Comparison between two screws for maxillary expansion: a multicenter randomized controlled trial on patient's reported outcome measures

Objective: The objective of this study was to compare an expansion screw of the maxilla that generates moderate and continuous forces versus a conventional screw for rapid maxillary expansion (RME) on patient-reported outcome measure (PROM) during the first 12 weeks of treatment. Trial design: This is a superiority, multicenter, two arms parallel balanced randomization trial. Methods: Patients in the mixed dentition were included with a transverse discrepancy between the two arches of at least 3 mm. An expansion screw using moderate continuous forces (Leaf group, treated with an expansion screw with Ni-Ti springs) was compared to a conventional RME screw that generates intermittent heavy forces (RME group). The primary response variable was the VAS on pain calculated in the first 12 weeks of therapy. The VAS scales on difficulty on speaking and oral hygiene, patient satisfaction and complications were also evaluated. A computer-generated block randomization was used with allocation concealed in sequentially numbered opaque sealed envelopes. Blinding was not applicable. Linear models were used for statistical analysis. Results: Twenty-eight patients in the Leaf group and 28 patients in the RME group were randomized and included in the study. There were no dropouts. The mean of the VAS for pain was 0.3 ± 0.4 in the Leaf group and 0.6 ± 0.5 in the RME group. The difference was -0.3 (95% CI from -0.5 to -0.0; P = 0.017) in favor of the Leaf group. The difference in pain was marked in the first week (Leaf group 2.2 ± 2.3; RME group 3.7 ± 2.6; difference -1.5; 95% CI from -2.7 to -0.3; P = 0.019). Conclusions: Patients in the Leaf group experienced a lower degree of pain, especially during the first week following the application of the expander. For the other variables no significant differences were reported between the two treatments. Registration: The study was registered in the ISRCTN register on 08/11/2016 with the number ISRCTN18263886. Funding: No funding or conflict of interest to be declared.