Factors Influencing the Predictability and Success of Invisalign Aligners: A Systematic Review

Invisalign clear aligners have become an increasingly popular alternative to fixed orthodontic appliances due to their esthetic appeal and comfort; however, their treatment outcomes remain variable across different patient groups and movement types. This systematic review aimed to evaluate clinical, biomechanical, and patient-related factors influencing the success and predictability of Invisalign treatment. Comprehensive searches were conducted in PubMed/MEDLINE, ScienceDirect, Google Scholar and the Cochrane Library for studies published up to August 2025. Eligible studies included randomized controlled trials, cohort, case-control, and cross-sectional designs assessing factors associated with Invisalign outcomes. Six studies met the inclusion criteria. The findings revealed that treatment success is multifactorial and primarily determined by patient compliance, treatment planning, and case complexity. Males and patients without prior orthodontic experience demonstrated higher compliance rates, while inadequate wear time was a major cause of suboptimal outcomes. Tooth movement predictability varied by type, with bucco-lingual tipping being most accurate, whereas rotation, intrusion, and expansion exhibited lower precision. Technological factors also played a role, as digital monitoring tools such as the Invisalign Progress Assessment were found to overestimate tooth movement. Compared with fixed appliances, Invisalign provided shorter treatment duration and improved comfort and esthetics, but less favorable results for certain smile parameters. Meta-analysis was not feasible due to heterogeneity in study design and outcome measures. Overall, the success of Invisalign therapy depends on a complex interaction of patient behavior, treatment planning, and technological precision. Further high-quality prospective studies are needed to standardize success criteria and refine predictive tools for improved treatment outcomes.