Vertical and sagittal changes produced by an expander with differential opening and fan-type expander: A post-hoc analysis of a randomised controlled trial

Abstract

Objective: To compare the sagittal and vertical cephalometric effects in participants treated with an expander with differential opening (EDO) versus the fan-type expander (FE). Design: Two-arm parallel randomised clinical trial (RCT). Methods: This study comprised cone-beam computed tomography-derived cephalometric images from 48 participants from a RCT. The sample was randomly allocated into two groups. The study was single-blinded. In total, 24 participants were treated with rapid maxillary expansion (RME) using EDO and 24 participants underwent RME using FE. The primary outcomes were the dentoskeletal vertical changes produced by RME. The secondary outcomes were the dentoskeletal sagittal changes. A cephalometric analysis was performed before treatment and 1 or 6 months after the active phase of RME using Dolphin Imaging Software. Intergroup comparisons of interphase changes were performed using the t-test and Mann–Whitney U test ( P < 0.05). Results: The final sample comprised 24 patients (11 men, 13 women; mean age = 7.6 ± 0.9 years) in the EDO group and 24 patients (10 men, 14 women; mean age = 7.8 ± 0.9 years) in the FE group. Both expanders produced a similar clockwise rotation of the mandible (FMA; mean difference [MD] = 0.09°, 95% confidence interval [CI] = −1.01 to 0.84). In the FE group, a greater increase of the SNA angle was observed after expansion compared to the EDO group (MD = 1.04°, 95% CI = −1.90 to −1.58). A greater palatal torque of maxillary incisors was observed in the FE group (MD = 1.32°, 95% CI = 0.05–2.56). Of the participants, 54% reported a little discomfort during the active phase of treatment and 46% of the participants did not report any discomfort. Conclusion: Both expanders produced similar vertical cephalometric changes. FEs caused slightly more maxillary anterior displacement after expansion with a compensatory palatal torque of the maxillary incisors compared to the EDOs. However, the amount of sagittal difference was not clinically relevant. Trial registration: The trial was registered at ClinicalTrials.gov, under the identifier NCT03705871.