Predictability of maxillary transverse changes with Invisalign in adults: A systematic review and meta-analysis

Background: To systematically evaluate the predictability of Invisalign for maxillary transverse expansion in adult patients. Methods: Five databases – PubMed, Embase, Scopus, Web of Science, and the Cochrane Library – were searched for clinical studies published between January 1, 2014, and August 1, 2024, that evaluated Invisalign for maxillary transverse expansion. After study selection and data extraction, meta-analyses were performed using Stata/MP, version 17.0 (StataCorp LLC). Results: Six retrospective clinical studies involving 233 patients were eligible for inclusion. The meta-analysis showed varying degrees of predictability across different regions of the maxilla treated with Invisalign. Specifically, the pooled predictability was 72.01% in the canine region (95% confidence interval [CI]: 59.67%–84.35%; P  = .001; I 2  = 74.7%), 80.73% in the 1st premolar region (95% CI: 73.78%–87.68%; P  = .115; I 2  = 43.5%), 78.74% in the 2nd premolar region (95% CI: 70.41%–87.08%; P  = .039; I 2  = 57.4%), and 71.57% in the 1st molar region (95% CI: 62.41%–80.73%; P  = .074; I 2  = 50.2%). Studies conducted in developed countries showed a higher pooled predictability (77.22%; 95% CI: 70.34%–84.10%; P  = .454; I 2  = 0.0%) than those conducted in developing countries (58.53%; 95% CI: 45.20%–71.86%; P  = .225; I 2  = 32.0%), with a statistically significant difference between the subgroups ( P  = .015). Studies using Geomagic software (3D Systems) for measurements generally showed lower heterogeneity. Conclusion: The available evidence suggests that Invisalign provides moderate predictability for maxillary transverse expansion, with the highest pooled predictability in the premolar regions and lower predictability in the canine and 1st molar regions. The canine estimate should be interpreted cautiously because of substantial heterogeneity and low-certainty evidence. Exploratory subgroup findings related to study-country classification, anatomical landmarks, and measurement software remain uncertain because of the small number of studies and methodological variability. Further well-designed prospective studies are needed to confirm these findings.