Predictability of clear aligners in achieving planned dental arch expansion during mixed dentition: a systematic review and meta-analysis

Objectives: To assess the predictability of Invisalign First in achieving planned dental arch expansion in mixed dentition. Materials and Methods: Following PRISMA guidelines and a PROSPERO-registered protocol (CRD420251083929), electronic databases were searched up to July 2025. Eligible studies included data evaluating Invisalign First for dental arch expansion in mixed dentition. Predictability, defined as ratio of achieved to planned expansion, was the primary outcome. Meta-analyses of proportions were performed separately for maxillary and mandibular arches using binomial modeling on logit scale. Correlation analyses and univariate linear regression were conducted to assess the relationship between planned expansion and achieved predictability, globally and by arch and tooth group. Risk of bias was evaluated with ROBINS-I and publication bias by funnel plot and Egger's and Begg's tests. Certainty of evidence was assessed with GRADE. Results: Nine studies were included in the systematic review and eight in the meta-analysis. Pooled predictability of expansion in the maxilla was 65%, with the lowest at permanent first molars (58%) and the highest at deciduous canines (70%). Expansion in the mandible showed higher predictability (71%), peaking at deciduous canines (75%). Correlation and regression analyses found no significant association between amount of planned expansion and achieved predictability in any subgroup. No evidence of publication bias was found, and findings remained robust on sensitivity analysis. GRADE certainty was low (maxilla) and moderate (mandible). Conclusions: Invisalign First demonstrates modest to moderate predictability for dental arch expansion in mixed dentition, particularly in the mandibular arch and anterior teeth, though limitations persist in the posterior maxilla.