Predicting transversal dental arch expansion outcomes with Invisalign aligners in permanent dentition: a systematic...

To evaluate the predictability of Invisalign in producing transverse dental arch expansion in permanent dentition and to identify clinical and methodological factors influencing expansion accuracy.

A systematic search of PubMed, Embase, Scopus, and WOS (up to November 2025) identified clinical studies reporting planned and achieved expansion. Predictability was defined as the achieved-to-planned expansion ratio and synthesized as logit-transformed proportions in random-effects meta-analyses. Tooth-group-specific pooled estimates were calculated for each arch. Meta-regressions, non-parametric correlations, linear and multivariable regressions, and hierarchical clustering explored the influence of publication year, age, arch, tooth type, material, aligner-change interval, and planned/achieved expansion. Risk of bias was assessed with ROBINS-I and certainty of evidence with GRADE.

Twenty-three studies (1391 patients) were included; 21 entered the meta-analyses. Average predictability was 75.5% in the maxilla and 80.6% in the mandible. Mandibular second premolars showed the highest pooled predictability (88%), whereas lower second molars were least reliable (73%). In subsets reporting both levels, gingival-margin predictability was consistently lower than cusp-level values. Prediction intervals were very wide in both arches. Meta-regressions showed small but significant reductions in predictability in more recent publications (p = 0.01) and with increasing patient age (p = 0.016); greater achieved expansion showed only a modest positive association with predictability. Multivariable regression identified younger age (p = 0.001), SmartTrack material (p < 0.001), and mandibular segments (p = 0.001) as independent predictors of higher predictability. Publication bias was evident, and overall certainty of evidence was rated very low.

Invisalign aligners provide moderate-to-high predictability for dentoalveolar transverse expansion in permanent dentition, particularly in premolar regions and in the mandibular arch. Expansion is mainly expressed as buccal crown tipping. Age, aligner material, and arch location modestly influence outcomes, underscoring the need for biologically realistic planning, selective overcorrections, and careful case selection.