The Efficacy of the RME II System Compared with a Herbst Appliance in the Treatment of Class II Skeletal Malocclusion in Growing Patients: A Retrospective Study

(1) Background: The objective of this study was to evaluate the efficacy of the Rapid Maxillary Expander (RME) II System compared to a Herbst appliance and a control group in the treatment of class II skeletal malocclusions in growing patients. (2) Methods: A total of 30 class II patients treated using the RME II System (group R) were compared with 30 patients treated with a Herbst appliance (group H) and 30 untreated class II children (group C). Cephalograms were compared at the start (T0) and after 24 months (T1). Nine cephalometric parameters were analyzed: SN-MP, SN-PO, ANB, AR-GO-ME, AR-GO-N, N-GO-ME, SN-PP, LFH, CO-GN, 1+SN, IMPA, OVERJET, and OVERBITE. Since the variables failed the normality test, a Wilcoxon test was performed for a pairwise comparison of the cephalometric measurements taken at T0 (pre-treatment) and at T1 (post-treatment). ANOVA with Tukey post hoc correction was used to evaluate the differences among the groups. (3) Results: ANOVA showed a statistically significant difference for all analyzed variables except for AR-GO-ME, AR-GO-N, and N-GO-ME. Post hoc Tukey's HSD test showed the following difference: the SN-PO angle in group H was 3.59° greater than in group R; the LFH in group H was 4.13 mm greater than in group R. The mandibular length (CO-GN) in group H was 3.94 mm greater than in group R; IMPA in group H was 6.4° greater than in group R; and the ANB angle in group H was 1.47° greater than in group R. (4) Conclusions: The RME II System is an effective therapeutic device for class II skeletal malocclusion treatment in growing patients.