Assessment of the Effectiveness and Predictability of Maxillary Molar Distalization with Clear Aligner Systems: A...

Background/Objectives: Maxillary molar distalization is a commonly used orthodontic approach for correcting dentoalveolar Class II malocclusions. However, the predictability of such movements when performed with clear aligners remains uncertain. This systematic review aimed to identify the effectiveness and most predictable protocol for achieving maxillary molar distalization using clear aligner systems. In this review, effectiveness was defined as the amount of distal movement achieved (mm), while predictability was defined as the ratio between achieved and planned movement (%). Methods: A systematic review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement across PubMed-Medline, Scopus, Embase, Web of Science, and Cochrane Handbook databases, with no restrictions on language or publication date. The search was performed up to April 2026. Studies evaluating maxillary molar distalization with clear aligners were screened based on predefined eligibility criteria. Results: Of the 1388 articles initially identified, 16 met the inclusion criteria (11 retrospective cohort studies and 5 prospective experimental studies), comprising a total of 461 patients. Reported distalization effectiveness varied widely, ranging from 31.1% to 88.4%. A meta-analysis could not be performed owing to substantial clinical and methodological heterogeneity. Conclusions: Clear aligners can achieve maxillary molar distalization; however, the effectiveness decreases as greater distal movement is prescribed, making it unlikely that the clinician's ideal plan will be fully realized. The use of auxiliary elements, such as Class II elastics, attachments, or skeletal anchorage devices, may reduce anterior proclination and enhance posterior anchorage. Longer aligner-wear intervals (e.g., 14 days) were associated with higher predictability in several of the included studies, although the current evidence is insufficient to establish this interval as definitively superior.