Received: 9 December 2019
Accepted: 8 April 2020
First Online: 11 May 2020
Ethics approval and consent to participate
: The design of this in vitro study had been approved by the Ethical Committee of the Postgraduate School in Orthodontics of the University of Ferrara
: Not applicable
: Some authors (Luca Lombardo, Mario Palone, Niki Arveda and Giuseppe Siciliani) contributed to development of the F22 aligner system, a product distributed and sold by the company Sweden&Martina (Due Carrare, Padua, Italy) investigated here. Therefore, they declare their competing interest.All the manufactures of the neither the aligners nor other materials used provided any financial support or other contribution to this study, or influenced its conclusions in any way. All costs were borne by the authors.