Mandibular Response in Class II Division 1 Growing Subjects: Clear Aligners vs. Rapid Maxillary Expansion Therapy. A Controlled Pilot Study

Objectives: The present study aimed to evaluate the skeletal and dental changes in two different groups of mixed dentition Class II division 1 patients treated with Clear Aligners and with Rapid Maxillary Expansion and to assess the post-treatment mandib- ular response in comparison with an untreated control group. Materials and Method: 33 subjects were recruited according to the following inclusion criteria: Caucasian ancestry, early mixed dentition with fully-erupted first permanent molars, bilateral Class II division 1, posterior transverse interarch discrep- ancy <5mm, CSV1–2, no previous orthodontic treatment/congenitally missing or extracted teeth/craniofacial syndromes. The Aligner Group (AG = 13, 6 males, 7 females, 9.2 ± 0.8 years) was treated with Clear Aligners following a standardized sequential expansion protocol “molars move first” without extractions and other auxiliaries than attachments; the RME group (RG = 10 pa- tients, 5 males, 5 females, 9.6 ± 0.7 years) was treated with RME banded on second primary molars; the Control Group (CG = 10, 6 males, 4 females, 9.6 ± 0.9 years) was followed up for 1 year without treatment. Panoramic radiographs and lateral cephalograms were collected pre-treatment (T0) and post-treatment (T1) (T1–T0=15.7±1.3months). The Kruskal–Wallis one-way test was used for the analysis of variance by ranks at T0 (baseline) and for the changes observed between T0 and T1 (p < 0.10). Results: On the sagittal plane, no significant post-treatment differences in mandibular response were found between the three analysed groups. On the vertical plane, the CA group showed a statistically significant reduction of SN-GoMe when compared to the CG (p = 0.023) and to the RG (p = 0.067). Conclusions: Clear Aligners and RME did not influence the sagittal skeletal relationship in prepubertal Class II division 1 pa- tients treated during early mixed dentition, compared to the untreated control group. On the vertical plane, patients treated with Clear Aligners showed a statistically significant reduction of SN-GoMe.