Effectiveness and accuracy of clear aligners in non-extraction Class II correction: a systematic review of maxillary molar distalization and rotation in the permanent dentition.

Objectives: To evaluate the effectiveness and accuracy of clear aligners (CA) in maxillary molar distalization and rotation for nonextraction Class II correction in the permanent dentition.

Materials and methods: This systematic review of the literature (2015-2024) followed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Studies included orthodontic patients in the permanent dentition with dental Class II, mild or no skeletal discrepancies, 2-6 mm crowding, treated with CA without extractions (except maxillary third molars) or adjunctive therapies beyond Class II elastics. Data focused on maxillary molar distalization, rotation, accuracy, and complications. Risk of bias was assessed using ROBIN-I, with evidence level graded per the SBU protocol.

Results: Sixteen studies were categorized into Group A (initial aligner or distalization outcomes) and Group B (including refinements). Group B reported greater accuracy and distalization due to sequential distalization protocols, Class II elastics, and refinements. After refinements, CA achieved 1.84-2.98 mm of maxillary molar distalization with 85% maximum accuracy. First-molar rotation reached 8.09°, with 78.4% maximum accuracy. No significant vertical skeletal changes were observed. Challenges included anterior anchorage loss, buccolingual tipping of upper molars, and patient compliance monitoring. Methodological variability and participant demographics prevented a meta-analysis.

Conclusions: CA effectively achieves maxillary molar distalization and rotation in nonextraction Class II patients. Sequential distalization protocols and refinements improve treatment outcomes, whereas early incorporation of Class II elastics, combined molar movements, and compliance monitoring may enhance treatment efficiency.