The Efficacy of the RME II System Compared with the Sander Bite-Jumping Appliance: A Retrospective Study

<b>Objective:</b> This paper aimed to assess the effectiveness of the Rapid Maxillary Expander (RME) II System, compared to the Sander bite-jumping appliance (SBJ) and an untreated control group, in the treatment of Class II skeletal malocclusion in children. <b>Methods:</b> Thirty Class II patients treated with the RME II System (Group R) were compared to 30 patients treated with the SBJ (Group S) and 30 untreated Class II children (Group C). Cephalograms were analysed at the beginning of the study (T0) and at the end of the treatment (T1). Eight cephalometric parameters were evaluated: the divergence angle (SN-MP), ANB, lower face height (LFH), CO-GN, 1 + SN, IMPA, overjet, and overbite. The Shapiro-Wilk normality test was conducted to assess the distribution of the data. A <i>t</i>-test was then used for pairwise comparisons of the cephalometric measurements between T0 and T1. Differences among the groups were analysed using one-way ANOVA with Tukey's post hoc correction. <b>Results:</b> ANOVA revealed a statistically significant difference for all analysed variables except 1 + SN. The post hoc Tukey's test identified the following differences: SN-MP was 2.51° greater in Group S than in Group R, LFH was 5.46 mm greater in Group C than in Group R and 3.11 mm greater in Group S than in Group R, IMPA was 4.01° greater in Group S than in Group R, and overbite was 1.96 mm lower in Group S than in Group R. <b>Conclusions:</b> The RME II System provides better control of mandibular plane inclination and lower incisor proclination during the correction of Class II skeletal malocclusion. Both devices are effective in correcting Class II skeletal malocclusion.