The Effectiveness of Functional Clear Aligners for Class II Correction in Growing Patients: A Systematic Review and Meta-Analysis

Abstract

Recent developments in aligner materials have enabled them to be a feasible choice for children and adolescents. Aligners offer a treatment modality for Class II correction in growing patients claiming to address a mandibular deficiency. This study aimed to assess the effectiveness of functional aligners in skeletal Class II treatment through a systematic review and meta-analysis of the existing literature. A comprehensive search was conducted in MEDLINE, Web of Science, EMBASE, Scopus and Cochrane's CENTRAL up to April 2024, with no language or date restrictions. Clinical studies that complied with the PICO question model were included, and the ROBINS-I tool was used to assess their risk of bias. We extracted relevant data from the included studies using customised data forms and pooled the results via a random-effects inverse variance meta-analysis. Different treatment approaches for growth modification, including Twin-Block, were compared to clear aligners. The primary outcomes measured were ANB, SNB and overjet. Additionally, secondary outcomes included SNA, wits appraisal, mandibular total length, ramal length, angle of convexity, overbite, molar relationship, vertical positions of incisors and molars, incisor angular shifts, interincisal angle, gonial angle, mandibular plane angle, lower anterior facial height, as well as soft tissue changes, such as the distance of the lips from the E-line. In our analysis of 21 studies evaluating the treatment outcomes of functional aligners for growing skeletal Class II patients, we observed significant reductions (p < 0.05) in ANB, Wits appraisal, angle of convexity, overbite, overjet, molar relationship, maxillary incisor angle. In addition, we found that SNB, mandibular incisor angle (IMPA), mandibular incisor horizontal position, mandibular molar vertical position, interincisal angle (L1-U1), mandibular total length, mandibular base length, ramal length and lower anterior facial height all exhibited a significant increase (p < 0.05). Thirteen of the included studies indicated no significant treatment difference between functional aligners and other functional appliances except for mandibular plane angle, lower incisor horizontal position, interincisal angle and ramal length. The findings show that aligners might be a viable option in addressing mild to moderate skeletal Class II malocclusions of growing patients. Compared to other functional appliances, there were no treatment differences in most parameters studied. Based on limited evidence, our results should be interpreted with caution and evaluated with further high-quality studies with long-term observation.

Trial Registration: PROSPERO (#CRD42023478039)