). Results: No significant differences in volumetric measurements representing the NMC were found between groups BT and NC. By comparing Group AT to NC, we found that all volumetric variables displayed statistically significant differences with an increase of those of Group AT. Linear transverse variables were increased in Group NC compared to Group BT and their differences were statistically significant. However, the same variables were larger in Group AT compared to Group NC. Conclusion: RME produces an increase of the NMC dimensions compared to normal controls, which supports the principle of overcorrection, needed to compensate the post-treatment relapse.