BackgroundAim was to systematically search the literature and assess the available evidence regarding the clinical effectiveness of the Invisalign® system.MethodsElectronic database searches of published and unpublished literature were performed. The reference lists of all eligible articles were examined for additional studies. Reporting of this review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.ResultsThree RCTs, 8 prospective, and 11 retrospective studies were included. In general, the level of evidence was moderate and the risk of bias ranged from low to high, given the low risk of bias in included RCTs and the moderate (n = 13) or high (n = 6) risk of the other studies. The lack of standardized protocols and the high amount of clinical and methodological heterogeneity across the studies precluded a valid interpretation of the actual results through pooled estimates. However, there was substantial consistency among studies that the Invisalign® system is a viable alternative to conventional orthodontic therapy in the correction of mild to moderate malocclusions in non-growing patients that do not require extraction. Moreover, Invisalign® aligners can predictably level, tip, and derotate teeth (except for cuspids and premolars). On the other hand, limited efficacy was identified in arch expansion through bodily tooth movement, extraction space closure, corrections of occlusal contacts, and larger antero-posterior and vertical discrepancies.ConclusionsAlthough this review included a considerable number of studies, no clear clinical recommendations can be made, based on solid scientific evidence, apart from non-extraction treatment of mild to moderate malocclusions in non-growing patients. Results should be interpreted with caution due to the high heterogeneity.Electronic supplementary materialThe online version of this article (10.1186/s40510-018-0235-z) contains supplementary material, which is available to authorized users.

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Background: The treatment of Class III malocclusion has been challenging for orthodontists. Among a plethora of treatment modalities, the chin-cup is considered a traditional appliance for early orthopedic intervention. Objective: The present study aims to investigate the current scientific evidence regarding the effectiveness of chin-cup therapy in Class III malocclusion of prognathic growing patients. Method: A systematic review of the literature was conducted using PubMed/Medline and the Cochrane Central Register of Controlled Trials from January 1954 to October 2015. Articles were selected based on established inclusion/ exclusion criteria. Results: The search strategy resulted in 3285 articles.14 studies were selected for the final analysis. They were all CCTs, 13 of retrospective and 1 of prospective design. Methodological quality was evaluated by a risk of bias assessment, as suggested by the Cochrane Risk of Bias Assessment Tool for Non-Randomized Studies on Interventions. The reported evidence presented favorable short-term outcomes both in hard and soft tissues improving the Class III profile, as well as desirable dento-alveolar changes, positively affecting the Class III malocclusion. Conclusion: There is considerable agreement between studies that chin-cup therapy can be considered for the short-term treatment of growing patients with Class III malocclusion, as indicated by favorable changes both in the hard and soft tissues. The existence of considerable risk of bias in all selected studies and the unclear long-term effectiveness of chin-cup therapy highlight the need for further investigation to draw reliable conclusions.

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